diff --git a/scons-2.2.0.tar.gz b/scons-2.2.0.tar.gz deleted file mode 100644 index 9526681..0000000 --- a/scons-2.2.0.tar.gz +++ /dev/null @@ -1,3 +0,0 @@ -version https://git-lfs.github.com/spec/v1 -oid sha256:f7fcd11a7af7ec13d587a2f7cf14a92e3223eea64bf078454a9856ec0ab465b9 -size 591836 diff --git a/scons-2.3.0.tar.gz b/scons-2.3.0.tar.gz new file mode 100644 index 0000000..8edc3e2 --- /dev/null +++ b/scons-2.3.0.tar.gz @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:9442069999cf4b2caa94a5886ab4c2c71de1718ed5e9176c18e2b6dbca463b4b +size 599514 diff --git a/scons-user.html b/scons-user.html deleted file mode 100644 index 5fd268e..0000000 --- a/scons-user.html +++ /dev/null @@ -1,45103 +0,0 @@ - -SCons User Guide 1.0.1

SCons User Guide 1.0.1

Steven Knight

Copyright © 2004, 2005, 2006, 2007, 2008 Steven Knight

- SCons User's Guide Copyright (c) 2004, 2005, 2006, 2007 Steven Knight - -

Table of Contents
Preface
1. SCons Principles
2. A Caveat About This Guide's Completeness
3. Acknowledgements
4. Contact
1. Building and Installing SCons
1.1. Installing Python
1.2. Installing SCons From Pre-Built Packages
1.2.1. Installing SCons on Red Hat (and Other RPM-based) Linux Systems
1.2.2. Installing SCons on Debian Linux Systems
1.2.3. Installing SCons on Windows Systems
1.3. Building and Installing SCons on Any System
1.3.1. Building and Installing Multiple Versions of SCons Side-by-Side
1.3.2. Installing SCons in Other Locations
1.3.3. Building and Installing SCons Without Administrative Privileges
2. Simple Builds
2.1. Building Simple C / C++ Programs
2.2. Building Object Files
2.3. Simple Java Builds
2.4. Cleaning Up After a Build
2.5. The SConstruct File
2.5.1. SConstruct Files Are Python Scripts
2.5.2. SCons Functions Are Order-Independent
2.6. Making the SCons Output Less Verbose
3. Less Simple Things to Do With Builds
3.1. Specifying the Name of the Target (Output) File
3.2. Compiling Multiple Source Files
3.3. Making a list of files with Glob
3.4. Specifying Single Files Vs. Lists of Files
3.5. Making Lists of Files Easier to Read
3.6. Keyword Arguments
3.7. Compiling Multiple Programs
3.8. Sharing Source Files Between Multiple Programs
4. Building and Linking with Libraries
4.1. Building Libraries
4.1.1. Building Libraries From Source Code or Object Files
4.1.2. Building Static Libraries Explicitly: the StaticLibrary Builder
4.1.3. Building Shared (DLL) Libraries: the SharedLibrary Builder
4.2. Linking with Libraries
4.3. Finding Libraries: the $LIBPATH Construction Variable
5. Node Objects
5.1. Builder Methods Return Lists of Target Nodes
5.2. Explicitly Creating File and Directory Nodes
5.3. Printing Node File Names
5.4. Using a Node's File Name as a String
6. Dependencies
6.1. Deciding When an Input File Has Changed: the Decider Function
6.1.1. Using MD5 Signatures to Decide if a File Has Changed
6.1.2. Using Time Stamps to Decide If a File Has Changed
6.1.3. Deciding If a File Has Changed Using Both MD Signatures and Time Stamps
6.1.4. Writing Your Own Custom Decider Function
6.1.5. Mixing Different Ways of Deciding If a File Has Changed
6.2. Older Functions for Deciding When an Input File Has Changed
6.2.1. The SourceSignatures Function
6.2.2. The TargetSignatures Function
6.3. Implicit Dependencies: The $CPPPATH Construction Variable
6.4. Caching Implicit Dependencies
6.4.1. The --implicit-deps-changed Option
6.4.2. The --implicit-deps-unchanged Option
6.5. Explicit Dependencies: the Depends Function
6.6. Dependencies From External Files: the ParseDepends - Function
6.7. Ignoring Dependencies: the Ignore Function
6.8. Order-Only Dependencies: the Requires Function
6.9. The AlwaysBuild Function
7. Environments
7.1. Using Values From the External Environment
7.2. Construction Environments
7.2.1. Creating a Construction Environment: the Environment Function
7.2.2. Fetching Values From a Construction Environment
7.2.3. Expanding Values From a Construction Environment: the subst Method
7.2.4. Controlling the Default Construction Environment: the DefaultEnvironment Function
7.2.5. Multiple Construction Environments
7.2.6. Making Copies of Construction Environments: the Clone Method
7.2.7. Replacing Values: the Replace Method
7.2.8. Setting Values Only If They're Not Already Defined: the SetDefault Method
7.2.9. Appending to the End of Values: the Append Method
7.2.10. Appending Unique Values: the AppendUnique Method
7.2.11. Appending to the Beginning of Values: the Prepend Method
7.2.12. Prepending Unique Values: the PrependUnique Method
7.3. Controlling the Execution Environment for Issued Commands
7.3.1. Propagating PATH From the External Environment
7.3.2. Adding to PATH Values in the Execution Environment
8. Merging Options into the Environment: the MergeFlags Function
9. Separating Compile Arguments into their Variables: the ParseFlags Function
10. Finding Installed Library Information: the ParseConfig Function
11. Controlling Build Output
11.1. Providing Build Help: the Help Function
11.2. Controlling How SCons Prints Build Commands: the $*COMSTR Variables
11.3. Providing Build Progress Output: the Progress Function
11.4. Printing Detailed Build Status: the GetBuildFailures Function
12. Controlling a Build From the Command Line
12.1. Command-Line Options
12.1.1. Not Having to Specify Command-Line Options Each Time: the SCONSFLAGS Environment Variable
12.1.2. Getting Values Set by Command-Line Options: the GetOption Function
12.1.3. Setting Values of Command-Line Options: the SetOption Function
12.1.4. Strings for Getting or Setting Values of SCons Command-Line Options
12.1.5. Adding Custom Command-Line Options: the AddOption Function
12.2. Command-Line variable=value Build Variables
12.2.1. Controlling Command-Line Build Variables
12.2.2. Providing Help for Command-Line Build Variables
12.2.3. Reading Build Variables From a File
12.2.4. Pre-Defined Build Variable Functions
12.2.5. Adding Multiple Command-Line Build Variables at Once
12.2.6. Handling Unknown Command-Line Build Variables: the UnknownVariables Function
12.3. Command-Line Targets
12.3.1. Fetching Command-Line Targets: the COMMAND_LINE_TARGETS Variable
12.3.2. Controlling the Default Targets: the Default Function
12.3.3. Fetching the List of Build Targets, Regardless of Origin: the BUILD_TARGETS Variable
13. Installing Files in Other Directories: the Install Builder
13.1. Installing Multiple Files in a Directory
13.2. Installing a File Under a Different Name
13.3. Installing Multiple Files Under Different Names
14. Platform-Independent File System Manipulation
14.1. Copying Files or Directories: The Copy Factory
14.2. Deleting Files or Directories: The Delete Factory
14.3. Moving (Renaming) Files or Directories: The Move Factory
14.4. Updating the Modification Time of a File: The Touch Factory
14.5. Creating a Directory: The Mkdir Factory
14.6. Changing File or Directory Permissions: The Chmod Factory
14.7. Executing an action immediately: the Execute Function
15. Controlling Removal of Targets
15.1. Preventing target removal during build: the Precious Function
15.2. Preventing target removal during clean: the NoClean Function
15.3. Removing additional files during clean: the Clean Function
16. Hierarchical Builds
16.1. SConscript Files
16.2. Path Names Are Relative to the SConscript Directory
16.3. Top-Level Path Names in Subsidiary SConscript Files
16.4. Absolute Path Names
16.5. Sharing Environments (and Other Variables) Between SConscript Files
16.5.1. Exporting Variables
16.5.2. Importing Variables
16.5.3. Returning Values From an SConscript File
17. Separating Source and Build Directories
17.1. Specifying a Variant Directory Tree as Part of an SConscript Call
17.2. Why SCons Duplicates Source Files in a Variant Directory Tree
17.3. Telling SCons to Not Duplicate Source Files in the Variant Directory Tree
17.4. The VariantDir Function
17.5. Using VariantDir With an SConscript File
17.6. Using Glob with VariantDir
18. Variant Builds
19. Writing Your Own Builders
19.1. Writing Builders That Execute External Commands
19.2. Attaching a Builder to a Construction Environment
19.3. Letting SCons Handle The File Suffixes
19.4. Builders That Execute Python Functions
19.5. Builders That Create Actions Using a Generator
19.6. Builders That Modify the Target or Source Lists Using an Emitter
19.7. Where To Put Your Custom Builders and Tools
20. Not Writing a Builder: the Command Builder
21. Pseudo-Builders: the AddMethod function
22. Writing Scanners
22.1. A Simple Scanner Example
23. Building From Code Repositories
23.1. The Repository Method
23.2. Finding source files in repositories
23.3. Finding #include files in repositories
23.3.1. Limitations on #include files in repositories
23.4. Finding the SConstruct file in repositories
23.5. Finding derived files in repositories
23.6. Guaranteeing local copies of files
24. Multi-Platform Configuration (Autoconf Functionality)
24.1. Configure Contexts
24.2. Checking for the Existence of Header Files
24.3. Checking for the Availability of a Function
24.4. Checking for the Availability of a Library
24.5. Checking for the Availability of a typedef
24.6. Adding Your Own Custom Checks
24.7. Not Configuring When Cleaning Targets
25. Caching Built Files
25.1. Specifying the Shared Cache Directory
25.2. Keeping Build Output Consistent
25.3. Not Using the Shared Cache for Specific Files
25.4. Disabling the Shared Cache
25.5. Populating a Shared Cache With Already-Built Files
25.6. Minimizing Cache Contention: the --random Option
26. Alias Targets
27. Java Builds
27.1. Building Java Class Files: the Java Builder
27.2. How SCons Handles Java Dependencies
27.3. Building Java Archive (.jar) Files: the Jar Builder
27.4. Building C Header and Stub Files: the JavaH Builder
27.5. Building RMI Stub and Skeleton Class Files: the RMIC Builder
28. Miscellaneous Functionality
28.1. Verifying the Python Version: the EnsurePythonVersion Function
28.2. Verifying the SCons Version: the EnsureSConsVersion Function
28.3. Explicitly Terminating SCons While Reading SConscript Files: the Exit Function
28.4. Searching for Files: the FindFile Function
28.5. Handling Nested Lists: the Flatten Function
28.6. Finding the Invocation Directory: the GetLaunchDir Function
29. Troubleshooting
29.1. Why is That Target Being Rebuilt? the --debug=explain Option
29.2. What's in That Construction Environment? the Dump Method
29.3. What Dependencies Does SCons Know About? the --tree Option
29.4. How is SCons Constructing the Command Lines It Executes? the --debug=presub Option
29.5. Where is SCons Searching for Libraries? the --debug=findlibs Option
29.6. Where is SCons Blowing Up? the --debug=stacktrace Option
29.7. How is SCons Making Its Decisions? the --taskmastertrace Option
A. Construction Variables
B. Builders
C. Tools
D. Handling Common Tasks
List of Examples
D-1. Wildcard globbing to create a list of filenames
D-2. Filename extension substitution
D-3. Appending a path prefix to a list of filenames
D-4. Substituting a path prefix with another one
D-5. Filtering a filename list to exclude/retain only a specific set -of extensions
D-6. The "backtick function": run a shell command and capture the -output

Preface

- Thank you for taking the time to read about SCons. - SCons is a next-generation - software construction tool, - or make tool--that is, a software utility - for building software (or other files) - and keeping built software up-to-date - whenever the underlying input files change. - -

- The most distinctive thing about SCons - is that its configuration files are - actually scripts, - written in the Python programming language. - This is in contrast to most alternative build tools, - which typically invent a new language to - configure the build. - SCons still has a learning curve, of course, - because you have to know what functions to call - to set up your build properly, - but the underlying syntax used should be familiar - to anyone who has ever looked at a Python script. - -

- Paradoxically, - using Python as the configuration file format - makes SCons - easier - for non-programmers to learn - than the cryptic languages of other build tools, - which are usually invented by programmers for other programmers. - This is in no small part due to the - consistency and readability that are built in to Python. - It just so happens that making a real, live - scripting language the basis for the - configuration files - makes it a snap for more accomplished programmers - to do more complicated things with builds, - as necessary. - -

1. SCons Principles

- There are a few overriding principles - we try to live up to in designing and implementing SCons: - -

Correctness

- First and foremost, - by default, SCons guarantees a correct build - even if it means sacrificing performance a little. - We strive to guarantee the build is correct - regardless of how the software being built is structured, - how it may have been written, - or how unusual the tools are that build it. - -

Performance

- Given that the build is correct, - we try to make SCons build software - as quickly as possible. - In particular, wherever we may have needed to slow - down the default SCons behavior to guarantee a correct build, - we also try to make it easy to speed up SCons - through optimization options that let you trade off - guaranteed correctness in all end cases for - a speedier build in the usual cases. - -

Convenience

- SCons tries to do as much for you out of the box as reasonable, - including detecting the right tools on your system - and using them correctly to build the software. - -

- In a nutshell, we try hard to make SCons just - "do the right thing" and build software correctly, - with a minimum of hassles. - -

2. A Caveat About This Guide's Completeness

- One word of warning as you read through this Guide: - Like too much Open Source software out there, - the SCons documentation isn't always - kept up-to-date with the available features. - In other words, - there's a lot that SCons can do that - isn't yet covered in this User's Guide. - (Come to think of it, - that also describes a lot of proprietary software, doesn't it?) - -

- Although this User's Guide isn't as complete as we'd like it to be, - our development process does emphasize - making sure that the SCons man page is kept up-to-date - with new features. - So if you're trying to figure out how to do something - that SCons supports - but can't find enough (or any) information here, - it would be worth your while to look - at the man page to see if the information is covered there. - And if you do, - maybe you'd even consider contributing - a section to the User's Guide - so the next person looking for - that information won't have to - go through the same thing...? - -

3. Acknowledgements

- SCons would not exist without a lot of help - from a lot of people, - many of whom may not even be aware - that they helped or served as inspiration. - So in no particular order, - and at the risk of leaving out someone: - -

- First and foremost, - SCons owes a tremendous debt to Bob Sidebotham, - the original author of the classic Perl-based Cons tool - which Bob first released to the world back around 1996. - Bob's work on Cons classic provided the underlying architecture - and model of specifying a build configuration - using a real scripting language. - My real-world experience working on Cons - informed many of the design decisions in SCons, - including the improved parallel build support, - making Builder objects easily definable by users, - and separating the build engine from the wrapping interface. - -

- Greg Wilson was instrumental in getting - SCons started as a real project - when he initiated the Software Carpentry design - competition in February 2000. - Without that nudge, - marrying the advantages of the Cons classic - architecture with the readability of Python - might have just stayed no more than a nice idea. - -

- The entire SCons team have been - absolutely wonderful to work with, - and SCons would be nowhere near as useful a - tool without the energy, enthusiasm - and time people have contributed over the past few years. - The "core team" - of Chad Austin, Anthony Roach, - Bill Deegan, Charles Crain, Steve Leblanc, Greg Noel, - Gary Oberbrunner, Greg Spencer and Christoph Wiedemann - have been great about reviewing my (and other) changes - and catching problems before they get in the code base. - Of particular technical note: - Anthony's outstanding and innovative work on the tasking engine - has given SCons a vastly superior parallel build model; - Charles has been the master of the crucial Node infrastructure; - Christoph's work on the Configure infrastructure - has added crucial Autoconf-like functionality; - and Greg has provided excellent support - for Microsoft Visual Studio. - -

- Special thanks to David Snopek for contributing - his underlying "Autoscons" code that formed - the basis of Christoph's work with the Configure functionality. - David was extremely generous in making - this code available to SCons, - given that he initially released it under the GPL - and SCons is released under a less-restrictive MIT-style license. - -

- Thanks to Peter Miller - for his splendid change management system, Aegis, - which has provided the SCons project - with a robust development methodology from day one, - and which showed me how you could - integrate incremental regression tests into - a practical development cycle - (years before eXtreme Programming arrived on the scene). - -

- And last, thanks to Guido van Rossum - for his elegant scripting language, - which is the basis not only for the SCons implementation, - but for the interface itself. - -

4. Contact

- The best way to contact people involved with SCons, - including the author, - is through the SCons mailing lists. - -

- If you want to ask general questions about how to use SCons - send email to users@scons.tigris.org. - -

- If you want to contact the SCons development community directly, - send email to dev@scons.tigris.org. - -

- If you want to receive announcements about SCons, - join the low-volume announce@scons.tigris.org mailing list. - -

Chapter 1. Building and Installing SCons

- This chapter will take you through the basic steps - of installing SCons on your system, - and building SCons if you don't have a - pre-built package available - (or simply prefer the flexibility of building it yourself). - Before that, however, this chapter will also describe the basic steps - involved in installing Python on your system, - in case that is necessary. - Fortunately, both SCons and Python - are very easy to install on almost any system, - and Python already comes installed on many systems. - -

1.1. Installing Python

- Because SCons is written in Python, - you must obviously have Python installed on your system - to use SCons. - Before you try to install Python, - you should check to see if Python is already - available on your system by typing - python -V - (capital 'V') - or - python --version - at your system's command-line prompt. - - 


       $ python -V
-       Python 2.5.1
-

- And on a Windows system with Python installed: - - 


       C:\>python -V
-       Python 2.5.1
-

- If Python is not installed on your system, - you will see an error message - stating something like "command not found" - (on UNIX or Linux) - or "'python' is not recognized - as an internal or external command, operable progam or batch file" - (on Windows). - In that case, you need to install Python - before you can install SCons. - -

- (Note that the -V option - was added to Python version 2.0, - so if your system only has an earlier version available - you may see an - "Unknown option: -V" - error message.) - -

- The standard location for information - about downloading and installing Python is - http://www.python.org/download/. - See that page for information about - how to download and install Python on your system. - -

- SCons will work with any version of Python from 1.5.2 or later. - If you need to install Python and have a choice, - we recommend using the most recent Python 2.5 version available. - Python 2.5 has significant improvements - the help speed up the performance of SCons'. - -

1.2. Installing SCons From Pre-Built Packages

- SCons comes pre-packaged for installation on a number of systems, - including Linux and Windows systems. - You do not need to read this entire section, - you should only need to read the section - appropriate to the type of system you're running on. - -

1.2.1. Installing SCons on Red Hat (and Other RPM-based) Linux Systems

- SCons comes in RPM (Red Hat Package Manager) format, - pre-built and ready to install on Red Hat Linux, - Fedora Core, - or any other Linux distribution that uses RPM. - Your distribution may - already have an SCons RPM built specifically for it; - many do, including SuSe, Mandrake and Fedora. - You can check for the availability of an SCons RPM - on your distribution's download servers, - or by consulting an RPM search site like - http://www.rpmfind.net/ or - http://rpm.pbone.net/. - -

- If your Linux distribution does not already have - a specific SCons RPM file, - you can download and install from the - generic RPM provided by the SCons project. - This will install the - SCons script(s) in /usr/bin, - and the SCons library modules in - /usr/lib/scons. - -

- To install from the command line, simply download the - appropriate .rpm file, - and then run: - - 


        # rpm -Uvh scons-0.96-1.noarch.rpm
-

- Or, you can use a graphical RPM package manager - like gnorpm. - See your package manager application's documention - for specific instructions about - how to use it to install a downloaded RPM. - -

1.2.2. Installing SCons on Debian Linux Systems

- Debian Linux systems use a different package management - format that also makes it very easy to install SCons. - -

- If your system is connected to the Internet, - you can install the latest official Debian package - by running: - - 


        # apt-get install scons
-

1.2.3. Installing SCons on Windows Systems

- SCons provides a Windows installer - that makes installation extremely easy. - Download the scons-0.95.win32.exe - file from the SCons download page at - http://www.scons.org/download.html. - Then all you need to do is execute the file - (usually by clicking on its icon in Windows Explorer). - These will take you through a small - sequence of windows that will install - SCons on your system. - - - -

1.3. Building and Installing SCons on Any System

- If a pre-built SCons package is not available for your system, - then you can still easily build and install SCons using the native - Python distutils package. - -

- The first step is to download either the - scons-1.0.1.tar.gz - or scons-1.0.1.zip, - which are available from the SCons download page at - http://www.scons.org/download.html. - -

- Unpack the archive you downloaded, - using a utility like tar - on Linux or UNIX, - or WinZip on Windows. - This will create a directory called - scons-1.0.1, - usually in your local directory. - Then change your working directory to that directory - and install SCons by executing the following commands: - - 


      # cd scons-1.0.1
-      # python setup.py install
-

- This will build SCons, - install the scons script - in the default system scripts directory - (/usr/local/bin or - C:\Python25\Scripts), - and will install the SCons build engine - in an appropriate stand-alone library directory - (/usr/local/lib/scons or - C:\Python25\scons). - Because these are system directories, - you may need root (on Linux or UNIX) or Administrator (on Windows) - privileges to install SCons like this. - -

1.3.1. Building and Installing Multiple Versions of SCons Side-by-Side

- The SCons setup.py script - has some extensions that support - easy installation of multiple versions of SCons - in side-by-side locations. - This makes it easier to download and - experiment with different versions of SCons - before moving your official build process to a new version, - for example. - -

- To install SCons in a version-specific location, - add the --version-lib option - when you call setup.py: - - 


        # python setup.py install --version-lib
-

- This will install the SCons build engine - in the - /usr/lib/scons-1.0.1 - or - C:\Python25\scons-1.0.1 - directory, for example. - -

- If you use the --version-lib option - the first time you install SCons, - you do not need to specify it each time you install - a new version. - The SCons setup.py script - will detect the version-specific directory name(s) - and assume you want to install all versions - in version-specific directories. - You can override that assumption in the future - by explicitly specifying the --standalone-lib option. - -

1.3.2. Installing SCons in Other Locations

- You can install SCons in locations other than - the default by specifying the --prefix= option: - - 


        # python setup.py install --prefix=/opt/scons
-

- This would - install the scons script in - /opt/scons/bin - and the build engine in - /opt/scons/lib/scons, - -

- Note that you can specify both the --prefix= - and the --version-lib options - at the same type, - in which case setup.py - will install the build engine - in a version-specific directory - relative to the specified prefix. - Adding --version-lib to the - above example would install the build engine in - /opt/scons/lib/scons-1.0.1. - -

1.3.3. Building and Installing SCons Without Administrative Privileges

- If you don't have the right privileges to install SCons - in a system location, - simply use the --prefix= option - to install it in a location of your choosing. - For example, - to install SCons in appropriate locations - relative to the user's $HOME directory, - the scons script in - $HOME/bin - and the build engine in - $HOME/lib/scons, - simply type: - - 


        $ python setup.py install --prefix=$HOME
-

- You may, of course, specify any other location you prefer, - and may use the --version-lib option - if you would like to install version-specific directories - relative to the specified prefix. - -

Chapter 2. Simple Builds

- In this chapter, - you will see several examples of - very simple build configurations using SCons, - which will demonstrate how easy - it is to use SCons to - build programs from several different programming languages - on different types of systems. - -

2.1. Building Simple C / C++ Programs

- Here's the famous "Hello, World!" program in C: - - 


      int
-      main()
-      {
-          printf("Hello, world!\n");
-      }
-

- And here's how to build it using SCons. - Enter the following into a file named SConstruct: - - 


      Program('hello.c')
-

- This minimal configuration file gives - SCons two pieces of information: - what you want to build - (an executable program), - and the input file from - which you want it built - (the hello.c file). - Program is a builder_method, - a Python call that tells SCons that you want to build an - executable program. - -

- That's it. Now run the scons command to build the program. - On a POSIX-compliant system like Linux or UNIX, - you'll see something like: - - 


      % scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      scons: done building targets.
-

- On a Windows system with the Microsoft Visual C++ compiler, - you'll see something like: - - 


      C:\>scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cl /nologo /c hello.c /Fohello.obj
-      link /nologo /OUT:hello.exe hello.obj
-      scons: done building targets.
-

- First, notice that you only need - to specify the name of the source file, - and that SCons correctly deduces the names of - the object and executable files to be built - from the base of the source file name. - -

- Second, notice that the same input SConstruct file, - without any changes, - generates the correct output file names on both systems: - hello.o and hello - on POSIX systems, - hello.obj and hello.exe - on Windows systems. - This is a simple example of how SCons - makes it extremely easy to - write portable software builds. - -

- (Note that we won't provide duplicate side-by-side - POSIX and Windows output for all of the examples in this guide; - just keep in mind that, unless otherwise specified, - any of the examples should work equally well on both types of systems.) - -

2.2. Building Object Files

- The Program builder method is only one of - many builder methods that SCons provides - to build different types of files. - Another is the Object builder method, - which tells SCons to build an object file - from the specified source file: - - 


      Object('hello.c')
-

- Now when you run the scons command to build the program, - it will build just the hello.o object file on a POSIX system: - - 


      % scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cc -o hello.o -c hello.c
-      scons: done building targets.
-

- And just the hello.obj object file - on a Windows system (with the Microsoft Visual C++ compiler): - - 


      C:\>scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cl /nologo /c hello.c /Fohello.obj
-      scons: done building targets.
-

2.3. Simple Java Builds

- SCons also makes building with Java extremely easy. - Unlike the Program and Object builder methods, - however, the Java builder method - requires that you specify - the name of a destination directory in which - you want the class files placed, - followed by the source directory - in which the .java files live: - - 


     Java('classes', 'src')
-

- If the src directory - contains a single hello.java file, - then the output from running the scons command - would look something like this - (on a POSIX system): - - 


      % scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      javac -d classes -sourcepath src src/hello.java
-      scons: done building targets.
-

- We'll cover Java builds in more detail, - including building Java archive (.jar) - and other types of file, - in Chapter 27. - -

2.4. Cleaning Up After a Build

- When using SCons, it is unnecessary to add special - commands or target names to clean up after a build. - Instead, you simply use the - -c or --clean - option when you invoke SCons, - and SCons removes the appropriate built files. - So if we build our example above - and then invoke scons -c - afterwards, the output on POSIX looks like: - - 


      % scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      scons: done building targets.
-      % scons -c
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Cleaning targets ...
-      Removed hello.o
-      Removed hello
-      scons: done cleaning targets.
-

- And the output on Windows looks like: - - 


      C:\>scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cl /nologo /c hello.c /Fohello.obj
-      link /nologo /OUT:hello.exe hello.obj
-      scons: done building targets.
-      C:\>scons -c
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Cleaning targets ...
-      Removed hello.obj
-      Removed hello.exe
-      scons: done cleaning targets.
-

- Notice that SCons changes its output to tell you that it - is Cleaning targets ... and - done cleaning targets. - -

2.5. The SConstruct File

- If you're used to build systems like Make - you've already figured out that the SConstruct file - is the SCons equivalent of a Makefile. - That is, the SConstruct file is the input file - that SCons reads to control the build. - -

2.5.1. SConstruct Files Are Python Scripts

- There is, however, an important difference between - an SConstruct file and a Makefile: - the SConstruct file is actually a Python script. - If you're not already familiar with Python, don't worry. - This User's Guide will introduce you step-by-step - to the relatively small amount of Python you'll - need to know to be able to use SCons effectively. - And Python is very easy to learn. - -

- One aspect of using Python as the - scripting language is that you can put comments - in your SConstruct file using Python's commenting convention; - that is, everything between a '#' and the end of the line - will be ignored: - - 


        # Arrange to build the "hello" program.
-        Program('hello.c')    # "hello.c" is the source file.
-

- You'll see throughout the remainder of this Guide - that being able to use the power of a - real scripting language - can greatly simplify the solutions - to complex requirements of real-world builds. - -

2.5.2. SCons Functions Are Order-Independent

- One important way in which the SConstruct - file is not exactly like a normal Python script, - and is more like a Makefile, - is that the order in which - the SCons functions are called in - the SConstruct file - does not - affect the order in which SCons - actually builds the programs and object files - you want it to build.[1] - In other words, when you call the Program builder - (or any other builder method), - you're not telling SCons to build - the program at the instant the builder method is called. - Instead, you're telling SCons to build the program - that you want, for example, - a program built from a file named hello.c, - and it's up to SCons to build that program - (and any other files) whenever it's necessary. - (We'll learn more about how - SCons decides when building or rebuilding a file - is necessary in Chapter 6, below.) - -

- SCons reflects this distinction between - calling a builder method like Program> - and actually building the program - by printing the status messages that indicate - when it's "just reading" the SConstruct file, - and when it's actually building the target files. - This is to make it clear when SCons is - executing the Python statements that make up the SConstruct file, - and when SCons is actually executing the - commands or other actions to - build the necessary files. - -

- Let's clarify this with an example. - Python has a print statement that - prints a string of characters to the screen. - If we put print statements around - our calls to the Program builder method: - - 


       print "Calling Program('hello.c')"
-       Program('hello.c')
-       print "Calling Program('goodbye.c')"
-       Program('goodbye.c')
-       print "Finished calling Program()"
-

- Then when we execute SCons, - we see the output from the print - statements in between the messages about - reading the SConscript files, - indicating that that is when the - Python statements are being executed: - - 


       % scons
-       scons: Reading SConscript files ...
-       Calling Program('hello.c')
-       Calling Program('goodbye.c')
-       Finished calling Program()
-       scons: done reading SConscript files.
-       scons: Building targets ...
-       cc -o goodbye.o -c goodbye.c
-       cc -o goodbye goodbye.o
-       cc -o hello.o -c hello.c
-       cc -o hello hello.o
-       scons: done building targets.
-

- Notice also that SCons built the goodbye program first, - even though the "reading SConscript" output - shows that we called Program('hello.c') - first in the SConstruct file. - -

2.6. Making the SCons Output Less Verbose

- You've already seen how SCons prints - some messages about what it's doing, - surrounding the actual commands used to build the software: - - 


      C:\>scons
-      scons: Reading SConscript files ...
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      cl /nologo /c hello.c /Fohello.obj
-      link /nologo /OUT:hello.exe hello.obj
-      scons: done building targets.
-

- These messages emphasize the - order in which SCons does its work: - all of the configuration files - (generically referred to as SConscript files) - are read and executed first, - and only then are the target files built. - Among other benefits, these messages help to distinguish between - errors that occur while the configuration files are read, - and errors that occur while targets are being built. - -

- One drawback, of course, is that these messages clutter the output. - Fortunately, they're easily disabled by using - the -Q option when invoking SCons: - - 


      C:\>scons -Q
-      cl /nologo /c hello.c /Fohello.obj
-      link /nologo /OUT:hello.exe hello.obj
-

- Because we want this User's Guide to focus - on what SCons is actually doing, - we're going to use the -Q option - to remove these messages from the - output of all the remaining examples in this Guide. - -

Chapter 3. Less Simple Things to Do With Builds

- In this chapter, - you will see several examples of - very simple build configurations using SCons, - which will demonstrate how easy - it is to use SCons to - build programs from several different programming languages - on different types of systems. - -

3.1. Specifying the Name of the Target (Output) File

- You've seen that when you call the Program builder method, - it builds the resulting program with the same - base name as the source file. - That is, the following call to build an - executable program from the hello.c source file - will build an executable program named hello on POSIX systems, - and an executable program named hello.exe on Windows systems: - - 


       Program('hello.c')
-

- If you want to build a program with - a different name than the base of the source file name, - you simply put the target file name - to the left of the source file name: - - 


       Program('new_hello', 'hello.c')
-

- (SCons requires the target file name first, - followed by the source file name, - so that the order mimics that of an - assignment statement in most programming languages, - including Python: - "program = source files".) - -

- Now SCons will build an executable program - named new_hello when run on a POSIX system: - - 


       % scons -Q
-       cc -o hello.o -c hello.c
-       cc -o new_hello hello.o
-

- And SCons will build an executable program - named new_hello.exe when run on a Windows system: - - 


       C:\>scons -Q
-       cl /nologo /c hello.c /Fohello.obj
-       link /nologo /OUT:new_hello.exe hello.obj
-

3.2. Compiling Multiple Source Files

- You've just seen how to configure SCons - to compile a program from a single source file. - It's more common, of course, - that you'll need to build a program from - many input source files, not just one. - To do this, you need to put the - source files in a Python list - (enclosed in square brackets), - like so: - - 


       Program(['prog.c', 'file1.c', 'file2.c'])
-

- A build of the above example would look like: - - 


       % scons -Q
-       cc -o file1.o -c file1.c
-       cc -o file2.o -c file2.c
-       cc -o prog.o -c prog.c
-       cc -o prog prog.o file1.o file2.o
-

- Notice that SCons - deduces the output program name - from the first source file specified - in the list--that is, - because the first source file was prog.c, - SCons will name the resulting program prog - (or prog.exe on a Windows system). - If you want to specify a different program name, - then (as we've seen in the previous section) - you slide the list of source files - over to the right - to make room for the output program file name. - (SCons puts the output file name to the left - of the source file names - so that the order mimics that of an - assignment statement: "program = source files".) - This makes our example: - - 


       Program('program', ['prog.c', 'file1.c', 'file2.c'])
-

- On Linux, a build of this example would look like: - - 


       % scons -Q
-       cc -o file1.o -c file1.c
-       cc -o file2.o -c file2.c
-       cc -o prog.o -c prog.c
-       cc -o program prog.o file1.o file2.o
-

- Or on Windows: - - 


       C:\>scons -Q
-       cl /nologo /c file1.c /Fofile1.obj
-       cl /nologo /c file2.c /Fofile2.obj
-       cl /nologo /c prog.c /Foprog.obj
-       link /nologo /OUT:program.exe prog.obj file1.obj file2.obj
-

3.3. Making a list of files with Glob

- You can also use the Glob function to find all files matching a - certain template, using the standard shell pattern matching - characters *, ? - and [abc] to match any of - a, b or c. - [!abc] is also supported, - to match any character except - a, b or c. - This makes many multi-source-file builds quite easy: - - 


       Program('program', Glob('*.c'))
-

- The SCons man page has more details on using Glob with Variant - directories and Repositories, and returning strings rather than Nodes. - -

3.4. Specifying Single Files Vs. Lists of Files

- We've now shown you two ways to specify - the source for a program, - one with a list of files: - - 


       Program('hello', ['file1.c', 'file2.c'])
-

- And one with a single file: - - 


       Program('hello', 'hello.c')
-

- You could actually put a single file name in a list, too, - which you might prefer just for the sake of consistency: - - 


       Program('hello', ['hello.c'])
-

- SCons functions will accept a single file name in either form. - In fact, internally, SCons treats all input as lists of files, - but allows you to omit the square brackets - to cut down a little on the typing - when there's only a single file name. - -

- Although SCons functions - are forgiving about whether or not you - use a string vs. a list for a single file name, - Python itself is more strict about - treating lists and strings differently. - So where SCons allows either - a string or list: - - 


       # The following two calls both work correctly:
-       Program('program1', 'program1.c')
-       Program('program2', ['program2.c'])
-

- Trying to do "Python things" that mix strings and - lists will cause errors or lead to incorrect results: - - 


       common_sources = ['file1.c', 'file2.c']
-
-       # THE FOLLOWING IS INCORRECT AND GENERATES A PYTHON ERROR
-       # BECAUSE IT TRIES TO ADD A STRING TO A LIST:
-       Program('program1', common_sources + 'program1.c')
-
-       # The following works correctly, because it's adding two
-       # lists together to make another list.
-       Program('program2', common_sources + ['program2.c'])
-

3.5. Making Lists of Files Easier to Read

- One drawback to the use of a Python list - for source files is that - each file name must be enclosed in quotes - (either single quotes or double quotes). - This can get cumbersome and difficult to read - when the list of file names is long. - Fortunately, SCons and Python provide a number of ways - to make sure that - the SConstruct file stays easy to read. - -

- To make long lists of file names - easier to deal with, SCons provides a - Split function - that takes a quoted list of file names, - with the names separated by spaces or other white-space characters, - and turns it into a list of separate file names. - Using the Split function turns the - previous example into: - - 


       Program('program', Split('main.c file1.c file2.c'))
-

- (If you're already familiar with Python, - you'll have realized that this is similar to the - split() method - in the Python standard string module. - Unlike the string.split() method, - however, the Split function - does not require a string as input - and will wrap up a single non-string object in a list, - or return its argument untouched if it's already a list. - This comes in handy as a way to make sure - arbitrary values can be passed to SCons functions - without having to check the type of the variable by hand.) - -

- Putting the call to the Split function - inside the Program call - can also be a little unwieldy. - A more readable alternative is to - assign the output from the Split call - to a variable name, - and then use the variable when calling the - Program function: - - 


       src_files = Split('main.c file1.c file2.c')
-       Program('program', src_files)
-

- Lastly, the Split function - doesn't care how much white space separates - the file names in the quoted string. - This allows you to create lists of file - names that span multiple lines, - which often makes for easier editing: - - 


       src_files = Split("""main.c
-                            file1.c
-                            file2.c""")
-       Program('program', src_files)
-

- (Note in this example that we used - the Python "triple-quote" syntax, - which allows a string to contain - multiple lines. - The three quotes can be either - single or double quotes.) - -

3.6. Keyword Arguments

- SCons also allows you to identify - the output file and input source files - using Python keyword arguments. - The output file is known as the - target, - and the source file(s) are known (logically enough) as the - source. - The Python syntax for this is: - - 


       src_files = Split('main.c file1.c file2.c')
-       Program(target = 'program', source = src_files)
-

- Because the keywords explicitly identify - what each argument is, - you can actually reverse the order if you prefer: - - 


       src_files = Split('main.c file1.c file2.c')
-       Program(source = src_files, target = 'program')
-

- Whether or not you choose to use keyword arguments - to identify the target and source files, - and the order in which you specify them - when using keywords, - are purely personal choices; - SCons functions the same regardless. - -

3.7. Compiling Multiple Programs

- In order to compile multiple programs - within the same SConstruct file, - simply call the Program method - multiple times, - once for each program you need to build: - - 


       Program('foo.c')
-       Program('bar', ['bar1.c', 'bar2.c'])
-

- SCons would then build the programs as follows: - - 


       % scons -Q
-       cc -o bar1.o -c bar1.c
-       cc -o bar2.o -c bar2.c
-       cc -o bar bar1.o bar2.o
-       cc -o foo.o -c foo.c
-       cc -o foo foo.o
-

- Notice that SCons does not necessarily build the - programs in the same order in which you specify - them in the SConstruct file. - SCons does, however, recognize that - the individual object files must be built - before the resulting program can be built. - We'll discuss this in greater detail in - the "Dependencies" section, below. - -

3.8. Sharing Source Files Between Multiple Programs

- It's common to re-use code by sharing source files - between multiple programs. - One way to do this is to create a library - from the common source files, - which can then be linked into resulting programs. - (Creating libraries is discussed in - Chapter 4, below.) - -

- A more straightforward, but perhaps less convenient, - way to share source files between multiple programs - is simply to include the common files - in the lists of source files for each program: - - 


       Program(Split('foo.c common1.c common2.c'))
-       Program('bar', Split('bar1.c bar2.c common1.c common2.c'))
-

- SCons recognizes that the object files for - the common1.c and common2.c source files - each only need to be built once, - even though the resulting object files are - each linked in to both of the resulting executable programs: - - 


       % scons -Q
-       cc -o bar1.o -c bar1.c
-       cc -o bar2.o -c bar2.c
-       cc -o common1.o -c common1.c
-       cc -o common2.o -c common2.c
-       cc -o bar bar1.o bar2.o common1.o common2.o
-       cc -o foo.o -c foo.c
-       cc -o foo foo.o common1.o common2.o
-

- If two or more programs - share a lot of common source files, - repeating the common files in the list for each program - can be a maintenance problem when you need to change the - list of common files. - You can simplify this by creating a separate Python list - to hold the common file names, - and concatenating it with other lists - using the Python + operator: - - 


       common = ['common1.c', 'common2.c']
-       foo_files = ['foo.c'] + common
-       bar_files = ['bar1.c', 'bar2.c'] + common
-       Program('foo', foo_files)
-       Program('bar', bar_files)
-

- This is functionally equivalent to the previous example. - -

Chapter 4. Building and Linking with Libraries

- It's often useful to organize large software projects - by collecting parts of the software into one or more libraries. - SCons makes it easy to create libraries - and to use them in the programs. - -

4.1. Building Libraries

- You build your own libraries by specifying Library - instead of Program: - - 


      Library('foo', ['f1.c', 'f2.c', 'f3.c'])
-

- SCons uses the appropriate library prefix and suffix for your system. - So on POSIX or Linux systems, - the above example would build as follows - (although ranlib may not be called on all systems): - - 


      % scons -Q
-      cc -o f1.o -c f1.c
-      cc -o f2.o -c f2.c
-      cc -o f3.o -c f3.c
-      ar rc libfoo.a f1.o f2.o f3.o
-      ranlib libfoo.a
-

- On a Windows system, - a build of the above example would look like: - - 


      C:\>scons -Q
-      cl /nologo /c f1.c /Fof1.obj
-      cl /nologo /c f2.c /Fof2.obj
-      cl /nologo /c f3.c /Fof3.obj
-      lib /nologo /OUT:foo.lib f1.obj f2.obj f3.obj
-

- The rules for the target name of the library - are similar to those for programs: - if you don't explicitly specify a target library name, - SCons will deduce one from the - name of the first source file specified, - and SCons will add an appropriate - file prefix and suffix if you leave them off. - -

4.1.1. Building Libraries From Source Code or Object Files

- The previous example shows building a library from a - list of source files. - You can, however, also give the Library call - object files, - and it will correctly realize - In fact, you can arbitrarily mix source code files - and object files in the source list: - - 


        Library('foo', ['f1.c', 'f2.o', 'f3.c', 'f4.o'])
-

- And SCons realizes that only the source code files - must be compiled into object files - before creating the final library: - - 


        % scons -Q
-        cc -o f1.o -c f1.c
-        cc -o f3.o -c f3.c
-        ar rc libfoo.a f1.o f2.o f3.o f4.o
-        ranlib libfoo.a
-

- Of course, in this example, the object files - must already exist for the build to succeed. - See Chapter 5, below, - for information about how you can - build object files explicitly - and include the built files in a library. - -

4.1.2. Building Static Libraries Explicitly: the StaticLibrary Builder

- The Library function builds a traditional static library. - If you want to be explicit about the type of library being built, - you can use the synonym StaticLibrary function - instead of Library: - - 


        StaticLibrary('foo', ['f1.c', 'f2.c', 'f3.c'])
-

- There is no functional difference between the - StaticLibrary and Library functions. - -

4.1.3. Building Shared (DLL) Libraries: the SharedLibrary Builder

- If you want to build a shared library (on POSIX systems) - or a DLL file (on Windows systems), - you use the SharedLibrary function: - - 


        SharedLibrary('foo', ['f1.c', 'f2.c', 'f3.c'])
-

- The output on POSIX: - - 


        % scons -Q
-        cc -o f1.os -c f1.c
-        cc -o f2.os -c f2.c
-        cc -o f3.os -c f3.c
-        cc -o libfoo.so -shared f1.os f2.os f3.os
-

- And the output on Windows: - - 


        C:\>scons -Q
-        cl /nologo /c f1.c /Fof1.obj
-        cl /nologo /c f2.c /Fof2.obj
-        cl /nologo /c f3.c /Fof3.obj
-        link /nologo /dll /out:foo.dll /implib:foo.lib f1.obj f2.obj f3.obj
-        RegServerFunc(target, source, env)
-

- Notice again that SCons takes care of - building the output file correctly, - adding the -shared option - for a POSIX compilation, - and the /dll option on Windows. - -

4.2. Linking with Libraries

- Usually, you build a library - because you want to link it with one or more programs. - You link libraries with a program by specifying - the libraries in the $LIBS construction variable, - and by specifying the directory in which - the library will be found in the - $LIBPATH construction variable: - - - - 


      Library('foo', ['f1.c', 'f2.c', 'f3.c'])
-      Program('prog.c', LIBS=['foo', 'bar'], LIBPATH='.')
-

- Notice, of course, that you don't need to specify a library - prefix (like lib) - or suffix (like .a or .lib). - SCons uses the correct prefix or suffix for the current system. - -

- On a POSIX or Linux system, - a build of the above example would look like: - - 


      % scons -Q
-      cc -o f1.o -c f1.c
-      cc -o f2.o -c f2.c
-      cc -o f3.o -c f3.c
-      ar rc libfoo.a f1.o f2.o f3.o
-      ranlib libfoo.a
-      cc -o prog.o -c prog.c
-      cc -o prog prog.o -L. -lfoo -lbar
-

- On a Windows system, - a build of the above example would look like: - - 


      C:\>scons -Q
-      cl /nologo /c f1.c /Fof1.obj
-      cl /nologo /c f2.c /Fof2.obj
-      cl /nologo /c f3.c /Fof3.obj
-      lib /nologo /OUT:foo.lib f1.obj f2.obj f3.obj
-      cl /nologo /c prog.c /Foprog.obj
-      link /nologo /OUT:prog.exe /LIBPATH:. foo.lib bar.lib prog.obj
-

- As usual, notice that SCons has taken care - of constructing the correct command lines - to link with the specified library on each system. - -

- Note also that, - if you only have a single library to link with, - you can specify the library name in single string, - instead of a Python list, - so that: - - 


      Program('prog.c', LIBS='foo', LIBPATH='.')
-

- is equivalent to: - - 


      Program('prog.c', LIBS=['foo'], LIBPATH='.')
-

- This is similar to the way that SCons - handles either a string or a list to - specify a single source file. - -

4.3. Finding Libraries: the $LIBPATH Construction Variable

- By default, the linker will only look in - certain system-defined directories for libraries. - SCons knows how to look for libraries - in directories that you specify with the - $LIBPATH construction variable. - $LIBPATH consists of a list of - directory names, like so: - - 


      Program('prog.c', LIBS = 'm',
-                        LIBPATH = ['/usr/lib', '/usr/local/lib'])
-

- Using a Python list is preferred because it's portable - across systems. Alternatively, you could put all of - the directory names in a single string, separated by the - system-specific path separator character: - a colon on POSIX systems: - - 


      LIBPATH = '/usr/lib:/usr/local/lib'
-

- or a semi-colon on Windows systems: - - 


      LIBPATH = 'C:\\lib;D:\\lib'
-

- (Note that Python requires that the backslash - separators in a Windows path name - be escaped within strings.) - -

- When the linker is executed, - SCons will create appropriate flags - so that the linker will look for - libraries in the same directories as SCons. - So on a POSIX or Linux system, - a build of the above example would look like: - - 


      % scons -Q
-      cc -o prog.o -c prog.c
-      cc -o prog prog.o -L/usr/lib -L/usr/local/lib -lm
-

- On a Windows system, - a build of the above example would look like: - - 


      C:\>scons -Q
-      cl /nologo /c prog.c /Foprog.obj
-      link /nologo /OUT:prog.exe /LIBPATH:\usr\lib /LIBPATH:\usr\local\lib m.lib prog.obj
-

- Note again that SCons has taken care of - the system-specific details of creating - the right command-line options. - -

Chapter 5. Node Objects

- Internally, SCons represents all of the files - and directories it knows about as Nodes. - These internal objects - (not object files) - can be used in a variety of ways - to make your SConscript - files portable and easy to read. - -

5.1. Builder Methods Return Lists of Target Nodes

- All builder methods return a list of - Node objects that identify the - target file or files that will be built. - These returned Nodes can be passed - as source files to other builder methods, - -

- For example, suppose that we want to build - the two object files that make up a program with different options. - This would mean calling the Object - builder once for each object file, - specifying the desired options: - - 


    Object('hello.c', CCFLAGS='-DHELLO')
-    Object('goodbye.c', CCFLAGS='-DGOODBYE')
-

- One way to combine these object files - into the resulting program - would be to call the Program - builder with the names of the object files - listed as sources: - - 


    Object('hello.c', CCFLAGS='-DHELLO')
-    Object('goodbye.c', CCFLAGS='-DGOODBYE')
-    Program(['hello.o', 'goodbye.o'])
-

- The problem with listing the names as strings - is that our SConstruct file is no longer portable - across operating systems. - It won't, for example, work on Windows - because the object files there would be - named hello.obj and goodbye.obj, - not hello.o and goodbye.o. - -

- A better solution is to assign the lists of targets - returned by the calls to the Object builder to variables, - which we can then concatenate in our - call to the Program builder: - - 


      hello_list = Object('hello.c', CCFLAGS='-DHELLO')
-      goodbye_list = Object('goodbye.c', CCFLAGS='-DGOODBYE')
-      Program(hello_list + goodbye_list)
-

- This makes our SConstruct file portable again, - the build output on Linux looking like: - - 


       % scons -Q
-       cc -o goodbye.o -c -DGOODBYE goodbye.c
-       cc -o hello.o -c -DHELLO hello.c
-       cc -o hello hello.o goodbye.o
-

- And on Windows: - - 


       C:\>scons -Q
-       cl -DGOODBYE /c goodbye.c /Fogoodbye.obj
-       cl -DHELLO /c hello.c /Fohello.obj
-       link /nologo /OUT:hello.exe hello.obj goodbye.obj
-

- We'll see examples of using the list of nodes - returned by builder methods throughout - the rest of this guide. - -

5.2. Explicitly Creating File and Directory Nodes

- It's worth mentioning here that - SCons maintains a clear distinction - between Nodes that represent files - and Nodes that represent directories. - SCons supports File and Dir - functions that, repectively, - return a file or directory Node: - - 


      hello_c = File('hello.c')
-      Program(hello_c)
-
-      classes = Dir('classes')
-      Java(classes, 'src')
-

- Normally, you don't need to call - File or Dir directly, - because calling a builder method automatically - treats strings as the names of files or directories, - and translates them into - the Node objects for you. - The File and Dir functions can come in handy - in situations where you need to explicitly - instruct SCons about the type of Node being - passed to a builder or other function, - or unambiguously refer to a specific - file in a directory tree. - - -

- There are also times when you may need to - refer to an entry in a file system - without knowing in advance - whether it's a file or a directory. - For those situations, - SCons also supports an Entry function, - which returns a Node - that can represent either a file or a directory. - - 


    xyzzy = Entry('xyzzy')
-

- The returned xyzzy Node - will be turned into a file or directory Node - the first time it is used by a builder method - or other function that - requires one vs. the other. - -

5.3. Printing Node File Names

- One of the most common things you can do - with a Node is use it to print the - file name that the node represents. - For example, the following SConstruct file: - - 


      hello_c = File('hello.c')
-      Program(hello_c)
-
-      classes = Dir('classes')
-      Java(classes, 'src')
-
-      object_list = Object('hello.c')
-      program_list = Program(object_list)
-      print "The object file is:", object_list[0]
-      print "The program file is:", program_list[0]
-

- Would print the following file names on a POSIX system: - - 


      % scons -Q
-      The object file is: hello.o
-      The program file is: hello
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-

- And the following file names on a Windows system: - - 


      C:\>scons -Q
-      The object file is: hello.obj
-      The program file is: hello.exe
-      cl /nologo /c hello.c /Fohello.obj
-      link /nologo /OUT:hello.exe hello.obj
-

5.4. Using a Node's File Name as a String

- Printing a Node's name - as described in the previous section - works because the string representation of a Node - is the name of the file. - If you want to do something other than - print the name of the file, - you can fetch it by using the builtin Python - str function. - For example, if you want to use the Python - os.path.exists - to figure out whether a file - exists while the SConstruct file - is being read and executed, - you can fetch the string as follows: - - 


      import os.path
-      program_list = Program('hello.c')
-      program_name = str(program_list[0])
-      if not os.path.exists(program_name):
-          print program_name, "does not exist!"
-

- Which executes as follows on a POSIX system: - - 


      % scons -Q
-      hello does not exist!
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-

Chapter 6. Dependencies

- So far we've seen how SCons handles one-time builds. - But one of the main functions of a build tool like SCons - is to rebuild only the necessary things - when source files change--or, put another way, - SCons should not - waste time rebuilding things that have already been built. - You can see this at work simply by re-invoking SCons - after building our simple hello example: - - 


     % scons -Q
-     cc -o hello.o -c hello.c
-     cc -o hello hello.o
-     % scons -Q
-     scons: `.' is up to date.
-

- The second time it is executed, - SCons realizes that the hello program - is up-to-date with respect to the current hello.c source file, - and avoids rebuilding it. - You can see this more clearly by naming - the hello program explicitly on the command line: - - 


     % scons -Q hello
-     cc -o hello.o -c hello.c
-     cc -o hello hello.o
-     % scons -Q hello
-     scons: `hello' is up to date.
-

- Note that SCons reports "...is up to date" - only for target files named explicitly on the command line, - to avoid cluttering the output. - -

6.1. Deciding When an Input File Has Changed: the Decider Function

- Another aspect of avoiding unnecessary rebuilds - is the fundamental build tool behavior - of rebuilding - things when an input file changes, - so that the built software is up to date. - By default, - SCons keeps track of this through an - MD5 signature, or checksum, of the contents of each file, - although you can easily configure - SCons to use the - modification times (or time stamps) - instead. - You can even specify your own Python function - for deciding if an input file has changed. - -

6.1.1. Using MD5 Signatures to Decide if a File Has Changed

- By default, - SCons keeps track of whether a file has changed - based on an MD5 checksum of the file's contents, - not the file's modification time. - This means that you may be surprised by the - default SCons behavior if you are used to the - Make convention of forcing - a rebuild by updating the file's modification time - (using the touch command, for example): - - 


         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % touch hello.c
-         % scons -Q hello
-         scons: `hello' is up to date.
-

- Even though the file's modification time has changed, - SCons realizes that the contents of the - hello.c file have not changed, - and therefore that the hello program - need not be rebuilt. - This avoids unnecessary rebuilds when, - for example, someone rewrites the - contents of a file without making a change. - But if the contents of the file really do change, - then SCons detects the change - and rebuilds the program as required: - - 


         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % edit hello.c
-             [CHANGE THE CONTENTS OF hello.c]
-         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-

- Note that you can, if you wish, - specify this default behavior - (MD5 signatures) explicitly - using the Decider function as follows: - - 


        Program('hello.c')
-        Decider('MD5')
-

- You can also use the string 'content' - as a synonym for 'MD5' - when calling the Decider function. - -

6.1.1.1. Ramifications of Using MD5 Signatures

- Using MD5 Signatures to decide if an input file has changed - has one surprising benefit: - if a source file has been changed - in such a way that the contents of the - rebuilt target file(s) - will be exactly the same as the last time - the file was built, - then any "downstream" target files - that depend on the rebuilt-but-not-changed target - file actually need not be rebuilt. - -

- So if, for example, - a user were to only change a comment in a hello.c file, - then the rebuilt hello.o file - would be exactly the same as the one previously built - (assuming the compiler doesn't put any build-specific - information in the object file). - SCons would then realize that it would not - need to rebuild the hello program as follows: - - 


           % scons -Q hello
-           cc -o hello.o -c hello.c
-           cc -o hello hello.o
-           % edit hello.c
-             [CHANGE A COMMENT IN hello.c]
-           % scons -Q hello
-           cc -o hello.o -c hello.c
-           scons: `hello' is up to date.
-

- In essence, SCons - "short-circuits" any dependent builds - when it realizes that a target file - has been rebuilt to exactly the same file as the last build. - This does take some extra processing time - to read the contents of the target (hello.o) file, - but often saves time when the rebuild that was avoided - would have been time-consuming and expensive. - -

6.1.2. Using Time Stamps to Decide If a File Has Changed

- If you prefer, you can - configure SCons to use the modification time - of a file, not the file contents, - when deciding if a target needs to be rebuilt. - SCons gives you two ways to use time stamps - to decide if an input file has changed - since the last time a target has been built. - -

- The most familiar way to use time stamps - is the way Make does: - that is, have SCons decide - and target must be rebuilt if - if a source file's modification time is - newer - than the target file. - To do this, call the Decider - function as follows: - - 


        Program('hello.c')
-        Decider('timestamp-newer')
-

- This makes SCons act like Make - when a file's modification time is updated - (using the touch command, for example): - - 


         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % touch hello.c
-         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-

- And, in fact, because this behavior is the same - as the behavior of Make, - you can also use the string 'make' - as a synonym for 'timestamp-newer' - when calling the Decider function: - - 


        Program('hello.c')
-        Decider('make')
-

- One drawback to using times stamps exactly like Make - is that if an input file's modification time suddenly - becomes older than a target file, - the target file will not be rebuilt. - This can happen if an old copy of a source file is restored - from a backup archive, for example. - The contents of the restored file will likely be different - than they were the last time a dependent target was built, - but the target won't be rebuilt - because the modification time of the source file - is not newer than the target. - -

- Because SCons actually stores information - about the source files' time stamps whenever a target is built, - it can handle this situation by checking for - an exact match of the source file time stamp, - instead of just whether or not the source file - is newer than the target file. - To do this, specify the argument - 'timestamp-match' - when calling the Decider function: - - 


        Program('hello.c')
-        Decider('timestamp-match')
-

- When configured this way, - SCons will rebuild a target whenever - a source file's modification time has changed. - So if we use the touch -t - option to change the modification time of - hello.c to an old date (January 1, 1989), - SCons will still rebuild the target file: - - 


         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % touch -t 198901010000 hello.c
-         % scons -Q hello
-         cc -o hello.o -c hello.c
-         scons: `hello' is up to date.
-

- In general, the only reason to prefer - timestamp-newer - instead of - timestamp-match, - would be if you have some specific reason - to require this Make-like behavior of - not rebuilding a target when an otherwise-modified - source file is older. - -

6.1.3. Deciding If a File Has Changed Using Both MD Signatures and Time Stamps

- As a performance enhancement, - SCons provides a way to use - MD5 checksums of file contents - but to only read the contents - whenever the file's timestamp has changed. - To do this, call the Decider - function with 'MD5-timestamp' - argument as follows: - - 


        Program('hello.c')
-        Decider('MD5-timestamp')
-

- So configured, SCons will still behave like - it does when using Decider('MD5'): - - 


         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % touch hello.c
-         % scons -Q hello
-         scons: `hello' is up to date.
-         % edit hello.c
-             [CHANGE THE CONTENTS OF hello.c]
-         % scons -Q hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-

- However, the second call to SCons in the above output, - when the build is up-to-date, - will have been performed by simply looking at the - modification time of the hello.c file, - not by opening it and performing - an MD5 checksum calcuation on its contents. - This can significantly speed up many up-to-date builds. - -

- The only drawback to using - Decider('MD5-timestamp') - is that SCons will not - rebuild a target file if a source file was modified - within one second of the last time SCons built the file. - While most developers are programming, - this isn't a problem in practice, - since it's unlikely that someone will have built - and then thought quickly enought to make a substantive - change to a source file within one second. - Certain build scripts or - continuous integration tools may, however, - rely on the ability to applying changes to files - automatically and then rebuild as quickly as possible, - in which case use of - Decider('MD5-timestamp') - may not be appropriate. - -

6.1.4. Writing Your Own Custom Decider Function

- The different string values that we've passed to - the Decider function are essentially used by SCons - to pick one of several specific internal functions - that implement various ways of deciding if a dependency - (usually a source file) - has changed since a target file has been built. - As it turns out, - you can also supply your own function - to decide if a dependency has changed. - -

- For example, suppose we have an input file - that contains a lot of data, - in some specific regular format, - that is used to rebuild a lot of different target files, - but each target file really only depends on - one particular section of the input file. - We'd like to have each target file depend on - only its section of the input file. - However, since the input file may contain a lot of data, - we only want to open the input file if its timestamp has changed. - This could done with a custom - Decider function that might look something like this: - - 


        Program('hello.c')
-        def decide_if_changed(dependency, target, prev_ni):
-            if self.get_timestamp() != prev_ni.timestamp:
-                dep = str(dependency)
-                tgt = str(target)
-                if specific_part_of_file_has_changed(dep, tgt):
-                    return True
-            return False
-        Decider(decide_if_changed)
-

- Note that in the function definition, - the dependency - (input file) is the first argument, - and then the target. - Both of these are passed to the functions as - SCons Node objects, - which we convert to strings using the Python - str(). - -

- The third argument, prev_ni, - is an object that holds the - signature or timestamp information - that was recorded about the dependency - the last time the target was built. - A prev_ni object can hold - different information, - depending on the type of thing that the - dependency argument represents. - For normal files, - the prev_ni object - has the following attributes: - -

.csig

The content signature, - or MD5 checksum, of the contents of the - dependency - file the list time the target was built. -

.size

The size in bytes of the dependency - file the list time the target was built. -

.timestamp

The modification time of the dependency - file the list time the target was built. -

- Note that ignoring some of the arguments - in your custom Decider function - is a perfectly normal thing to do, - if they don't impact the way you want to - decide if the dependency file has changed. - -

6.1.5. Mixing Different Ways of Deciding If a File Has Changed

- The previous examples have all demonstrated calling - the global Decider function - to configure all dependency decisions that SCons makes. - Sometimes, however, you want to be able to configure - different decision-making for different targets. - When that's necessary, you can use the - env.Decider - method to affect only the configuration - decisions for targets built with a - specific construction environment. - -

- For example, if we arbitrarily want to build - one program using MD5 checkums - and another use file modification times - from the same source - we might configure it this way: - - 


        env1 = Environment(CPPPATH = ['.'])
-        env2 = env1.Clone()
-        env2.Decider('timestamp-match')
-        env1.Program('prog-MD5', 'program1.c')
-        env2.Program('prog-timestamp', 'program2.c')
-

- If both of the programs include the same - inc.h file, - then updating the modification time of - inc.h - (using the touch command) - will cause only prog-timestamp - to be rebuilt: - - 


         % scons -Q
-         cc -o program1.o -c -I. program1.c
-         cc -o prog-MD5 program1.o
-         cc -o program2.o -c -I. program2.c
-         cc -o prog-timestamp program2.o
-         % touch inc.h
-         % scons -Q
-         cc -o program2.o -c -I. program2.c
-         cc -o prog-timestamp program2.o
-

6.2. Older Functions for Deciding When an Input File Has Changed

- SCons still supports two functions that used to be the - primary methods for configuring the - decision about whether or not an input file has changed. - Although they're not officially deprecated yet, - their use is discouraged, - mainly because they rely on a somewhat - confusing distinction between how - source files and target files are handled. - These functions are documented here mainly in case you - encounter them in existing SConscript files. - -

6.2.1. The SourceSignatures Function

- The SourceSignatures function is fairly straightforward, - and supports two different argument values - to configure whether source file changes should be decided - using MD5 signatures: - - 


        Program('hello.c')
-        SourceSignatures('MD5')
-

- Or using time stamps: - - 


        Program('hello.c')
-        SourceSignatures('timestamp')
-

- These are roughly equivalent to specifying - Decider('MD5') - or - Decider('timestamp-match'), - respectively, - although it only affects how SCons makes - decisions about dependencies on - source files--that is, - files that are not built from any other files. - -

6.2.2. The TargetSignatures Function

- The TargetSignatures function - specifies how SCons decides - when a target file has changed - when it is used as a - dependency of (input to) another target--that is, - the TargetSignatures function configures - how the signatures of "intermediate" target files - are used when deciding if a "downstream" target file - must be rebuilt. - [2] - -

- The TargetSignatures function supports the same - 'MD5' and 'timestamp' - argument values that are supported by the SourceSignatures, - with the same meanings, but applied to target files. - That is, in the example: - - 


        Program('hello.c')
-        TargetSignatures('MD5')
-

- The MD5 checksum of the hello.o target file - will be used to decide if it has changed since the last - time the "downstream" hello target file was built. - And in the example: - - 


        Program('hello.c')
-        TargetSignatures('timestamp')
-

- The modification time of the hello.o target file - will be used to decide if it has changed since the last - time the "downstream" hello target file was built. - -

- The TargetSignatures function supports - two additional argument values: - 'source' and 'build'. - The 'source' argument - specifies that decisions involving - whether target files have changed - since a previous build - should use the same behavior - for the decisions configured for source files - (using the SourceSignatures function). - So in the example: - - 


        Program('hello.c')
-        TargetSignatures('source')
-        SourceSignatures('timestamp')
-

- All files, both targets and sources, - will use modification times - when deciding if an input file - has changed since the last - time a target was built. - -

- Lastly, the 'build' argument - specifies that SCons should examine - the build status of a target file - and always rebuild a "downstream" target - if the target file was itself rebuilt, - without re-examining the contents or timestamp - of the newly-built target file. - If the target file was not rebuilt during - this scons invocation, - then the target file will be examined - the same way as configured by - the SourceSignature call - to decide if it has changed. - -

- This mimics the behavior of - build signatures - in earlier versions of SCons. - A build signature re-combined - signatures of all the input files - that went into making the target file, - so that the target file itself - did not need to have its contents read - to compute an MD5 signature. - This can improve performance for some configurations, - but is generally not as effective as using - Decider('MD5-timestamp'). - -

6.3. Implicit Dependencies: The $CPPPATH Construction Variable

- Now suppose that our "Hello, World!" program - actually has an #include line - to include the hello.h file in the compilation: - - 


       #include <hello.h>
-       int
-       main()
-       {
-           printf("Hello, %s!\n", string);
-       }
-

- And, for completeness, the hello.h file looks like this: - - 


       #define string    "world"
-

- In this case, we want SCons to recognize that, - if the contents of the hello.h file change, - the hello program must be recompiled. - To do this, we need to modify the - SConstruct file like so: - - 


       Program('hello.c', CPPPATH = '.')
-

- The $CPPPATH value - tells SCons to look in the current directory - ('.') - for any files included by C source files - (.c or .h files). - With this assignment in the SConstruct file: - - 


       % scons -Q hello
-       cc -o hello.o -c -I. hello.c
-       cc -o hello hello.o
-       % scons -Q hello
-       scons: `hello' is up to date.
-       % edit hello.h
-           [CHANGE THE CONTENTS OF hello.h]
-       % scons -Q hello
-       cc -o hello.o -c -I. hello.c
-       cc -o hello hello.o
-

- First, notice that SCons - added the -I. argument - from the $CPPPATH variable - so that the compilation would find the - hello.h file in the local directory. - -

- Second, realize that SCons knows that the hello - program must be rebuilt - because it scans the contents of - the hello.c file - for the #include lines that indicate - another file is being included in the compilation. - SCons records these as - implicit dependencies - of the target file, - Consequently, - when the hello.h file changes, - SCons realizes that the hello.c file includes it, - and rebuilds the resulting hello program - that depends on both the hello.c and hello.h files. - -

- Like the $LIBPATH variable, - the $CPPPATH variable - may be a list of directories, - or a string separated by - the system-specific path separation character - (':' on POSIX/Linux, ';' on Windows). - Either way, SCons creates the - right command-line options - so that the following example: - - 


       Program('hello.c', CPPPATH = ['include', '/home/project/inc'])
-

- Will look like this on POSIX or Linux: - - 


       % scons -Q hello
-       cc -o hello.o -c -Iinclude -I/home/project/inc hello.c
-       cc -o hello hello.o
-

- And like this on Windows: - - 


       C:\>scons -Q hello.exe
-       cl /nologo /Iinclude /I\home\project\inc /c hello.c /Fohello.obj
-       link /nologo /OUT:hello.exe hello.obj
-

6.4. Caching Implicit Dependencies

- Scanning each file for #include lines - does take some extra processing time. - When you're doing a full build of a large system, - the scanning time is usually a very small percentage - of the overall time spent on the build. - You're most likely to notice the scanning time, - however, when you rebuild - all or part of a large system: - SCons will likely take some extra time to "think about" - what must be built before it issues the - first build command - (or decides that everything is up to date - and nothing must be rebuilt). - - - -

- In practice, having SCons scan files saves time - relative to the amount of potential time - lost to tracking down subtle problems - introduced by incorrect dependencies. - Nevertheless, the "waiting time" - while SCons scans files can annoy - individual developers waiting for their builds to finish. - Consequently, SCons lets you cache - the implicit dependencies - that its scanners find, - for use by later builds. - You can do this by specifying the - --implicit-cache option on the command line: - - 


       % scons -Q --implicit-cache hello
-       cc -o hello.o -c hello.c
-       cc -o hello hello.o
-       % scons -Q hello
-       scons: `hello' is up to date.
-

- If you don't want to specify --implicit-cache - on the command line each time, - you can make it the default behavior for your build - by setting the implicit_cache option - in an SConscript file: - - 


       SetOption('implicit_cache', 1)
-

- SCons does not cache implicit dependencies like this by default - because the --implicit-cache causes SCons to simply use the implicit - dependencies stored during the last run, without any checking - for whether or not those dependencies are still correct. - Specifically, this means --implicit-cache instructs SCons - to not rebuild "correctly" in the - following cases: - - -

  • - When --implicit-cache is used, SCons will ignore any changes that - may have been made to search paths - (like $CPPPATH or $LIBPATH,). - This can lead to SCons not rebuilding a file if a change to - $CPPPATH would normally cause a different, same-named file from - a different directory to be used. - -

  • - When --implicit-cache is used, SCons will not detect if a - same-named file has been added to a directory that is earlier in - the search path than the directory in which the file was found - last time. - -

6.4.1. The --implicit-deps-changed Option

- When using cached implicit dependencies, - sometimes you want to "start fresh" - and have SCons re-scan the files - for which it previously cached the dependencies. - For example, - if you have recently installed a new version of - external code that you use for compilation, - the external header files will have changed - and the previously-cached implicit dependencies - will be out of date. - You can update them by - running SCons with the --implicit-deps-changed option: - - 


         % scons -Q --implicit-deps-changed hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % scons -Q hello
-         scons: `hello' is up to date.
-

- In this case, SCons will re-scan all of the implicit dependencies - and cache updated copies of the information. - -

6.4.2. The --implicit-deps-unchanged Option

- By default when caching dependencies, - SCons notices when a file has been modified - and re-scans the file for any updated - implicit dependency information. - Sometimes, however, you may want - to force SCons to use the cached implicit dependencies, - even if the source files changed. - This can speed up a build for example, - when you have changed your source files - but know that you haven't changed - any #include lines. - In this case, - you can use the --implicit-deps-unchanged option: - - 


         % scons -Q --implicit-deps-unchanged hello
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % scons -Q hello
-         scons: `hello' is up to date.
-

- In this case, - SCons will assume that the cached implicit - dependencies are correct and - will not bother to re-scan changed files. - For typical builds after small, - incremental changes to source files, - the savings may not be very big, - but sometimes every bit of - improved performance counts. - -

6.5. Explicit Dependencies: the Depends Function

- Sometimes a file depends on another file - that is not detected by an SCons scanner. - For this situation, - SCons allows you to specific explicitly that one file - depends on another file, - and must be rebuilt whenever that file changes. - This is specified using the Depends method: - - 


       hello = Program('hello.c')
-       Depends(hello, 'other_file')
-    

       % scons -Q hello
-       cc -c hello.c -o hello.o
-       cc -o hello hello.o
-       % scons -Q hello
-       scons: `hello' is up to date.
-       % edit other_file
-           [CHANGE THE CONTENTS OF other_file]
-       % scons -Q hello
-       cc -c hello.c -o hello.o
-       cc -o hello hello.o
-

- Note that the dependency - (the second argument to Depends) - may also be a list of Node objects - (for example, as returned by a call to a Builder): - - 


       hello = Program('hello.c')
-       goodbye = Program('goodbye.c')
-       Depends(hello, goodbye)
-

- in which case the dependency or dependencies - will be built before the target(s): - - 


       % scons -Q hello
-       cc -c goodbye.c -o goodbye.o
-       cc -o goodbye goodbye.o
-       cc -c hello.c -o hello.o
-       cc -o hello hello.o
-

6.6. Dependencies From External Files: the ParseDepends - Function

- SCons has built-in scanners for a number of languages. Sometimes - these scanners fail to extract certain implicit dependencies due - to limitations of the scanner implementation. - -

- The following example illustrates a case where the built-in C - scanner is unable to extract the implicit dependency on a header - file. - - 


      #define FOO_HEADER <foo.h>
-      #include FOO_HEADER
-
-      int main() {
-          return FOO;
-      }
-    

      % scons -Q
-      cc -o hello.o -c -I. hello.c
-      cc -o hello hello.o
-      % edit foo.h
-         [CHANGE CONTENTS OF foo.h]
-      % scons -Q
-      scons: `.' is up to date.
-

- Apparently, the scanner does not know about the header dependency. - Being not a full-fledged C preprocessor, the scanner does not - expand the macro. - -

- In these cases, you may also use the compiler to extract the - implicit dependencies. ParseDepends can parse the contents of - the compiler output in the style of Make, and explicitly - establish all of the listed dependencies. - -

- The following example uses ParseDepends to process a compiler - generated dependency file which is generated as a side effect - during compilation of the object file: - - 


      obj = Object('hello.c', CCFLAGS='-MD -MF hello.d', CPPPATH='.')
-      SideEffect('hello.d', obj)
-      ParseDepends('hello.d')
-      Program('hello', obj)
-    

      % scons -Q
-      cc -o hello.o -c -MD -MF hello.d -I. hello.c
-      cc -o hello hello.o
-      % edit foo.h
-         [CHANGE CONTENTS OF foo.h]
-      % scons -Q
-      cc -o hello.o -c -MD -MF hello.d -I. hello.c
-

- Parsing dependencies from a compiler-generated - .d file has a chicken-and-egg problem, that - causes unnecessary rebuilds: - - 


      % scons -Q
-      cc -o hello.o -c -MD -MF hello.d -I. hello.c
-      cc -o hello hello.o
-      % scons -Q --debug=explain
-      scons: rebuilding `hello.o' because `foo.h' is a new dependency
-      cc -o hello.o -c -MD -MF hello.d -I. hello.c
-      % scons -Q
-      scons: `.' is up to date.
-

- In the first pass, the dependency file is generated while the - object file is compiled. At that time, SCons does not know about - the dependency on foo.h. In the second pass, - the object file is regenerated because foo.h - is detected as a new dependency. - -

- ParseDepends immediately reads the specified file at invocation - time and just returns if the file does not exist. A dependency - file generated during the build process is not automatically - parsed again. Hence, the compiler-extracted dependencies are not - stored in the signature database during the same build pass. This - limitation of ParseDepends leads to unnecessary recompilations. - Therefore, ParseDepends should only be used if scanners are not - available for the employed language or not powerful enough for the - specific task. - -

6.7. Ignoring Dependencies: the Ignore Function

- Sometimes it makes sense - to not rebuild a program, - even if a dependency file changes. - In this case, - you would tell SCons specifically - to ignore a dependency as follows: - - 


      hello = Program('hello.c')
-      Ignore(hello, 'hello.h')
-    

      % scons -Q hello
-      cc -c -o hello.o hello.c
-      cc -o hello hello.o
-      % scons -Q hello
-      scons: `hello' is up to date.
-      % edit hello.h
-        [CHANGE THE CONTENTS OF hello.h]
-      % scons -Q hello
-      scons: `hello' is up to date.
-

- Now, the above example is a little contrived, - because it's hard to imagine a real-world situation - where you wouldn't want to rebuild hello - if the hello.h file changed. - A more realistic example - might be if the hello - program is being built in a - directory that is shared between multiple systems - that have different copies of the - stdio.h include file. - In that case, - SCons would notice the differences between - the different systems' copies of stdio.h - and would rebuild hello - each time you change systems. - You could avoid these rebuilds as follows: - - 


       hello = Program('hello.c', CPPPATH=['/usr/include'])
-       Ignore(hello, '/usr/include/stdio.h')
-

Ignore can also be used to prevent a generated file from being built - by default. This is due to the fact that directories depend on - their contents. So to ignore a generated file from the default build, - you specify that the directory should ignore the generated file. - Note that the file will still be built if the user specifically - requests the target on scons command line, or if the file is - a dependency of another file which is requested and/or is built - by default. - 


      hello_obj=Object('hello.c')
-      hello = Program(hello_obj)
-      Ignore('.',[hello,hello_obj])
-    

      % scons -Q
-      scons: `.' is up to date.
-      % scons -Q hello
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q hello
-      scons: `hello' is up to date.
-

6.8. Order-Only Dependencies: the Requires Function

- Occasionally, - it may be useful to specify that a certain - file or directory must, if necessary, - be built or created before some other target is built, - but that changes to that file or directory - do not - require that the target itself be rebuilt. - Such a relationship is called an - order-only dependency - because it only affects the order in which - things must be built--the dependency before the target--but - it is not a strict dependency relationship - because the target should not - change in response to changes in the dependent file. - -

- For example, suppose that you want to create a file - every time you run a build - that identifies the time the build was performed, - the version number, etc., - and which is included in every program that you build. - The version file's contents will change every build. - If you specify a normal dependency relationship, - then every program that depends on - that file would be rebuilt every time you ran SCons. - For example, we could use some Python code in - a SConstruct file to create a new version.c file - with a string containing the current date every time - we run SCons, - and then link a program with the resulting object file - by listing version.c in the sources: - - 


      import time
-
-      version_c_text = """
-      char *date = "%s";
-      """ % time.ctime(time.time())
-      open('version.c', 'w').write(version_c_text)
-
-      hello = Program(['hello.c', 'version.c'])
-

- If we list version.c as an actual source file, - though, then version.o - will get rebuilt every time we run SCons - (because the SConstruct file itself changes - the contents of version.c) - and the hello executable - will get re-linked every time - (because the version.o file changes): - - 


      % scons -Q
-      gcc -o hello.o -c hello.c
-      gcc -o version.o -c version.c
-      gcc -o hello hello.o version.o
-      % scons -Q
-      gcc -o version.o -c version.c
-      gcc -o hello hello.o version.o
-      % scons -Q
-      gcc -o version.o -c version.c
-      gcc -o hello hello.o version.o
-

- One solution is to use the Requires function - to specify that the version.o - must be rebuilt before it is used by the link step, - but that changes to version.o - should not actually cause the hello - executable to be re-linked: - - 


      import time
-
-      version_c_text = """
-      char *date = "%s";
-      """ % time.ctime(time.time())
-      open('version.c', 'w').write(version_c_text)
-
-      version_obj = Object('version.c')
-
-      hello = Program('hello.c',
-                      LINKFLAGS = str(version_obj[0]))
-
-      Requires(hello, version_obj)
-

- Notice that because we can no longer list version.c - as one of the sources for the hello program, - we have to find some other way to get it into the link command line. - For this example, we're cheating a bit and stuffing the - object file name (extracted from version_obj - list returned by the Object call) - into the $LINKFLAGS variable, - because $LINKFLAGS is already included - in the $LINKCOM command line. - -

- With these changes, - we get the desired behavior of - re-building the version.o file, - and therefore re-linking the hello executable, - only when the hello.c has changed: - - 


      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o version.o -c version.c
-      cc -o hello version.o hello.o
-      % scons -Q
-      scons: `.' is up to date.
-      % edit hello.c
-          [CHANGE THE CONTENTS OF hello.c]
-      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello version.o hello.o
-      % scons -Q
-      scons: `.' is up to date.
-

6.9. The AlwaysBuild Function

- How SCons handles dependencies can also be affected - by the AlwaysBuild method. - When a file is passed to the AlwaysBuild method, - like so: - - 


      hello = Program('hello.c')
-      AlwaysBuild(hello)
-

- Then the specified target file (hello in our example) - will always be considered out-of-date and - rebuilt whenever that target file is evaluated - while walking the dependency graph: - - 


      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q
-      cc -o hello hello.o
-

- The AlwaysBuild function has a somewhat misleading name, - because it does not actually mean the target file will - be rebuilt every single time SCons is invoked. - Instead, it means that the target will, in fact, - be rebuilt whenever the target file is encountered - while evaluating the targets specified on - the command line (and their dependencies). - So specifying some other target on the command line, - a target that does not - itself depend on the AlwaysBuild target, - will still be rebuilt only if it's out-of-date - with respect to its dependencies: - - 


      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q hello.o
-      scons: `hello.o' is up to date.
-

Chapter 7. Environments

- An environment - is a collection of values that - can affect how a program executes. - SCons distinguishes between three - different types of environments - that can affect the behavior of SCons itself - (subject to the configuration in the SConscript files), - as well as the compilers and other tools it executes: - -

External Environment

- The external environment - is the set of variables in the user's environment - at the time the user runs SCons. - These variables are available within the SConscript files - through the Python os.environ dictionary. - See Section 7.1, below. - -

Construction Environment

- A construction environment - is a distinct object creating within - a SConscript file and - and which contains values that - affect how SCons decides - what action to use to build a target, - and even to define which targets - should be built from which sources. - One of the most powerful features of SCons - is the ability to create multiple construction environments, - including the ability to clone a new, customized - construction environment from an existing construction environment. - See Section 7.2, below. - -

Execution Environment

- An execution environment - is the values that SCons sets - when executing an external - command (such as a compiler or linker) - to build one or more targets. - Note that this is not the same as - the external environment - (see above). - See Section 7.3, below. - -

- Unlike Make, SCons does not automatically - copy or import values between different environments - (with the exception of explicit clones of construction environments, - which inherit values from their parent). - This is a deliberate design choice - to make sure that builds are, - by default, repeatable regardless of - the values in the user's external environment. - This avoids a whole class of problems with builds - where a developer's local build works - because a custom variable setting - causes a different comiler or build option to be used, - but the checked-in change breaks the official build - because it uses different environment variable settings. - -

- Note that the SConscript writer can - easily arrange for variables to be - copied or imported between environments, - and this is often very useful - (or even downright necessary) - to make it easy for developers - to customize the build in appropriate ways. - The point is not - that copying variables between different environments - is evil and must always be avoided. - Instead, it should be up to the - implementer of the build system - to make conscious choices - about how and when to import - a variable from one environment to another, - making informed decisions about - striking the right balance - between making the build - repeatable on the one hand - and convenient to use on the other. - -

7.1. Using Values From the External Environment

- The external environment - variable settings that - the user has in force - when executing SCons - are available through the normal Python - os.environ - dictionary. - This means that you must add an - import os statuement - to any SConscript file - in which you want to use - values from the user's external environment. - - 


     import os
-

- More usefully, you can use the - os.environ - dictionary in your SConscript - files to initialize construction environments - with values from the user's external environment. - See the next section, - Section 7.2, - for information on how to do this. - -

7.2. Construction Environments

- It is rare that all of the software in a large, - complicated system needs to be built the same way. - For example, different source files may need different options - enabled on the command line, - or different executable programs need to be linked - with different libraries. - SCons accommodates these different build - requirements by allowing you to create and - configure multiple construction environments - that control how the software is built. - A construction environment is an object - that has a number of associated - construction variables, each with a name and a value. - (A construction environment also has an attached - set of Builder methods, - about which we'll learn more later.) - -

7.2.1. Creating a Construction Environment: the Environment Function

- A construction environment is created by the Environment method: - - 


         env = Environment()
-

- By default, SCons initializes every - new construction environment - with a set of construction variables - based on the tools that it finds on your system, - plus the default set of builder methods - necessary for using those tools. - The construction variables - are initialized with values describing - the C compiler, - the Fortran compiler, - the linker, - etc., - as well as the command lines to invoke them. - -

- When you initialize a construction environment - you can set the values of the - environment's construction variables - to control how a program is built. - For example: - - 


     import os
-
-         env = Environment(CC = 'gcc',
-                           CCFLAGS = '-O2')
-
-         env.Program('foo.c')
-

- The construction environment in this example - is still initialized with the same default - construction variable values, - except that the user has explicitly specified use of the - GNU C compiler gcc, - and further specifies that the -O2 - (optimization level two) - flag should be used when compiling the object file. - In other words, the explicit initializations of - $CC and $CCFLAGS - override the default values in the newly-created - construction environment. - So a run from this example would look like: - - 


         % scons -Q
-         gcc -o foo.o -c -O2 foo.c
-         gcc -o foo foo.o
-

7.2.2. Fetching Values From a Construction Environment

- You can fetch individual construction variables - using the normal syntax - for accessing individual named items in a Python dictionary: - - 


         env = Environment()
-         print "CC is:", env['CC']
-

- This example SConstruct file doesn't build anything, - but because it's actually a Python script, - it will print the value of $CC for us: - - 


         % scons -Q
-         CC is: cc
-         scons: `.' is up to date.
-

- A construction environment, however, - is actually an object with associated methods, etc. - If you want to have direct access to only the - dictionary of construction variables, - you can fetch this using the Dictionary method: - - 


         env = Environment(FOO = 'foo', BAR = 'bar')
-         dict = env.Dictionary()
-         for key in ['OBJSUFFIX', 'LIBSUFFIX', 'PROGSUFFIX']:
-             print "key = %s, value = %s" % (key, dict[key])
-

- This SConstruct file - will print the specified dictionary items for us on POSIX - systems as follows: - - 


         % scons -Q
-         key = OBJSUFFIX, value = .o
-         key = LIBSUFFIX, value = .a
-         key = PROGSUFFIX, value = 
-         scons: `.' is up to date.
-

- And on Windows: - - 


         C:\>scons -Q
-         key = OBJSUFFIX, value = .obj
-         key = LIBSUFFIX, value = .lib
-         key = PROGSUFFIX, value = .exe
-         scons: `.' is up to date.
-

- If you want to loop and print the values of - all of the construction variables in a construction environment, - the Python code to do that in sorted order might look something like: - - 


         env = Environment()
-         dict = env.Dictionary()
-         keys = dict.keys()
-         keys.sort()
-         for key in keys:
-             print "construction variable = '%s', value = '%s'" % (key, dict[key])
-

7.2.3. Expanding Values From a Construction Environment: the subst Method

- Another way to get information from - a construction environment. - is to use the subst method - on a string containing $ expansions - of construction variable names. - As a simple example, - the example from the previous - section that used - env['CC'] - to fetch the value of $CC - could also be written as: - - 


        env = Environment()
-        print "CC is:", env.subst('$CC')
-

- One advantage of using - subst to expand strings is - that construction variables - in the result get re-expanded until - there are no expansions left in the string. - So a simple fetch of a value like - $CCCOM: - - 


        env = Environment(CCFLAGS = '-DFOO')
-        print "CCCOM is:", env['CCCOM']
-

- Will print the unexpanded value of $CCCOM, - showing us the construction - variables that still need to be expanded: - - 


        % scons -Q
-        CCCOM is: $CC $CCFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS -c -o $TARGET $SOURCES
-        scons: `.' is up to date.
-

- Calling the subst method on $CCOM, - however: - - 


        env = Environment(CCFLAGS = '-DFOO')
-        print "CCCOM is:", env.subst('$CCCOM')
-

- Will recursively expand all of - the construction variables prefixed - with $ (dollar signs), - showing us the final output: - - 


        % scons -Q
-        CCCOM is: gcc -DFOO -c -o
-        scons: `.' is up to date.
-

- Note that because we're not expanding this - in the context of building something - there are no target or source files - for $TARGET and $SOURCES to expand. - -

7.2.4. Controlling the Default Construction Environment: the DefaultEnvironment Function

- All of the Builder functions that we've introduced so far, - like Program and Library, - actually use a default construction environment - that contains settings - for the various compilers - and other tools that - SCons configures by default, - or otherwise knows about - and has discovered on your system. - The goal of the default construction environment - is to make many configurations to "just work" - to build software using - readily available tools - with a minimum of configuration changes. - -

- You can, however, control the settings - in the default contstruction environment - by using the DefaultEnvironment function - to initialize various settings: - - 


-      DefaultEnvironment(CC = '/usr/local/bin/gcc')
-
-

- When configured as above, - all calls to the Program - or Object Builder - will build object files with the - /usr/local/bin/gcc - compiler. - -

- Note that the DefaultEnvironment function - returns the initialized - default construction environment object, - which can then be manipulated like any - other construction environment. - So the following - would be equivalent to the - previous example, - setting the $CC - variable to /usr/local/bin/gcc - but as a separate step after - the default construction environment has been initialized: - - 


-      env = DefaultEnvironment()
-      env['CC'] = '/usr/local/bin/gcc'
-
-

- One very common use of the DefaultEnvironment function - is to speed up SCons initialization. - As part of trying to make most default - configurations "just work," - SCons will actually - search the local system for installed - compilers and other utilities. - This search can take time, - especially on systems with - slow or networked file systems. - If you know which compiler(s) and/or - other utilities you want to configure, - you can control the search - that SCons performs - by specifying some specific - tool modules with which to - initialize the default construction environment: - - 


-      env = DefaultEnvironment(tools = ['gcc', 'gnulink'],
-                               CC = '/usr/local/bin/gcc')
-
-

- So the above example would tell SCons - to explicitly configure the default environment - to use its normal GNU Compiler and GNU Linker settings - (without having to search for them, - or any other utilities for that matter), - and specifically to use the compiler found at - /usr/local/bin/gcc. - -

7.2.5. Multiple Construction Environments

- The real advantage of construction environments - is that you can create as many different construction - environments as you need, - each tailored to a different way to build - some piece of software or other file. - If, for example, we need to build - one program with the -O2 flag - and another with the -g (debug) flag, - we would do this like so: - - 


         opt = Environment(CCFLAGS = '-O2')
-         dbg = Environment(CCFLAGS = '-g')
-
-         opt.Program('foo', 'foo.c')
-
-         dbg.Program('bar', 'bar.c')
-      

         % scons -Q
-         cc -o bar.o -c -g bar.c
-         cc -o bar bar.o
-         cc -o foo.o -c -O2 foo.c
-         cc -o foo foo.o
-

- We can even use multiple construction environments to build - multiple versions of a single program. - If you do this by simply trying to use the - Program builder with both environments, though, - like this: - - 


         opt = Environment(CCFLAGS = '-O2')
-         dbg = Environment(CCFLAGS = '-g')
-
-         opt.Program('foo', 'foo.c')
-
-         dbg.Program('foo', 'foo.c')
-

- Then SCons generates the following error: - - 


         % scons -Q
-         
-         scons: *** Two environments with different actions were specified for the same target: foo.o
-         File "/home/my/project/SConstruct", line 6, in <module>
-

- This is because the two Program calls have - each implicitly told SCons to generate an object file named - foo.o, - one with a $CCFLAGS value of - -O2 - and one with a $CCFLAGS value of - -g. - SCons can't just decide that one of them - should take precedence over the other, - so it generates the error. - To avoid this problem, - we must explicitly specify - that each environment compile - foo.c - to a separately-named object file - using the Object builder, like so: - - 


         opt = Environment(CCFLAGS = '-O2')
-         dbg = Environment(CCFLAGS = '-g')
-
-         o = opt.Object('foo-opt', 'foo.c')
-         opt.Program(o)
-
-         d = dbg.Object('foo-dbg', 'foo.c')
-         dbg.Program(d)
-

- Notice that each call to the Object builder - returns a value, - an internal SCons object that - represents the object file that will be built. - We then use that object - as input to the Program builder. - This avoids having to specify explicitly - the object file name in multiple places, - and makes for a compact, readable - SConstruct file. - Our SCons output then looks like: - - 


         % scons -Q
-         cc -o foo-dbg.o -c -g foo.c
-         cc -o foo-dbg foo-dbg.o
-         cc -o foo-opt.o -c -O2 foo.c
-         cc -o foo-opt foo-opt.o
-

7.2.6. Making Copies of Construction Environments: the Clone Method

- Sometimes you want more than one construction environment - to share the same values for one or more variables. - Rather than always having to repeat all of the common - variables when you create each construction environment, - you can use the Clone method - to create a copy of a construction environment. - -

- Like the Environment call that creates a construction environment, - the Clone method takes construction variable assignments, - which will override the values in the copied construction environment. - For example, suppose we want to use gcc - to create three versions of a program, - one optimized, one debug, and one with neither. - We could do this by creating a "base" construction environment - that sets $CC to gcc, - and then creating two copies, - one which sets $CCFLAGS for optimization - and the other which sets $CCFLAGS for debugging: - - 


         env = Environment(CC = 'gcc')
-         opt = env.Clone(CCFLAGS = '-O2')
-         dbg = env.Clone(CCFLAGS = '-g')
-
-         env.Program('foo', 'foo.c')
-
-         o = opt.Object('foo-opt', 'foo.c')
-         opt.Program(o)
-
-         d = dbg.Object('foo-dbg', 'foo.c')
-         dbg.Program(d)
-

- Then our output would look like: - - 


         % scons -Q
-         gcc -o foo.o -c foo.c
-         gcc -o foo foo.o
-         gcc -o foo-dbg.o -c -g foo.c
-         gcc -o foo-dbg foo-dbg.o
-         gcc -o foo-opt.o -c -O2 foo.c
-         gcc -o foo-opt foo-opt.o
-

7.2.7. Replacing Values: the Replace Method

- You can replace existing construction variable values - using the Replace method: - - 


         env = Environment(CCFLAGS = '-DDEFINE1')
-         env.Replace(CCFLAGS = '-DDEFINE2')
-         env.Program('foo.c')
-

- The replacing value - (-DDEFINE2 in the above example) - completely replaces the value in the - construction environment: - - 


         % scons -Q
-         cc -o foo.o -c -DDEFINE2 foo.c
-         cc -o foo foo.o
-

- You can safely call Replace - for construction variables that - don't exist in the construction environment: - - 


         env = Environment()
-         env.Replace(NEW_VARIABLE = 'xyzzy')
-         print "NEW_VARIABLE =", env['NEW_VARIABLE']
-

- In this case, - the construction variable simply - gets added to the construction environment: - - 


         % scons -Q
-         NEW_VARIABLE = xyzzy
-         scons: `.' is up to date.
-

- Because the variables - aren't expanded until the construction environment - is actually used to build the targets, - and because SCons function and method calls - are order-independent, - the last replacement "wins" - and is used to build all targets, - regardless of the order in which - the calls to Replace() are - interspersed with calls to - builder methods: - - 


         env = Environment(CCFLAGS = '-DDEFINE1')
-         print "CCFLAGS =", env['CCFLAGS']
-         env.Program('foo.c')
-
-         env.Replace(CCFLAGS = '-DDEFINE2')
-         print "CCFLAGS =", env['CCFLAGS']
-         env.Program('bar.c')
-

- The timing of when the replacement - actually occurs relative - to when the targets get built - becomes apparent - if we run scons without the -Q - option: - - 


         % scons
-         scons: Reading SConscript files ...
-         CCFLAGS = -DDEFINE1
-         CCFLAGS = -DDEFINE2
-         scons: done reading SConscript files.
-         scons: Building targets ...
-         cc -o bar.o -c -DDEFINE2 bar.c
-         cc -o bar bar.o
-         cc -o foo.o -c -DDEFINE2 foo.c
-         cc -o foo foo.o
-         scons: done building targets.
-

- Because the replacement occurs while - the SConscript files are being read, - the $CCFLAGS - variable has already been set to - -DDEFINE2 - by the time the foo.o target is built, - even though the call to the Replace - method does not occur until later in - the SConscript file. - -

7.2.8. Setting Values Only If They're Not Already Defined: the SetDefault Method

- Sometimes it's useful to be able to specify - that a construction variable should be - set to a value only if the construction environment - does not already have that variable defined - You can do this with the SetDefault method, - which behaves similarly to the set_default - method of Python dictionary objects: - - 


      env.SetDefault(SPECIAL_FLAG = '-extra-option')
-

- This is especially useful - when writing your own Tool modules - to apply variables to construction environments. - - -

7.2.9. Appending to the End of Values: the Append Method

- You can append a value to - an existing construction variable - using the Append method: - - 


         env = Environment(CCFLAGS = ['-DMY_VALUE'])
-         env.Append(CCFLAGS = ['-DLAST'])
-         env.Program('foo.c')
-

- SCons then supplies both the -DMY_VALUE and - -DLAST flags when compiling the object file: - - 


         % scons -Q
-         cc -o foo.o -c -DMY_VALUE -DLAST foo.c
-         cc -o foo foo.o
-

- If the construction variable doesn't already exist, - the Append method will create it: - - 


         env = Environment()
-         env.Append(NEW_VARIABLE = 'added')
-         print "NEW_VARIABLE =", env['NEW_VARIABLE']
-

- Which yields: - - 


         % scons -Q
-         NEW_VARIABLE = added
-         scons: `.' is up to date.
-

- Note that the Append function tries to be "smart" - about how the new value is appended to the old value. - If both are strings, the previous and new strings - are simply concatenated. - Similarly, if both are lists, - the lists are concatenated. - If, however, one is a string and the other is a list, - the string is added as a new element to the list. - -

7.2.10. Appending Unique Values: the AppendUnique Method

- Some times it's useful to add a new value - only if the existing construction variable - doesn't already contain the value. - This can be done using the AppendUnique method: - - 


      env.AppendUnique(CCFLAGS=['-g'])
-

- In the above example, - the -g would be added - only if the $CCFLAGS variable - does not already contain a -g value. - -

7.2.11. Appending to the Beginning of Values: the Prepend Method

- You can append a value to the beginning of - an existing construction variable - using the Prepend method: - - 


         env = Environment(CCFLAGS = ['-DMY_VALUE'])
-         env.Prepend(CCFLAGS = ['-DFIRST'])
-         env.Program('foo.c')
-

- SCons then supplies both the -DFIRST and - -DMY_VALUE flags when compiling the object file: - - 


         % scons -Q
-         cc -o foo.o -c -DFIRST -DMY_VALUE foo.c
-         cc -o foo foo.o
-

- If the construction variable doesn't already exist, - the Prepend method will create it: - - 


         env = Environment()
-         env.Prepend(NEW_VARIABLE = 'added')
-         print "NEW_VARIABLE =", env['NEW_VARIABLE']
-

- Which yields: - - 


         % scons -Q
-         NEW_VARIABLE = added
-         scons: `.' is up to date.
-

- Like the Append function, - the Prepend function tries to be "smart" - about how the new value is appended to the old value. - If both are strings, the previous and new strings - are simply concatenated. - Similarly, if both are lists, - the lists are concatenated. - If, however, one is a string and the other is a list, - the string is added as a new element to the list. - -

7.2.12. Prepending Unique Values: the PrependUnique Method

- Some times it's useful to add a new value - to the beginning of a construction variable - only if the existing value - doesn't already contain the to-be-added value. - This can be done using the PrependUnique method: - - 


      env.PrependUnique(CCFLAGS=['-g'])
-

- In the above example, - the -g would be added - only if the $CCFLAGS variable - does not already contain a -g value. - -

7.3. Controlling the Execution Environment for Issued Commands

- When SCons builds a target file, - it does not execute the commands with - the same external environment - that you used to execute SCons. - Instead, it uses the dictionary - stored in the $ENV construction variable - as the external environment - for executing commands. - -

- The most important ramification of this behavior - is that the PATH environment variable, - which controls where the operating system - will look for commands and utilities, - is not the same as in the external environment - from which you called SCons. - This means that SCons will not, by default, - necessarily find all of the tools - that you can execute from the command line. - -

- The default value of the PATH environment variable - on a POSIX system - is /usr/local/bin:/bin:/usr/bin. - The default value of the PATH environment variable - on a Windows system comes from the Windows registry - value for the command interpreter. - If you want to execute any commands--compilers, linkers, etc.--that - are not in these default locations, - you need to set the PATH value - in the $ENV dictionary - in your construction environment. - -

- The simplest way to do this is to initialize explicitly - the value when you create the construction environment; - this is one way to do that: - - 


      path = ['/usr/local/bin', '/bin', '/usr/bin']
-      env = Environment(ENV = {'PATH' : path})
-

- Assign a dictionary to the $ENV - construction variable in this way - completely resets the external environment - so that the only variable that will be - set when external commands are executed - will be the PATH value. - If you want to use the rest of - the values in $ENV and only - set the value of PATH, - the most straightforward way is probably: - - 


      env['ENV']['PATH'] = ['/usr/local/bin', '/bin', '/usr/bin']
-

- Note that SCons does allow you to define - the directories in the PATH in a string, - separated by the pathname-separator character - for your system (':' on POSIX systems, ';' on Windows): - - 


      env['ENV']['PATH'] = '/usr/local/bin:/bin:/usr/bin'
-

- But doing so makes your SConscript file less portable, - (although in this case that may not be a huge concern - since the directories you list are likley system-specific, anyway). - -

7.3.1. Propagating PATH From the External Environment

- You may want to propagate the external PATH - to the execution environment for commands. - You do this by initializing the PATH - variable with the PATH value from - the os.environ - dictionary, - which is Python's way of letting you - get at the external environment: - - 


        import os
-        env = Environment(ENV = {'PATH' : os.environ['PATH']})
-

- Alternatively, you may find it easier - to just propagate the entire external - environment to the execution environment - for commands. - This is simpler to code than explicity - selecting the PATH value: - - 


        import os
-        env = Environment(ENV = os.environ)
-

- Either of these will guarantee that - SCons will be able to execute - any command that you can execute from the command line. - The drawback is that the build can behave - differently if it's run by people with - different PATH values in their environment--for example, - if both the /bin and - /usr/local/bin directories - have different cc commands, - then which one will be used to compile programs - will depend on which directory is listed - first in the user's PATH variable. - -

7.3.2. Adding to PATH Values in the Execution Environment

- One of the most common requirements - for manipulating a variable in the execution environment - is to add one or more custom directories to a search - like the $PATH variable on Linux or POSIX systems, - or the %PATH% variable on Windows, - so that a locally-installed compiler or other utility - can be found when SCons tries to execute it to update a target. - SCons provides PrependENVPath and AppendENVPath functions - to make adding things to execution variables convenient. - You call these functions by specifying the variable - to which you want the value added, - and then value itself. - So to add some /usr/local directories - to the $PATH and $LIB variables, - you might: - - 


        env = Environment(ENV = os.environ)
-        env.PrependENVPath('PATH', '/usr/local/bin')
-        env.AppendENVPath('LIB', '/usr/local/lib')
-

- Note that the added values are strings, - and if you want to add multiple directories to - a variable like $PATH, - you must include the path separate character - (: on Linux or POSIX, - ; on Windows) - in the string. - -

Chapter 8. Merging Options into the Environment: the MergeFlags Function

- SCons construction environments have a MergeFlags method - that merges a dictionary of values into the construction environment. - MergeFlags treats each value in the dictionary - as a list of options such as one might pass to a command - (such as a compiler or linker). - MergeFlags will not duplicate an option - if it already exists in the construction environment variable. - -

- MergeFlags tries to be intelligent about merging options. - When merging options to any variable - whose name ends in PATH, - MergeFlags keeps the leftmost occurrence of the option, - because in typical lists of directory paths, - the first occurrence "wins." - When merging options to any other variable name, - MergeFlags keeps the rightmost occurrence of the option, - because in a list of typical command-line options, - the last occurrence "wins." - - 


    env = Environment()
-    env.Append(CCFLAGS = '-option -O3 -O1')
-    flags = { 'CCFLAGS' : '-whatever -O3' }
-    env.MergeFlags(flags)
-    print env['CCFLAGS']
- 

    % scons -Q
-    ['-option', '-O1', '-whatever', '-O3']
-    scons: `.' is up to date.
-

- Note that the default value for $CCFLAGS - - is an internal SCons object - which automatically converts - the options we specified as a string into a list. - - 


    env = Environment()
-    env.Append(CPPPATH = ['/include', '/usr/local/include', '/usr/include'])
-    flags = { 'CPPPATH' : ['/usr/opt/include', '/usr/local/include'] }
-    env.MergeFlags(flags)
-    print env['CPPPATH']
- 

    % scons -Q
-    ['/include', '/usr/local/include', '/usr/include', '/usr/opt/include']
-    scons: `.' is up to date.
-

- Note that the default value for $CPPPATH - - is a normal Python list, - so we must specify its values as a list - in the dictionary we pass to the MergeFlags function. - -

- If MergeFlags is passed anything other than a dictionary, - it calls the ParseFlags method to convert it into a dictionary. - - 


    env = Environment()
-    env.Append(CCFLAGS = '-option -O3 -O1')
-    env.Append(CPPPATH = ['/include', '/usr/local/include', '/usr/include'])
-    env.MergeFlags('-whatever -I/usr/opt/include -O3 -I/usr/local/include')
-    print env['CCFLAGS']
-    print env['CPPPATH']
- 

    % scons -Q
-    ['-option', '-O1', '-whatever', '-O3']
-    ['/include', '/usr/local/include', '/usr/include', '/usr/opt/include']
-    scons: `.' is up to date.
-

- In the combined example above, - ParseFlags has sorted the options into their corresponding variables - and returned a dictionary for MergeFlags to apply - to the construction variables - in the specified construction environment. - -

Chapter 9. Separating Compile Arguments into their Variables: the ParseFlags Function

- SCons has a bewildering array of construction variables - for different types of options when building programs. - Sometimes you may not know exactly which variable - should be used for a particular option. - -

- SCons construction environments have a ParseFlags method - that takes a set of typical command-line options - and distrbutes them into the appropriate construction variables. - Historically, it was created to support the ParseConfig method, - so it focuses on options used by the GNU Compiler Collection (GCC) - for the C and C++ toolchains. - -

- ParseFlags returns a dictionary containing the options - distributed into their respective construction variables. - Normally, this dictionary would be passed to MergeFlags - to merge the options into a construction environment, - but the dictionary can be edited if desired to provide - additional functionality. - (Note that if the flags are not going to be edited, - calling MergeFlags with the options directly - will avoid an additional step.) - - 


    env = Environment()
-    d = env.ParseFlags("-I/opt/include -L/opt/lib -lfoo")
-    l = d.items()
-    l.sort()
-    for k,v in l:
-        if v:
-            print k, v
-    env.MergeFlags(d)
-    env.Program('f1.c')
- 

    % scons -Q
-    CPPPATH ['/opt/include']
-    LIBPATH ['/opt/lib']
-    LIBS ['foo']
-    cc -o f1.o -c -I/opt/include f1.c
-    cc -o f1 f1.o -L/opt/lib -lfoo
-

- Note that if the options are limited to generic types - like those above, - they will be correctly translated for other platform types: - - 


    C:\>scons -Q
-    CPPPATH ['/opt/include']
-    LIBPATH ['/opt/lib']
-    LIBS ['foo']
-    cl /nologo /I\opt\include /c f1.c /Fof1.obj
-    link /nologo /OUT:f1.exe /LIBPATH:\opt\lib foo.lib f1.obj
-

- Since the assumption is that the flags are used for the GCC toolchain, - unrecognized flags are placed in $CCFLAGS - so they will be used for both C and C++ compiles: - - 


    env = Environment()
-    d = env.ParseFlags("-whatever")
-    l = d.items()
-    l.sort()
-    for k,v in l:
-        if v:
-            print k, v
-    env.MergeFlags(d)
-    env.Program('f1.c')
- 

    % scons -Q
-    CCFLAGS -whatever
-    cc -o f1.o -c -whatever f1.c
-    cc -o f1 f1.o
-

- ParseFlags will also accept a (recursive) list of strings as input; - the list is flattened before the strings are processed: - - 


    env = Environment()
-    d = env.ParseFlags(["-I/opt/include", ["-L/opt/lib", "-lfoo"]])
-    l = d.items()
-    l.sort()
-    for k,v in l:
-        if v:
-            print k, v
-    env.MergeFlags(d)
-    env.Program('f1.c')
- 

    % scons -Q
-    CPPPATH ['/opt/include']
-    LIBPATH ['/opt/lib']
-    LIBS ['foo']
-    cc -o f1.o -c -I/opt/include f1.c
-    cc -o f1 f1.o -L/opt/lib -lfoo
-

- If a string begins with a "!" (an exclamation mark, often called a bang), - the string is passed to the shell for execution. - The output of the command is then parsed: - - 


    env = Environment()
-    d = env.ParseFlags(["!echo -I/opt/include", "!echo -L/opt/lib", "-lfoo"])
-    l = d.items()
-    l.sort()
-    for k,v in l:
-        if v:
-            print k, v
-    env.MergeFlags(d)
-    env.Program('f1.c')
- 

    % scons -Q
-    CPPPATH ['/opt/include']
-    LIBPATH ['/opt/lib']
-    LIBS ['foo']
-    cc -o f1.o -c -I/opt/include f1.c
-    cc -o f1 f1.o -L/opt/lib -lfoo
-

- ParseFlags is regularly updated for new options; - consult the man page for details about those currently recognized. - -

Chapter 10. Finding Installed Library Information: the ParseConfig Function

- Configuring the right options to build programs to work with - libraries--especially shared libraries--that are available - on POSIX systems can be very complicated. - To help this situation, - various utilies with names that end in config - return the command-line options for the GNU Compiler Collection (GCC) - that are needed to use these libraries; - for example, the command-line options - to use a library named lib - would be found by calling a utility named lib-config. - -

- A more recent convention is that these options - are available from the generic pkg-config program, - which has common framework, error handling, and the like, - so that all the package creator has to do is provide the set of strings - for his particular package. - -

- SCons construction environments have a ParseConfig method - that executes a *config utility - (either pkg-config or a - more specific utility) - and configures the appropriate construction variables - in the environment - based on the command-line options - returned by the specified command. - - 


    env = Environment()
-    env['CPPPATH'] = ['/lib/compat']
-    env.ParseConfig("pkg-config x11 --cflags --libs")
-    print env['CPPPATH']
-

- SCons will execute the specified command string, - parse the resultant flags, - and add the flags to the appropriate environment variables. - - 


    % scons -Q
-    ['/lib/compat', '/usr/X11/include']
-    scons: `.' is up to date.
-

- In the example above, SCons has added the include directory to - CPPPATH. - (Depending upon what other flags are emitted by the - pkg-config command, - other variables may have been extended as well.) - -

- Note that the options are merged with existing options using - the MergeFlags method, - so that each option only occurs once in the construction variable: - - 


    env = Environment()
-    env.ParseConfig("pkg-config x11 --cflags --libs")
-    env.ParseConfig("pkg-config x11 --cflags --libs")
-    print env['CPPPATH']
- 

    % scons -Q
-    ['/usr/X11/include']
-    scons: `.' is up to date.
-

Chapter 11. Controlling Build Output

- A key aspect of creating a usable build configuration - is providing good output from the build - so its users can readily understand - what the build is doing - and get information about how to control the build. - SCons provides several ways of - controlling output from the build configuration - to help make the build - more useful and understandable. - -

11.1. Providing Build Help: the Help Function

- It's often very useful to be able to give - users some help that describes the - specific targets, build options, etc., - that can be used for your build. - SCons provides the Help function - to allow you to specify this help text: - - 


       Help("""
-       Type: 'scons program' to build the production program,
-             'scons debug' to build the debug version.
-       """)
-

- (Note the above use of the Python triple-quote syntax, - which comes in very handy for - specifying multi-line strings like help text.) - -

- When the SConstruct or SConscript files - contain such a call to the Help function, - the specified help text will be displayed in response to - the SCons -h option: - - 


       % scons -h
-       scons: Reading SConscript files ...
-       scons: done reading SConscript files.
-       
-       Type: 'scons program' to build the production program,
-             'scons debug' to build the debug version.
-       
-       Use scons -H for help about command-line options.
-

- The SConscript files may contain - multiple calls to the Help function, - in which case the specified text(s) - will be concatenated when displayed. - This allows you to split up the - help text across multiple SConscript files. - In this situation, the order in - which the SConscript files are called - will determine the order in which the Help functions are called, - which will determine the order in which - the various bits of text will get concatenated. - -

- Another use would be to make the help text conditional - on some variable. - For example, suppose you only want to display - a line about building a Windows-only - version of a program when actually - run on Windows. - The following SConstruct file: - - 


       env = Environment()
-
-       Help("\nType: 'scons program' to build the production program.\n")
-
-       if env['PLATFORM'] == 'win32':
-           Help("\nType: 'scons windebug' to build the Windows debug version.\n")
-

- Will display the complete help text on Windows: - - 


       C:\>scons -h
-       scons: Reading SConscript files ...
-       scons: done reading SConscript files.
-       
-       Type: 'scons program' to build the production program.
-       
-       Type: 'scons windebug' to build the Windows debug version.
-       
-       Use scons -H for help about command-line options.
-

- But only show the relevant option on a Linux or UNIX system: - - 


       % scons -h
-       scons: Reading SConscript files ...
-       scons: done reading SConscript files.
-       
-       Type: 'scons program' to build the production program.
-       
-       Use scons -H for help about command-line options.
-

- If there is no Help text in the SConstruct or - SConscript files, - SCons will revert to displaying its - standard list that describes the SCons command-line - options. - This list is also always displayed whenever - the -H option is used. - -

11.2. Controlling How SCons Prints Build Commands: the $*COMSTR Variables

- Sometimes the commands executed - to compile object files or link programs - (or build other targets) - can get very long, - long enough to make it difficult for users - to distinguish error messages or - other important build output - from the commands themselves. - All of the default $*COM variables - that specify the command lines - used to build various types of target files - have a corresponding $*COMSTR variable - that can be set to an alternative - string that will be displayed - when the target is built. - -

- For example, suppose you want to - have SCons display a - "Compiling" - message whenever it's compiling an object file, - and a - "Linking" - when it's linking an executable. - You could write a SConstruct file - that looks like: - - 


       env = Environment(CCCOMSTR = "Compiling $TARGET",
-                         LINKCOMSTR = "Linking $TARGET")
-       env.Program('foo.c')
-

- Which would then yield the output: - - 


       % scons -Q
-       Compiling foo.o
-       Linking foo
-

- SCons performs complete variable substitution - on $*COMSTR variables, - so they have access to all of the - standard variables like $TARGET $SOURCES, etc., - as well as any construction variables - that happen to be configured in - the construction environment - used to build a specific target. - -

- Of course, sometimes it's still important to - be able to see the exact command - that SCons will execute to build a target. - For example, you may simply need to verify - that SCons is configured to supply - the right options to the compiler, - or a developer may want to - cut-and-paste a comiloe command - to add a few options - for a custom test. - -

- One common way to give users - control over whether or not - SCons should print the actual command line - or a short, configured summary - is to add support for a - VERBOSE - command-line variable to your SConstruct file. - A simple configuration for this might look like: - - 


       env = Environment()
-       if ARGUMENTS.get('VERBOSE') != "1':
-           env['CCCOMSTR'] = "Compiling $TARGET"
-           env['LINKCOMSTR'] = "Linking $TARGET"
-       env.Program('foo.c')
-

- - By only setting the appropriate - $*COMSTR variables - if the user specifies - VERBOSE=1 - on the command line, - the user has control - over how SCons - displays these particular command lines: - - 


       % scons -Q
-       Compiling foo.o
-       Linking foo
-       % scons -Q -c
-       Removed foo.o
-       Removed foo
-       % scons -Q VERBOSE=1
-       cc -o foo.o -c foo.c
-       cc -o foo foo.o
-

11.3. Providing Build Progress Output: the Progress Function

- Another aspect of providing good build output - is to give the user feedback - about what SCons is doing - even when nothing is being built at the moment. - This can be especially true for large builds - when most of the targets are already up-to-date. - Because SCons can take a long time - making absolutely sure that every - target is, in fact, up-to-date - with respect to a lot of dependency files, - it can be easy for users to mistakenly - conclude that SCons is hung - or that there is some other problem with the build. - -

- One way to deal with this perception - is to configure SCons to print something to - let the user know what it's "thinking about." - The Progress function - allows you to specify a string - that will be printed for every file - that SCons is "considering" - while it is traversing the dependency graph - to decide what targets are or are not up-to-date. - - 


        Progress('Evaluating $TARGET\n')
-        Program('f1.c')
-        Program('f2.c')
-

- Note that the Progress function does not - arrange for a newline to be printed automatically - at the end of the string (as does the Python - print statement), - and we must specify the - \n - that we want printed at the end of the configured string. - This configuration, then, - will have SCons - print that it is Evaluating - each file that it encounters - in turn as it traverses the dependency graph: - - 


       % scons -Q
-       Evaluating SConstruct
-       Evaluating f1.c
-       Evaluating f1.o
-       cc -o f1.o -c f1.c
-       Evaluating f1
-       cc -o f1 f1.o
-       Evaluating f2.c
-       Evaluating f2.o
-       cc -o f2.o -c f2.c
-       Evaluating f2
-       cc -o f2 f2.o
-       Evaluating .
-

- Of course, normally you don't want to add - all of these additional lines to your build output, - as that can make it difficult for the user - to find errors or other important messages. - A more useful way to display - this progress might be - to have the file names printed - directly to the user's screen, - not to the same standard output - stream where build output is printed, - and to use a carriage return character - (\r) - so that each file name gets re-printed on the same line. - Such a configuration would look like: - - 


        Progress('$TARGET\r',
-                 file=open('/dev/tty', 'w'),
-                 overwrite=True)
-        Program('f1.c')
-        Program('f2.c')
-

- Note that we also specified the - overwrite=True argument - to the Progress function, - which causes SCons to - "wipe out" the previous string with space characters - before printing the next Progress string. - Without the - overwrite=True argument, - a shorter file name would not overwrite - all of the charactes in a longer file name that - precedes it, - making it difficult to tell what the - actual file name is on the output. - Also note that we opened up the - /dev/tty file - for direct access (on POSIX) to - the user's screen. - On Windows, the equivalent would be to open - the con: file name. - -

- Also, it's important to know that although you can use - $TARGET to substitute the name of - the node in the string, - the Progress function does not - perform general variable substitution - (because there's not necessarily a construction - environment involved in evaluating a node - like a source file, for example). - -

- You can also specify a list of strings - to the Progress function, - in which case SCons will - display each string in turn. - This can be used to implement a "spinner" - by having SCons cycle through a - sequence of strings: - - 


        Progress(['-\r', '\\\r', '|\r', '/\r'], interval=5)
-        Program('f1.c')
-        Program('f2.c')
-

- Note that here we have also used the - interval= - keyword argument to have SCons - only print a new "spinner" string - once every five evaluated nodes. - Using an interval= count, - even with strings that use $TARGET like - our examples above, - can be a good way to lessen the - work that SCons expends printing Progress strings, - while still giving the user feedback - that indicates SCons is still - working on evaluating the build. - -

- Lastly, you can have direct control - over how to print each evaluated node - by passing a Python function - (or other Python callable) - to the Progress function. - Your function will be called - for each evaluated node, - allowing you to - implement more sophisticated logic - like adding a counter: - - 


        screen = open('/dev/tty', 'w')
-        count = 0
-        def progress_function(node)
-            count += 1
-            screen.write('Node %4d: %s\r' % (count, node))
-
-        Progress(progress_function)
-

- Of course, if you choose, - you could completely ignore the - node argument to the function, - and just print a count, - or anything else you wish. - -

- (Note that there's an obvious follow-on question here: - how would you find the total number of nodes - that will be - evaluated so you can tell the user how - close the build is to finishing? - Unfortunately, in the general case, - there isn't a good way to do that, - short of having SCons evaluate its - dependency graph twice, - first to count the total and - the second time to actually build the targets. - This would be necessary because - you can't know in advance which - target(s) the user actually requested - to be built. - The entire build may consist of thousands of Nodes, - for example, - but maybe the user specifically requested - that only a single object file be built.) - -

11.4. Printing Detailed Build Status: the GetBuildFailures Function

- SCons, like most build tools, returns zero status to - the shell on success and nonzero status on failure. - Sometimes it's useful to give more information about - the build status at the end of the run, for instance - to print an informative message, send an email, or - page the poor slob who broke the build. - -

- SCons provides a GetBuildFailures method that - you can use in a python atexit function - to get a list of objects describing the actions that failed - while attempting to build targets. There can be more - than one if you're using -j. Here's a - simple example: - - 


        import atexit
-
-        def print_build_failures():
-            from SCons.Script import GetBuildFailures
-            for bf in GetBuildFailures():
-                print "%s failed: %s" % (bf.node, bf.errstr)
-        atexit.register(print_build_failures)
-

- The atexit.register call - registers print_build_failures - as an atexit callback, to be called - before SCons exits. When that function is called, - it calls GetBuildFailures to fetch the list of failed objects. - See the man page - for the detailed contents of the returned objects; - some of the more useful attributes are - .node, - .errstr, - .filename, and - .command. - The filename is not necessarily - the same file as the node; the - node is the target that was - being built when the error occurred, while the - filenameis the file or dir that - actually caused the error. - Note: only call GetBuildFailures at the end of the - build; calling it at any other time is undefined. - -

- - Here is a more complete example showing how to - turn each element of GetBuildFailures into a string: - - 


        # Make the build fail if we pass fail=1 on the command line
-        if ARGUMENTS.get('fail', 0):
-            Command('target', 'source', ['/bin/false'])
-
-        def bf_to_str(bf):
-            """Convert an element of GetBuildFailures() to a string
-            in a useful way."""
-            import SCons.Errors
-            if bf is None: # unknown targets product None in list
-                return '(unknown tgt)'
-            elif isinstance(bf, SCons.Errors.StopError):
-                return str(bf)
-            elif bf.node:
-                return str(bf.node) + ': ' + bf.errstr
-            elif bf.filename:
-                return bf.filename + ': ' + bf.errstr
-            return 'unknown failure: ' + bf.errstr
-        import atexit
-
-        def build_status():
-            """Convert the build status to a 2-tuple, (status, msg)."""
-            from SCons.Script import GetBuildFailures
-            bf = GetBuildFailures()
-            if bf:
-                # bf is normally a list of build failures; if an element is None,
-                # it's because of a target that scons doesn't know anything about.
-                status = 'failed'
-                failures_message = "\n".join(["Failed building %s" % bf_to_str(x)
-                                   for x in bf if x is not None])
-            else:
-                # if bf is None, the build completed successfully.
-                status = 'ok'
-                failures_message = ''
-            return (status, failures_message)
-
-        def display_build_status():
-            """Display the build status.  Called by atexit.
-            Here you could do all kinds of complicated things."""
-            status, failures_message = build_status()
-            if status == 'failed':
-               print "FAILED!!!!"  # could display alert, ring bell, etc.
-            elif status == 'ok':
-               print "Build succeeded."
-            print failures_message
-
-        atexit.register(display_build_status)
-

- When this runs, you'll see the appropriate output: - - 


          % scons -Q
-          scons: `.' is up to date.
-          Build succeeded.
-          % scons -Q fail=1
-          scons: *** Source `source' not found, needed by target `target'.  Stop.
-          FAILED!!!!
-          Failed building Source `source' not found, needed by target `target'.
-

Chapter 12. Controlling a Build From the Command Line

- SCons provides a number of ways - for the writer of the SConscript files - to give the users who will run SCons - a great deal of control over the build execution. - The arguments that the user can specify on - the command line are broken down into three types: - -

Options

- Command-line options always begin with - one or two - (hyphen) characters. - SCons provides ways for you to examind - and set options values from within your SConscript files, - as well as the ability to define your own - custom options. - See Section 12.1, below. - -

Variables

- Any command-line argument containing an = - (equal sign) is considered a variable setting with the form - variable=value - SCons provides direct access to - all of the command-line variable settings, - the ability to apply command-line variable settings - to construction environments, - and functions for configuring - specific types of variables - (Boolean values, path names, etc.) - with automatic validation of the user's specified values. - See Section 12.2, below. - -

Targets

- Any command-line argument that is not an option - or a variable setting - (does not begin with a hyphen - and does not contain an equal sign) - is considered a target that the user - (presumably) wants SCons to build. - A list of Node objects representing - the target or targets to build. - SCons provides access to the list of specified targets, - as well as ways to set the default list of targets - from within the SConscript files. - See Section 12.3, below. - -

12.1. Command-Line Options

- SCons has many command-line options - that control its behavior. - A SCons command-line option - always begins with one or two - (hyphen) - characters. - -

12.1.1. Not Having to Specify Command-Line Options Each Time: the SCONSFLAGS Environment Variable

- Users may find themselves supplying - the same command-line options every time - they run SCons. - For example, you might find it saves time - to specify a value of -j 2 - to have SCons run up to two build commands in parallel. - To avoid having to type -j 2 by hand - every time, - you can set the external environment variable - SCONSFLAGS to a string containing - command-line options that you want SCons to use. - -

- If, for example, - you're using a POSIX shell that's - compatible with the Bourne shell, - and you always want SCons to use the - -Q option, - you can set the SCONSFLAGS - environment as follows: - - 


        % scons
-        scons: Reading SConscript files ...
-        scons: done reading SConscript files.
-        scons: Building targets ...
-            ... [build output] ...
-        scons: done building targets.
-        % export SCONSFLAGS="-Q"
-        % scons
-            ... [build output] ...
-

- Users of csh-style shells on POSIX systems - can set the SCONSFLAGS environment as follows: - - 


        $ setenv SCONSFLAGS "-Q"
-

- Windows users may typically want to set the - SCONSFLAGS in the appropriate tab of the - System Properties window. - -

12.1.2. Getting Values Set by Command-Line Options: the GetOption Function

- SCons provides the GetOption function - to get the values set by the various command-line options. - One common use of this is to check whether or not - the -h or --help option - has been specified. - Normally, SCons does not print its help text - until after it has read all of the SConscript files, - because it's possible that help text has been added - by some subsidiary SConscript file deep in the - source tree hierarchy. - Of course, reading all of the SConscript files - takes extra time. - -

- If you know that your configuration does not define - any additional help text in subsidiary SConscript files, - you can speed up the command-line help available to users - by using the GetOption function to load the - subsidiary SConscript files only if the - the user has not specified - the -h or --help option, - like so: - - 


-      In general, the string that you pass to the
-      GetOption function to fetch the value of a command-line
-      option setting is the same as the "most common" long option name
-      (beginning with two hyphen characters),
-      although there are some exceptions.
-      The list of SCons command-line options
-      and the GetOption strings for fetching them,
-      are available in the
-      Section 12.1.4 section,
-      below.
-
-      
12.1.3. Setting Values of Command-Line Options:  the SetOption Function

-      You can also set the values of SCons
-      command-line options from within the SConscript files
-      by using the SetOption function.
-      The strings that you use to set the values of SCons
-      command-line options are available in the
-      Section 12.1.4 section,
-      below.
-
-      

-      One use of the SetOption function is to
-      specify a value for the -j
-      or --jobs option,
-      so that users get the improved performance
-      of a parallel build without having to specify the option by hand.
-      A complicating factor is that a good value
-      for the -j option is
-      somewhat system-dependent.
-      One rough guideline is that the more processors
-      your system has,
-      the higher you want to set the
-      -j value,
-      in order to take advantage of the number of CPUs.
-
-      

-      For example, suppose the administrators
-      of your development systems
-      have standardized on setting a
-      NUM_CPU environment variable
-      to the number of processors on each system.
-      A little bit of Python code
-      to access the environment variable
-      and the SetOption function
-      provide the right level of flexibility:
-
-      

        import os
-        num_cpu = int(os.environ.get('NUM_CPU', 2))
-        SetOption('num_jobs', num_cpu)
-        print "running with -j", GetOption('num_jobs')
-      

-      The above snippet of code
-      sets the value of the --jobs option
-      to the value specified in the
-      $NUM_CPU environment variable.
-      (This is one of the exception cases
-      where the string is spelled differently from
-      the from command-line option.
-      The string for fetching or setting the --jobs
-      value is num_jobs
-      for historical reasons.)
-      The code in this example prints the num_jobs
-      value for illustrative purposes.
-      It uses a default value of 2
-      to provide some minimal parallelism even on
-      single-processor systems:
-
-      

        % scons -Q
-        running with -j 2
-        scons: `.' is up to date.
-      

-      But if the $NUM_CPU
-      environment variable is set,
-      then we use that for the default number of jobs:
-
-      

        % export NUM_CPU="4"
-        % scons -Q
-        running with -j 4
-        scons: `.' is up to date.
-      

-      But any explicit
-      -j or --jobs
-      value the user specifies an the command line is used first,
-      regardless of whether or not
-      the $NUM_CPU environment
-      variable is set:
-
-      

        % scons -Q -j 7
-        running with -j 7
-        scons: `.' is up to date.
-        % export NUM_CPU="4"
-        % scons -Q -j 3
-        running with -j 3
-        scons: `.' is up to date.
-      
12.1.4. Strings for Getting or Setting Values of SCons Command-Line Options

-      The strings that you can pass to the GetOption
-      and SetOption functions usually correspond to the
-      first long-form option name
-      (beginning with two hyphen characters:  --),
-      after replacing any remaining hyphen characters
-      with underscores.
-
-      

-      The full list of strings and the variables they
-      correspond to is as follows:
-
-      
String for GetOption and SetOptionCommand-Line Option(s)
cache_debug--cache-debug
cache_disable--cache-disable
cache_force--cache-force
cache_show--cache-show
clean-c,
-           --clean,
-           --remove
config--config
directory-C,
-             --directory
diskcheck--diskcheck
duplicate--duplicate
file-f,
-             --file,
-             --makefile ,
-             --sconstruct
help-h,
-             --help
ignore_errors--ignore-errors
implicit_cache--implicit-cache
implicit_deps_changed--implicit-deps-changed
implicit_deps_unchanged--implicit-deps-unchanged
interactive--interact,
-             --interactive
keep_going-k,
-             --keep-going
max_drift--max-drift
no_exec-n,
-             --no-exec,
-             --just-print,
-             --dry-run,
-             --recon
no_site_dir--no-site-dir
num_jobs-j,
-             --jobs
profile_file--profile
question-q,
-             --question
random--random
repository-Y,
-             --repository,
-             --srcdir
silent-s,
-             --silent,
-             --quiet
site_dir--site-dir
stack_size--stack-size
taskmastertrace_file--taskmastertrace
warn--warn --warning
12.1.5. Adding Custom Command-Line Options:  the AddOption Function

-      SCons also allows you to define your own
-      command-line options with the AddOption function.
-      The AddOption function takes the same arguments
-      as the optparse.add_option function
-      from the standard Python library.
-      [3]
-      Once you have added a custom command-line option
-      with the AddOption function,
-      the value of the option (if any) is immediately available
-      using the standard GetOption function.
-      (The value can also be set using SetOption,
-      although that's not very useful in practice
-      because a default value can be specified in
-      directly in the AddOption call.)
-
-      

-      One useful example of using this functionality
-      is to provide a --prefix for users:
-
-      

        AddOption('--prefix',
-                  dest='prefix',
-                  type='string',
-                  nargs=1,
-                  action='store',
-                  metavar='DIR',
-                  help='installation prefix')
-
-        env = Environment(PREFIX = GetOption('prefix'))
-
-        installed_foo = env.Install('$PREFIX/usr/bin', 'foo.in')
-        Default(installed_foo)
-      

-      The above code uses the GetOption function
-      to set the $PREFIX
-      construction variable to any
-      value that the user specifies with a command-line
-      option of --prefix.
-      Because $PREFIX
-      will expand to a null string if it's not initialized,
-      running SCons without the
-      option of --prefix
-      will install the file in the
-      /usr/bin/ directory:
-
-      

        % scons -Q -n
-        Install file: "foo.in" as "/usr/bin/foo.in"
-      

-      But specifying --prefix=/tmp/install
-      on the command line causes the file to be installed in the
-      /tmp/install/usr/bin/ directory:
-
-      

        % scons -Q -n --prefix=/tmp/install
-        Install file: "foo.in" as "/tmp/install/usr/bin/foo.in"
-      
12.2. Command-Line variable=value Build Variables

-    You may want to control various aspects
-    of your build by allowing the user
-    to specify variable=value
-    values on the command line.
-    For example, suppose you
-    want users to be able to
-    build a debug version of a program
-    by running SCons as follows:
-
-    

      % scons -Q debug=1
-    

-    SCons provides an ARGUMENTS dictionary
-    that stores all of the
-    variable=value
-    assignments from the command line.
-    This allows you to modify
-    aspects of your build in response
-    to specifications on the command line.
-    (Note that unless you want to require
-    that users always
-    specify a variable,
-    you probably want to use
-    the Python
-    ARGUMENTS.get() function,
-    which allows you to specify a default value
-    to be used if there is no specification
-    on the command line.)
-
-    

-    The following code sets the $CCFLAGS construction
-    variable in response to the debug
-    flag being set in the ARGUMENTS dictionary:
-
-    

       env = Environment()
-       debug = ARGUMENTS.get('debug', 0)
-       if int(debug):
-           env.Append(CCFLAGS = '-g')
-       env.Program('prog.c')
-    

-    This results in the -g
-    compiler option being used when
-    debug=1
-    is used on the command line:
-
-    

       % scons -Q debug=0
-       cc -o prog.o -c prog.c
-       cc -o prog prog.o
-       % scons -Q debug=0
-       scons: `.' is up to date.
-       % scons -Q debug=1
-       cc -o prog.o -c -g prog.c
-       cc -o prog prog.o
-       % scons -Q debug=1
-       scons: `.' is up to date.
-    

-    Notice that SCons keeps track of
-    the last values used to build the object files,
-    and as a result correctly rebuilds
-    the object and executable files
-    only when the value of the debug
-    argument has changed.
-
-    

-    The ARGUMENTS dictionary has two minor drawbacks.
-    First, because it is a dictionary,
-    it can only store one value for each specified keyword,
-    and thus only "remembers" the last setting
-    for each keyword on the command line.
-    This makes the ARGUMENTS dictionary
-    inappropriate if users should be able to
-    specify multiple values
-    on the command line for a given keyword.
-    Second, it does not preserve
-    the order in which the variable settings
-    were specified,
-    which is a problem if
-    you want the configuration to
-    behave differently in response
-    to the order in which the build
-    variable settings were specified on the command line.
-
-    

-    To accomodate these requirements,
-    SCons provides an ARGLIST variable
-    that gives you direct access to
-    variable=value
-    settings on the command line,
-    in the exact order they were specified,
-    and without removing any duplicate settings.
-    Each element in the ARGLIST variable
-    is itself a two-element list
-    containing the keyword and the value
-    of the setting,
-    and you must loop through,
-    or otherwise select from,
-    the elements of ARGLIST to
-    process the specific settings you want
-    in whatever way is appropriate for your configuration.
-    For example,
-    the following code to let the user
-    add to the CPPDEFINES construction variable
-    by specifying multiple
-    define=
-    settings on the command line:
-
-    

       cppdefines = []
-       for key, value in ARGLIST:
-           if key == 'define':
-               cppdefines.append(value)
-       env = Environment(CPPDEFINES = cppdefines)
-       env.Object('prog.c')
-    

-    Yields the followig output:
-
-    

       % scons -Q define=FOO
-       cc -o prog.o -c -DFOO prog.c
-       % scons -Q define=FOO define=BAR
-       cc -o prog.o -c -DFOO -DBAR prog.c
-    

-    Note that the ARGLIST and ARGUMENTS
-    variables do not interfere with each other,
-    but merely provide slightly different views
-    into how the user specified
-    variable=value
-    settings on the command line.
-    You can use both variables in the same
-    SCons configuration.
-    In general, the ARGUMENTS dictionary
-    is more convenient to use,
-    (since you can just fetch variable
-    settings through a dictionary access),
-    and the ARGLIST list
-    is more flexible
-    (since you can examine the
-    specific order in which
-    the user's command-line variabe settings).
-
-    
12.2.1. Controlling Command-Line Build Variables

-      Being able to use a command-line build variable like
-      debug=1 is handy,
-      but it can be a chore to write specific Python code
-      to recognize each such variable,
-      check for errors and provide appropriate messages,
-      and apply the values to a construction variable.
-      To help with this,
-      SCons supports a class to
-      define such build variables easily,
-      and a mechanism to apply the
-      build variables to a construction environment.
-      This allows you to control how the build variables affect
-      construction environments.
-
-      

-      For example, suppose that you want users to set
-      a RELEASE construction variable on the
-      command line whenever the time comes to build
-      a program for release,
-      and that the value of this variable
-      should be added to the command line
-      with the appropriate -D option
-      (or other command line option)
-      to pass the value to the C compiler.
-      Here's how you might do that by setting
-      the appropriate value in a dictionary for the
-      $CPPDEFINES construction variable:
-
-      

           vars = Variables()
-           vars.Add('RELEASE', 'Set to 1 to build for release', 0)
-           env = Environment(variables = vars,
-                             CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'})
-           env.Program(['foo.c', 'bar.c'])
-      

-      This SConstruct file first creates a Variables object
-      (the vars = Variables() call),
-      and then uses the object's Add
-      method to indicate that the RELEASE
-      variable can be set on the command line,
-      and that its default value will be 0
-      (the third argument to the Add method).
-      The second argument is a line of help text;
-      we'll learn how to use it in the next section.
-
-      

-      We then pass the created Variables
-      object as a variables keyword argument
-      to the Environment call
-      used to create the construction environment.
-      This then allows a user to set the
-      RELEASE build variable on the command line
-      and have the variable show up in
-      the command line used to build each object from
-      a C source file:
-
-      

        % scons -Q RELEASE=1
-        cc -o bar.o -c -DRELEASE_BUILD=1 bar.c
-        cc -o foo.o -c -DRELEASE_BUILD=1 foo.c
-        cc -o foo foo.o bar.o
-      

-      NOTE:  Before SCons release 0.98.1, these build variables
-      were known as "command-line build options."
-      The class was actually named the Options class,
-      and in the sections below,
-      the various functions were named
-      BoolOption, EnumOption, ListOption,
-      PathOption, PackageOption and AddOptions.
-      These older names still work,
-      and you may encounter them in older
-      SConscript fles,
-      but their use is discouraged
-      and will be officially deprecated some day.
-
-      
12.2.2. Providing Help for Command-Line Build Variables

-      To make command-line build variables most useful,
-      you ideally want to provide
-      some help text that will describe
-      the available variables
-      when the user runs scons -h.
-      You could write this text by hand,
-      but SCons provides an easier way.
-      Variables objects support a
-      GenerateHelpText method
-      that will, as its name suggests,
-      generate text that describes
-      the various variables that
-      have been added to it.
-      You then pass the output from this method to
-      the Help function:
-
-      

           vars = Variables('custom.py')
-           vars.Add('RELEASE', 'Set to 1 to build for release', 0)
-           env = Environment(variables = vars)
-           Help(vars.GenerateHelpText(env))
-      

-      SCons will now display some useful text
-      when the -h option is used:
-
-      

        % scons -Q -h
-        
-        RELEASE: Set to 1 to build for release
-            default: 0
-            actual: 0
-        
-        Use scons -H for help about command-line options.
-      

-      Notice that the help output shows the default value,
-      and the current actual value of the build variable.
-
-      
12.2.3. Reading Build Variables From a File

-      Giving the user a way to specify the
-      value of a build variable on the command line
-      is useful,
-      but can still be tedious
-      if users must specify the variable
-      every time they run SCons.
-      We can let users provide customized build variable settings
-      in a local file by providing a
-      file name when we create the
-      Variables object:
-
-      

           vars = Variables('custom.py')
-           vars.Add('RELEASE', 'Set to 1 to build for release', 0)
-           env = Environment(variables = vars,
-                             CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'})
-           env.Program(['foo.c', 'bar.c'])
-           Help(vars.GenerateHelpText(env))
-      

-      This then allows the user to control the RELEASE
-      variable by setting it in the custom.py file:
-
-      

        RELEASE = 1
-        

-      Note that this file is actually executed
-      like a Python script.
-      Now when we run SCons:
-
-      

        % scons -Q
-        cc -o bar.o -c -DRELEASE_BUILD=1 bar.c
-        cc -o foo.o -c -DRELEASE_BUILD=1 foo.c
-        cc -o foo foo.o bar.o
-      

-      And if we change the contents of custom.py to:
-
-      

        RELEASE = 0
-      

-      The object files are rebuilt appropriately
-      with the new variable:
-
-      

        % scons -Q
-        cc -o bar.o -c -DRELEASE_BUILD=0 bar.c
-        cc -o foo.o -c -DRELEASE_BUILD=0 foo.c
-        cc -o foo foo.o bar.o
-      
12.2.4. Pre-Defined Build Variable Functions

-      SCons provides a number of functions
-      that provide ready-made behaviors
-      for various types of command-line build variables.
-
-      
12.2.4.1. True/False Values:  the BoolVariable Build Variable Function

-        It's often handy to be able to specify a
-        variable that controls a simple Boolean variable
-        with a true or false value.
-        It would be even more handy to accomodate
-        users who have different preferences for how to represent
-        true or false values.
-        The BoolVariable function
-        makes it easy to accomodate these
-        common representations of
-        true or false.
-
-        

-        The BoolVariable function takes three arguments:
-        the name of the build variable,
-        the default value of the build variable,
-        and the help string for the variable.
-        It then returns appropriate information for
-        passing to the Add method of a Variables object, like so:
-
-        

             vars = Variables('custom.py')
-             vars.Add(BoolVariable('RELEASE', 'Set to build for release', 0))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'})
-             env.Program('foo.c')
-        

-        With this build variable,
-        the RELEASE variable can now be enabled by
-        setting it to the value yes
-        or t:
-
-        

          % scons -Q RELEASE=yes foo.o
-          cc -o foo.o -c -DRELEASE_BUILD=True foo.c
-        

          % scons -Q RELEASE=t foo.o
-          cc -o foo.o -c -DRELEASE_BUILD=True foo.c
-        

-        Other values that equate to true include
-        y,
-        1,
-        on
-        and
-        all.
-
-        

-        Conversely, RELEASE may now be given a false
-        value by setting it to
-        no
-        or
-        f:
-
-        

          % scons -Q RELEASE=no foo.o
-          cc -o foo.o -c -DRELEASE_BUILD=False foo.c
-        

          % scons -Q RELEASE=f foo.o
-          cc -o foo.o -c -DRELEASE_BUILD=False foo.c
-        

-        Other values that equate to false include
-        n,
-        0,
-        off
-        and
-        none.
-
-        

-        Lastly, if a user tries to specify
-        any other value,
-        SCons supplies an appropriate error message:
-
-        

          % scons -Q RELEASE=bad_value foo.o
-          
-          scons: *** Error converting option: RELEASE
-          Invalid value for boolean option: bad_value
-          File "/home/my/project/SConstruct", line 4, in <module>
-        
12.2.4.2. Single Value From a List:  the EnumVariable Build Variable Function

-        Suppose that we want a user to be able to
-        set a COLOR variable
-        that selects a background color to be
-        displayed by an application,
-        but that we want to restrict the
-        choices to a specific set of allowed colors.
-        This can be set up quite easily
-        using the EnumVariable,
-        which takes a list of allowed_values        in addition to the variable name,
-        default value,
-        and help text arguments:
-
-        

             vars = Variables('custom.py')
-             vars.Add(EnumVariable('COLOR', 'Set background color', 'red',
-                                 allowed_values=('red', 'green', 'blue')))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'COLOR' : '"${COLOR}"'})
-             env.Program('foo.c')
-        

-        The user can now explicity set the COLOR build variable
-        to any of the specified allowed values:
-
-        

          % scons -Q COLOR=red foo.o
-          cc -o foo.o -c -DCOLOR="red" foo.c
-          % scons -Q COLOR=blue foo.o
-          cc -o foo.o -c -DCOLOR="blue" foo.c
-          % scons -Q COLOR=green foo.o
-          cc -o foo.o -c -DCOLOR="green" foo.c
-        

-        But, almost more importantly,
-        an attempt to set COLOR
-        to a value that's not in the list
-        generates an error message:
-
-        

          % scons -Q COLOR=magenta foo.o
-          
-          scons: *** Invalid value for option COLOR: magenta
-          File "/home/my/project/SConstruct", line 5, in <module>
-        

-        The EnumVariable function also supports a way
-        to map alternate names to allowed values.
-        Suppose, for example,
-        that we want to allow the user
-        to use the word navy as a synonym for
-        blue.
-        We do this by adding a map dictionary
-        that will map its key values
-        to the desired legal value:
-
-        

             vars = Variables('custom.py')
-             vars.Add(EnumVariable('COLOR', 'Set background color', 'red',
-                                 allowed_values=('red', 'green', 'blue'),
-                                 map={'navy':'blue'}))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'COLOR' : '"${COLOR}"'})
-             env.Program('foo.c')
-        

-        As desired, the user can then use
-        navy on the command line,
-        and SCons will translate it into blue
-        when it comes time to use the COLOR
-        variable to build a target:
-
-        

          % scons -Q COLOR=navy foo.o
-          cc -o foo.o -c -DCOLOR="blue" foo.c
-        

-        By default, when using the EnumVariable function,
-        arguments that differ
-        from the legal values
-        only in case
-        are treated as illegal values:
-
-        

          % scons -Q COLOR=Red foo.o
-          
-          scons: *** Invalid value for option COLOR: Red
-          File "/home/my/project/SConstruct", line 5, in <module>
-          % scons -Q COLOR=BLUE foo.o
-          
-          scons: *** Invalid value for option COLOR: BLUE
-          File "/home/my/project/SConstruct", line 5, in <module>
-          % scons -Q COLOR=nAvY foo.o
-          
-          scons: *** Invalid value for option COLOR: nAvY
-          File "/home/my/project/SConstruct", line 5, in <module>
-        

-        The EnumVariable function can take an additional
-        ignorecase keyword argument that,
-        when set to 1,
-        tells SCons to allow case differences
-        when the values are specified:
-
-        

             vars = Variables('custom.py')
-             vars.Add(EnumVariable('COLOR', 'Set background color', 'red',
-                                 allowed_values=('red', 'green', 'blue'),
-                                 map={'navy':'blue'},
-                                 ignorecase=1))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'COLOR' : '"${COLOR}"'})
-             env.Program('foo.c')
-        

-        Which yields the output:
-
-        

          % scons -Q COLOR=Red foo.o
-          cc -o foo.o -c -DCOLOR="Red" foo.c
-          % scons -Q COLOR=BLUE foo.o
-          cc -o foo.o -c -DCOLOR="BLUE" foo.c
-          % scons -Q COLOR=nAvY foo.o
-          cc -o foo.o -c -DCOLOR="blue" foo.c
-          % scons -Q COLOR=green foo.o
-          cc -o foo.o -c -DCOLOR="green" foo.c
-        

-        Notice that an ignorecase value of 1
-        preserves the case-spelling that the user supplied.
-        If you want SCons to translate the names
-        into lower-case,
-        regardless of the case used by the user,
-        specify an ignorecase value of 2:
-
-        

             vars = Variables('custom.py')
-             vars.Add(EnumVariable('COLOR', 'Set background color', 'red',
-                                 allowed_values=('red', 'green', 'blue'),
-                                 map={'navy':'blue'},
-                                 ignorecase=2))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'COLOR' : '"${COLOR}"'})
-             env.Program('foo.c')
-        

-        Now SCons will use values of
-        red,
-        green or
-        blue
-        regardless of how the user spells
-        those values on the command line:
-
-        

          % scons -Q COLOR=Red foo.o
-          cc -o foo.o -c -DCOLOR="red" foo.c
-          % scons -Q COLOR=nAvY foo.o
-          cc -o foo.o -c -DCOLOR="blue" foo.c
-          % scons -Q COLOR=GREEN foo.o
-          cc -o foo.o -c -DCOLOR="green" foo.c
-        
12.2.4.3. Multiple Values From a List:  the ListVariable Build Variable Function

-        Another way in which you might want to allow users
-        to control a build variable is to
-        specify a list of one or more legal values.
-        SCons supports this through the ListVariable function.
-        If, for example, we want a user to be able to set a
-        COLORS variable to one or more of the legal list of values:
-
-        

             vars = Variables('custom.py')
-             vars.Add(ListVariable('COLORS', 'List of colors', 0,
-                                 ['red', 'green', 'blue']))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'COLORS' : '"${COLORS}"'})
-             env.Program('foo.c')
-        

-        A user can now specify a comma-separated list
-        of legal values,
-        which will get translated into a space-separated
-        list for passing to the any build commands:
-
-        

          % scons -Q COLORS=red,blue foo.o
-          cc -o foo.o -c -DCOLORS="red blue" foo.c
-          % scons -Q COLORS=blue,green,red foo.o
-          cc -o foo.o -c -DCOLORS="blue green red" foo.c
-        

-        In addition, the ListVariable function
-        allows the user to specify explicit keywords of
-        all or none
-        to select all of the legal values,
-        or none of them, respectively:
-
-        

          % scons -Q COLORS=all foo.o
-          cc -o foo.o -c -DCOLORS="red green blue" foo.c
-          % scons -Q COLORS=none foo.o
-          cc -o foo.o -c -DCOLORS="" foo.c
-        

-        And, of course, an illegal value
-        still generates an error message:
-
-        

          % scons -Q COLORS=magenta foo.o
-          
-          scons: *** Error converting option: COLORS
-          Invalid value(s) for option: magenta
-          File "/home/my/project/SConstruct", line 5, in <module>
-        
12.2.4.4. Path Names:  the PathVariable Build Variable Function

-        SCons supports a PathVariable function
-        to make it easy to create a build variable
-        to control an expected path name.
-        If, for example, you need to
-        define a variable in the preprocessor
-        that controls the location of a
-        configuration file:
-
-        

             vars = Variables('custom.py')
-             vars.Add(PathVariable('CONFIG',
-                                 'Path to configuration file',
-                                 '/etc/my_config'))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'CONFIG_FILE' : '"$CONFIG"'})
-             env.Program('foo.c')
-        

-        This then allows the user to
-        override the CONFIG build variable
-        on the command line as necessary:
-
-        

          % scons -Q foo.o
-          cc -o foo.o -c -DCONFIG_FILE="/etc/my_config" foo.c
-          % scons -Q CONFIG=/usr/local/etc/other_config foo.o
-          scons: `foo.o' is up to date.
-        

-        By default, PathVariable checks to make sure
-        that the specified path exists and generates an error if it
-        doesn't:
-
-        

          % scons -Q CONFIG=/does/not/exist foo.o
-          
-          scons: *** Path for option CONFIG does not exist: /does/not/exist
-          File "/home/my/project/SConstruct", line 6, in <module>
-        

-        PathVariable provides a number of methods
-        that you can use to change this behavior.
-        If you want to ensure that any specified paths are,
-        in fact, files and not directories,
-        use the PathVariable.PathIsFile method:
-
-        

             vars = Variables('custom.py')
-             vars.Add(PathVariable('CONFIG',
-                                 'Path to configuration file',
-                                 '/etc/my_config',
-                                 PathVariable.PathIsFile))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'CONFIG_FILE' : '"$CONFIG"'})
-             env.Program('foo.c')
-        

-        Conversely, to ensure that any specified paths are
-        directories and not files,
-        use the PathVariable.PathIsDir method:
-
-        

             vars = Variables('custom.py')
-             vars.Add(PathVariable('DBDIR',
-                                 'Path to database directory',
-                                 '/var/my_dbdir',
-                                 PathVariable.PathIsDir))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'DBDIR' : '"$DBDIR"'})
-             env.Program('foo.c')
-        

-        If you want to make sure that any specified paths
-        are directories,
-        and you would like the directory created
-        if it doesn't already exist,
-        use the PathVariable.PathIsDirCreate method:
-
-        

             vars = Variables('custom.py')
-             vars.Add(PathVariable('DBDIR',
-                                 'Path to database directory',
-                                 '/var/my_dbdir',
-                                 PathVariable.PathIsDirCreate))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'DBDIR' : '"$DBDIR"'})
-             env.Program('foo.c')
-        

-        Lastly, if you don't care whether the path exists,
-        is a file, or a directory,
-        use the PathVariable.PathAccept method
-        to accept any path that the user supplies:
-
-        

             vars = Variables('custom.py')
-             vars.Add(PathVariable('OUTPUT',
-                                 'Path to output file or directory',
-                                 None,
-                                 PathVariable.PathAccept))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'OUTPUT' : '"$OUTPUT"'})
-             env.Program('foo.c')
-        
12.2.4.5. Enabled/Disabled Path Names: the PackageVariable Build Variable Function

-        Sometimes you want to give users
-        even more control over a path name variable,
-        allowing them to explicitly enable or
-        disable the path name
-        by using yes or no keywords,
-        in addition to allow them
-        to supply an explicit path name.
-        SCons supports the PackageVariable
-        function to support this:
-
-        

             vars = Variables('custom.py')
-             vars.Add(PackageVariable('PACKAGE',
-                                    'Location package',
-                                    '/opt/location'))
-             env = Environment(variables = vars,
-                               CPPDEFINES={'PACKAGE' : '"$PACKAGE"'})
-             env.Program('foo.c')
-        

-        When the SConscript file uses the PackageVariable funciton,
-        user can now still use the default
-        or supply an overriding path name,
-        but can now explicitly set the
-        specified variable to a value
-        that indicates the package should be enabled
-        (in which case the default should be used)
-        or disabled:
-
-        

          % scons -Q foo.o
-          cc -o foo.o -c -DPACKAGE="/opt/location" foo.c
-          % scons -Q PACKAGE=/usr/local/location foo.o
-          cc -o foo.o -c -DPACKAGE="/usr/local/location" foo.c
-          % scons -Q PACKAGE=yes foo.o
-          cc -o foo.o -c -DPACKAGE="True" foo.c
-          % scons -Q PACKAGE=no foo.o
-          cc -o foo.o -c -DPACKAGE="False" foo.c
-        
12.2.5. Adding Multiple Command-Line Build Variables at Once

-      Lastly, SCons provides a way to add
-      multiple build variables to a Variables object at once.
-      Instead of having to call the Add method
-      multiple times,
-      you can call the AddVariables
-      method with a list of build variables
-      to be added to the object.
-      Each build variable is specified
-      as either a tuple of arguments,
-      just like you'd pass to the Add method itself,
-      or as a call to one of the pre-defined
-      functions for pre-packaged command-line build variables.
-      in any order:
-
-      

          vars = Variables()
-          vars.AddVariables(
-              ('RELEASE', 'Set to 1 to build for release', 0),
-              ('CONFIG', 'Configuration file', '/etc/my_config'),
-              BoolVariable('warnings', 'compilation with -Wall and similiar', 1),
-              EnumVariable('debug', 'debug output and symbols', 'no',
-                         allowed_values=('yes', 'no', 'full'),
-                         map={}, ignorecase=0),  # case sensitive
-              ListVariable('shared',
-                         'libraries to build as shared libraries',
-                         'all',
-                         names = list_of_libs),
-              PackageVariable('x11',
-                            'use X11 installed here (yes = search some places)',
-                            'yes'),
-              PathVariable('qtdir', 'where the root of Qt is installed', qtdir),
-          )
-      

      
12.2.6. Handling Unknown Command-Line Build Variables:  the UnknownVariables Function

-      Users may, of course,
-      occasionally misspell variable names in their command-line settings.
-      SCons does not generate an error or warning
-      for any unknown variables the users specifies on the command line.
-      (This is in no small part because you may be
-      processing the arguments directly using the ARGUMENTS dictionary,
-      and therefore SCons can't know in the general case
-      whether a given "misspelled" variable is
-      really unknown and a potential problem,
-      or something that your SConscript file
-      will handle directly with some Python code.)
-
-      

-      If, however, you're using a Variables object to
-      define a specific set of command-line build variables
-      that you expect users to be able to set,
-      you may want to provide an error
-      message or warning of your own
-      if the user supplies a variable setting
-      that is not among
-      the defined list of variable names known to the Variables object.
-      You can do this by calling the UnknownVariables
-      method of the Variables object:
-
-      

           vars = Variables(None)
-           vars.Add('RELEASE', 'Set to 1 to build for release', 0)
-           env = Environment(variables = vars,
-                             CPPDEFINES={'RELEASE_BUILD' : '${RELEASE}'})
-           unknown = vars.UnknownVariables()
-           if unknown:
-               print "Unknown variables:", unknown.keys()
-               Exit(1)
-           env.Program('foo.c')
-      

-      The UnknownVariables method returns a dictionary
-      containing the keywords and values
-      of any variables the user specified on the command line
-      that are not
-      among the variables known to the Variables object
-      (from having been specified using
-      the Variables object'sAdd method).
-      In the examble above,
-      we check for whether the dictionary
-      returned by the UnknownVariables is non-empty,
-      and if so print the Python list
-      containing the names of the unknwown variables
-      and then call the Exit function
-      to terminate SCons:
-
-      

        % scons -Q NOT_KNOWN=foo
-        Unknown variables: ['NOT_KNOWN']
-      

-      Of course, you can process the items in the
-      dictionary returned by the UnknownVariables function
-      in any way appropriate to your bulid configuration,
-      including just printing a warning message
-      but not exiting,
-      logging an error somewhere,
-      etc.
-
-      

-      Note that you must delay the call of UnknownVariables
-      until after you have applied the Variables object
-      to a construction environment
-      with the variables=
-      keyword argument of an Environment call.
-
-      
12.3. Command-Line Targets
12.3.1. Fetching Command-Line Targets: the COMMAND_LINE_TARGETS Variable

-      SCons supports a COMMAND_LINE_TARGETS variable
-      that lets you fetch the list of targets that the
-      user specified on the command line.
-      You can use the targets to manipulate the
-      build in any way you wish.
-      As a simple example,
-      suppose that you want to print a reminder
-      to the user whenever a specific program is built.
-      You can do this by checking for the
-      target in the COMMAND_LINE_TARGETS list:
-
-      

        if 'bar' in COMMAND_LINE_TARGETS:
-            print "Don't forget to copy `bar' to the archive!"
-        Default(Program('foo.c'))
-        Program('bar.c')
-      

-      Then, running SCons with the default target
-      works as it always does,
-      but explicity specifying the bar target
-      on the command line generates the warning message:
-
-      

        % scons -Q
-        cc -o foo.o -c foo.c
-        cc -o foo foo.o
-        % scons -Q bar
-        Don't forget to copy `bar' to the archive!
-        cc -o bar.o -c bar.c
-        cc -o bar bar.o
-      

-      Another practical use for the COMMAND_LINE_TARGETS variable
-      might be to speed up a build
-      by only reading certain subsidiary SConscript
-      files if a specific target is requested.
-
-      
12.3.2. Controlling the Default Targets:  the Default Function

-      One of the most basic things you can control
-      is which targets SCons will build by default--that is,
-      when there are no targets specified on the command line.
-      As mentioned previously,
-      SCons will normally build every target
-      in or below the current directory
-      by default--that is, when you don't
-      explicitly specify one or more targets
-      on the command line.
-      Sometimes, however, you may want
-      to specify explicitly that only
-      certain programs, or programs in certain directories,
-      should be built by default.
-      You do this with the Default function:
-
-      

         env = Environment()
-         hello = env.Program('hello.c')
-         env.Program('goodbye.c')
-         Default(hello)
-      

-      This SConstruct file knows how to build two programs,
-      hello and goodbye,
-      but only builds the
-      hello program by default:
-
-      

         % scons -Q
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-         % scons -Q
-         scons: `hello' is up to date.
-         % scons -Q goodbye
-         cc -o goodbye.o -c goodbye.c
-         cc -o goodbye goodbye.o
-      

-      Note that, even when you use the Default
-      function in your SConstruct file,
-      you can still explicitly specify the current directory
-      (.) on the command line
-      to tell SCons to build
-      everything in (or below) the current directory:
-
-      

         % scons -Q .
-         cc -o goodbye.o -c goodbye.c
-         cc -o goodbye goodbye.o
-         cc -o hello.o -c hello.c
-         cc -o hello hello.o
-      

-      You can also call the Default
-      function more than once,
-      in which case each call
-      adds to the list of targets to be built by default:
-
-      

         env = Environment()
-         prog1 = env.Program('prog1.c')
-         Default(prog1)
-         prog2 = env.Program('prog2.c')
-         prog3 = env.Program('prog3.c')
-         Default(prog3)
-      

-      Or you can specify more than one target
-      in a single call to the Default function:
-
-      

         env = Environment()
-         prog1 = env.Program('prog1.c')
-         prog2 = env.Program('prog2.c')
-         prog3 = env.Program('prog3.c')
-         Default(prog1, prog3)
-      

-      Either of these last two examples
-      will build only the
-      prog1
-      and
-      prog3
-      programs by default:
-
-      

         % scons -Q
-         cc -o prog1.o -c prog1.c
-         cc -o prog1 prog1.o
-         cc -o prog3.o -c prog3.c
-         cc -o prog3 prog3.o
-         % scons -Q .
-         cc -o prog2.o -c prog2.c
-         cc -o prog2 prog2.o
-      

-      You can list a directory as
-      an argument to Default:
-
-      

         env = Environment()
-         env.Program(['prog1/main.c', 'prog1/foo.c'])
-         env.Program(['prog2/main.c', 'prog2/bar.c'])
-         Default('prog1')
-      

-      In which case only the target(s) in that
-      directory will be built by default:
-
-      

         % scons -Q
-         cc -o prog1/foo.o -c prog1/foo.c
-         cc -o prog1/main.o -c prog1/main.c
-         cc -o prog1/main prog1/main.o prog1/foo.o
-         % scons -Q
-         scons: `prog1' is up to date.
-         % scons -Q .
-         cc -o prog2/bar.o -c prog2/bar.c
-         cc -o prog2/main.o -c prog2/main.c
-         cc -o prog2/main prog2/main.o prog2/bar.o
-      

-      Lastly, if for some reason you don't want
-      any targets built by default,
-      you can use the Python None
-      variable:
-
-      

         env = Environment()
-         prog1 = env.Program('prog1.c')
-         prog2 = env.Program('prog2.c')
-         Default(None)
-      

-      Which would produce build output like:
-
-      

         % scons -Q
-         scons: *** No targets specified and no Default() targets found.  Stop.
-         % scons -Q .
-         cc -o prog1.o -c prog1.c
-         cc -o prog1 prog1.o
-         cc -o prog2.o -c prog2.c
-         cc -o prog2 prog2.o
-      
12.3.2.1. Fetching the List of Default Targets: the DEFAULT_TARGETS Variable

-        SCons supports a DEFAULT_TARGETS variable
-        that lets you get at the current list of default targets.
-        The DEFAULT_TARGETS variable has
-        two important differences from the COMMAND_LINE_TARGETS variable.
-        First, the DEFAULT_TARGETS variable is a list of
-        internal SCons nodes,
-        so you need to convert the list elements to strings
-        if you want to print them or look for a specific target name.
-        Fortunately, you can do this easily
-        by using the Python map function
-        to run the list through str:
-
-        

           prog1 = Program('prog1.c')
-           Default(prog1)
-           print "DEFAULT_TARGETS is", map(str, DEFAULT_TARGETS)
-        

-        (Keep in mind that all of the manipulation of the
-        DEFAULT_TARGETS list takes place during the
-        first phase when SCons is reading up the SConscript files,
-        which is obvious if
-        we leave off the -Q flag when we run SCons:)
-
-        

           % scons
-           scons: Reading SConscript files ...
-           DEFAULT_TARGETS is ['prog1']
-           scons: done reading SConscript files.
-           scons: Building targets ...
-           cc -o prog1.o -c prog1.c
-           cc -o prog1 prog1.o
-           scons: done building targets.
-        

-        Second,
-        the contents of the DEFAULT_TARGETS list change
-        in response to calls to the Default: function,
-        as you can see from the following SConstruct file:
-
-        

           prog1 = Program('prog1.c')
-           Default(prog1)
-           print "DEFAULT_TARGETS is now", map(str, DEFAULT_TARGETS)
-           prog2 = Program('prog2.c')
-           Default(prog2)
-           print "DEFAULT_TARGETS is now", map(str, DEFAULT_TARGETS)
-        

-        Which yields the output:
-
-        

           % scons
-           scons: Reading SConscript files ...
-           DEFAULT_TARGETS is now ['prog1']
-           DEFAULT_TARGETS is now ['prog1', 'prog2']
-           scons: done reading SConscript files.
-           scons: Building targets ...
-           cc -o prog1.o -c prog1.c
-           cc -o prog1 prog1.o
-           cc -o prog2.o -c prog2.c
-           cc -o prog2 prog2.o
-           scons: done building targets.
-        

-        In practice, this simply means that you
-        need to pay attention to the order in
-        which you call the Default function
-        and refer to the DEFAULT_TARGETS list,
-        to make sure that you don't examine the
-        list before you've added the default targets
-        you expect to find in it.
-
-        
12.3.3. Fetching the List of Build Targets, Regardless of Origin: the BUILD_TARGETS Variable

-      We've already been introduced to the
-      COMMAND_LINE_TARGETS variable,
-      which contains a list of targets specified on the command line,
-      and the DEFAULT_TARGETS variable,
-      which contains a list of targets specified
-      via calls to the Default method or function.
-      Sometimes, however,
-      you want a list of whatever targets
-      SCons will try to build,
-      regardless of whether the targets came from the
-      command line or a Default call.
-      You could code this up by hand, as follows:
-
-      

        if COMMAND_LINE_TARGETS:
-            targets = COMMAND_LINE_TARGETS
-        else:
-            targets = DEFAULT_TARGETS
-      

-      SCons, however, provides a convenient
-      BUILD_TARGETS variable
-      that eliminates the need for this by-hand manipulation.
-      Essentially, the BUILD_TARGETS variable
-      contains a list of the command-line targets,
-      if any were specified,
-      and if no command-line targets were specified,
-      it contains a list of the targets specified
-      via the Default method or function.
-
-      

-      Because BUILD_TARGETS may contain a list of SCons nodes,
-      you must convert the list elements to strings
-      if you want to print them or look for a specific target name,
-      just like the DEFAULT_TARGETS list:
-
-      

        prog1 = Program('prog1.c')
-        Program('prog2.c')
-        Default(prog1)
-        print "BUILD_TARGETS is", map(str, BUILD_TARGETS)
-      

-      Notice how the value of BUILD_TARGETS
-      changes depending on whether a target is
-      specified on the command line:
-
-      

        % scons -Q
-        BUILD_TARGETS is ['prog1']
-        cc -o prog1.o -c prog1.c
-        cc -o prog1 prog1.o
-        % scons -Q prog2
-        BUILD_TARGETS is ['prog2']
-        cc -o prog2.o -c prog2.c
-        cc -o prog2 prog2.o
-        % scons -Q -c .
-        BUILD_TARGETS is ['.']
-        Removed prog1.o
-        Removed prog1
-        Removed prog2.o
-        Removed prog2
-      
Chapter 13. Installing Files in Other Directories:  the Install Builder

-  Once a program is built,
-  it is often appropriate to install it in another
-  directory for public use.
-  You use the Install method 
-  to arrange for a program, or any other file,
-  to be copied into a destination directory:
-
-  

     env = Environment()
-     hello = env.Program('hello.c')
-     env.Install('/usr/bin', hello)
-  

-  Note, however, that installing a file is
-  still considered a type of file "build."
-  This is important when you remember that
-  the default behavior of SCons is
-  to build files in or below the current directory.
-  If, as in the example above,
-  you are installing files in a directory
-  outside of the top-level SConstruct file's directory tree,
-  you must specify that directory
-  (or a higher directory, such as /)
-  for it to install anything there:
-
-  

     % scons -Q
-     cc -o hello.o -c hello.c
-     cc -o hello hello.o
-     % scons -Q /usr/bin
-     Install file: "hello" as "/usr/bin/hello"
-  

-  It can, however, be cumbersome to remember
-  (and type) the specific destination directory
-  in which the program (or any other file)
-  should be installed.
-  This is an area where the Alias
-  function comes in handy,
-  allowing you, for example,
-  to create a pseudo-target named install
-  that can expand to the specified destination directory:
-
-  

     env = Environment()
-     hello = env.Program('hello.c')
-     env.Install('/usr/bin', hello)
-     env.Alias('install', '/usr/bin')
-  

-  This then yields the more natural
-  ability to install the program
-  in its destination as follows:
-
-  

     % scons -Q
-     cc -o hello.o -c hello.c
-     cc -o hello hello.o
-     % scons -Q install
-     Install file: "hello" as "/usr/bin/hello"
-  
13.1. Installing Multiple Files in a Directory

-    You can install multiple files into a directory
-    simply by calling the Install function multiple times:
-
-    

       env = Environment()
-       hello = env.Program('hello.c')
-       goodbye = env.Program('goodbye.c')
-       env.Install('/usr/bin', hello)
-       env.Install('/usr/bin', goodbye)
-       env.Alias('install', '/usr/bin')
-    

-    Or, more succinctly, listing the multiple input
-    files in a list
-    (just like you can do with any other builder):
-
-    

       env = Environment()
-       hello = env.Program('hello.c')
-       goodbye = env.Program('goodbye.c')
-       env.Install('/usr/bin', [hello, goodbye])
-       env.Alias('install', '/usr/bin')
-    

-    Either of these two examples yields:
-
-    

       % scons -Q install
-       cc -o goodbye.o -c goodbye.c
-       cc -o goodbye goodbye.o
-       Install file: "goodbye" as "/usr/bin/goodbye"
-       cc -o hello.o -c hello.c
-       cc -o hello hello.o
-       Install file: "hello" as "/usr/bin/hello"
-    
13.2. Installing a File Under a Different Name

-    The Install method preserves the name
-    of the file when it is copied into the
-    destination directory.
-    If you need to change the name of the file
-    when you copy it, use the InstallAs function:
-
-    

       env = Environment()
-       hello = env.Program('hello.c')
-       env.InstallAs('/usr/bin/hello-new', hello)
-       env.Alias('install', '/usr/bin')
-    

-    This installs the hello
-    program with the name hello-new
-    as follows:
-
-    

       % scons -Q install
-       cc -o hello.o -c hello.c
-       cc -o hello hello.o
-       Install file: "hello" as "/usr/bin/hello-new"
-    
13.3. Installing Multiple Files Under Different Names

-    Lastly, if you have multiple files that all
-    need to be installed with different file names,
-    you can either call the InstallAs function
-    multiple times, or as a shorthand,
-    you can supply same-length lists
-    for both the target and source arguments:
-
-    

       env = Environment()
-       hello = env.Program('hello.c')
-       goodbye = env.Program('goodbye.c')
-       env.InstallAs(['/usr/bin/hello-new',
-                      '/usr/bin/goodbye-new'],
-                     [hello, goodbye])
-       env.Alias('install', '/usr/bin')
-    

-    In this case, the InstallAs function
-    loops through both lists simultaneously,
-    and copies each source file into its corresponding
-    target file name:
-
-    

       % scons -Q install
-       cc -o goodbye.o -c goodbye.c
-       cc -o goodbye goodbye.o
-       Install file: "goodbye" as "/usr/bin/goodbye-new"
-       cc -o hello.o -c hello.c
-       cc -o hello hello.o
-       Install file: "hello" as "/usr/bin/hello-new"
-    
Chapter 14. Platform-Independent File System Manipulation

-  SCons provides a number of platform-independent functions,
-  called factories,
-  that perform common file system manipulations
-  like copying, moving or deleting files and directories,
-  or making directories.
-  These functions are factories
-  because they don't perform the action
-  at the time they're called,
-  they each return an Action object
-  that can be executed at the appropriate time.
-
-  
14.1. Copying Files or Directories:  The Copy Factory

-    Suppose you want to arrange to make a copy of a file,
-    and don't have a suitable pre-existing builder.
-    [4]
-    One way would be to use the Copy action factory
-    in conjunction with the Command builder:
-
-    

        Command("file.out", "file.in", Copy("$TARGET", "$SOURCE"))
-    

-    Notice that the action returned by the Copy factory
-    will expand the $TARGET and $SOURCE strings
-    at the time file.out is built,
-    and that the order of the arguments
-    is the same as that of a builder itself--that is,
-    target first, followed by source:
-
-    

       % scons -Q
-       Copy("file.out", "file.in")
-    

-    You can, of course, name a file explicitly
-    instead of using $TARGET or $SOURCE:
-
-    

      Command("file.out", [], Copy("$TARGET", "file.in"))
-    

-    Which executes as:
-
-    

      % scons -Q
-      Copy("file.out", "file.in")
-    

-    The usefulness of the Copy factory
-    becomes more apparent when
-    you use it in a list of actions
-    passed to the Command builder.
-    For example, suppose you needed to run a
-    file through a utility that only modifies files in-place,
-    and can't "pipe" input to output.
-    One solution is to copy the source file
-    to a temporary file name,
-    run the utility,
-    and then copy the modified temporary file to the target,
-    which the Copy factory makes extremely easy:
-
-    

      Command("file.out", "file.in",
-              [
-                Copy("tempfile", "$SOURCE"),
-                "modify tempfile",
-                Copy("$TARGET", "tempfile"),
-              ])
-    

-    The output then looks like:
-
-    

      % scons -Q
-      Copy("tempfile", "file.in")
-      modify tempfile
-      Copy("file.out", "tempfile")
-    
14.2. Deleting Files or Directories:  The Delete Factory

-    If you need to delete a file,
-    then the Delete factory
-    can be used in much the same way as
-    the Copy factory.
-    For example, if we want to make sure that
-    the temporary file
-    in our last example doesn't exist before
-    we copy to it,
-    we could add Delete to the beginning
-    of the command list:
-
-    

      Command("file.out", "file.in",
-              [
-                Delete("tempfile"),
-                Copy("tempfile", "$SOURCE"),
-                "modify tempfile",
-                Copy("$TARGET", "tempfile"),
-              ])
-    

-    When then executes as follows:
-
-    

      % scons -Q
-      Delete("tempfile")
-      Copy("tempfile", "file.in")
-      modify tempfile
-      Copy("file.out", "tempfile")
-    

-    Of course, like all of these Action factories,
-    the Delete factory also expands
-    $TARGET and $SOURCE variables appropriately.
-    For example:
-
-    

      Command("file.out", "file.in",
-              [
-                Delete("$TARGET"),
-                Copy("$TARGET", "$SOURCE")
-              ])
-    

-    Executes as:
-
-    

      % scons -Q
-      Delete("file.out")
-      Copy("file.out", "file.in")
-    

-    Note, however, that you typically don't need to
-    call the Delete factory explicitly in this way;
-    by default, SCons deletes its target(s)
-    for you before executing any action.
-
-    

-    One word of caution about using the Delete factory:
-    it has the same variable expansions available
-    as any other factory, including the $SOURCE variable.
-    Specifying Delete("$SOURCE")
-    is not something you usually want to do!
-
-    
14.3. Moving (Renaming) Files or Directories:  The Move Factory

-    The Move factory
-    allows you to rename a file or directory.
-    For example, if we don't want to copy the temporary file,
-    we could use:
-
-    

      Command("file.out", "file.in",
-              [
-                Copy("tempfile", "$SOURCE"),
-                "modify tempfile",
-                Move("$TARGET", "tempfile"),
-              ])
-    

-    Which would execute as:
-
-    

      % scons -Q
-      Copy("tempfile", "file.in")
-      modify tempfile
-      Move("file.out", "tempfile")
-    
14.4. Updating the Modification Time of a File:  The Touch Factory

-    If you just need to update the
-    recorded modification time for a file,
-    use the Touch factory:
-
-    

      Command("file.out", "file.in",
-              [
-                Copy("$TARGET", "$SOURCE"),
-                Touch("$TARGET"),
-              ])
-    

-    Which executes as:
-
-    

      % scons -Q
-      Copy("file.out", "file.in")
-      Touch("file.out")
-    
14.5. Creating a Directory:  The Mkdir Factory

-    If you need to create a directory,
-    use the Mkdir factory.
-    For example, if we need to process
-    a file in a temporary directory
-    in which the processing tool
-    will create other files that we don't care about, 
-    you could use:
-
-    

      Command("file.out", "file.in",
-              [
-                Delete("tempdir"),
-                Mkdir("tempdir"),
-                Copy("tempdir/${SOURCE.file}", "$SOURCE"),
-                "process tempdir",
-                Move("$TARGET", "tempdir/output_file"),
-                Delete("tempdir"),
-              ])
-    

-    Which executes as:
-
-    

      % scons -Q
-      Delete("tempdir")
-      Mkdir("tempdir")
-      Copy("tempdir/file.in", "file.in")
-      process tempdir
-      Move("file.out", "tempdir/output_file")
-      scons: *** [file.out] No such file or directory
-    
14.6. Changing File or Directory Permissions:  The Chmod Factory

-    To change permissions on a file or directory,
-    use the Chmod factory.
-    The permission argument uses POSIX-style
-    permission bits and should typically
-    be expressed as an octal,
-    not decimal, number:
-
-    

      Command("file.out", "file.in",
-              [
-                Copy("$TARGET", "$SOURCE"),
-                Chmod("$TARGET", 0755),
-              ])
-    

-    Which executes:
-
-    

      % scons -Q
-      Copy("file.out", "file.in")
-      Chmod("file.out", 0755)
-    
14.7. Executing an action immediately:  the Execute Function

-    We've been showing you how to use Action factories
-    in the Command function.
-    You can also execute an Action returned by a factory
-    (or actually, any Action)
-    at the time the SConscript file is read
-    by using the Execute function.
-    For example, if we need to make sure that
-    a directory exists before we build any targets,
-
-    

      Execute(Mkdir('/tmp/my_temp_directory'))
-    

-    Notice that this will
-    create the directory while
-    the SConscript file is being read:
-
-    

      % scons
-      scons: Reading SConscript files ...
-      Mkdir("/tmp/my_temp_directory")
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      scons: `.' is up to date.
-      scons: done building targets.
-    

-    If you're familiar with Python,
-    you may wonder why you would want to use this
-    instead of just calling the native Python
-    os.mkdir() function.
-    The advantage here is that the Mkdir
-    action will behave appropriately if the user
-    specifies the SCons -n or
-    -q options--that is,
-    it will print the action but not actually
-    make the directory when -n is specified,
-    or make the directory but not print the action
-    when -q is specified.
-
-    

-    The Execute function returns the exit status
-    or return value of the underlying action being executed.
-    It will also print an error message if the action
-    fails and returns a non-zero value.
-    SCons will not, however,
-    actually stop the build if the action fails.
-    If you want the build to stop
-    in response to a failure in an action called by Execute,
-    you must do so by explicitly
-    checking the return value
-    and calling the Exit function
-    (or a Python equivalent):
-
-    

    if Execute(Mkdir('/tmp/my_temp_directory')):
-        # A problem occurred while making the temp directory.
-        Exit(1)
-    
Chapter 15. Controlling Removal of Targets

-  There are two occasions when SCons will,
-  by default, remove target files.
-  The first is when SCons determines that
-  an target file needs to be rebuilt
-  and removes the existing version of the target
-  before executing
-  The second is when SCons is invoked with the
-  -c option to "clean"
-  a tree of its built targets.
-
-  These behaviours can be suppressed with the
-  Precious and NoClean functions, respectively.
-
-  
15.1. Preventing target removal during build: the Precious Function

-    By default, SCons removes targets before building them.
-    Sometimes, however, this is not what you want.
-    For example, you may want to update a library incrementally,
-    not by having it deleted and then rebuilt from all
-    of the constituent object files.
-    In such cases, you can use the
-    Precious method to prevent
-    SCons from removing the target before it is built:
-
-    

        env = Environment(RANLIBCOM='')
-        lib = env.Library('foo', ['f1.c', 'f2.c', 'f3.c'])
-        env.Precious(lib)
-    

-    Although the output doesn't look any different,
-    SCons does not, in fact,
-    delete the target library before rebuilding it:
-
-    

        % scons -Q
-        cc -o f1.o -c f1.c
-        cc -o f2.o -c f2.c
-        cc -o f3.o -c f3.c
-        ar rc libfoo.a f1.o f2.o f3.o
-    

-    SCons will, however, still delete files marked as Precious
-    when the -c option is used.
-
-    
15.2. Preventing target removal during clean: the NoClean Function

-    By default, SCons removes all built targets when invoked
-    with the -c option to clean a source tree
-    of built targets.
-    Sometimes, however, this is not what you want.
-    For example, you may want to remove only intermediate generated files
-    (such as object files),
-    but leave the final targets
-    (the libraries)
-    untouched.
-
-    In such cases, you can use the NoClean method to prevent SCons
-    from removing a target during a clean:
-
-    

        env = Environment(RANLIBCOM='')
-        lib = env.Library('foo', ['f1.c', 'f2.c', 'f3.c'])
-        env.NoClean(lib)
-    

-    Notice that the libfoo.a
-    is not listed as a removed file:
-
-    

        % scons -Q
-        cc -o f1.o -c f1.c
-        cc -o f2.o -c f2.c
-        cc -o f3.o -c f3.c
-        ar rc libfoo.a f1.o f2.o f3.o
-        % scons -c
-        scons: Reading SConscript files ...
-        scons: done reading SConscript files.
-        scons: Cleaning targets ...
-        Removed f1.o
-        Removed f2.o
-        Removed f3.o
-        scons: done cleaning targets.
-    
15.3. Removing additional files during clean: the Clean Function

-    There may be additional files that you want removed
-    when the -c option is used,
-    but which SCons doesn't know about
-    because they're not normal target files.
-    For example, perhaps a command you invoke
-    creates a log file as
-    part of building the target file you want.
-    You would like the log file cleaned,
-    but you don't want to have to teach
-    SCons that the command
-    "builds" two files.
-
-    

-    You can use the Clean function to arrange for additional files
-    to be removed when the -c option is used.
-    Notice, however, that the Clean function takes two arguments,
-    and the second argument
-    is the name of the additional file you want cleaned
-    (foo.log in this example):
-
-    

        t = Command('foo.out', 'foo.in', 'build -o $TARGET $SOURCE')
-        Clean(t, 'foo.log')
-    

-    The first argument is the target with which you want
-    the cleaning of this additional file associated.
-    In the above example,
-    we've used the return value from the
-    Command function,
-    which represents the
-    foo.out
-    target.
-    Now whenever the
-    foo.out target is cleaned
-    by the -c option,
-    the foo.log file
-    will be removed as well:
-
-    

        % scons -Q
-        build -o foo.out foo.in
-        % scons -Q -c
-        Removed foo.out
-        Removed foo.log
-    
Chapter 16. Hierarchical Builds

-  The source code for large software projects
-  rarely stays in a single directory,
-  but is nearly always divided into a
-  hierarchy of directories.
-  Organizing a large software build using SCons
-  involves creating a hierarchy of build scripts
-  using the SConscript function.
-
-  
16.1. SConscript Files

-    As we've already seen,
-    the build script at the top of the tree is called SConstruct.
-    The top-level SConstruct file can
-    use the SConscript function to
-    include other subsidiary scripts in the build.
-    These subsidiary scripts can, in turn,
-    use the SConscript function
-    to include still other scripts in the build.
-    By convention, these subsidiary scripts are usually
-    named SConscript.
-    For example, a top-level SConstruct file might
-    arrange for four subsidiary scripts to be included
-    in the build as follows:
-
-    

      SConscript(['drivers/display/SConscript',
-                  'drivers/mouse/SConscript',
-                  'parser/SConscript',
-                  'utilities/SConscript'])
-    

-    In this case, the SConstruct file
-    lists all of the SConscript files in the build explicitly.
-    (Note, however, that not every directory in the tree
-    necessarily has an SConscript file.)
-    Alternatively, the drivers
-    subdirectory might contain an intermediate
-    SConscript file,
-    in which case the SConscript call in
-    the top-level SConstruct file
-    would look like:
-
-    

      SConscript(['drivers/SConscript',
-                  'parser/SConscript',
-                  'utilities/SConscript'])
-    

-    And the subsidiary SConscript file in the
-    drivers subdirectory
-    would look like:
-
-    

      SConscript(['display/SConscript',
-                  'mouse/SConscript'])
-    

-    Whether you list all of the SConscript files in the
-    top-level SConstruct file,
-    or place a subsidiary SConscript file in
-    intervening directories,
-    or use some mix of the two schemes,
-    is up to you and the needs of your software.
-
-    
16.2. Path Names Are Relative to the SConscript Directory

-    Subsidiary SConscript files make it easy to create a build
-    hierarchy because all of the file and directory names
-    in a subsidiary SConscript files are interpreted
-    relative to the directory in which the SConscript file lives.
-    Typically, this allows the SConscript file containing the
-    instructions to build a target file
-    to live in the same directory as the source files
-    from which the target will be built,
-    making it easy to update how the software is built
-    whenever files are added or deleted
-    (or other changes are made).
-
-    

-    For example, suppose we want to build two programs
-    prog1 and prog2 in two separate directories
-    with the same names as the programs.
-    One typical way to do this would be
-    with a top-level SConstruct file like this:
-
-    

      SConscript(['prog1/SConscript',
-                  'prog2/SConscript'])
-    

-    And subsidiary SConscript files that look like this:
-
-    

      env = Environment()
-      env.Program('prog1', ['main.c', 'foo1.c', 'foo2.c'])
-      

-    And this:
-
-    

      env = Environment()
-      env.Program('prog2', ['main.c', 'bar1.c', 'bar2.c'])
-      

-    Then, when we run SCons in the top-level directory,
-    our build looks like:
-
-    

       % scons -Q
-       cc -o prog1/foo1.o -c prog1/foo1.c
-       cc -o prog1/foo2.o -c prog1/foo2.c
-       cc -o prog1/main.o -c prog1/main.c
-       cc -o prog1/prog1 prog1/main.o prog1/foo1.o prog1/foo2.o
-       cc -o prog2/bar1.o -c prog2/bar1.c
-       cc -o prog2/bar2.o -c prog2/bar2.c
-       cc -o prog2/main.o -c prog2/main.c
-       cc -o prog2/prog2 prog2/main.o prog2/bar1.o prog2/bar2.o
-    

-    Notice the following:
-
-    First, you can have files with the same names
-    in multiple directories, like main.c in the above example.
-
-    Second, unlike standard recursive use of Make,
-    SCons stays in the top-level directory
-    (where the SConstruct file lives)
-    and issues commands that use the path names
-    from the top-level directory to the
-    target and source files within the hierarchy.
-
-    
16.3. Top-Level Path Names in Subsidiary SConscript Files

-    If you need to use a file from another directory,
-    it's sometimes more convenient to specify
-    the path to a file in another directory
-    from the top-level SConstruct directory,
-    even when you're using that file in
-    a subsidiary SConscript file in a subdirectory.
-    You can tell SCons to interpret a path name
-    as relative to the top-level SConstruct directory,
-    not the local directory of the SConscript file,
-    by appending a # (hash mark)
-    to the beginning of the path name:
-
-    

       env = Environment()
-       env.Program('prog', ['main.c', '#lib/foo1.c', 'foo2.c'])
-    

-    In this example,
-    the lib directory is
-    directly underneath the top-level SConstruct directory.
-    If the above SConscript file is in a subdirectory
-    named src/prog,
-    the output would look like:
-
-    

       % scons -Q
-       cc -o lib/foo1.o -c lib/foo1.c
-       cc -o src/prog/foo2.o -c src/prog/foo2.c
-       cc -o src/prog/main.o -c src/prog/main.c
-       cc -o src/prog/prog src/prog/main.o lib/foo1.o src/prog/foo2.o
-    

-    (Notice that the lib/foo1.o object file
-    is built in the same directory as its source file.
-    See Chapter 17, below,
-    for information about
-    how to build the object file in a different subdirectory.)
-
-    
16.4. Absolute Path Names

-    Of course, you can always specify
-    an absolute path name for a file--for example:
-
-    

       env = Environment()
-       env.Program('prog', ['main.c', '/usr/joe/lib/foo1.c', 'foo2.c'])
-    

-    Which, when executed, would yield:
-
-    

       % scons -Q
-       cc -o src/prog/foo2.o -c src/prog/foo2.c
-       cc -o src/prog/main.o -c src/prog/main.c
-       cc -o /usr/joe/lib/foo1.o -c /usr/joe/lib/foo1.c
-       cc -o src/prog/prog src/prog/main.o /usr/joe/lib/foo1.o src/prog/foo2.o
-    

-    (As was the case with top-relative path names,
-    notice that the /usr/joe/lib/foo1.o object file
-    is built in the same directory as its source file.
-    See Chapter 17, below,
-    for information about
-    how to build the object file in a different subdirectory.)
-
-    
16.5. Sharing Environments (and Other Variables) Between SConscript Files

-    In the previous example,
-    each of the subsidiary SConscript files
-    created its own construction environment
-    by calling Environment separately.
-    This obviously works fine,
-    but if each program must be built
-    with the same construction variables,
-    it's cumbersome and error-prone to initialize
-    separate construction environments
-    in the same way over and over in each subsidiary
-    SConscript file.
-
-    

-    SCons supports the ability to export variables
-    from a parent SConscript file
-    to its subsidiary SConscript files,
-    which allows you to share common initialized
-    values throughout your build hierarchy.
-
-    
16.5.1. Exporting Variables

-      There are two ways to export a variable,
-      such as a construction environment,
-      from an SConscript file,
-      so that it may be used by other SConscript files.
-      First, you can call the Export
-      function with a list of variables,
-      or a string of white-space separated variable names.
-      Each call to Export adds one
-      or more variables to a global list
-      of variables that are available for import
-      by other SConscript files.
-
-      

        env = Environment()
-        Export('env')
-      

-      You may export more than one variable name at a time:
-
-      

        env = Environment()
-        debug = ARGUMENTS['debug']
-        Export('env', 'debug')
-      

-      Because white space is not legal in Python variable names,
-      the Export function will even automatically split
-      a string into separate names for you:
-
-      

        Export('env debug')
-      

-      Second, you can specify a list of
-      variables to export as a second argument
-      to the SConscript function call:
-
-      

        SConscript('src/SConscript', 'env')
-      

-      Or as the exports keyword argument:
-
-      

        SConscript('src/SConscript', exports='env')
-      

-      These calls export the specified variables
-      to only the listed SConscript files.
-      You may, however, specify more than one
-      SConscript file in a list:
-
-      

        SConscript(['src1/SConscript',
-                    'src2/SConscript'], exports='env')
-      

-      This is functionally equivalent to
-      calling the SConscript function
-      multiple times with the same exports argument,
-      one per SConscript file.
-
-      
16.5.2. Importing Variables

-      Once a variable has been exported from a calling
-      SConscript file,
-      it may be used in other SConscript files
-      by calling the Import function:
-
-      

        Import('env')
-        env.Program('prog', ['prog.c'])
-      

-      The Import call makes the env construction
-      environment available to the SConscript file,
-      after which the variable can be used to build
-      programs, libraries, etc.
-
-      

-      Like the Export function,
-      the Import function can be used
-      with multiple variable names:
-
-      

        Import('env', 'debug')
-        env = env.Clone(DEBUG = debug)
-        env.Program('prog', ['prog.c'])
-      

-      And the Import function will similarly
-      split a string along white-space
-      into separate variable names:
-
-      

        Import('env debug')
-        env = env.Clone(DEBUG = debug)
-        env.Program('prog', ['prog.c'])
-      

-      Lastly, as a special case,
-      you may import all of the variables that
-      have been exported by supplying an asterisk
-      to the Import function:
-
-      

        Import('*')
-        env = env.Clone(DEBUG = debug)
-        env.Program('prog', ['prog.c'])
-      

-      If you're dealing with a lot of SConscript files,
-      this can be a lot simpler than keeping
-      arbitrary lists of imported variables in each file.
-
-      
16.5.3. Returning Values From an SConscript File

-      Sometimes, you would like to be able to
-      use information from a subsidiary
-      SConscript file in some way.
-      For example,
-      suppose that you want to create one
-      library from source files
-      scattered throughout a number
-      of subsidiary SConscript files.
-      You can do this by using the Return
-      function to return values
-      from the subsidiary SConscript files
-      to the calling file.
-
-      

-      If, for example, we have two subdirectories
-      foo and bar
-      that should each contribute a source
-      file to a Library,
-      what we'd like to be able to do is
-      collect the object files
-      from the subsidiary SConscript calls
-      like this:
-
-      

          env = Environment()
-          Export('env')
-          objs = []
-          for subdir in ['foo', 'bar']:
-              o = SConscript('%s/SConscript' % subdir)
-              objs.append(o)
-          env.Library('prog', objs)
-      

-      We can do this by using the Return
-      function in the
-      foo/SConscript file like this:
-
-      

          Import('env')
-          obj = env.Object('foo.c')
-          Return('obj')
-        

-      (The corresponding
-      bar/SConscript
-      file should be pretty obvious.)
-      Then when we run SCons,
-      the object files from the subsidiary subdirectories
-      are all correctly archived in the desired library:
-
-      

        % scons -Q
-        cc -o bar/bar.o -c bar/bar.c
-        cc -o foo/foo.o -c foo/foo.c
-        ar rc libprog.a foo/foo.o bar/bar.o
-        ranlib libprog.a
-      
Chapter 17. Separating Source and Build Directories

-  It's often useful to keep any built files completely
-  separate from the source files.
-  In SCons, this is usually done by creating one or more separate
-  variant directory trees
-  that are used to hold the built objects files, libraries,
-  and executable programs, etc.
-  for a specific flavor, or variant, of build.
-  SCons provides two ways to do this,
-  one through the SConscript function that we've already seen,
-  and the second through a more flexible VariantDir function.
-
-  

-  One historical note:  the VariantDir function
-  used to be called BuildDir.
-  That name is still supported
-  but has been deprecated
-  because the SCons functionality
-  differs from the model of a "build directory"
-  implemented by other build systems like the GNU Autotools.
-
-  
17.1. Specifying a Variant Directory Tree as Part of an SConscript Call

-    The most straightforward way to establish a variant directory tree
-    uses the fact that the usual way to
-    set up a build hierarchy is to have an
-    SConscript file in the source subdirectory.
-    If you then pass a variant_dir argument to the
-    SConscript function call:
-
-    

      SConscript('src/SConscript', variant_dir='build')
-    

-    SCons will then build all of the files in
-    the build subdirectory:
-
-    

      % ls src
-      SConscript  hello.c
-      % scons -Q
-      cc -o build/hello.o -c build/hello.c
-      cc -o build/hello build/hello.o
-      % ls build
-      SConscript  hello  hello.c  hello.o
-    

-    But wait a minute--what's going on here?
-    SCons created the object file
-    build/hello.o
-    in the build subdirectory,
-    as expected.
-    But even though our hello.c file lives in the src subdirectory,
-    SCons has actually compiled a
-    build/hello.c file
-    to create the object file.
-
-    

-    What's happened is that SCons has duplicated
-    the hello.c file from the src subdirectory
-    to the build subdirectory,
-    and built the program from there.
-    The next section explains why SCons does this.
-
-    
17.2. Why SCons Duplicates Source Files in a Variant Directory Tree

-    SCons duplicates source files in variant directory trees
-    because it's the most straightforward way to guarantee a correct build
-    regardless of include-file directory paths,
-    relative references between files,
-    or tool support for putting files in different locations,
-    and the SCons philosophy is to, by default,
-    guarantee a correct build in all cases.
-
-    

-    The most direct reason to duplicate source files
-    in variant directories
-    is simply that some tools (mostly older vesions)
-    are written to only build their output files
-    in the same directory as the source files.
-    In this case, the choices are either
-    to build the output file in the source directory
-    and move it to the variant directory,
-    or to duplicate the source files in the variant directory.
-
-    

-    Additionally,
-    relative references between files
-    can cause problems if we don't
-    just duplicate the hierarchy of source files
-    in the variant directory.
-    You can see this at work in
-    use of the C preprocessor #include
-    mechanism with double quotes, not angle brackets:
-
-    

      #include "file.h"
-    

-    The de facto standard behavior
-    for most C compilers in this case
-    is to first look in the same directory
-    as the source file that contains the #include line,
-    then to look in the directories in the preprocessor search path.
-    Add to this that the SCons implementation of
-    support for code repositories
-    (described below)
-    means not all of the files
-    will be found in the same directory hierarchy,
-    and the simplest way to make sure
-    that the right include file is found
-    is to duplicate the source files into the variant directory,
-    which provides a correct build
-    regardless of the original location(s) of the source files.
-
-    

-    Although source-file duplication guarantees a correct build
-    even in these end-cases,
-    it can usually be safely disabled.
-    The next section describes
-    how you can disable the duplication of source files
-    in the variant directory.
-
-    
17.3. Telling SCons to Not Duplicate Source Files in the Variant Directory Tree

-    In most cases and with most tool sets,
-    SCons can place its target files in a build subdirectory
-    without
-    duplicating the source files
-    and everything will work just fine.
-    You can disable the default SCons behavior
-    by specifying duplicate=0
-    when you call the SConscript function:
-
-    

      SConscript('src/SConscript', variant_dir='build', duplicate=0)
-    

-    When this flag is specified,
-    SCons uses the variant directory
-    like most people expect--that is,
-    the output files are placed in the variant directory
-    while the source files stay in the source directory:
-
-    

      % ls src
-      SConscript
-      hello.c
-      % scons -Q
-      cc -c src/hello.c -o build/hello.o
-      cc -o build/hello build/hello.o
-      % ls build
-      hello
-      hello.o
-    
17.4. The VariantDir Function

-    Use the VariantDir function to establish that target
-    files should be built in a separate directory
-    from the source files:
-
-    

      VariantDir('build', 'src')
-      env = Environment()
-      env.Program('build/hello.c')
-    

-    Note that when you're not using
-    an SConscript file in the src subdirectory,
-    you must actually specify that
-    the program must be built from
-    the build/hello.c
-    file that SCons will duplicate in the
-    build subdirectory.
-
-    

-    When using the VariantDir function directly,
-    SCons still duplicates the source files
-    in the variant directory by default:
-
-    

      % ls src
-      hello.c
-      % scons -Q
-      cc -o build/hello.o -c build/hello.c
-      cc -o build/hello build/hello.o
-      % ls build
-      hello  hello.c  hello.o
-    

-    You can specify the same duplicate=0 argument
-    that you can specify for an SConscript call:
-
-    

      VariantDir('build', 'src', duplicate=0)
-      env = Environment()
-      env.Program('build/hello.c')
-    

-    In which case SCons
-    will disable duplication of the source files:
-
-    

      % ls src
-      hello.c
-      % scons -Q
-      cc -o build/hello.o -c src/hello.c
-      cc -o build/hello build/hello.o
-      % ls build
-      hello  hello.o
-    
17.5. Using VariantDir With an SConscript File

-    Even when using the VariantDir function,
-    it's much more natural to use it with
-    a subsidiary SConscript file.
-    For example, if the
-    src/SConscript
-    looks like this:
-
-    

      env = Environment()
-      env.Program('hello.c')
-    

-    Then our SConstruct file could look like:
-
-    

      VariantDir('build', 'src')
-      SConscript('build/SConscript')
-      

-    Yielding the following output:
-
-    

      % ls src
-      SConscript  hello.c
-      % scons -Q
-      cc -o build/hello.o -c build/hello.c
-      cc -o build/hello build/hello.o
-      % ls build
-      SConscript  hello  hello.c  hello.o
-    

-    Notice that this is completely equivalent
-    to the use of SConscript that we
-    learned about in the previous section.
-
-    
17.6. Using Glob with VariantDir

-    The Glob file name pattern matching function
-    works just as usual when using VariantDir.
-    For example, if the
-    src/SConscript
-    looks like this:
-
-    

      env = Environment()
-      env.Program('hello', Glob('*.c'))
-    

-    Then with the same SConstruct file as in the previous section,
-    and source files f1.c
-    and f2.c in src,
-    we would see the following output:
-
-    

      % ls src
-      SConscript  f1.c  f2.c  f2.h
-      % scons -Q
-      cc -o build/f1.o -c build/f1.c
-      cc -o build/f2.o -c build/f2.c
-      cc -o build/hello build/f1.o build/f2.o
-      % ls build
-      SConscript  f1.c  f1.o  f2.c  f2.h  f2.o  hello
-    

-    The Glob function returns Nodes in the
-    build/ tree, as you'd expect.
-
-    
Chapter 18. Variant Builds

-  The variant_dir keyword argument of
-  the SConscript function provides everything
-  we need to show how easy it is to create
-  variant builds using SCons.
-  Suppose, for example, that we want to
-  build a program for both Windows and Linux platforms,
-  but that we want to build it in a shared directory
-  with separate side-by-side build directories
-  for the Windows and Linux versions of the program.
-
-  

    platform = ARGUMENTS.get('OS', Platform())
-
-    include = "#export/$PLATFORM/include"
-    lib = "#export/$PLATFORM/lib"
-    bin = "#export/$PLATFORM/bin"
-
-    env = Environment(PLATFORM = platform,
-                      BINDIR = bin,
-                      INCDIR = include,
-                      LIBDIR = lib,
-                      CPPPATH = [include],
-                      LIBPATH = [lib],
-                      LIBS = 'world')
-
-    Export('env')
-
-    env.SConscript('src/SConscript', variant_dir='build/$PLATFORM')
-  

-  This SConstruct file,
-  when run on a Linux system, yields:
-
-  

    % scons -Q OS=linux
-    Install file: "build/linux/world/world.h" as "export/linux/include/world.h"
-    cc -o build/linux/hello/hello.o -c -Iexport/linux/include build/linux/hello/hello.c
-    cc -o build/linux/world/world.o -c -Iexport/linux/include build/linux/world/world.c
-    ar rc build/linux/world/libworld.a build/linux/world/world.o
-    ranlib build/linux/world/libworld.a
-    Install file: "build/linux/world/libworld.a" as "export/linux/lib/libworld.a"
-    cc -o build/linux/hello/hello build/linux/hello/hello.o -Lexport/linux/lib -lworld
-    Install file: "build/linux/hello/hello" as "export/linux/bin/hello"
-  

-  The same SConstruct file on Windows would build:
-
-  

    C:\>scons -Q OS=windows
-    Install file: "build/windows/world/world.h" as "export/windows/include/world.h"
-    cl /nologo /Iexport\windows\include /c build\windows\hello\hello.c /Fobuild\windows\hello\hello.obj
-    cl /nologo /Iexport\windows\include /c build\windows\world\world.c /Fobuild\windows\world\world.obj
-    lib /nologo /OUT:build\windows\world\world.lib build\windows\world\world.obj
-    Install file: "build/windows/world/world.lib" as "export/windows/lib/world.lib"
-    link /nologo /OUT:build\windows\hello\hello.exe /LIBPATH:export\windows\lib world.lib build\windows\hello\hello.obj
-    Install file: "build/windows/hello/hello.exe" as "export/windows/bin/hello.exe"
-  
Chapter 19. Writing Your Own Builders

-  Although SCons provides many useful methods
-  for building common software products:
-  programs, libraries, documents.
-  you frequently want to be
-  able to build some other type of file
-  not supported directly by SCons
-  Fortunately, SCons makes it very easy
-  to define your own Builder objects
-  for any custom file types you want to build.
-  (In fact, the SCons interfaces for creating
-  Builder objects are flexible enough and easy enough to use
-  that all of the the SCons built-in Builder objects
-  are created the mechanisms described in this section.)
-
-  
19.1. Writing Builders That Execute External Commands

-    The simplest Builder to create is
-    one that executes an external command.
-    For example, if we want to build
-    an output file by running the contents
-    of the input file through a command named
-    foobuild,
-    creating that Builder might look like:
-
-    

       bld = Builder(action = 'foobuild < $SOURCE > $TARGET')
-    

-    All the above line does is create a free-standing
-    Builder object.
-    The next section will show us how to actually use it.
-
-    
19.2. Attaching a Builder to a Construction Environment

-    A Builder object isn't useful
-    until it's attached to a construction environment
-    so that we can call it to arrange
-    for files to be built.
-    This is done through the $BUILDERS
-    construction variable in an environment.
-    The $BUILDERS variable is a Python dictionary
-    that maps the names by which you want to call
-    various Builder objects to the objects themselves.
-    For example, if we want to call the
-    Builder we just defined by the name
-    Foo,
-    our SConstruct file might look like:
-
-    

       bld = Builder(action = 'foobuild < $SOURCE > $TARGET')
-       env = Environment(BUILDERS = {'Foo' : bld})
-    

-    With the Builder so attached to our construction environment
-    we can now actually call it like so:
-
-    

       env.Foo('file.foo', 'file.input')
-    

-    Then when we run SCons it looks like:
-
-    

      % scons -Q
-      foobuild < file.input > file.foo
-    

-    Note, however, that the default $BUILDERS
-    variable in a construction environment
-    comes with a default set of Builder objects
-    already defined:
-    Program, Library, etc.
-    And when we explicitly set the $BUILDERS variable
-    when we create the construction environment,
-    the default Builders are no longer part of
-    the environment:
-
-    

       bld = Builder(action = 'foobuild < $SOURCE > $TARGET')
-       env = Environment(BUILDERS = {'Foo' : bld})
-       env.Foo('file.foo', 'file.input')
-       env.Program('hello.c')
-    

      % scons -Q
-      AttributeError: SConsEnvironment instance has no attribute 'Program':
-        File "/home/my/project/SConstruct", line 4:
-          env.Program('hello.c')
-    

-    To be able to use both our own defined Builder objects
-    and the default Builder objects in the same construction environment,
-    you can either add to the $BUILDERS variable
-    using the Append function:
-
-    

       env = Environment()
-       bld = Builder(action = 'foobuild < $SOURCE > $TARGET')
-       env.Append(BUILDERS = {'Foo' : bld})
-       env.Foo('file.foo', 'file.input')
-       env.Program('hello.c')
-    

-    Or you can explicitly set the appropriately-named
-    key in the $BUILDERS dictionary:
-
-    

       env = Environment()
-       bld = Builder(action = 'foobuild < $SOURCE > $TARGET')
-       env['BUILDERS']['Foo'] = bld
-       env.Foo('file.foo', 'file.input')
-       env.Program('hello.c')
-    

-    Either way, the same construction environment
-    can then use both the newly-defined
-    Foo Builder
-    and the default Program Builder:
-
-    

      % scons -Q
-      foobuild < file.input > file.foo
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-    
19.3. Letting SCons Handle The File Suffixes

-    By supplying additional information
-    when you create a Builder,
-    you can let SCons add appropriate file
-    suffixes to the target and/or the source file.
-    For example, rather than having to specify
-    explicitly that you want the Foo
-    Builder to build the file.foo
-    target file from the file.input source file,
-    you can give the .foo
-    and .input suffixes to the Builder,
-    making for more compact and readable calls to
-    the Foo Builder:
-
-    

       bld = Builder(action = 'foobuild < $SOURCE > $TARGET',
-                     suffix = '.foo',
-                     src_suffix = '.input')
-       env = Environment(BUILDERS = {'Foo' : bld})
-       env.Foo('file1')
-       env.Foo('file2')
-    

      % scons -Q
-      foobuild < file1.input > file1.foo
-      foobuild < file2.input > file2.foo
-    

-    You can also supply a prefix keyword argument
-    if it's appropriate to have SCons append a prefix
-    to the beginning of target file names.
-
-    
19.4. Builders That Execute Python Functions

-    In SCons, you don't have to call an external command
-    to build a file.
-    You can, instead, define a Python function
-    that a Builder object can invoke
-    to build your target file (or files).
-    Such a builder function definition looks like:
-
-    

       def build_function(target, source, env):
-           # Code to build "target" from "source"
-           return None
-    

-    The arguments of a builder function are:
-
-    
target

-      A list of Node objects representing
-      the target or targets to be
-      built by this builder function.
-      The file names of these target(s)
-      may be extracted using the Python str function.
-
-      
source

-      A list of Node objects representing
-      the sources to be
-      used by this builder function to build the targets.
-      The file names of these source(s)
-      may be extracted using the Python str function.
-
-      
env

-      The construction environment used for building the target(s).
-      The builder function may use any of the
-      environment's construction variables
-      in any way to affect how it builds the targets.
-
-      

-    The builder function must
-    return a 0 or None value
-    if the target(s) are built successfully.
-    The builder function
-    may raise an exception
-    or return any non-zero value
-    to indicate that the build is unsuccessful,
-
-    

-    Once you've defined the Python function
-    that will build your target file,
-    defining a Builder object for it is as
-    simple as specifying the name of the function,
-    instead of an external command,
-    as the Builder's
-    action
-    argument:
-
-    

       def build_function(target, source, env):
-           # Code to build "target" from "source"
-           return None
-       bld = Builder(action = build_function,
-                     suffix = '.foo',
-                     src_suffix = '.input')
-       env = Environment(BUILDERS = {'Foo' : bld})
-       env.Foo('file')
-    

-    And notice that the output changes slightly,
-    reflecting the fact that a Python function,
-    not an external command,
-    is now called to build the target file:
-
-    

      % scons -Q
-      build_function(["file.foo"], ["file.input"])
-    
19.5. Builders That Create Actions Using a Generator

-    SCons Builder objects can create an action "on the fly"
-    by using a function called a generator.
-    This provides a great deal of flexibility to
-    construct just the right list of commands
-    to build your target.
-    A generator looks like:
-
-    

       def generate_actions(source, target, env, for_signature):
-           return 'foobuild < %s > %s' % (target[0], source[0])
-    

-    The arguments of a generator are:
-
-    
source

-      A list of Node objects representing
-      the sources to be built
-      by the command or other action
-      generated by this function.
-      The file names of these source(s)
-      may be extracted using the Python str function.
-
-      
target

-      A list of Node objects representing
-      the target or targets to be built
-      by the command or other action
-      generated by this function.
-      The file names of these target(s)
-      may be extracted using the Python str function.
-
-      
env

-      The construction environment used for building the target(s).
-      The generator may use any of the
-      environment's construction variables
-      in any way to determine what command
-      or other action to return.
-
-      
for_signature

-      A flag that specifies whether the
-      generator is being called to contribute to a build signature,
-      as opposed to actually executing the command.
-
-      
-
-      

-    The generator must return a
-    command string or other action that will be used to
-    build the specified target(s) from the specified source(s).
-
-    

-    Once you've defined a generator,
-    you create a Builder to use it
-    by specifying the generator keyword argument
-    instead of action.
-
-    

       def generate_actions(source, target, env, for_signature):
-           return 'foobuild < %s > %s' % (source[0], target[0])
-       bld = Builder(generator = generate_actions,
-                     suffix = '.foo',
-                     src_suffix = '.input')
-       env = Environment(BUILDERS = {'Foo' : bld})
-       env.Foo('file')
-    

      % scons -Q
-      foobuild < file.input > file.foo
-    

-    Note that it's illegal to specify both an
-    action
-    and a
-    generator
-    for a Builder.
-
-    
19.6. Builders That Modify the Target or Source Lists Using an Emitter

-    SCons supports the ability for a Builder to modify the
-    lists of target(s) from the specified source(s).
-    You do this by defining an emitter function
-    that takes as its arguments
-    the list of the targets passed to the builder,
-    the list of the sources passed to the builder,
-    and the construction environment.
-    The emitter function should return the modified
-    lists of targets that should be built
-    and sources from which the targets will be built.
-
-    

-    For example, suppose you want to define a Builder
-    that always calls a foobuild program,
-    and you want to automatically add
-    a new target file named
-    new_target
-    and a new source file named
-    new_source
-    whenever it's called.
-    The SConstruct file might look like this:
-
-    

       def modify_targets(target, source, env):
-           target.append('new_target')
-           source.append('new_source')
-           return target, source
-       bld = Builder(action = 'foobuild $TARGETS - $SOURCES',
-                     suffix = '.foo',
-                     src_suffix = '.input',
-                     emitter = modify_targets)
-       env = Environment(BUILDERS = {'Foo' : bld})
-       env.Foo('file')
-    

    
-    And would yield the following output:
-
-    

      % scons -Q
-      foobuild file.foo new_target - file.input new_source
-    

-    One very flexible thing that you can is specify
-    use a construction variable to specify
-    different emitter functions for different
-    construction variable.
-    To do this, specify a string
-    containing a construction variable
-    expansion as the emitter when you call
-    the Builder function,
-    and set that construction variable to
-    the desired emitter function
-    in different construction environments:
-
-    

        bld = Builder(action = 'my_command $SOURCES > $TARGET',
-                      suffix = '.foo',
-                      src_suffix = '.input',
-                      emitter = '$MY_EMITTER')
-        def modify1(target, source, env):
-            return target, source + ['modify1.in']
-        def modify2(target, source, env):
-            return target, source + ['modify2.in']
-        env1 = Environment(BUILDERS = {'Foo' : bld},
-                           MY_EMITTER = modify1)
-        env2 = Environment(BUILDERS = {'Foo' : bld},
-                           MY_EMITTER = modify2)
-        env1.Foo('file1')
-        env2.Foo('file2')
-        import os
-        env1['ENV']['PATH'] = env2['ENV']['PATH'] + os.pathsep + os.getcwd()
-        env2['ENV']['PATH'] = env2['ENV']['PATH'] + os.pathsep + os.getcwd()
-      
-
-    

      bld = Builder(action = 'my_command $SOURCES > $TARGET',
-                    suffix = '.foo',
-                    src_suffix = '.input',
-                    emitter = '$MY_EMITTER')
-      def modify1(target, source, env):
-          return target, source + ['modify1.in']
-      def modify2(target, source, env):
-          return target, source + ['modify2.in']
-      env1 = Environment(BUILDERS = {'Foo' : bld},
-                         MY_EMITTER = modify1)
-      env2 = Environment(BUILDERS = {'Foo' : bld},
-                         MY_EMITTER = modify2)
-      env1.Foo('file1')
-      env2.Foo('file2')
-      
-    

-    In this example, the modify1.in
-    and modify2.in files
-    get added to the source lists
-    of the different commands:
-
-    

      % scons -Q
-      my_command file1.input modify1.in > file1.foo
-      my_command file2.input modify2.in > file2.foo
-    
19.7. Where To Put Your Custom Builders and Tools

-  The site_scons directory gives you a place to
-  put Python modules you can import into your SConscripts
-  (site_scons), add-on tools that can integrate into SCons
-  (site_scons/site_tools), and a site_scons/site_init.py file that
-  gets read before any SConstruct or SConscript, allowing you to
-  change SCons's default behavior.
-
-  

-  If you get a tool from somewhere (the SCons wiki or a third party,
-  for instance) and you'd like to use it in your project, the
-  site_scons dir is the simplest place to put it.
-  Tools come in two flavors; either a Python function that operates on
-  an Environment or a Python file containing two functions, exists()
-  and generate().
-
-  

-  A single-function Tool can just be included in your
-  site_scons/site_init.py file where it will be
-  parsed and made available for use.  For instance, you could have a
-  site_scons/site_init.py file like this:
-
-  

      def TOOL_ADD_HEADER(env):
-         """A Tool to add a header from $HEADER to the source file"""
-         add_header = Builder(action=['echo "$HEADER" > $TARGET',
-                                      'cat $SOURCE >> $TARGET'])
-         env.Append(BUILDERS = {'AddHeader' : add_header})
-         env['HEADER'] = '' # set default value
-  

-  and a SConstruct like this:
-
-  

      # Use TOOL_ADD_HEADER from site_scons/site_init.py
-      env=Environment(tools=['default', TOOL_ADD_HEADER], HEADER="=====")
-      env.AddHeader('tgt', 'src')
-  

-    The TOOL_ADD_HEADER tool method will be
-    called to add the AddHeader tool to the
-    environment.
-
-  

    Similarly, a more full-fledged tool with
-    exists() and generate()
-    methods can be installed in
-    site_scons/site_tools/toolname.py.  Since
-    site_scons/site_tools is automatically added
-    to the head of the tool search path, any tool found there will be
-    available to all environments.  Furthermore, a tool found there
-    will override a built-in tool of the same name, so if you need to
-    change the behavior of a built-in tool, site_scons gives you the
-    hook you need.
-  

    Many people have a library of utility Python functions they'd like
-    to include in SConscripts; just put that module in
-    site_scons/my_utils.py or any valid Python module name of your
-    choice.  For instance you can do something like this in
-    site_scons/my_utils.py to add a build_id method:
-  

      def build_id():
-         """Return a build ID (stub version)"""
-         return "100"
-  

-  And then in your SConscript or any sub-SConscript anywhere in
-  your build, you can import my_utils and use it:
-
-  

      import my_utils
-      print "build_id=" + my_utils.build_id()
-  

-    If you have a machine-wide site dir you'd like to use instead of
-    ./site_scons, use the
-    --site-dir option to point to your dir.
-    site_init.py and
-    site_tools will be located under that dir.
-    To avoid using a site_scons dir at all, even
-    if it exists, use the --no-site-dir option.
-
-  
Chapter 20. Not Writing a Builder:  the Command Builder

-  Creating a Builder and attaching it to a construction environment
-  allows for a lot of flexibility when you
-  want to re-use actions
-  to build multiple files of the same type.
-  This can, however, be cumbersome
-  if you only need to execute one specific command
-  to build a single file (or group of files).
-  For these situations, SCons supports a
-  Command Builder that arranges
-  for a specific action to be executed
-  to build a specific file or files.
-  This looks a lot like the other builders
-  (like Program, Object, etc.),
-  but takes as an additional argument
-  the command to be executed to build the file:
-
-  

     env = Environment()
-     env.Command('foo.out', 'foo.in', "sed 's/x/y/' < $SOURCE > $TARGET")
-  

-  When executed,
-  SCons runs the specified command,
-  substituting $SOURCE and $TARGET
-  as expected:
-
-  

    % scons -Q
-    sed 's/x/y/' < foo.in > foo.out
-  

-  This is often more convenient than
-  creating a Builder object
-  and adding it to the $BUILDERS variable
-  of a construction environment
-
-  

-  Note that the action you specify to the
-  Command Builder can be any legal SCons Action,
-  such as a Python function:
-
-  

     env = Environment()
-     def build(target, source, env):
-         # Whatever it takes to build
-         return None
-     env.Command('foo.out', 'foo.in', build)
-  

-  Which executes as follows:
-
-  

    % scons -Q
-    build(["foo.out"], ["foo.in"])
-  
Chapter 21. Pseudo-Builders:  the AddMethod function

-  The AddMethod function is used to add a method
-  to an environment.  It's typically used to add a "pseudo-builder,"
-  a function that looks like a Builder but
-  wraps up calls to multiple other Builders
-  or otherwise processes its arguments
-  before calling one or more Builders.
-  In the following example,
-  we want to install the program into the standard
-  /usr/bin directory hierarchy,
-  but also copy it into a local install/bin
-  directory from which a package might be built:
-
-  

     def install_in_bin_dirs(env, source):
-         """Install source in both bin dirs"""
-         i1 = env.Install("$BIN", source)
-         i2 = env.Install("$LOCALBIN", source)
-         return [i1[0], i2[0]] # Return a list, like a normal builder
-     env = Environment(BIN='/usr/bin', LOCALBIN='#install/bin')
-     env.AddMethod(install_in_bin_dirs, "InstallInBinDirs")
-     env.InstallInBinDirs(Program('hello.c')) # installs hello in both bin dirs     
-  

  This produces the following:
-  

    % scons -Q /
-    cc -o hello.o -c hello.c
-    cc -o hello hello.o
-    Install file: "hello" as "/usr/bin/hello"
-    Install file: "hello" as "install/bin/hello"
-  

-  As mentioned, a psuedo-builder also provides more flexibility
-  in parsing arguments than you can get with a Builder.
-  The next example shows a pseudo-builder with a
-  named argument that modifies the filename, and a separate argument
-  for the resource file (rather than having the builder figure it out
-  by file extension).  This example also demonstrates using the global
-  AddMethod function to add a method to the global Environment class,
-  so it will be used in all subsequently created environments.
-
-  

     def BuildTestProg(env, testfile, resourcefile, testdir="tests"):
-         """Build the test program;
-         prepends "test_" to src and target,
-         and puts target into testdir."""
-         srcfile = "test_%s.c" % testfile
-         target = "%s/test_%s" % (testdir, testfile)
-         if env['PLATFORM'] == 'win32':
-             resfile = env.RES(resourcefile)
-             p = env.Program(target, [srcfile, resfile])
-         else:
-             p = env.Program(target, srcfile)
-         return p
-     AddMethod(Environment, BuildTestProg)
-
-     env = Environment()
-     env.BuildTestProg('stuff', resourcefile='res.rc')
-  

  This produces the following on Linux:
-  

    % scons -Q
-    cc -o test_stuff.o -c test_stuff.c
-    cc -o tests/test_stuff test_stuff.o
-  

  And the following on Windows:
-  

    C:\>scons -Q
-    rc /fores.res res.rc
-    cl /nologo /c test_stuff.c /Fotest_stuff.obj
-    link /nologo /OUT:tests\test_stuff.exe test_stuff.obj res.res
-  

  Using AddMethod is better than just adding an instance method
-  to a construction environment because it gets called as a proper method,
-  and because AddMethod provides for copying the method
-  to any clones of the construction environment instance.
-  
Chapter 22. Writing Scanners

-    SCons has built-in scanners that know how to look in
-    C, Fortran and IDL source files for information about
-    other files that targets built from those files depend on--for example,
-    in the case of files that use the C preprocessor,
-    the .h files that are specified
-    using #include lines in the source.
-    You can use the same mechanisms that SCons uses to create
-    its built-in scanners to write scanners of your own for file types
-    that SCons does not know how to scan "out of the box."
-
-  
22.1. A Simple Scanner Example

-      Suppose, for example, that we want to create a simple scanner
-      for .foo files.
-      A .foo file contains some text that
-      will be processed,
-      and can include other files on lines that begin
-      with include
-      followed by a file name:
-
-    

      include filename.foo
-    

-      Scanning a file will be handled by a Python function
-      that you must supply.
-      Here is a function that will use the Python
-      re module
-      to scan for the include lines in our example:
-
-    

      import re
-      
-      include_re = re.compile(r'^include\s+(\S+)$', re.M)
-      
-      def kfile_scan(node, env, path, arg):
-          contents = node.get_contents()
-          return include_re.findall(contents)
-    

-      The scanner function must
-      accept the four specified arguments
-      and return a list of implicit dependencies.
-      Presumably, these would be dependencies found
-      from examining the contents of the file,
-      although the function can perform any
-      manipulation at all to generate the list of
-      dependencies.
-
-    
node

-      An SCons node object representing the file being scanned.
-      The path name to the file can be
-      used by converting the node to a string
-      using the str() function,
-      or an internal SCons get_contents()
-      object method can be used to fetch the contents.
-
-      
env

-      The construction environment in effect for this scan.
-      The scanner function may choose to use construction
-      variables from this environment to affect its behavior.
-
-      
path

-      A list of directories that form the search path for included files
-      for this scanner.
-      This is how SCons handles the $CPPPATH and $LIBPATH
-      variables.
-
-      
arg

-      An optional argument that you can choose to
-      have passed to this scanner function by
-      various scanner instances.
-
-      

-    A Scanner object is created using the Scanner function,
-    which typically takes an skeys argument
-    to associate the type of file suffix with this scanner.
-    The Scanner object must then be associated with the
-    $SCANNERS construction variable of a construction environment,
-    typically by using the Append method:
-
-    

       kscan = Scanner(function = kfile_scan,
-                       skeys = ['.k'])
-       env.Append(SCANNERS = kscan)
-    

-    When we put it all together, it looks like:
-
-    

        import re
-
-        include_re = re.compile(r'^include\s+(\S+)$', re.M)
-
-        def kfile_scan(node, env, path):
-            contents = node.get_contents()
-            includes = include_re.findall(contents)
-            return includes
-
-        kscan = Scanner(function = kfile_scan,
-                        skeys = ['.k'])
-
-        env = Environment(ENV = {'PATH' : '/usr/local/bin'})
-        env.Append(SCANNERS = kscan)
-
-        env.Command('foo', 'foo.k', 'kprocess < $SOURCES > $TARGET')
-    
Chapter 23. Building From Code Repositories

-  Often, a software project will have
-  one or more central repositories,
-  directory trees that contain
-  source code, or derived files, or both.
-  You can eliminate additional unnecessary
-  rebuilds of files by having SCons
-  use files from one or more code repositories
-  to build files in your local build tree.
-
-  
23.1. The Repository Method

-    It's often useful to allow multiple programmers working
-    on a project to build software from
-    source files and/or derived files that
-    are stored in a centrally-accessible repository,
-    a directory copy of the source code tree.
-    (Note that this is not the sort of repository
-    maintained by a source code management system
-    like BitKeeper, CVS, or Subversion.)
-    
-    You use the Repository method
-    to tell SCons to search one or more
-    central code repositories (in order)
-    for any source files and derived files
-    that are not present in the local build tree:
-
-    

       env = Environment()
-       env.Program('hello.c')
-       Repository('/usr/repository1', '/usr/repository2')
-    

-    Multiple calls to the Repository method
-    will simply add repositories to the global list
-    that SCons maintains,
-    with the exception that SCons will automatically eliminate
-    the current directory and any non-existent
-    directories from the list.
-
-    
23.2. Finding source files in repositories

-    The above example
-    specifies that SCons
-    will first search for files under
-    the /usr/repository1 tree
-    and next under the /usr/repository2 tree.
-    SCons expects that any files it searches
-    for will be found in the same position
-    relative to the top-level directory.
-    In the above example, if the hello.c file is not
-    found in the local build tree,
-    SCons will search first for
-    a /usr/repository1/hello.c file
-    and then for a /usr/repository2/hello.c file
-    to use in its place.
-
-    

-    So given the SConstruct file above,
-    if the hello.c file exists in the local
-    build directory,
-    SCons will rebuild the hello program
-    as normal:
-
-    

      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-    

-    If, however, there is no local hello.c file,
-    but one exists in /usr/repository1,
-    SCons will recompile the hello program
-    from the source file it finds in the repository:
-
-    

      % scons -Q
-      cc -o hello.o -c /usr/repository1/hello.c
-      cc -o hello hello.o
-    

-    And similarly, if there is no local hello.c file
-    and no /usr/repository1/hello.c,
-    but one exists in /usr/repository2:
-
-    

      % scons -Q
-      cc -o hello.o -c /usr/repository2/hello.c
-      cc -o hello hello.o
-    

-    
23.3. Finding #include files in repositories

-    We've already seen that SCons will scan the contents of
-    a source file for #include file names
-    and realize that targets built from that source file
-    also depend on the #include file(s).
-    For each directory in the $CPPPATH list,
-    SCons will actually search the corresponding directories
-    in any repository trees and establish the
-    correct dependencies on any
-    #include files that it finds
-    in repository directory.
-
-    

-    Unless the C compiler also knows about these directories
-    in the repository trees, though,
-    it will be unable to find the #include files.
-    If, for example, the hello.c file in
-    our previous example includes the hello.h;
-    in its current directory,
-    and the hello.h; only exists in the repository:
-
-    

      % scons -Q
-      cc -o hello.o -c hello.c
-      hello.c:1: hello.h: No such file or directory
-    

-    In order to inform the C compiler about the repositories,
-    SCons will add appropriate
-    -I flags to the compilation commands
-    for each directory in the $CPPPATH list.
-    So if we add the current directory to the
-    construction environment $CPPPATH like so:
-
-    

       env = Environment(CPPPATH = ['.'])
-       env.Program('hello.c')
-       Repository('/usr/repository1')
-    

-    Then re-executing SCons yields:
-
-    

      % scons -Q
-      cc -o hello.o -c -I. -I/usr/repository1 hello.c
-      cc -o hello hello.o
-    

-    The order of the -I options replicates,
-    for the C preprocessor,
-    the same repository-directory search path
-    that SCons uses for its own dependency analysis.
-    If there are multiple repositories and multiple $CPPPATH
-    directories, SCons will add the repository directories
-    to the beginning of each $CPPPATH directory,
-    rapidly multiplying the number of -I flags.
-    If, for example, the $CPPPATH contains three directories
-    (and shorter repository path names!):
-
-    

       env = Environment(CPPPATH = ['dir1', 'dir2', 'dir3'])
-       env.Program('hello.c')
-       Repository('/r1', '/r2')
-    

-    Then we'll end up with nine -I options
-    on the command line,
-    three (for each of the $CPPPATH directories)
-    times three (for the local directory plus the two repositories):
-
-    

      % scons -Q
-      cc -o hello.o -c -Idir1 -I/r1/dir1 -I/r2/dir1 -Idir2 -I/r1/dir2 -I/r2/dir2 -Idir3 -I/r1/dir3 -I/r2/dir3 hello.c
-      cc -o hello hello.o
-    
23.3.1. Limitations on #include files in repositories

-      SCons relies on the C compiler's
-      -I options to control the order in which
-      the preprocessor will search the repository directories
-      for #include files.
-      This causes a problem, however, with how the C preprocessor
-      handles #include lines with
-      the file name included in double-quotes.
-
-      

-      As we've seen,
-      SCons will compile the hello.c file from
-      the repository if it doesn't exist in
-      the local directory.
-      If, however, the hello.c file in the repository contains
-      a #include line with the file name in
-      double quotes:
-
-      

        #include "hello.h"
-        int
-        main(int argc, char *argv[])
-        {
-            printf(HELLO_MESSAGE);
-            return (0);
-        }
-      

-      Then the C preprocessor will always
-      use a hello.h file from the repository directory first,
-      even if there is a hello.h file in the local directory,
-      despite the fact that the command line specifies
-      -I as the first option:
-
-      

        % scons -Q
-        cc -o hello.o -c -I. -I/usr/repository1 /usr/repository1/hello.c
-        cc -o hello hello.o
-      

-      This behavior of the C preprocessor--always search
-      for a #include file in double-quotes
-      first in the same directory as the source file,
-      and only then search the -I--can
-      not, in general, be changed.
-      In other words, it's a limitation
-      that must be lived with if you want to use
-      code repositories in this way.
-      There are three ways you can possibly
-      work around this C preprocessor behavior:
-
-      
  1. 
-        Some modern versions of C compilers do have an option
-        to disable or control this behavior.
-        If so, add that option to $CFLAGS
-        (or $CXXFLAGS or both) in your construction environment(s).
-        Make sure the option is used for all construction
-        environments that use C preprocessing!
-
-        
  2. 
-        Change all occurrences of #include "file.h"
-        to #include <file.h>.
-        Use of #include with angle brackets
-        does not have the same behavior--the -I
-        directories are searched first
-        for #include files--which
-        gives SCons direct control over the list of
-        directories the C preprocessor will search.
-
-        
  3. 
-        Require that everyone working with compilation from
-        repositories check out and work on entire directories of files,
-        not individual files.
-        (If you use local wrapper scripts around
-        your source code control system's command,
-        you could add logic to enforce this restriction there.
-
-        
23.4. Finding the SConstruct file in repositories

-    SCons will also search in repositories
-    for the SConstruct file and any specified SConscript files.
-    This poses a problem, though:  how can SCons search a
-    repository tree for an SConstruct file
-    if the SConstruct file itself contains the information
-    about the pathname of the repository?
-    To solve this problem, SCons allows you
-    to specify repository directories
-    on the command line using the -Y option:
-
-    

      % scons -Q -Y /usr/repository1 -Y /usr/repository2
-    

-    When looking for source or derived files,
-    SCons will first search the repositories
-    specified on the command line,
-    and then search the repositories
-    specified in the SConstruct or SConscript files.
-
-    
23.5. Finding derived files in repositories

-    If a repository contains not only source files,
-    but also derived files (such as object files,
-    libraries, or executables), SCons will perform
-    its normal MD5 signature calculation to
-    decide if a derived file in a repository is up-to-date,
-    or the derived file must be rebuilt in the local build directory.
-    For the SCons signature calculation to work correctly,
-    a repository tree must contain the .sconsign files
-    that SCons uses to keep track of signature information.
-
-    

-    Usually, this would be done by a build integrator
-    who would run SCons in the repository
-    to create all of its derived files and .sconsign files,
-    or who would run SCons in a separate build directory
-    and copy the resulting tree to the desired repository:
-
-    

      % cd /usr/repository1
-      % scons -Q
-      cc -o file1.o -c file1.c
-      cc -o file2.o -c file2.c
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o file1.o file2.o
-    

    
-    (Note that this is safe even if the SConstruct file
-    lists /usr/repository1 as a repository,
-    because SCons will remove the current build directory
-    from its repository list for that invocation.)
-
-    

-    Now, with the repository populated,
-    we only need to create the one local source file
-    we're interested in working with at the moment,
-    and use the -Y option to
-    tell SCons to fetch any other files it needs
-    from the repository:
-
-    

      % cd $HOME/build
-      % edit hello.c
-      % scons -Q -Y /usr/repository1
-      cc -c -o hello.o hello.c
-      cc -o hello hello.o /usr/repository1/file1.o /usr/repository1/file2.o
-    

-    Notice that SCons realizes that it does not need to
-    rebuild local copies file1.o and file2.o files,
-    but instead uses the already-compiled files
-    from the repository.
-
-    
23.6. Guaranteeing local copies of files

-    If the repository tree contains the complete results of a build,
-    and we try to build from the repository
-    without any files in our local tree,
-    something moderately surprising happens:
-
-    

      % mkdir $HOME/build2
-      % cd $HOME/build2
-      % scons -Q -Y /usr/all/repository hello
-      scons: `hello' is up-to-date.
-    

-    Why does SCons say that the hello program
-    is up-to-date when there is no hello program
-    in the local build directory?
-    Because the repository (not the local directory)
-    contains the up-to-date hello program,
-    and SCons correctly determines that nothing
-    needs to be done to rebuild that
-    up-to-date copy of the file.
-
-    

-    There are, however, many times when you want to ensure that a
-    local copy of a file always exists.
-    A packaging or testing script, for example,
-    may assume that certain generated files exist locally.
-    To tell SCons to make a copy of any up-to-date repository
-    file in the local build directory,
-    use the Local function:
-
-    

       env = Environment()
-       hello = env.Program('hello.c')
-       Local(hello)
-    

-    If we then run the same command,
-    SCons will make a local copy of the program
-    from the repository copy,
-    and tell you that it is doing so:
-
-    

      % scons -Y /usr/all/repository hello
-      Local copy of hello from /usr/all/repository/hello
-      scons: `hello' is up-to-date.
-    

-    (Notice that, because the act of making the local copy
-    is not considered a "build" of the hello file,
-    SCons still reports that it is up-to-date.)
-
-    
Chapter 24. Multi-Platform Configuration (Autoconf Functionality)

-  SCons has integrated support for multi-platform build configuration
-  similar to that offered by GNU Autoconf,
-  such as
-  figuring out what libraries or header files
-  are available on the local system.
-  This section describes how to use
-  this SCons feature.
-
-  

  This chapter is still under development,
-  so not everything is explained as well as it should be.
-  See the SCons man page for additional information.
-  
24.1. Configure Contexts

-    The basic framework for multi-platform build configuration
-    in SCons is to attach a configure context to a
-    construction environment by calling the Configure function,
-    perform a number of checks for
-    libraries, functions, header files, etc.,
-    and to then call the configure context's Finish method
-    to finish off the configuration:
-
-    

    env = Environment()
-    conf = Configure(env)
-    # Checks for libraries, header files, etc. go here!
-    env = conf.Finish()
-    

-    SCons provides a number of basic checks,
-    as well as a mechanism for adding your own custom checks.
-
-    

-    Note that SCons uses its own dependency
-    mechanism to determine when a check
-    needs to be run--that is,
-    SCons does not run the checks
-    every time it is invoked,
-    but caches the values returned by previous checks
-    and uses the cached values unless something has changed.
-    This saves a tremendous amount
-    of developer time while working on
-    cross-platform build issues.
-
-    

-    The next sections describe
-    the basic checks that SCons supports,
-    as well as how to add your own custom checks.
-
-    
24.2. Checking for the Existence of Header Files

-    Testing the existence of a header file
-    requires knowing what language the header file is.
-    A configure context has a CheckCHeader method
-    that checks for the existence of a C header file:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckCHeader('math.h'):
-        print 'Math.h must be installed!'
-        Exit(1)
-    if conf.CheckCHeader('foo.h'):
-        conf.env.Append('-DHAS_FOO_H')
-    env = conf.Finish()
-    

-    Note that you can choose to terminate
-    the build if a given header file doesn't exist,
-    or you can modify the construction environment
-    based on the existence of a header file.
-
-    

-    If you need to check for the existence
-    a C++ header file,
-    use the CheckCXXHeader method:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckCXXHeader('vector.h'):
-        print 'vector.h must be installed!'
-        Exit(1)
-    env = conf.Finish()
-    
24.3. Checking for the Availability of a Function

-    Check for the availability of a specific function
-    using the CheckFunc method:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckFunc('strcpy'):
-        print 'Did not find strcpy(), using local version'
-        conf.env.Append('-Dstrcpy=my_local_strcpy')
-    env = conf.Finish()
-    
24.4. Checking for the Availability of a Library

-    Check for the availability of a library
-    using the CheckLib method.
-    You only specify the basename of the library,
-    you don't need to add a lib
-    prefix or a .a or .lib suffix:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckLib('m'):
-        print 'Did not find libm.a or m.lib, exiting!'
-        Exit(1)
-    env = conf.Finish()
-    

-    Because the ability to use a library successfully
-    often depends on having access to a header file
-    that describes the library's interface,
-    you can check for a library
-    and a header file
-    at the same time by using the
-    CheckLibWithHeader method:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckLibWithHeader('m', 'math.h', 'c'):
-        print 'Did not find libm.a or m.lib, exiting!'
-        Exit(1)
-    env = conf.Finish()
-    

-    This is essentially shorthand for
-    separate calls to the CheckHeader and CheckLib
-    functions.
-
-    
24.5. Checking for the Availability of a typedef

-    Check for the availability of a typedef
-    by using the CheckType method:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckType('off_t'):
-        print 'Did not find off_t typedef, assuming int'
-        conf.env.Append(CCFLAGS = '-Doff_t=int')
-    env = conf.Finish()
-    

-    You can also add a string that will be
-    placed at the beginning of the test file
-    that will be used to check for the typedef.
-    This provide a way to specify
-    files that must be included to find the typedef:
-
-    

    env = Environment()
-    conf = Configure(env)
-    if not conf.CheckType('off_t', '#include <sys/types.h>\n'):
-        print 'Did not find off_t typedef, assuming int'
-        conf.env.Append(CCFLAGS = '-Doff_t=int')
-    env = conf.Finish()
-    
24.6. Adding Your Own Custom Checks

-    A custom check is a Python function
-    that checks for a certain condition to exist
-    on the running system,
-    usually using methods that SCons
-    supplies to take care of the details
-    of checking whether a compilation succeeds,
-    a link succeeds,
-    a program is runnable,
-    etc.
-    A simple custom check for the existence of
-    a specific library might look as follows:
-
-    

    mylib_test_source_file = """
-    #include <mylib.h>
-    int main(int argc, char **argv)
-    {
-        MyLibrary mylib(argc, argv);
-        return 0;
-    }
-    """
-
-    def CheckMyLibrary(context):
-        context.Message('Checking for MyLibrary...')
-        result = context.TryLink(mylib_test_source_file, '.c')
-        context.Result(result)
-        return result
-    

-    The Message and Result methods
-    should typically begin and end a custom check to
-    let the user know what's going on:
-    the Message call prints the
-    specified message (with no trailing newline)
-    and the Result call prints
-    ok if the check succeeds and
-    failed if it doesn't.
-    The TryLink method
-    actually tests for whether the
-    specified program text
-    will successfully link.
-
-    

-    (Note that a custom check can modify
-    its check based on any arguments you
-    choose to pass it,
-    or by using or modifying the configure context environment
-    in the context.env attribute.)
-
-    

-    This custom check function is
-    then attached to the configure context
-    by passing a dictionary
-    to the Configure call
-    that maps a name of the check
-    to the underlying function:
-
-    

    env = Environment()
-    conf = Configure(env, custom_tests = {'CheckMyLibrary' : CheckMyLibrary})
-    

-    You'll typically want to make
-    the check and the function name the same,
-    as we've done here,
-    to avoid potential confusion.
-
-    

-    We can then put these pieces together
-    and actually call the CheckMyLibrary check
-    as follows:
-
-    

    mylib_test_source_file = """
-    #include <mylib.h>
-    int main(int argc, char **argv)
-    {
-        MyLibrary mylib(argc, argv);
-        return 0;
-    }
-    """
-
-    def CheckMyLibrary(context):
-        context.Message('Checking for MyLibrary... ')
-        result = context.TryLink(mylib_test_source_file, '.c')
-        context.Result(result)
-        return result
-
-    env = Environment()
-    conf = Configure(env, custom_tests = {'CheckMyLibrary' : CheckMyLibrary})
-    if not conf.CheckMyLibrary():
-        print 'MyLibrary is not installed!'
-        Exit(1)
-    env = conf.Finish()
-
-    # We would then add actual calls like Program() to build
-    # something using the "env" construction environment.
-    

-    If MyLibrary is not installed on the system,
-    the output will look like:
-
-    

    % scons
-    scons: Reading SConscript file ...
-    Checking for MyLibrary... failed
-    MyLibrary is not installed!
-    

-    If MyLibrary is installed,
-    the output will look like:
-
-    

    % scons
-    scons: Reading SConscript file ...
-    Checking for MyLibrary... failed
-    scons: done reading SConscript
-    scons: Building targets ...
-        .
-        .
-        .
-    
24.7. Not Configuring When Cleaning Targets

-    Using multi-platform configuration
-    as described in the previous sections
-    will run the configuration commands
-    even when invoking
-    scons -c
-    to clean targets:
-
-    

    % scons -Q -c
-    Checking for MyLibrary... ok
-    Removed foo.o
-    Removed foo
-    

-    Although running the platform checks
-    when removing targets doesn't hurt anything,
-    it's usually unnecessary.
-    You can avoid this by using the
-    GetOption(); method to
-    check whether the -c (clean)
-    option has been invoked on the command line:
-
-    

    env = Environment()
-    if not env.GetOption('clean'):
-        conf = Configure(env, custom_tests = {'CheckMyLibrary' : CheckMyLibrary})
-        if not conf.CheckMyLibrary():
-            print 'MyLibrary is not installed!'
-            Exit(1)
-        env = conf.Finish()
-    

    % scons -Q -c
-    Removed foo.o
-    Removed foo
-    
Chapter 25. Caching Built Files

-  On multi-developer software projects,
-  you can sometimes speed up every developer's builds a lot by
-  allowing them to share the derived files that they build.
-  SCons makes this easy, as well as reliable.
-
-  
25.1. Specifying the Shared Cache Directory

-    To enable sharing of derived files,
-    use the CacheDir function
-    in any SConscript file:
-
-    

       CacheDir('/usr/local/build_cache')
-    

-    Note that the directory you specify must already exist
-    and be readable and writable by all developers
-    who will be sharing derived files.
-    It should also be in some central location
-    that all builds will be able to access.
-    In environments where developers are using separate systems
-    (like individual workstations) for builds,
-    this directory would typically be
-    on a shared or NFS-mounted file system.
-
-    

-    Here's what happens:
-    When a build has a CacheDir specified,
-    every time a file is built,
-    it is stored in the shared cache directory
-    along with its MD5 build signature.
-      [5]
-    On subsequent builds,
-    before an action is invoked to build a file,
-    SCons will check the shared cache directory
-    to see if a file with the exact same build
-    signature already exists.
-    If so, the derived file will not be built locally,
-    but will be copied into the local build directory
-    from the shared cache directory,
-    like so:
-
-    

      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q -c
-      Removed hello.o
-      Removed hello
-      % scons -Q
-      Retrieved `hello.o' from cache
-      Retrieved `hello' from cache
-    

-    Note that the CacheDir feature still calculates
-    MD5 build sigantures for the shared cache file names
-    even if you configure SCons to use timestamps
-    to decide if files are up to date.
-    (See the Chapter 6
-    chapter for information about the Decider function.)
-    Consequently, using CacheDir may reduce or eliminate any
-    potential performance improvements
-    from using timestamps for up-to-date decisions.
-
-    
25.2. Keeping Build Output Consistent

-    One potential drawback to using a shared cache
-    is that the output printed by SCons
-    can be inconsistent from invocation to invocation,
-    because any given file may be rebuilt one time
-    and retrieved from the shared cache the next time.
-    This can make analyzing build output more difficult,
-    especially for automated scripts that
-    expect consistent output each time.
-
-    

-    If, however, you use the --cache-show option,
-    SCons will print the command line that it
-    would have executed
-    to build the file,
-    even when it is retrieving the file from the shared cache.
-    This makes the build output consistent
-    every time the build is run:
-
-    

      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q -c
-      Removed hello.o
-      Removed hello
-      % scons -Q --cache-show
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-    

-    The trade-off, of course, is that you no longer
-    know whether or not SCons
-    has retrieved a derived file from cache
-    or has rebuilt it locally.
-
-    
25.3. Not Using the Shared Cache for Specific Files

-    You may want to disable caching for certain
-    specific files in your configuration.
-    For example, if you only want to put
-    executable files in a central cache,
-    but not the intermediate object files,
-    you can use the NoCache
-    function to specify that the
-    object files should not be cached:
-
-    

       env = Environment()
-       obj = env.Object('hello.c')
-       env.Program('hello.c')
-       CacheDir('cache')
-       NoCache('hello.o')
-    

-    Then when you run scons after cleaning
-    the built targets,
-    it will recompile the object file locally
-    (since it doesn't exist in the shared cache directory),
-    but still realize that the shared cache directory
-    contains an up-to-date executable program
-    that can be retrieved instead of re-linking:
-
-    

      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q -c
-      Removed hello.o
-      Removed hello
-      % scons -Q
-      cc -o hello.o -c hello.c
-      Retrieved `hello' from cache
-    
25.4. Disabling the Shared Cache

-    Retrieving an already-built file
-    from the shared cache
-    is usually a significant time-savings
-    over rebuilding the file,
-    but how much of a savings
-    (or even whether it saves time at all)
-    can depend a great deal on your
-    system or network configuration.
-    For example, retrieving cached files
-    from a busy server over a busy network
-    might end up being slower than
-    rebuilding the files locally.
-
-    

-    In these cases, you can specify
-    the --cache-disable
-    command-line option to tell SCons
-    to not retrieve already-built files from the
-    shared cache directory:
-
-    

      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q -c
-      Removed hello.o
-      Removed hello
-      % scons -Q
-      Retrieved `hello.o' from cache
-      Retrieved `hello' from cache
-      % scons -Q -c
-      Removed hello.o
-      Removed hello
-      % scons -Q --cache-disable
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-    
25.5. Populating a Shared Cache With Already-Built Files

-    Sometimes, you may have one or more derived files
-    already built in your local build tree
-    that you wish to make available to other people doing builds.
-    For example, you may find it more effective to perform
-    integration builds with the cache disabled
-    (per the previous section)
-    and only populate the shared cache directory
-    with the built files after the integration build
-    has completed successfully.
-    This way, the cache will only get filled up
-    with derived files that are part of a complete, successful build
-    not with files that might be later overwritten
-    while you debug integration problems.
-
-    

-    In this case, you can use the
-    the --cache-force option
-    to tell SCons to put all derived files in the cache,
-    even if the files already exist in your local tree
-    from having been built by a previous invocation:
-
-    

      % scons -Q --cache-disable
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q -c
-      Removed hello.o
-      Removed hello
-      % scons -Q --cache-disable
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-      % scons -Q --cache-force
-      scons: `.' is up to date.
-      % scons -Q
-      scons: `.' is up to date.
-    

-    Notice how the above sample run
-    demonstrates that the --cache-disable
-    option avoids putting the built
-    hello.o
-    and
-    hello files in the cache,
-    but after using the --cache-force option,
-    the files have been put in the cache
-    for the next invocation to retrieve.
-
-    
25.6. Minimizing Cache Contention:  the --random Option

-    If you allow multiple builds to update the
-    shared cache directory simultaneously,
-    two builds that occur at the same time
-    can sometimes start "racing"
-    with one another to build the same files
-    in the same order.
-    If, for example,
-    you are linking multiple files into an executable program:
-
-    

       Program('prog',
-               ['f1.c', 'f2.c', 'f3.c', 'f4.c', 'f5.c'])
-    

-    SCons will normally build the input object files
-    on which the program depends in their normal, sorted order:
-
-    

      % scons -Q
-      cc -o f1.o -c f1.c
-      cc -o f2.o -c f2.c
-      cc -o f3.o -c f3.c
-      cc -o f4.o -c f4.c
-      cc -o f5.o -c f5.c
-      cc -o prog f1.o f2.o f3.o f4.o f5.o
-    

-    But if two such builds take place simultaneously,
-    they may each look in the cache at nearly the same
-    time and both decide that f1.o
-    must be rebuilt and pushed into the shared cache directory,
-    then both decide that f2.o
-    must be rebuilt (and pushed into the shared cache directory),
-    then both decide that f3.o
-    must be rebuilt...
-    This won't cause any actual build problems--both
-    builds will succeed,
-    generate correct output files,
-    and populate the cache--but
-    it does represent wasted effort.
-
-    

-    To alleviate such contention for the cache,
-    you can use the --random command-line option
-    to tell SCons to build dependencies
-    in a random order:
-
-    

      % scons -Q --random
-      cc -o f3.o -c f3.c
-      cc -o f1.o -c f1.c
-      cc -o f5.o -c f5.c
-      cc -o f2.o -c f2.c
-      cc -o f4.o -c f4.c
-      cc -o prog f1.o f2.o f3.o f4.o f5.o
-    

-    Multiple builds using the --random option
-    will usually build their dependencies in different,
-    random orders,
-    which minimizes the chances for a lot of
-    contention for same-named files
-    in the shared cache directory.
-    Multiple simultaneous builds might still race to try to build
-    the same target file on occasion,
-    but long sequences of inefficient contention
-    should be rare.
-
-    

-    Note, of course,
-    the --random option
-    will cause the output that SCons prints
-    to be inconsistent from invocation to invocation,
-    which may be an issue when
-    trying to compare output from different build runs.
-
-    

-    If you want to make sure dependencies will be built
-    in a random order without having to specify
-    the --random on very command line,
-    you can use the SetOption function to
-    set the random option
-    within any SConscript file:
-
-    

       Program('prog',
-               ['f1.c', 'f2.c', 'f3.c', 'f4.c', 'f5.c'])
-
-       SetOption('random', 1)
-       Program('prog',
-               ['f1.c', 'f2.c', 'f3.c', 'f4.c', 'f5.c'])
-    
Chapter 26. Alias Targets

-  We've already seen how you can use the Alias
-  function to create a target named install:
-
-  

     env = Environment()
-     hello = env.Program('hello.c')
-     env.Install('/usr/bin', hello)
-     env.Alias('install', '/usr/bin')
-  

-  You can then use this alias on the command line
-  to tell SCons more naturally that you want to install files:
-
-  

     % scons -Q install
-     cc -o hello.o -c hello.c
-     cc -o hello hello.o
-     Install file: "hello" as "/usr/bin/hello"
-  

-  Like other Builder methods, though,
-  the Alias method returns an object
-  representing the alias being built.
-  You can then use this object as input to anothother Builder.
-  This is especially useful if you use such an object
-  as input to another call to the Alias Builder,
-  allowing you to create a hierarchy
-  of nested aliases:
-
-  

     env = Environment()
-     p = env.Program('foo.c')
-     l = env.Library('bar.c')
-     env.Install('/usr/bin', p)
-     env.Install('/usr/lib', l)
-     ib = env.Alias('install-bin', '/usr/bin')
-     il = env.Alias('install-lib', '/usr/lib')
-     env.Alias('install', [ib, il])
-  

-  This example defines separate install,
-  install-bin,
-  and install-lib aliases,
-  allowing you finer control over what gets installed:
-
-  

     % scons -Q install-bin
-     cc -o foo.o -c foo.c
-     cc -o foo foo.o
-     Install file: "foo" as "/usr/bin/foo"
-     % scons -Q install-lib
-     cc -o bar.o -c bar.c
-     ar rc libbar.a bar.o
-     ranlib libbar.a
-     Install file: "libbar.a" as "/usr/lib/libbar.a"
-     % scons -Q -c /
-     Removed foo.o
-     Removed foo
-     Removed /usr/bin/foo
-     Removed bar.o
-     Removed libbar.a
-     Removed /usr/lib/libbar.a
-     % scons -Q install
-     cc -o foo.o -c foo.c
-     cc -o foo foo.o
-     Install file: "foo" as "/usr/bin/foo"
-     cc -o bar.o -c bar.c
-     ar rc libbar.a bar.o
-     ranlib libbar.a
-     Install file: "libbar.a" as "/usr/lib/libbar.a"
-  
Chapter 27. Java Builds

-  So far, we've been using examples of
-  building C and C++ programs
-  to demonstrate the features of SCons.
-  SCons also supports building Java programs,
-  but Java builds are handled slightly differently,
-  which reflects the ways in which
-  the Java compiler and tools
-  build programs differently than
-  other languages' tool chains.
-
-  
27.1. Building Java Class Files:  the Java Builder

-    The basic activity when programming in Java,
-    of course, is to take one or more .java files
-    containing Java source code
-    and to call the Java compiler
-    to turn them into one or more
-    .class files.
-    In SCons, you do this
-    by giving the Java Builder
-    a target directory in which
-    to put the .class files,
-    and a source directory that contains
-    the .java files:
-
-    

      Java('classes', 'src')
-    

-    If the src directory contains
-    three .java source files,
-    then running SCons might look like this:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java
-    

-    SCons will actually search the src
-    directory tree for all of the .java files.
-    The Java compiler will then create the
-    necessary class files in the classes subdirectory,
-    based on the class names found in the .java files.
-
-    
27.2. How SCons Handles Java Dependencies

-    In addition to searching the source directory for
-    .java files,
-    SCons actually runs the .java files
-    through a stripped-down Java parser that figures out
-    what classes are defined.
-    In other words, SCons knows,
-    without you having to tell it,
-    what .class files
-    will be produced by the javac call.
-    So our one-liner example from the preceding section:
-
-    

      Java('classes', 'src')
-    

-    Will not only tell you reliably
-    that the .class files
-    in the classes subdirectory 
-    are up-to-date:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java
-      % scons -Q classes
-      scons: `classes' is up to date.
-    

-    But it will also remove all of the generated
-    .class files,
-    even for inner classes,
-    without you having to specify them manually.
-    For example, if our
-    Example1.java
-    and
-    Example3.java
-    files both define additional classes,
-    and the class defined in Example2.java
-    has an inner class,
-    running scons -c
-    will clean up all of those .class files
-    as well:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java
-      % scons -Q -c classes
-      Removed classes/Example1.class
-      Removed classes/AdditionalClass1.class
-      Removed classes/Example2$Inner2.class
-      Removed classes/Example2.class
-      Removed classes/Example3.class
-      Removed classes/AdditionalClass3.class
-    
27.3. Building Java Archive (.jar) Files:  the Jar Builder

-    After building the class files,
-    it's common to collect them into
-    a Java archive (.jar) file,
-    which you do by calling the Jar Builder method.
-    If you want to just collect all of the
-    class files within a subdirectory,
-    you can just specify that subdirectory
-    as the Jar source:
-
-    

      Java(target = 'classes', source = 'src')
-      Jar(target = 'test.jar', source = 'classes')
-    

-    SCons will then pass that directory
-    to the jar command,
-    which will collect all of the underlying
-    .class files:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src src/Example1.java src/Example2.java src/Example3.java
-      jar cf test.jar classes
-    

-    If you want to keep all of the
-    .class files
-    for multiple programs in one location,
-    and only archive some of them in
-    each .jar file,
-    you can pass the Jar builder a
-    list of files as its source.
-    It's extremely simple to create multiple
-    .jar files this way,
-    using the lists of target class files created
-    by calls to the Java builder
-    as sources to the various Jar calls:
-
-    

      prog1_class_files = Java(target = 'classes', source = 'prog1')
-      prog2_class_files = Java(target = 'classes', source = 'prog2')
-      Jar(target = 'prog1.jar', source = prog1_class_files)
-      Jar(target = 'prog2.jar', source = prog2_class_files)
-    

-    This will then create
-    prog1.jar
-    and prog2.jar
-    next to the subdirectories
-    that contain their .java files:
-
-    

      % scons -Q
-      javac -d classes -sourcepath prog1 prog1/Example1.java prog1/Example2.java
-      javac -d classes -sourcepath prog2 prog2/Example3.java prog2/Example4.java
-      jar cf prog1.jar -C classes Example1.class -C classes Example2.class
-      jar cf prog2.jar -C classes Example3.class -C classes Example4.class
-    
27.4. Building C Header and Stub Files:  the JavaH Builder

-    You can generate C header and source files
-    for implementing native methods,
-    by using the JavaH Builder.
-    There are several ways of using the JavaH Builder.
-    One typical invocation might look like:
-
-    

      classes = Java(target = 'classes', source = 'src/pkg/sub')
-      JavaH(target = 'native', source = classes)
-    

-    The source is a list of class files generated by the
-    call to the Java Builder,
-    and the target is the output directory in
-    which we want the C header files placed.
-    The target
-    gets converted into the -d
-    when SCons runs javah:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java src/pkg/sub/Example3.java
-      javah -d native -classpath classes pkg.sub.Example1 pkg.sub.Example2 pkg.sub.Example3
-    

-    In this case,
-    the call to javah
-    will generate the header files
-    native/pkg_sub_Example1.h,
-    native/pkg_sub_Example2.h
-    and
-    native/pkg_sub_Example3.h.
-    Notice that SCons remembered that the class
-    files were generated with a target directory of
-    classes,
-    and that it then specified that target directory
-    as the -classpath option
-    to the call to javah.
-
-    

-    Although it's more convenient to use
-    the list of class files returned by
-    the Java Builder
-    as the source of a call to the JavaH Builder,
-    you can
-    specify the list of class files
-    by hand, if you prefer.
-    If you do,
-    you need to set the
-    $JAVACLASSDIR construction variable
-    when calling JavaH:
-
-    

      Java(target = 'classes', source = 'src/pkg/sub')
-      class_file_list = ['classes/pkg/sub/Example1.class',
-                         'classes/pkg/sub/Example2.class',
-                         'classes/pkg/sub/Example3.class']
-      JavaH(target = 'native', source = class_file_list, JAVACLASSDIR = 'classes')
-    

-    The $JAVACLASSDIR value then
-    gets converted into the -classpath
-    when SCons runs javah:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java src/pkg/sub/Example3.java
-      javah -d native -classpath classes pkg.sub.Example1 pkg.sub.Example2 pkg.sub.Example3
-    

-    Lastly, if you don't want a separate header file
-    generated for each source file,
-    you can specify an explicit File Node
-    as the target of the JavaH Builder:
-
-    

      classes = Java(target = 'classes', source = 'src/pkg/sub')
-      JavaH(target = File('native.h'), source = classes)
-    

-    Because SCons assumes by default
-    that the target of the JavaH builder is a directory,
-    you need to use the File function
-    to make sure that SCons doesn't
-    create a directory named native.h.
-    When a file is used, though,
-    SCons correctly converts the file name
-    into the javah -o option:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java src/pkg/sub/Example3.java
-      javah -o native.h -classpath classes pkg.sub.Example1 pkg.sub.Example2 pkg.sub.Example3
-    
27.5. Building RMI Stub and Skeleton Class Files:  the RMIC Builder

-    You can generate Remote Method Invocation stubs
-    by using the RMIC Builder.
-    The source is a list of directories,
-    typically returned by a call to the Java Builder,
-    and the target is an output directory
-    where the _Stub.class
-    and _Skel.class files will
-    be placed:
-
-    

      classes = Java(target = 'classes', source = 'src/pkg/sub')
-      RMIC(target = 'outdir', source = classes)
-    

-    As it did with the JavaH Builder,
-    SCons remembers the class directory
-    and passes it as the -classpath option
-    to rmic:
-
-    

      % scons -Q
-      javac -d classes -sourcepath src/pkg/sub src/pkg/sub/Example1.java src/pkg/sub/Example2.java
-      rmic -d outdir -classpath classes pkg.sub.Example1 pkg.sub.Example2
-    

-    This example would generate the files
-    outdir/pkg/sub/Example1_Skel.class,
-    outdir/pkg/sub/Example1_Stub.class,
-    outdir/pkg/sub/Example2_Skel.class and
-    outdir/pkg/sub/Example2_Stub.class.
-
-    
Chapter 28. Miscellaneous Functionality

-  SCons supports a lot of additional functionality
-  that doesn't readily fit into the other chapters.
-
-  
28.1. Verifying the Python Version:  the EnsurePythonVersion Function

-    Although the SCons code itself will run 
-    on any Python version 1.5.2 or later,
-    you are perfectly free to make use of
-    Python syntax and modules from more modern versions
-    (for example, Python 2.4 or 2.5)
-    when writing your SConscript files
-    or your own local modules.
-    If you do this, it's usually helpful to
-    configure SCons to exit gracefully with an error message
-    if it's being run with a version of Python
-    that simply won't work with your code.
-    This is especially true if you're going to use SCons
-    to build source code that you plan to distribute publicly,
-    where you can't be sure of the Python version
-    that an anonymous remote user might use
-    to try to build your software.
-
-    

-    SCons provides an EnsurePythonVersion function for this.
-    You simply pass it the major and minor versions
-    numbers of the version of Python you require:
-
-    

      EnsurePythonVersion(2, 5)
-    

-    And then SCons will exit with the following error
-    message when a user runs it with an unsupported
-    earlier version of Python:
-
-    

      % scons -Q
-      Python 2.5 or greater required, but you have Python 2.3.6
-    
28.2. Verifying the SCons Version:  the EnsureSConsVersion Function

-    You may, of course, write your SConscript files
-    to use features that were only added in
-    recent versions of SCons.
-    When you publicly distribute software that is built using SCons,
-    it's helpful to have SCons
-    verify the version being used and
-    exit gracefully with an error message
-    if the user's version of SCons won't work
-    with your SConscript files.
-    SCons provides an EnsureSConsVersion function
-    that verifies the version of SCons
-    in the same
-    the EnsurePythonVersion function
-    verifies the version of Python,
-    by passing in the major and minor versions
-    numbers of the version of SCons you require:
-
-    

      EnsureSConsVersion(1, 0)
-    

-    And then SCons will exit with the following error
-    message when a user runs it with an unsupported
-    earlier version of SCons:
-
-    

      % scons -Q
-      SCons 1.0 or greater required, but you have SCons 0.98.5
-    
28.3. Explicitly Terminating SCons While Reading SConscript Files:  the Exit Function

-    SCons supports an Exit function
-    which can be used to terminate SCons
-    while reading the SConscript files,
-    usually because you've detected a condition
-    under which it doesn't make sense to proceed:
-
-    

      if ARGUMENTS.get('FUTURE'):
-          print "The FUTURE option is not supported yet!"
-          Exit(2)
-      env = Environment()
-      env.Program('hello.c')
-    

      % scons -Q FUTURE=1
-      The FUTURE option is not supported yet!
-      % scons -Q
-      cc -o hello.o -c hello.c
-      cc -o hello hello.o
-    

-    The Exit function takes as an argument
-    the (numeric) exit status that you want SCons to exit with.
-    If you don't specify a value,
-    the default is to exit with 0,
-    which indicates successful execution.
-
-    

-    Note that the Exit function
-    is equivalent to calling the Python
-    sys.exit function
-    (which the it actually calls),
-    but because Exit is a SCons function,
-    you don't have to import the Python
-    sys module to use it.
-
-    
28.4. Searching for Files:  the FindFile Function

-     The FindFile function searches for a file in a list of directories.
-     If there is only one directory, it can be given as a simple string.
-     The function returns a File node if a matching file exists,
-     or None if no file is found.
-     (See the documentation for the Glob function for an alternative way
-     of searching for entries in a directory.)
-
-    

       # one directory
-       print FindFile('missing', '.')
-       t = FindFile('exists', '.')
-       print t.__class__, t
-    

       % scons -Q
-       None
-       SCons.Node.FS.File exists
-       scons: `.' is up to date.
-    

       # several directories
-       includes = [ '.', 'include', 'src/include']
-       headers = [ 'nonesuch.h', 'config.h', 'private.h', 'dist.h']
-       for hdr in headers:
-           print '%-12s' % ('%s:' % hdr), FindFile(hdr, includes)
-

       % scons -Q
-       nonesuch.h:  None
-       config.h:    config.h
-       private.h:   src/include/private.h
-       dist.h:      include/dist.h
-       scons: `.' is up to date.
-    

-     If the file exists in more than one directory,
-     only the first occurrence is returned.
-
-    

        print FindFile('multiple', ['sub1', 'sub2', 'sub3'])
-        print FindFile('multiple', ['sub2', 'sub3', 'sub1'])
-        print FindFile('multiple', ['sub3', 'sub1', 'sub2'])
-    

       % scons -Q
-       sub1/multiple
-       sub2/multiple
-       sub3/multiple
-       scons: `.' is up to date.
-    

-    In addition to existing files, FindFile will also find derived files
-    (that is, non-leaf files) that haven't been built yet.
-    (Leaf files should already exist, or the build will fail!)
-
-    

       # Neither file exists, so build will fail
-       Command('derived', 'leaf', 'cat >$TARGET $SOURCE')
-       print FindFile('leaf', '.')
-       print FindFile('derived', '.')
-    

       % scons -Q
-       None
-       derived
-       scons: *** Source `leaf' not found, needed by target `derived'.  Stop.
-    

       # Neither file exists, so build will fail
-       Command('derived', 'leaf', 'cat >$TARGET $SOURCE')
-       print FindFile('leaf', '.')
-       print FindFile('derived', '.')
-
-       # Only 'leaf' exists
-       Command('derived', 'leaf', 'cat >$TARGET $SOURCE')
-       print FindFile('leaf', '.')
-       print FindFile('derived', '.')
-    

       % scons -Q
-       leaf
-       derived
-       cat > derived leaf
-    

-    If a source file exists, FindFile will correctly return the name
-    in the build directory.
-
-    

       # Only 'src/leaf' exists
-       VariantDir('build', 'src')
-       print FindFile('leaf', 'build')
-    

       % scons -Q
-       build/leaf
-       scons: `.' is up to date.
-    
28.5. Handling Nested Lists:  the Flatten Function

-    SCons supports a Flatten function
-    which takes an input Python sequence
-    (list or tuple)
-    and returns a flattened list
-    containing just the individual elements of
-    the sequence.
-    This can be handy when trying to examine
-    a list composed of the lists
-    returned by calls to various Builders.
-    For example, you might collect
-    object files built in different ways
-    into one call to the Program Builder
-    by just enclosing them in a list, as follows:
-
-    

      objects = [
-          Object('prog1.c'),
-          Object('prog2.c', CCFLAGS='-DFOO'),
-      ]
-      Program(objects)
-    

-    Because the Builder calls in SCons
-    flatten their input lists,
-    this works just fine to build the program:
-
-    

      % scons -Q
-      cc -o prog1.o -c prog1.c
-      cc -o prog2.o -c -DFOO prog2.c
-      cc -o prog1 prog1.o prog2.o
-    

-    But if you were debugging your build
-    and wanted to print the absolute path
-    of each object file in the
-    objects list,
-    you might try the following simple approach,
-    trying to print each Node's
-    abspath
-    attribute:
-
-    

      objects = [
-          Object('prog1.c'),
-          Object('prog2.c', CCFLAGS='-DFOO'),
-      ]
-      Program(objects)
-
-      for object_file in objects:
-          print object_file.abspath
-    

-    This does not work as expected
-    because each call to str
-    is operating an embedded list returned by
-    each Object call,
-    not on the underlying Nodes within those lists:
-
-    

      % scons -Q
-      AttributeError: NodeList instance has no attribute 'abspath':
-        File "/home/my/project/SConstruct", line 8:
-          print object_file.abspath
-    

-    The solution is to use the Flatten function
-    so that you can pass each Node to
-    the str separately:
-
-    

      objects = [
-          Object('prog1.c'),
-          Object('prog2.c', CCFLAGS='-DFOO'),
-      ]
-      Program(objects)
-
-      for object_file in Flatten(objects):
-          print object_file.abspath
-    

      % scons -Q
-      /home/me/project/prog1.o
-      /home/me/project/prog2.o
-      cc -o prog1.o -c prog1.c
-      cc -o prog2.o -c -DFOO prog2.c
-      cc -o prog1 prog1.o prog2.o
-    
28.6. Finding the Invocation Directory:  the GetLaunchDir Function

-    If you need to find the directory from
-    which the user invoked the scons command,
-    you can use the GetLaunchDir function:
-
-    

      env = Environment(
-          LAUNCHDIR = GetLaunchDir(),
-      )
-      env.Command('directory_build_info',
-                  '$LAUNCHDIR/build_info'
-                  Copy('$TARGET', '$SOURCE'))
-    

-    Because SCons is usually invoked from the top-level
-    directory in which the SConstruct file lives,
-    the Python os.getcwd()
-    is often equivalent.
-    However, the SCons
-    -u,
-    -U
-    and
-    -D
-    command-line options,
-    when invoked from a subdirectory,
-    will cause SCons to change to the directory
-    in which the SConstruct file is found.
-    When those options are used,
-    GetLaunchDir will still return the path to the
-    user's invoking subdirectory,
-    allowing the SConscript configuration
-    to still get at configuration (or other) files
-    from the originating directory.
-
-    
Chapter 29. Troubleshooting

-  The experience of configuring any
-  software build tool to build a large code base
-  usually, at some point,
-  involves trying to figure out why
-  the tool is behaving a certain way,
-  and how to get it to behave the way you want.
-  SCons is no different.
-  This appendix contains a number of
-  different ways in which you can
-  get some additional insight into SCons' behavior.
-
-  

-  Note that we're always interested in trying to
-  improve how you can troubleshoot configuration problems.
-  If you run into a problem that has
-  you scratching your head,
-  and which there just doesn't seem to be a good way to debug,
-  odds are pretty good that someone else will run into
-  the same problem, too.
-  If so, please let the SCons development team know
-  (preferably by filing a bug report
-  or feature request at our project pages at tigris.org)
-  so that we can use your feedback
-  to try to come up with a better way to help you,
-  and others, get the necessary insight into SCons behavior
-  to help identify and fix configuration issues.
-
-  
29.1. Why is That Target Being Rebuilt?  the --debug=explain Option

-    Let's look at a simple example of
-    a misconfigured build
-    that causes a target to be rebuilt
-    every time SCons is run:
-
-    

      # Intentionally misspell the output file name in the
-      # command used to create the file:
-      Command('file.out', 'file.in', 'cp $SOURCE file.oout')
-    

-    (Note to Windows users:  The POSIX cp command
-    copies the first file named on the command line
-    to the second file.
-    In our example, it copies the file.in file
-    to the file.out file.)
-
-    

-    Now if we run SCons multiple times on this example,
-    we see that it re-runs the cp
-    command every time:
-
-    

      % scons -Q
-      cp file.in file.oout
-      % scons -Q
-      cp file.in file.oout
-      % scons -Q
-      cp file.in file.oout
-    

-    In this example,
-    the underlying cause is obvious:
-    we've intentionally misspelled the output file name
-    in the cp command,
-    so the command doesn't actually
-    build the file.out file that we've told SCons to expect.
-    But if the problem weren't obvious,
-    it would be helpful
-    to specify the --debug=explain option
-    on the command line
-    to have SCons tell us very specifically
-    why it's decided to rebuild the target:
-
-    

      % scons -Q --debug=explain
-      scons: building `file.out' because it doesn't exist
-      cp file.in file.oout
-    

-    If this had been a more complicated example
-    involving a lot of build output,
-    having SCons tell us that
-    it's trying to rebuild the target file
-    because it doesn't exist
-    would be an important clue
-    that something was wrong with
-    the command that we invoked to build it.
-
-    

-    The --debug=explain option also comes in handy
-    to help figure out what input file changed.
-    Given a simple configuration that builds
-    a program from three source files,
-    changing one of the source files
-    and rebuilding with the --debug=explain
-    option shows very specifically
-    why SCons rebuilds the files that it does:
-
-    

      % scons -Q
-      cc -o file1.o -c file1.c
-      cc -o file2.o -c file2.c
-      cc -o file3.o -c file3.c
-      cc -o prog file1.o file2.o file3.o
-      % edit file2.c
-          [CHANGE THE CONTENTS OF file2.c]
-      % scons -Q --debug=explain
-      scons: rebuilding `file2.o' because `file2.c' changed
-      cc -o file2.o -c file2.c
-      scons: rebuilding `prog' because `file2.o' changed
-      cc -o prog file1.o file2.o file3.o
-    

-    This becomes even more helpful
-    in identifying when a file is rebuilt
-    due to a change in an implicit dependency,
-    such as an incuded .h file.
-    If the file1.c
-    and file3.c files
-    in our example
-    both included a hello.h file,
-    then changing that included file
-    and re-running SCons with the --debug=explain option
-    will pinpoint that it's the change to the included file
-    that starts the chain of rebuilds:
-
-    

      % scons -Q
-      cc -o file1.o -c -I. file1.c
-      cc -o file2.o -c -I. file2.c
-      cc -o file3.o -c -I. file3.c
-      cc -o prog file1.o file2.o file3.o
-      % edit hello.h
-          [CHANGE THE CONTENTS OF hello.h]
-      % scons -Q --debug=explain
-      scons: rebuilding `file1.o' because `hello.h' changed
-      cc -o file1.o -c -I. file1.c
-      scons: rebuilding `file3.o' because `hello.h' changed
-      cc -o file3.o -c -I. file3.c
-      scons: rebuilding `prog' because:
-                 `file1.o' changed
-                 `file3.o' changed
-      cc -o prog file1.o file2.o file3.o
-    

-    (Note that the --debug=explain option will only tell you
-    why SCons decided to rebuild necessary targets.
-    It does not tell you what files it examined
-    when deciding not
-    to rebuild a target file,
-    which is often a more valuable question to answer.)
-
-    
29.2. What's in That Construction Environment?  the Dump Method

-    When you create a construction environment,
-    SCons populates it
-    with construction variables that are set up
-    for various compilers, linkers and utilities
-    that it finds on your system.
-    Although this is usually helpful and what you want,
-    it might be frustrating if SCons
-    doesn't set certain variables that you
-    expect to be set.
-    In situations like this,
-    it's sometimes helpful to use the
-    construction environment Dump method
-    to print all or some of
-    the construction variables.
-    Note that the Dump method
-    returns
-    the representation of the variables
-    in the environment
-    for you to print (or otherwise manipulate):
-
-    

         env = Environment()
-         print env.Dump()
-    

-    On a POSIX system with gcc installed,
-    this might generate:
-
-    

      % scons
-      scons: Reading SConscript files ...
-      { 'BUILDERS': {'_InternalInstall': <function InstallBuilderWrapper at 0x700000>, '_InternalInstallAs': <function InstallAsBuilderWrapper at 0x700000>},
-        'CONFIGUREDIR': '#/.sconf_temp',
-        'CONFIGURELOG': '#/config.log',
-        'CPPSUFFIXES': [ '.c',
-                         '.C',
-                         '.cxx',
-                         '.cpp',
-                         '.c++',
-                         '.cc',
-                         '.h',
-                         '.H',
-                         '.hxx',
-                         '.hpp',
-                         '.hh',
-                         '.F',
-                         '.fpp',
-                         '.FPP',
-                         '.m',
-                         '.mm',
-                         '.S',
-                         '.spp',
-                         '.SPP'],
-        'DSUFFIXES': ['.d'],
-        'Dir': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'Dirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'ENV': {'PATH': '/usr/local/bin:/opt/bin:/bin:/usr/bin'},
-        'ESCAPE': <function escape at 0x700000>,
-        'File': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'IDLSUFFIXES': ['.idl', '.IDL'],
-        'INSTALL': <function copyFunc at 0x700000>,
-        'LATEXSUFFIXES': ['.tex', '.ltx', '.latex'],
-        'LIBPREFIX': 'lib',
-        'LIBPREFIXES': ['$LIBPREFIX'],
-        'LIBSUFFIX': '.a',
-        'LIBSUFFIXES': ['$LIBSUFFIX', '$SHLIBSUFFIX'],
-        'MAXLINELENGTH': 128072,
-        'OBJPREFIX': '',
-        'OBJSUFFIX': '.o',
-        'PLATFORM': 'posix',
-        'PROGPREFIX': '',
-        'PROGSUFFIX': '',
-        'PSPAWN': <function piped_env_spawn at 0x700000>,
-        'RDirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'SCANNERS': [],
-        'SHELL': 'sh',
-        'SHLIBPREFIX': '$LIBPREFIX',
-        'SHLIBSUFFIX': '.so',
-        'SHOBJPREFIX': '$OBJPREFIX',
-        'SHOBJSUFFIX': '$OBJSUFFIX',
-        'SPAWN': <function spawnvpe_spawn at 0x700000>,
-        'TEMPFILE': <class SCons.Platform.TempFileMunge at 0x700000>,
-        'TEMPFILEPREFIX': '@',
-        'TOOLS': ['install', 'install'],
-        '_CPPDEFFLAGS': '${_defines(CPPDEFPREFIX, CPPDEFINES, CPPDEFSUFFIX, __env__)}',
-        '_CPPINCFLAGS': '$( ${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)',
-        '_LIBDIRFLAGS': '$( ${_concat(LIBDIRPREFIX, LIBPATH, LIBDIRSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)',
-        '_LIBFLAGS': '${_concat(LIBLINKPREFIX, LIBS, LIBLINKSUFFIX, __env__)}',
-        '__RPATH': '$_RPATH',
-        '_concat': <function _concat at 0x700000>,
-        '_defines': <function _defines at 0x700000>,
-        '_stripixes': <function _stripixes at 0x700000>}
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      scons: `.' is up to date.
-      scons: done building targets.
-    

-    On a Windows system with Visual C++
-    the output might look like:
-
-    

      C:\>scons
-      scons: Reading SConscript files ...
-      { 'BUILDERS': {'_InternalInstall': <function InstallBuilderWrapper at 0x700000>, 'Object': <SCons.Builder.CompositeBuilder instance at 0x700000>, 'PCH': <SCons.Builder.BuilderBase instance at 0x700000>, 'RES': <SCons.Builder.BuilderBase instance at 0x700000>, 'SharedObject': <SCons.Builder.CompositeBuilder instance at 0x700000>, 'StaticObject': <SCons.Builder.CompositeBuilder instance at 0x700000>, '_InternalInstallAs': <function InstallAsBuilderWrapper at 0x700000>},
-        'CC': 'cl',
-        'CCCOM': <SCons.Action.FunctionAction instance at 0x700000>,
-        'CCCOMFLAGS': '$CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS /c $SOURCES /Fo$TARGET $CCPCHFLAGS $CCPDBFLAGS',
-        'CCFLAGS': ['/nologo'],
-        'CCPCHFLAGS': ['${(PCH and "/Yu%s /Fp%s"%(PCHSTOP or "",File(PCH))) or ""}'],
-        'CCPDBFLAGS': ['${(PDB and "/Z7") or ""}'],
-        'CFILESUFFIX': '.c',
-        'CFLAGS': [],
-        'CONFIGUREDIR': '#/.sconf_temp',
-        'CONFIGURELOG': '#/config.log',
-        'CPPDEFPREFIX': '/D',
-        'CPPDEFSUFFIX': '',
-        'CPPSUFFIXES': [ '.c',
-                         '.C',
-                         '.cxx',
-                         '.cpp',
-                         '.c++',
-                         '.cc',
-                         '.h',
-                         '.H',
-                         '.hxx',
-                         '.hpp',
-                         '.hh',
-                         '.F',
-                         '.fpp',
-                         '.FPP',
-                         '.m',
-                         '.mm',
-                         '.S',
-                         '.spp',
-                         '.SPP'],
-        'CXX': '$CC',
-        'CXXCOM': '$CXX $CXXFLAGS $CCCOMFLAGS',
-        'CXXFILESUFFIX': '.cc',
-        'CXXFLAGS': ['$CCFLAGS', '$(', '/TP', '$)'],
-        'DSUFFIXES': ['.d'],
-        'Dir': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'Dirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'ENV': { 'INCLUDE': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\include',
-                 'LIB': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\lib',
-                 'PATH': 'C:\\Program Files\\Microsoft Visual Studio\\Common\\tools\\WIN95;C:\\Program Files\\Microsoft Visual Studio\\Common\\MSDev98\\bin;C:\\Program Files\\Microsoft Visual Studio\\Common\\tools;C:\\Program Files\\Microsoft Visual Studio/VC98\\bin',
-                 'PATHEXT': '.COM;.EXE;.BAT;.CMD',
-                 'SystemRoot': 'C:/WINDOWS'},
-        'ESCAPE': <function escape at 0x700000>,
-        'File': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'IDLSUFFIXES': ['.idl', '.IDL'],
-        'INCPREFIX': '/I',
-        'INCSUFFIX': '',
-        'INSTALL': <function copyFunc at 0x700000>,
-        'LATEXSUFFIXES': ['.tex', '.ltx', '.latex'],
-        'LIBPREFIX': '',
-        'LIBPREFIXES': ['$LIBPREFIX'],
-        'LIBSUFFIX': '.lib',
-        'LIBSUFFIXES': ['$LIBSUFFIX'],
-        'MAXLINELENGTH': 2048,
-        'MSVS': {'VERSION': '6.0', 'VERSIONS': ['6.0']},
-        'MSVS_VERSION': '6.0',
-        'OBJPREFIX': '',
-        'OBJSUFFIX': '.obj',
-        'PCHCOM': '$CXX $CXXFLAGS $CPPFLAGS $_CPPDEFFLAGS $_CPPINCFLAGS /c $SOURCES /Fo${TARGETS[1]} /Yc$PCHSTOP /Fp${TARGETS[0]} $CCPDBFLAGS $PCHPDBFLAGS',
-        'PCHPDBFLAGS': ['${(PDB and "/Yd") or ""}'],
-        'PLATFORM': 'win32',
-        'PROGPREFIX': '',
-        'PROGSUFFIX': '.exe',
-        'PSPAWN': <function piped_spawn at 0x700000>,
-        'RC': 'rc',
-        'RCCOM': <SCons.Action.FunctionAction instance at 0x700000>,
-        'RCFLAGS': [],
-        'RDirs': <SCons.Defaults.Variable_Method_Caller instance at 0x700000>,
-        'SCANNERS': [],
-        'SHCC': '$CC',
-        'SHCCCOM': <SCons.Action.FunctionAction instance at 0x700000>,
-        'SHCCFLAGS': ['$CCFLAGS'],
-        'SHCFLAGS': ['$CFLAGS'],
-        'SHCXX': '$CXX',
-        'SHCXXCOM': '$SHCXX $SHCXXFLAGS $CCCOMFLAGS',
-        'SHCXXFLAGS': ['$CXXFLAGS'],
-        'SHELL': None,
-        'SHLIBPREFIX': '',
-        'SHLIBSUFFIX': '.dll',
-        'SHOBJPREFIX': '$OBJPREFIX',
-        'SHOBJSUFFIX': '$OBJSUFFIX',
-        'SPAWN': <function spawn at 0x700000>,
-        'STATIC_AND_SHARED_OBJECTS_ARE_THE_SAME': 1,
-        'TEMPFILE': <class SCons.Platform.TempFileMunge at 0x700000>,
-        'TEMPFILEPREFIX': '@',
-        'TOOLS': ['msvc', 'install', 'install'],
-        '_CPPDEFFLAGS': '${_defines(CPPDEFPREFIX, CPPDEFINES, CPPDEFSUFFIX, __env__)}',
-        '_CPPINCFLAGS': '$( ${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)',
-        '_LIBDIRFLAGS': '$( ${_concat(LIBDIRPREFIX, LIBPATH, LIBDIRSUFFIX, __env__, RDirs, TARGET, SOURCE)} $)',
-        '_LIBFLAGS': '${_concat(LIBLINKPREFIX, LIBS, LIBLINKSUFFIX, __env__)}',
-        '_concat': <function _concat at 0x700000>,
-        '_defines': <function _defines at 0x700000>,
-        '_stripixes': <function _stripixes at 0x700000>}
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      scons: `.' is up to date.
-      scons: done building targets.
-    

-    The construction environments in these examples have
-    actually been restricted to just gcc and Visual C++,
-    respectively.
-    In a real-life situation,
-    the construction environments will
-    likely contain a great many more variables.
-    Also note that we've massaged the example output above
-    to make the memory address of all objects a constant 0x700000.
-    In reality, you would see a different hexadecimal
-    number for each object.
-
-    

-    To make it easier to see just what you're
-    interested in,
-    the Dump method allows you to
-    specify a specific constrcution variable
-    that you want to disply.
-    For example,
-    it's not unusual to want to verify
-    the external environment used to execute build commands,
-    to make sure that the PATH and other
-    environment variables are set up the way they should be.
-    You can do this as follows:
-
-    

         env = Environment()
-         print env.Dump('ENV')
-    

-    Which might display the following when executed on a POSIX system:
-
-    

      % scons
-      scons: Reading SConscript files ...
-      {'PATH': '/usr/local/bin:/opt/bin:/bin:/usr/bin'}
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      scons: `.' is up to date.
-      scons: done building targets.
-    

-    And the following when executed on a Windows system:
-
-    

      C:\>scons
-      scons: Reading SConscript files ...
-      { 'INCLUDE': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\include',
-        'LIB': 'C:\\Program Files\\Microsoft Visual Studio/VC98\\lib',
-        'PATH': 'C:\\Program Files\\Microsoft Visual Studio\\Common\\tools\\WIN95;C:\\Program Files\\Microsoft Visual Studio\\Common\\MSDev98\\bin;C:\\Program Files\\Microsoft Visual Studio\\Common\\tools;C:\\Program Files\\Microsoft Visual Studio/VC98\\bin',
-        'PATHEXT': '.COM;.EXE;.BAT;.CMD',
-        'SystemRoot': 'C:/WINDOWS'}
-      scons: done reading SConscript files.
-      scons: Building targets ...
-      scons: `.' is up to date.
-      scons: done building targets.
-    
29.3. What Dependencies Does SCons Know About?  the --tree Option

-    Sometimes the best way to try to figure out what
-    SCons is doing is simply to take a look at the
-    dependency graph that it constructs
-    based on your SConscript files.
-    The --tree option
-    will display all or part of the
-    SCons dependency graph in an
-    "ASCII art" graphical format
-    that shows the dependency hierarchy.
-
-    

-    For example, given the following input SConstruct file:
-
-    

         env = Environment(CPPPATH = ['.'])
-         env.Program('prog', ['f1.c', 'f2.c', 'f3.c'])
-    

-    Running SCons with the --tree=all
-    option yields:
-
-    

      % scons -Q --tree=all
-      cc -o f1.o -c -I. f1.c
-      cc -o f2.o -c -I. f2.c
-      cc -o f3.o -c -I. f3.c
-      cc -o prog f1.o f2.o f3.o
-      +-.
-        +-SConstruct
-        +-f1.c
-        +-f1.o
-        | +-f1.c
-        | +-inc.h
-        +-f2.c
-        +-f2.o
-        | +-f2.c
-        | +-inc.h
-        +-f3.c
-        +-f3.o
-        | +-f3.c
-        | +-inc.h
-        +-inc.h
-        +-prog
-          +-f1.o
-          | +-f1.c
-          | +-inc.h
-          +-f2.o
-          | +-f2.c
-          | +-inc.h
-          +-f3.o
-            +-f3.c
-            +-inc.h
-    

-    The tree will also be printed when the
-    -n (no execute) option is used,
-    which allows you to examine the dependency graph
-    for a configuration without actually
-    rebuilding anything in the tree.
-
-    

-    The --tree option only prints
-    the dependency graph for the specified targets
-    (or the default target(s) if none are specified on the command line).
-    So if you specify a target like f2.o
-    on the command line,
-    the --tree option will only
-    print the dependency graph for that file:
-
-    

      % scons -Q --tree=all f2.o
-      cc -o f2.o -c -I. f2.c
-      +-f2.o
-        +-f2.c
-        +-inc.h
-    

-    This is, of course, useful for
-    restricting the output from a very large
-    build configuration to just a
-    portion in which you're interested.
-    Multiple targets are fine,
-    in which case a tree will be printed
-    for each specified target:
-
-    

      % scons -Q --tree=all f1.o f3.o
-      cc -o f1.o -c -I. f1.c
-      +-f1.o
-        +-f1.c
-        +-inc.h
-      cc -o f3.o -c -I. f3.c
-      +-f3.o
-        +-f3.c
-        +-inc.h
-    

-    The status argument may be used
-    to tell SCons to print status information about
-    each file in the dependency graph:
-
-    

      % scons -Q --tree=status
-      cc -o f1.o -c -I. f1.c
-      cc -o f2.o -c -I. f2.c
-      cc -o f3.o -c -I. f3.c
-      cc -o prog f1.o f2.o f3.o
-       E         = exists
-        R        = exists in repository only
-         b       = implicit builder
-         B       = explicit builder
-          S      = side effect
-           P     = precious
-            A    = always build
-             C   = current
-              N  = no clean
-               H = no cache
-      
-      [E b      ]+-.
-      [E     C  ]  +-SConstruct
-      [E     C  ]  +-f1.c
-      [E B   C  ]  +-f1.o
-      [E     C  ]  | +-f1.c
-      [E     C  ]  | +-inc.h
-      [E     C  ]  +-f2.c
-      [E B   C  ]  +-f2.o
-      [E     C  ]  | +-f2.c
-      [E     C  ]  | +-inc.h
-      [E     C  ]  +-f3.c
-      [E B   C  ]  +-f3.o
-      [E     C  ]  | +-f3.c
-      [E     C  ]  | +-inc.h
-      [E     C  ]  +-inc.h
-      [E B   C  ]  +-prog
-      [E B   C  ]    +-f1.o
-      [E     C  ]    | +-f1.c
-      [E     C  ]    | +-inc.h
-      [E B   C  ]    +-f2.o
-      [E     C  ]    | +-f2.c
-      [E     C  ]    | +-inc.h
-      [E B   C  ]    +-f3.o
-      [E     C  ]      +-f3.c
-      [E     C  ]      +-inc.h
-    

-    Note that --tree=all,status is equivalent;
-    the all
-    is assumed if only status is present.
-    As an alternative to all,
-    you can specify --tree=derived
-    to have SCons only print derived targets
-    in the tree output,
-    skipping source files
-    (like .c and .h files):
-
-    

      % scons -Q --tree=derived
-      cc -o f1.o -c -I. f1.c
-      cc -o f2.o -c -I. f2.c
-      cc -o f3.o -c -I. f3.c
-      cc -o prog f1.o f2.o f3.o
-      +-.
-        +-f1.o
-        +-f2.o
-        +-f3.o
-        +-prog
-          +-f1.o
-          +-f2.o
-          +-f3.o
-    

-    You can use the status
-    modifier with derived as well:
-
-    

      % scons -Q --tree=derived,status
-      cc -o f1.o -c -I. f1.c
-      cc -o f2.o -c -I. f2.c
-      cc -o f3.o -c -I. f3.c
-      cc -o prog f1.o f2.o f3.o
-       E         = exists
-        R        = exists in repository only
-         b       = implicit builder
-         B       = explicit builder
-          S      = side effect
-           P     = precious
-            A    = always build
-             C   = current
-              N  = no clean
-               H = no cache
-      
-      [E b      ]+-.
-      [E B   C  ]  +-f1.o
-      [E B   C  ]  +-f2.o
-      [E B   C  ]  +-f3.o
-      [E B   C  ]  +-prog
-      [E B   C  ]    +-f1.o
-      [E B   C  ]    +-f2.o
-      [E B   C  ]    +-f3.o
-    

-    Note that the order of the --tree=
-    arguments doesn't matter;
-    --tree=status,derived is
-    completely equivalent.
-
-    

-    The default behavior of the --tree option
-    is to repeat all of the dependencies each time the library dependency
-    (or any other dependency file) is encountered in the tree.
-    If certain target files share other target files,
-    such as two programs that use the same library:
-
-    

         env = Environment(CPPPATH = ['.'],
-                           LIBS = ['foo'],
-                           LIBPATH = ['.'])
-         env.Library('foo', ['f1.c', 'f2.c', 'f3.c'])
-         env.Program('prog1.c')
-         env.Program('prog2.c')
-    

-    Then there can be a lot of repetition in the
-    --tree= output:
-
-    

      % scons -Q --tree=all
-      cc -o f1.o -c -I. f1.c
-      cc -o f2.o -c -I. f2.c
-      cc -o f3.o -c -I. f3.c
-      ar rc libfoo.a f1.o f2.o f3.o
-      ranlib libfoo.a
-      cc -o prog1.o -c -I. prog1.c
-      cc -o prog1 prog1.o -L. -lfoo
-      cc -o prog2.o -c -I. prog2.c
-      cc -o prog2 prog2.o -L. -lfoo
-      +-.
-        +-SConstruct
-        +-f1.c
-        +-f1.o
-        | +-f1.c
-        | +-inc.h
-        +-f2.c
-        +-f2.o
-        | +-f2.c
-        | +-inc.h
-        +-f3.c
-        +-f3.o
-        | +-f3.c
-        | +-inc.h
-        +-inc.h
-        +-libfoo.a
-        | +-f1.o
-        | | +-f1.c
-        | | +-inc.h
-        | +-f2.o
-        | | +-f2.c
-        | | +-inc.h
-        | +-f3.o
-        |   +-f3.c
-        |   +-inc.h
-        +-prog1
-        | +-prog1.o
-        | | +-prog1.c
-        | | +-inc.h
-        | +-libfoo.a
-        |   +-f1.o
-        |   | +-f1.c
-        |   | +-inc.h
-        |   +-f2.o
-        |   | +-f2.c
-        |   | +-inc.h
-        |   +-f3.o
-        |     +-f3.c
-        |     +-inc.h
-        +-prog1.c
-        +-prog1.o
-        | +-prog1.c
-        | +-inc.h
-        +-prog2
-        | +-prog2.o
-        | | +-prog2.c
-        | | +-inc.h
-        | +-libfoo.a
-        |   +-f1.o
-        |   | +-f1.c
-        |   | +-inc.h
-        |   +-f2.o
-        |   | +-f2.c
-        |   | +-inc.h
-        |   +-f3.o
-        |     +-f3.c
-        |     +-inc.h
-        +-prog2.c
-        +-prog2.o
-          +-prog2.c
-          +-inc.h
-    

-    In a large configuration with many internal libraries
-    and include files,
-    this can very quickly lead to huge output trees.
-    To help make this more manageable,
-    a prune modifier may
-    be added to the option list,
-    in which case SCons
-    will print the name of a target that has
-    already been visited during the tree-printing
-    in [square brackets]
-    as an indication that the dependencies
-    of the target file may be found
-    by looking farther up the tree:
-
-    

      % scons -Q --tree=prune
-      cc -o f1.o -c -I. f1.c
-      cc -o f2.o -c -I. f2.c
-      cc -o f3.o -c -I. f3.c
-      ar rc libfoo.a f1.o f2.o f3.o
-      ranlib libfoo.a
-      cc -o prog1.o -c -I. prog1.c
-      cc -o prog1 prog1.o -L. -lfoo
-      cc -o prog2.o -c -I. prog2.c
-      cc -o prog2 prog2.o -L. -lfoo
-      +-.
-        +-SConstruct
-        +-f1.c
-        +-f1.o
-        | +-f1.c
-        | +-inc.h
-        +-f2.c
-        +-f2.o
-        | +-f2.c
-        | +-inc.h
-        +-f3.c
-        +-f3.o
-        | +-f3.c
-        | +-inc.h
-        +-inc.h
-        +-libfoo.a
-        | +-[f1.o]
-        | +-[f2.o]
-        | +-[f3.o]
-        +-prog1
-        | +-prog1.o
-        | | +-prog1.c
-        | | +-inc.h
-        | +-[libfoo.a]
-        +-prog1.c
-        +-[prog1.o]
-        +-prog2
-        | +-prog2.o
-        | | +-prog2.c
-        | | +-inc.h
-        | +-[libfoo.a]
-        +-prog2.c
-        +-[prog2.o]
-    

-    Like the status keyword,
-    the prune argument by itself
-    is equivalent to --tree=all,prune.
-
-    
29.4. How is SCons Constructing the Command Lines It Executes?  the --debug=presub Option

-    Sometimes it's useful to look at the
-    pre-substitution string
-    that SCons uses to generate
-    the command lines it executes.
-    This can be done with the --debug=presub option:
-
-    

      % scons -Q --debug=presub
-      Building prog.o with action:
-        $CC -o $TARGET -c $CFLAGS $CCFLAGS $_CCOMCOM $SOURCES
-      cc -o prog.o -c -I. prog.c
-      Building prog with action:
-        $SMART_LINKCOM
-      cc -o prog prog.o
-    
29.5. Where is SCons Searching for Libraries?  the --debug=findlibs Option

-    To get some insight into what library names
-    SCons is searching for,
-    and in which directories it is searching,
-    Use the --debug=findlibs option.
-    Given the following input SConstruct file:
-
-    

        env = Environment(LIBPATH = ['libs1', 'libs2'])
-        env.Program('prog.c', LIBS=['foo', 'bar'])
-    

-    And the libraries libfoo.a
-    and libbar.a
-    in libs1 and libs2,
-    respectively,
-    use of the --debug=findlibs option yields:
-
-    

      % scons -Q --debug=findlibs
-        findlibs: looking for 'libfoo.a' in 'libs1' ...
-        findlibs: ... FOUND 'libfoo.a' in 'libs1'
-        findlibs: looking for 'libfoo.so' in 'libs1' ...
-        findlibs: looking for 'libfoo.so' in 'libs2' ...
-        findlibs: looking for 'libbar.a' in 'libs1' ...
-        findlibs: looking for 'libbar.a' in 'libs2' ...
-        findlibs: ... FOUND 'libbar.a' in 'libs2'
-        findlibs: looking for 'libbar.so' in 'libs1' ...
-        findlibs: looking for 'libbar.so' in 'libs2' ...
-      cc -o prog.o -c prog.c
-      cc -o prog prog.o -Llibs1 -Llibs2 -lfoo -lbar
-    
29.6. Where is SCons Blowing Up?  the --debug=stacktrace Option

-    In general, SCons tries to keep its error
-    messages short and informative.
-    That means we usually try to avoid showing
-    the stack traces that are familiar
-    to experienced Python programmers,
-    since they usually contain much more
-    information than is useful to most people.
-
-    

-    For example, the following SConstruct file:
-
-    

         Program('prog.c')
-    

-    Generates the following error if the
-    prog.c file
-    does not exist:
-
-    

      % scons -Q
-      scons: *** Source `prog.c' not found, needed by target `prog.o'.  Stop.
-    

-    In this case,
-    the error is pretty obvious.
-    But if it weren't,
-    and you wanted to try to get more information
-    about the error,
-    the --debug=stacktrace option
-    would show you exactly where in the SCons source code
-    the problem occurs:
-
-    

      % scons -Q --debug=stacktrace
-      scons: *** Source `prog.c' not found, needed by target `prog.o'.  Stop.
-      scons: internal stack trace:
-        File "bootstrap/src/engine/SCons/Job.py", line 198, in start
-        File "bootstrap/src/engine/SCons/Script/Main.py", line 169, in prepare
-        File "bootstrap/src/engine/SCons/Taskmaster.py", line 184, in prepare
-        File "bootstrap/src/engine/SCons/Executor.py", line 171, in prepare
-    

-    Of course, if you do need to dive into the SCons source code,
-    we'd like to know if, or how,
-    the error messages or troubleshooting options
-    could have been improved to avoid that.
-    Not everyone has the necessary time or
-    Python skill to dive into the source code,
-    and we'd like to improve SCons
-    for those people as well...
-
-    
29.7. How is SCons Making Its Decisions?  the --taskmastertrace Option

-    The internal SCons subsystem that handles walking
-    the dependency graph
-    and controls the decision-making about what to rebuild
-    is the Taskmaster.
-    SCons supports a --taskmastertrace
-    option that tells the Taskmaster to print
-    information about the children (dependencies)
-    of the various Nodes on its walk down the graph,
-    which specific dependent Nodes are being evaluated,
-    and in what order.
-
-    

-    The --taskmastertrace option
-    takes as an argument the name of a file in
-    which to put the trace output,
-    with - (a single hyphen)
-    indicating that the trace messages
-    should be printed to the standard output:
-
-    

      env = Environment(CPPPATH = ['.'])
-      env.Program('prog.c')
-    

      % scons -Q --taskmastertrace=- prog
-      
-      Taskmaster: Looking for a node to evaluate
-      Taskmaster:     Considering node <no_state   0   'prog'> and its children:
-      Taskmaster:        <no_state   0   'prog.o'>
-      Taskmaster:      adjusting ref count: <pending    1   'prog'>
-      Taskmaster:     Considering node <no_state   0   'prog.o'> and its children:
-      Taskmaster:        <no_state   0   'prog.c'>
-      Taskmaster:        <no_state   0   'inc.h'>
-      Taskmaster:      adjusting ref count: <pending    1   'prog.o'>
-      Taskmaster:      adjusting ref count: <pending    2   'prog.o'>
-      Taskmaster:     Considering node <no_state   0   'prog.c'> and its children:
-      Taskmaster: Evaluating <pending    0   'prog.c'>
-      
-      Taskmaster: Looking for a node to evaluate
-      Taskmaster:     Considering node <no_state   0   'inc.h'> and its children:
-      Taskmaster: Evaluating <pending    0   'inc.h'>
-      
-      Taskmaster: Looking for a node to evaluate
-      Taskmaster:     Considering node <pending    0   'prog.o'> and its children:
-      Taskmaster:        <up_to_date 0   'prog.c'>
-      Taskmaster:        <up_to_date 0   'inc.h'>
-      Taskmaster: Evaluating <pending    0   'prog.o'>
-      cc -o prog.o -c -I. prog.c
-      
-      Taskmaster: Looking for a node to evaluate
-      Taskmaster:     Considering node <pending    0   'prog'> and its children:
-      Taskmaster:        <executed   0   'prog.o'>
-      Taskmaster: Evaluating <pending    0   'prog'>
-      cc -o prog prog.o
-      
-      Taskmaster: Looking for a node to evaluate
-      Taskmaster: No candidate anymore.
-    

-    The --taskmastertrace option
-    doesn't provide information about the actual
-    calculations involved in deciding if a file is up-to-date,
-    but it does show all of the dependencies
-    it knows about for each Node,
-    and the order in which those dependencies are evaluated.
-    This can be useful as an alternate way to determine
-    whether or not your SCons configuration,
-    or the implicit dependency scan,
-    has actually identified all the correct dependencies
-    you want it to.
-
-    
Appendix A. Construction Variables

-This appendix contains descriptions of all of the
-construction variables that are potentially
-available "out of the box" in this version of SCons.
-Whether or not setting a construction variable
-in a construction environment
-will actually have an effect depends on
-whether any of the Tools and/or Builders
-that use the variable have been
-included in the construction environment.
-
-

-In this appendix, we have
-appended the initial $
-(dollar sign) to the beginning of each
-variable name when it appears in the text,
-but left off the dollar sign
-in the left-hand column
-where the name appears for each entry.
-
-
AR

The static library archiver.
-
ARCHITECTURE

Specifies the system architecture for which
-the package is being built.
-The default is the system architecture
-of the machine on which SCons is running.
-This is used to fill in the
-Architecture:
-field in an Ipkg
-control file,
-and as part of the name of a generated RPM file.
-
ARCOM

The command line used to generate a static library from object files.
-
ARCOMSTR

The string displayed when an object file
-is generated from an assembly-language source file.
-If this is not set, then $ARCOM (the command line) is displayed.
-

env = Environment(ARCOMSTR = "Archiving $TARGET")
-
ARFLAGS

General options passed to the static library archiver.
-
AS

The assembler.
-
ASCOM

The command line used to generate an object file
-from an assembly-language source file.
-
ASCOMSTR

The string displayed when an object file
-is generated from an assembly-language source file.
-If this is not set, then $ASCOM (the command line) is displayed.
-

env = Environment(ASCOMSTR = "Assembling $TARGET")
-
ASFLAGS

General options passed to the assembler.
-
ASPPCOM

The command line used to assemble an assembly-language
-source file into an object file
-after first running the file through the C preprocessor.
-Any options specified
-in the $ASFLAGS and $CPPFLAGS construction variables
-are included on this command line.
-
ASPPCOMSTR

The string displayed when an object file
-is generated from an assembly-language source file
-after first running the file through the C preprocessor.
-If this is not set, then $ASPPCOM (the command line) is displayed.
-

env = Environment(ASPPCOMSTR = "Assembling $TARGET")
-
ASPPFLAGS

General options when an assembling an assembly-language
-source file into an object file
-after first running the file through the C preprocessor.
-The default is to use the value of $ASFLAGS.
-
BIBTEX

The bibliography generator for the TeX formatter and typesetter and the
-LaTeX structured formatter and typesetter.
-
BIBTEXCOM

The command line used to call the bibliography generator for the
-TeX formatter and typesetter and the LaTeX structured formatter and
-typesetter.
-
BIBTEXCOMSTR

The string displayed when generating a bibliography
-for TeX or LaTeX.
-If this is not set, then $BIBTEXCOM (the command line) is displayed.
-

env = Environment(BIBTEXCOMSTR = "Generating bibliography $TARGET")
-
BIBTEXFLAGS

General options passed to the bibliography generator for the TeX formatter
-and typesetter and the LaTeX structured formatter and typesetter.
-
BITKEEPER

The BitKeeper executable.
-
BITKEEPERCOM

The command line for
-fetching source files using BitKeeper.
-
BITKEEPERCOMSTR

The string displayed when fetching
-a source file using BitKeeper.
-If this is not set, then $BITKEEPERCOM
-(the command line) is displayed.
-
BITKEEPERGET

The command ($BITKEEPER) and subcommand
-for fetching source files using BitKeeper.
-
BITKEEPERGETFLAGS

Options that are passed to the BitKeeper
-get
-subcommand.
-
BUILDERS

A dictionary mapping the names of the builders
-available through this environment
-to underlying Builder objects.
-Builders named
-Alias, CFile, CXXFile, DVI, Library, Object, PDF, PostScript, and Program
-are available by default.
-If you initialize this variable when an
-Environment is created:
-

env = Environment(BUILDERS = {'NewBuilder' : foo})
-

the default Builders will no longer be available.
-To use a new Builder object in addition to the default Builders,
-add your new Builder object like this:
-

env = Environment()
-env.Append(BUILDERS = {'NewBuilder' : foo})
-

or this:
-

env = Environment()
-env['BUILDERS]['NewBuilder'] = foo
-
CC

The C compiler.
-
CCCOM

The command line used to compile a C source file to a (static) object
-file.  Any options specified in the $CFLAGS, $CCFLAGS and
-$CPPFLAGS construction variables are included on this command
-line.
-
CCCOMSTR

The string displayed when a C source file
-is compiled to a (static) object file.
-If this is not set, then $CCCOM (the command line) is displayed.
-

env = Environment(CCCOMSTR = "Compiling static object $TARGET")
-
CCFLAGS

General options that are passed to the C and C++ compilers.
-
CCPCHFLAGS

Options added to the compiler command line
-to support building with precompiled headers.
-The default value expands expands to the appropriate
-Microsoft Visual C++ command-line options
-when the $PCH construction variable is set.
-
CCPDBFLAGS

Options added to the compiler command line
-to support storing debugging information in a
-Microsoft Visual C++ PDB file.
-The default value expands expands to appropriate
-Microsoft Visual C++ command-line options
-when the $PDB construction variable is set.
The Visual C++ compiler option that SCons uses by default
-to generate PDB information is /Z7.
-This works correctly with parallel (-j) builds
-because it embeds the debug information in the intermediate object files,
-as opposed to sharing a single PDB file between multiple object files.
-This is also the only way to get debug information
-embedded into a static library.
-Using the /Zi instead may yield improved
-link-time performance,
-although parallel builds will no longer work.
You can generate PDB files with the /Zi
-switch by overriding the default $CCPDBFLAGS variable as follows:
-

env['CCPDBFLAGS'] = ['${(PDB and "/Zi /Fd%s" % File(PDB)) or ""}']
-

An alternative would be to use the /Zi
-to put the debugging information in a separate .pdb
-file for each object file by overriding
-the $CCPDBFLAGS variable as follows:
-

env['CCPDBFLAGS'] = '/Zi /Fd${TARGET}.pdb'
-
CCVERSION

The version number of the C compiler.
-This may or may not be set,
-depending on the specific C compiler being used.
-
CFILESUFFIX

The suffix for C source files.
-This is used by the internal CFile builder
-when generating C files from Lex (.l) or YACC (.y) input files.
-The default suffix, of course, is
-.c
-(lower case).
-On case-insensitive systems (like Windows),
-SCons also treats
-.C
-(upper case) files
-as C files.
-
CFLAGS

General options that are passed to the C compiler (C only; not C++).
-
CHANGE_SPECFILE

A hook for modifying the file that controls the packaging build
-(the .spec for RPM,
-the control for Ipkg,
-the .wxs for MSI).
-If set, the function will be called
-after the SCons template for the file has been written.
-XXX
-
CHANGELOG

The name of a file containing the change log text
-to be included in the package.
-This is included as the
-%changelog
-section of the RPM
-.spec file.
-
_concat

A function used to produce variables like $_CPPINCFLAGS. It takes
-four or five
-arguments: a prefix to concatenate onto each element, a list of
-elements, a suffix to concatenate onto each element, an environment
-for variable interpolation, and an optional function that will be
-called to transform the list before concatenation.
-

env['_CPPINCFLAGS'] = '$( ${_concat(INCPREFIX, CPPPATH, INCSUFFIX, __env__, RDirs)} $)',
-
CONFIGUREDIR

The name of the directory in which
-Configure context test files are written.
-The default is
-.sconf_temp
-in the top-level directory
-containing the
-SConstruct
-file.
-
CONFIGURELOG

The name of the Configure context log file.
-The default is
-config.log
-in the top-level directory
-containing the
-SConstruct
-file.
-
_CPPDEFFLAGS

An automatically-generated construction variable
-containing the C preprocessor command-line options
-to define values.
-The value of $_CPPDEFFLAGS is created
-by appending $CPPDEFPREFIX and $CPPDEFSUFFIX
-to the beginning and end
-of each directory in $CPPDEFINES.
-
CPPDEFINES

A platform independent specification of C preprocessor definitions.
-The definitions will be added to command lines
-through the automatically-generated
-$_CPPDEFFLAGS construction variable (see above),
-which is constructed according to
-the type of value of $CPPDEFINES:
If $CPPDEFINES is a string,
-the values of the
-$CPPDEFPREFIX and $CPPDEFSUFFIX
-construction variables
-will be added to the beginning and end.
-

# Will add -Dxyz to POSIX compiler command lines,
-# and /Dxyz to Microsoft Visual C++ command lines.
-env = Environment(CPPDEFINES='xyz')
-

If $CPPDEFINES is a list,
-the values of the
-$CPPDEFPREFIX and $CPPDEFSUFFIX
-construction variables
-will be appended to the beginning and end
-of each element in the list.
-If any element is a list or tuple,
-then the first item is the name being
-defined and the second item is its value:
-

# Will add -DB=2 -DA to POSIX compiler command lines,
-# and /DB=2 /DA to Microsoft Visual C++ command lines.
-env = Environment(CPPDEFINES=[('B', 2), 'A'])
-

If $CPPDEFINES is a dictionary,
-the values of the
-$CPPDEFPREFIX and $CPPDEFSUFFIX
-construction variables
-will be appended to the beginning and end
-of each item from the dictionary.
-The key of each dictionary item
-is a name being defined
-to the dictionary item's corresponding value;
-if the value is
-None,
-then the name is defined without an explicit value.
-Note that the resulting flags are sorted by keyword
-to ensure that the order of the options on the
-command line is consistent each time
-scons
-is run.
-

# Will add -DA -DB=2 to POSIX compiler command lines,
-# and /DA /DB=2 to Microsoft Visual C++ command lines.
-env = Environment(CPPDEFINES={'B':2, 'A':None})
-
CPPDEFPREFIX

The prefix used to specify preprocessor definitions
-on the C compiler command line.
-This will be appended to the beginning of each definition
-in the $CPPDEFINES construction variable
-when the $_CPPDEFFLAGS variable is automatically generated.
-
CPPDEFSUFFIX

The suffix used to specify preprocessor definitions
-on the C compiler command line.
-This will be appended to the end of each definition
-in the $CPPDEFINES construction variable
-when the $_CPPDEFFLAGS variable is automatically generated.
-
CPPFLAGS

User-specified C preprocessor options.
-These will be included in any command that uses the C preprocessor,
-including not just compilation of C and C++ source files
-via the $CCCOM,
-$SHCCCOM,
-$CXXCOM and
-$SHCXXCOM command lines,
-but also the $FORTRANPPCOM,
-$SHFORTRANPPCOM,
-$F77PPCOM and
-$SHF77PPCOM command lines
-used to compile a Fortran source file,
-and the $ASPPCOM command line
-used to assemble an assembly language source file,
-after first running each file through the C preprocessor.
-Note that this variable does
-not
-contain
--I
-(or similar) include search path options
-that scons generates automatically from $CPPPATH.
-See $_CPPINCFLAGS, below,
-for the variable that expands to those options.
-
_CPPINCFLAGS

An automatically-generated construction variable
-containing the C preprocessor command-line options
-for specifying directories to be searched for include files.
-The value of $_CPPINCFLAGS is created
-by appending $INCPREFIX and $INCSUFFIX
-to the beginning and end
-of each directory in $CPPPATH.
-
CPPPATH

The list of directories that the C preprocessor will search for include
-directories. The C/C++ implicit dependency scanner will search these
-directories for include files. Don't explicitly put include directory
-arguments in CCFLAGS or CXXFLAGS because the result will be non-portable
-and the directories will not be searched by the dependency scanner. Note:
-directory names in CPPPATH will be looked-up relative to the SConscript
-directory when they are used in a command. To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-

env = Environment(CPPPATH='#/include')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

include = Dir('include')
-env = Environment(CPPPATH=include)
-

The directory list will be added to command lines
-through the automatically-generated
-$_CPPINCFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$INCPREFIX and $INCSUFFIX
-construction variables
-to the beginning and end
-of each directory in $CPPPATH.
-Any command lines you define that need
-the CPPPATH directory list should
-include $_CPPINCFLAGS:
-

env = Environment(CCCOM="my_compiler $_CPPINCFLAGS -c -o $TARGET $SOURCE")
-
CPPSUFFIXES

The list of suffixes of files that will be scanned
-for C preprocessor implicit dependencies
-(#include lines).
-The default list is:
-

[".c", ".C", ".cxx", ".cpp", ".c++", ".cc",
- ".h", ".H", ".hxx", ".hpp", ".hh",
- ".F", ".fpp", ".FPP",
- ".m", ".mm",
- ".S", ".spp", ".SPP"]
-
CVS

The CVS executable.
-
CVSCOFLAGS

Options that are passed to the CVS checkout subcommand.
-
CVSCOM

The command line used to
-fetch source files from a CVS repository.
-
CVSCOMSTR

The string displayed when fetching
-a source file from a CVS repository.
-If this is not set, then $CVSCOM
-(the command line) is displayed.
-
CVSFLAGS

General options that are passed to CVS.
-By default, this is set to
--d $CVSREPOSITORY
-to specify from where the files must be fetched.
-
CVSREPOSITORY

The path to the CVS repository.
-This is referenced in the default
-$CVSFLAGS value.
-
CXX

The C++ compiler.
-
CXXCOM

The command line used to compile a C++ source file to an object file.
-Any options specified in the $CXXFLAGS and
-$CPPFLAGS construction variables
-are included on this command line.
-
CXXCOMSTR

The string displayed when a C++ source file
-is compiled to a (static) object file.
-If this is not set, then $CXXCOM (the command line) is displayed.
-

env = Environment(CXXCOMSTR = "Compiling static object $TARGET")
-
CXXFILESUFFIX

The suffix for C++ source files.
-This is used by the internal CXXFile builder
-when generating C++ files from Lex (.ll) or YACC (.yy) input files.
-The default suffix is
-.cc.
-SCons also treats files with the suffixes
-.cpp,
-.cxx,
-.c++,
-and
-.C++
-as C++ files,
-and files with
-.mm
-suffixes as Objective C++ files.
-On case-sensitive systems (Linux, UNIX, and other POSIX-alikes),
-SCons also treats
-.C
-(upper case) files
-as C++ files.
-
CXXFLAGS

General options that are passed to the C++ compiler.
-By default, this includes the value of $CCFLAGS,
-so that setting $CCFLAGS affects both C and C++ compilation.
-If you want to add C++-specific flags,
-you must set or override the value of $CXXFLAGS.
-
CXXVERSION

The version number of the C++ compiler.
-This may or may not be set,
-depending on the specific C++ compiler being used.
-
DESCRIPTION

A long description of the project being packaged.
-This is included in the relevant section
-of the file that controls the packaging build.
-
DESCRIPTION_lang

A language-specific long description for
-the specified lang.
-This is used to populate a
-%description -l
-section of an RPM
-.spec file.
-
Dir

A function that converts a string
-into a Dir instance relative to the target being built.
-
Dirs

A function that converts a list of strings
-into a list of Dir instances relative to the target being built.
-
DSUFFIXES

The list of suffixes of files that will be scanned
-for imported D package files.
-The default list is:
-

['.d']
-
DVIPDF

The TeX DVI file to PDF file converter.
-
DVIPDFCOM

The command line used to convert TeX DVI files into a PDF file.
-
DVIPDFCOMSTR

The string displayed when a TeX DVI file
-is converted into a PDF file.
-If this is not set, then $DVIPDFCOM (the command line) is displayed.
-
DVIPDFFLAGS

General options passed to the TeX DVI file to PDF file converter.
-
DVIPS

The TeX DVI file to PostScript converter.
-
DVIPSFLAGS

General options passed to the TeX DVI file to PostScript converter.
-
ENV

A dictionary of environment variables
-to use when invoking commands. When
-$ENV is used in a command all list
-values will be joined using the path separator and any other non-string
-values will simply be coerced to a string.
-Note that, by default,
-scons
-does
-not
-propagate the environment in force when you
-execute
-scons
-to the commands used to build target files.
-This is so that builds will be guaranteed
-repeatable regardless of the environment
-variables set at the time
-scons
-is invoked.
If you want to propagate your
-environment variables
-to the commands executed
-to build target files,
-you must do so explicitly:
-

import os
-env = Environment(ENV = os.environ)
-

Note that you can choose only to propagate
-certain environment variables.
-A common example is
-the system
-PATH
-environment variable,
-so that
-scons
-uses the same utilities
-as the invoking shell (or other process):
-

import os
-env = Environment(ENV = {'PATH' : os.environ['PATH']})
-
ESCAPE

A function that will be called to escape shell special characters in
-command lines. The function should take one argument: the command line
-string to escape; and should return the escaped command line.
-
F77

The Fortran 77 compiler.
-You should normally set the $FORTRAN variable,
-which specifies the default Fortran compiler
-for all Fortran versions.
-You only need to set $F77 if you need to use a specific compiler
-or compiler version for Fortran 77 files.
-
F77COM

The command line used to compile a Fortran 77 source file to an object file.
-You only need to set $F77COM if you need to use a specific
-command line for Fortran 77 files.
-You should normally set the $FORTRANCOM variable,
-which specifies the default command line
-for all Fortran versions.
-
F77COMSTR

The string displayed when a Fortran 77 source file
-is compiled to an object file.
-If this is not set, then $F77COM or $FORTRANCOM
-(the command line) is displayed.
-
F77FILESUFFIXES

The list of file extensions for which the F77 dialect will be used. By
-default, this is ['.f77']
-
F77FLAGS

General user-specified options that are passed to the Fortran 77 compiler.
-Note that this variable does
-not
-contain
--I
-(or similar) include search path options
-that scons generates automatically from $F77PATH.
-See
-$_F77INCFLAGS
-below,
-for the variable that expands to those options.
-You only need to set $F77FLAGS if you need to define specific
-user options for Fortran 77 files.
-You should normally set the $FORTRANFLAGS variable,
-which specifies the user-specified options
-passed to the default Fortran compiler
-for all Fortran versions.
-
_F77INCFLAGS

An automatically-generated construction variable
-containing the Fortran 77 compiler command-line options
-for specifying directories to be searched for include files.
-The value of $_F77INCFLAGS is created
-by appending $INCPREFIX and $INCSUFFIX
-to the beginning and end
-of each directory in $F77PATH.
-
F77PATH

The list of directories that the Fortran 77 compiler will search for include
-directories. The implicit dependency scanner will search these
-directories for include files. Don't explicitly put include directory
-arguments in $F77FLAGS because the result will be non-portable
-and the directories will not be searched by the dependency scanner. Note:
-directory names in $F77PATH will be looked-up relative to the SConscript
-directory when they are used in a command. To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-You only need to set $F77PATH if you need to define a specific
-include path for Fortran 77 files.
-You should normally set the $FORTRANPATH variable,
-which specifies the include path
-for the default Fortran compiler
-for all Fortran versions.
-

env = Environment(F77PATH='#/include')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

include = Dir('include')
-env = Environment(F77PATH=include)
-

The directory list will be added to command lines
-through the automatically-generated
-$_F77INCFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$INCPREFIX and $INCSUFFIX
-construction variables
-to the beginning and end
-of each directory in $F77PATH.
-Any command lines you define that need
-the F77PATH directory list should
-include $_F77INCFLAGS:
-

env = Environment(F77COM="my_compiler $_F77INCFLAGS -c -o $TARGET $SOURCE")
-
F77PPCOM

The command line used to compile a Fortran 77 source file to an object file
-after first running the file through the C preprocessor.
-Any options specified in the $F77FLAGS and $CPPFLAGS construction variables
-are included on this command line.
-You only need to set $F77PPCOM if you need to use a specific
-C-preprocessor command line for Fortran 77 files.
-You should normally set the $FORTRANPPCOM variable,
-which specifies the default C-preprocessor command line
-for all Fortran versions.
-
F77PPCOMSTR

The string displayed when a Fortran 77 source file
-is compiled to an object file
-after first running the file through the C preprocessor.
-If this is not set, then $F77PPCOM or $FORTRANPPCOM
-(the command line) is displayed.
-
F77PPFILESUFFIXES

The list of file extensions for which the compilation + preprocessor pass for
-F77 dialect will be used. By default, this is empty
-
F90

The Fortran 90 compiler.
-You should normally set the $FORTRAN variable,
-which specifies the default Fortran compiler
-for all Fortran versions.
-You only need to set $F90 if you need to use a specific compiler
-or compiler version for Fortran 90 files.
-
F90COM

The command line used to compile a Fortran 90 source file to an object file.
-You only need to set $F90COM if you need to use a specific
-command line for Fortran 90 files.
-You should normally set the $FORTRANCOM variable,
-which specifies the default command line
-for all Fortran versions.
-
F90COMSTR

The string displayed when a Fortran 90 source file
-is compiled to an object file.
-If this is not set, then $F90COM or $FORTRANCOM
-(the command line) is displayed.
-
F90FILESUFFIXES

The list of file extensions for which the F90 dialect will be used. By
-default, this is ['.f90']
-
F90FLAGS

General user-specified options that are passed to the Fortran 90 compiler.
-Note that this variable does
-not
-contain
--I
-(or similar) include search path options
-that scons generates automatically from $F90PATH.
-See
-$_F90INCFLAGS
-below,
-for the variable that expands to those options.
-You only need to set $F90FLAGS if you need to define specific
-user options for Fortran 90 files.
-You should normally set the $FORTRANFLAGS variable,
-which specifies the user-specified options
-passed to the default Fortran compiler
-for all Fortran versions.
-
_F90INCFLAGS

An automatically-generated construction variable
-containing the Fortran 90 compiler command-line options
-for specifying directories to be searched for include files.
-The value of $_F90INCFLAGS is created
-by appending $INCPREFIX and $INCSUFFIX
-to the beginning and end
-of each directory in $F90PATH.
-
F90PATH

The list of directories that the Fortran 90 compiler will search for include
-directories. The implicit dependency scanner will search these
-directories for include files. Don't explicitly put include directory
-arguments in $F90FLAGS because the result will be non-portable
-and the directories will not be searched by the dependency scanner. Note:
-directory names in $F90PATH will be looked-up relative to the SConscript
-directory when they are used in a command. To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-You only need to set $F90PATH if you need to define a specific
-include path for Fortran 90 files.
-You should normally set the $FORTRANPATH variable,
-which specifies the include path
-for the default Fortran compiler
-for all Fortran versions.
-

env = Environment(F90PATH='#/include')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

include = Dir('include')
-env = Environment(F90PATH=include)
-

The directory list will be added to command lines
-through the automatically-generated
-$_F90INCFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$INCPREFIX and $INCSUFFIX
-construction variables
-to the beginning and end
-of each directory in $F90PATH.
-Any command lines you define that need
-the F90PATH directory list should
-include $_F90INCFLAGS:
-

env = Environment(F90COM="my_compiler $_F90INCFLAGS -c -o $TARGET $SOURCE")
-
F90PPCOM

The command line used to compile a Fortran 90 source file to an object file
-after first running the file through the C preprocessor.
-Any options specified in the $F90FLAGS and $CPPFLAGS construction variables
-are included on this command line.
-You only need to set $F90PPCOM if you need to use a specific
-C-preprocessor command line for Fortran 90 files.
-You should normally set the $FORTRANPPCOM variable,
-which specifies the default C-preprocessor command line
-for all Fortran versions.
-
F90PPCOMSTR

The string displayed when a Fortran 90 source file
-is compiled after first running the file through the C preprocessor.
-If this is not set, then $F90PPCOM or $FORTRANPPCOM
-(the command line) is displayed.
-
F90PPFILESUFFIXES

The list of file extensions for which the compilation + preprocessor pass for
-F90 dialect will be used. By default, this is empty
-
F95

The Fortran 95 compiler.
-You should normally set the $FORTRAN variable,
-which specifies the default Fortran compiler
-for all Fortran versions.
-You only need to set $F95 if you need to use a specific compiler
-or compiler version for Fortran 95 files.
-
F95COM

The command line used to compile a Fortran 95 source file to an object file.
-You only need to set $F95COM if you need to use a specific
-command line for Fortran 95 files.
-You should normally set the $FORTRANCOM variable,
-which specifies the default command line
-for all Fortran versions.
-
F95COMSTR

The string displayed when a Fortran 95 source file
-is compiled to an object file.
-If this is not set, then $F95COM or $FORTRANCOM
-(the command line) is displayed.
-
F95FILESUFFIXES

The list of file extensions for which the F95 dialect will be used. By
-default, this is ['.f95']
-
F95FLAGS

General user-specified options that are passed to the Fortran 95 compiler.
-Note that this variable does
-not
-contain
--I
-(or similar) include search path options
-that scons generates automatically from $F95PATH.
-See
-$_F95INCFLAGS
-below,
-for the variable that expands to those options.
-You only need to set $F95FLAGS if you need to define specific
-user options for Fortran 95 files.
-You should normally set the $FORTRANFLAGS variable,
-which specifies the user-specified options
-passed to the default Fortran compiler
-for all Fortran versions.
-
_F95INCFLAGS

An automatically-generated construction variable
-containing the Fortran 95 compiler command-line options
-for specifying directories to be searched for include files.
-The value of $_F95INCFLAGS is created
-by appending $INCPREFIX and $INCSUFFIX
-to the beginning and end
-of each directory in $F95PATH.
-
F95PATH

The list of directories that the Fortran 95 compiler will search for include
-directories. The implicit dependency scanner will search these
-directories for include files. Don't explicitly put include directory
-arguments in $F95FLAGS because the result will be non-portable
-and the directories will not be searched by the dependency scanner. Note:
-directory names in $F95PATH will be looked-up relative to the SConscript
-directory when they are used in a command. To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-You only need to set $F95PATH if you need to define a specific
-include path for Fortran 95 files.
-You should normally set the $FORTRANPATH variable,
-which specifies the include path
-for the default Fortran compiler
-for all Fortran versions.
-

env = Environment(F95PATH='#/include')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

include = Dir('include')
-env = Environment(F95PATH=include)
-

The directory list will be added to command lines
-through the automatically-generated
-$_F95INCFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$INCPREFIX and $INCSUFFIX
-construction variables
-to the beginning and end
-of each directory in $F95PATH.
-Any command lines you define that need
-the F95PATH directory list should
-include $_F95INCFLAGS:
-

env = Environment(F95COM="my_compiler $_F95INCFLAGS -c -o $TARGET $SOURCE")
-
F95PPCOM

The command line used to compile a Fortran 95 source file to an object file
-after first running the file through the C preprocessor.
-Any options specified in the $F95FLAGS and $CPPFLAGS construction variables
-are included on this command line.
-You only need to set $F95PPCOM if you need to use a specific
-C-preprocessor command line for Fortran 95 files.
-You should normally set the $FORTRANPPCOM variable,
-which specifies the default C-preprocessor command line
-for all Fortran versions.
-
F95PPCOMSTR

The string displayed when a Fortran 95 source file
-is compiled to an object file
-after first running the file through the C preprocessor.
-If this is not set, then $F95PPCOM or $FORTRANPPCOM
-(the command line) is displayed.
-
F95PPFILESUFFIXES

The list of file extensions for which the compilation + preprocessor pass for
-F95 dialect will be used. By default, this is empty
-
File

A function that converts a string into a File instance relative to the
-target being built.
-
FORTRAN

The default Fortran compiler
-for all versions of Fortran.
-
FORTRANCOM

The command line used to compile a Fortran source file to an object file.
-By default, any options specified
-in the $FORTRANFLAGS,
-$CPPFLAGS,
-$_CPPDEFFLAGS,
-$_FORTRANMODFLAG, and
-$_FORTRANINCFLAGS construction variables
-are included on this command line.
-
FORTRANCOMSTR

The string displayed when a Fortran source file
-is compiled to an object file.
-If this is not set, then $FORTRANCOM
-(the command line) is displayed.
-
FORTRANFILESUFFIXES

The list of file extensions for which the FORTRAN dialect will be used. By
-default, this is ['.f', '.for', '.ftn']
-
FORTRANFLAGS

General user-specified options that are passed to the Fortran compiler.
-Note that this variable does
-not
-contain
--I
-(or similar) include or module search path options
-that scons generates automatically from $FORTRANPATH.
-See
-$_FORTRANINCFLAGS and $_FORTRANMODFLAG,
-below,
-for the variables that expand those options.
-
_FORTRANINCFLAGS

An automatically-generated construction variable
-containing the Fortran compiler command-line options
-for specifying directories to be searched for include
-files and module files.
-The value of $_FORTRANINCFLAGS is created
-by prepending/appending $INCPREFIX and $INCSUFFIX
-to the beginning and end
-of each directory in $FORTRANPATH.
-
FORTRANMODDIR

Directory location where the Fortran compiler should place
-any module files it generates.  This variable is empty, by default. Some
-Fortran compilers will internally append this directory in the search path
-for module files, as well.
-
FORTRANMODDIRPREFIX

The prefix used to specify a module directory on the Fortran compiler command
-line.
-This will be appended to the beginning of the directory
-in the $FORTRANMODDIR construction variables
-when the $_FORTRANMODFLAG variables is automatically generated.
-
FORTRANMODDIRSUFFIX

The suffix used to specify a module directory on the Fortran compiler command
-line.
-This will be appended to the beginning of the directory
-in the $FORTRANMODDIR construction variables
-when the $_FORTRANMODFLAG variables is automatically generated.
-
_FORTRANMODFLAG

An automatically-generated construction variable
-containing the Fortran compiler command-line option
-for specifying the directory location where the Fortran
-compiler should place any module files that happen to get
-generated during compilation.
-The value of $_FORTRANMODFLAG is created
-by prepending/appending $FORTRANMODDIRPREFIX and
-$FORTRANMODDIRSUFFIX
-to the beginning and end of the directory in $FORTRANMODDIR.
-
FORTRANMODPREFIX

The module file prefix used by the Fortran compiler.  SCons assumes that
-the Fortran compiler follows the quasi-standard naming convention for
-module files of
-module_name.mod.
-As a result, this variable is left empty, by default.  For situations in
-which the compiler does not necessarily follow the normal convention,
-the user may use this variable.  Its value will be appended to every
-module file name as scons attempts to resolve dependencies.
-
FORTRANMODSUFFIX

The module file suffix used by the Fortran compiler.  SCons assumes that
-the Fortran compiler follows the quasi-standard naming convention for
-module files of
-module_name.mod.
-As a result, this variable is set to ".mod", by default.  For situations
-in which the compiler does not necessarily follow the normal convention,
-the user may use this variable.  Its value will be appended to every
-module file name as scons attempts to resolve dependencies.
-
FORTRANPATH

The list of directories that the Fortran compiler will search for
-include files and (for some compilers) module files. The Fortran implicit
-dependency scanner will search these directories for include files (but
-not module files since they are autogenerated and, as such, may not
-actually exist at the time the scan takes place). Don't explicitly put
-include directory arguments in FORTRANFLAGS because the result will be
-non-portable and the directories will not be searched by the dependency
-scanner. Note: directory names in FORTRANPATH will be looked-up relative
-to the SConscript directory when they are used in a command. To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-

env = Environment(FORTRANPATH='#/include')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

include = Dir('include')
-env = Environment(FORTRANPATH=include)
-

The directory list will be added to command lines
-through the automatically-generated
-$_FORTRANINCFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$INCPREFIX and $INCSUFFIX
-construction variables
-to the beginning and end
-of each directory in $FORTRANPATH.
-Any command lines you define that need
-the FORTRANPATH directory list should
-include $_FORTRANINCFLAGS:
-

env = Environment(FORTRANCOM="my_compiler $_FORTRANINCFLAGS -c -o $TARGET $SOURCE")
-
FORTRANPPCOM

The command line used to compile a Fortran source file to an object file
-after first running the file through the C preprocessor.
-By default, any options specified in the $FORTRANFLAGS,
-$CPPFLAGS,
-$_CPPDEFFLAGS,
-$_FORTRANMODFLAG, and
-$_FORTRANINCFLAGS
-construction variables are included on this command line.
-
FORTRANPPCOMSTR

The string displayed when a Fortran source file
-is compiled to an object file
-after first running the file throught the C preprocessor.
-If this is not set, then $FORTRANPPCOM
-(the command line) is displayed.
-
FORTRANPPFILESUFFIXES

The list of file extensions for which the compilation + preprocessor pass for
-FORTRAN dialect will be used. By default, this is ['.fpp', '.FPP']
-
FORTRANSUFFIXES

The list of suffixes of files that will be scanned
-for Fortran implicit dependencies
-(INCLUDE lines and USE statements).
-The default list is:
-

[".f", ".F", ".for", ".FOR", ".ftn", ".FTN", ".fpp", ".FPP",
-".f77", ".F77", ".f90", ".F90", ".f95", ".F95"]
-
FRAMEWORKPATH

On Mac OS X with gcc,
-a list containing the paths to search for frameworks.
-Used by the compiler to find framework-style includes like
-#include <Fmwk/Header.h>.
-Used by the linker to find user-specified frameworks when linking (see
-$FRAMEWORKS).
-For example:
-

 env.AppendUnique(FRAMEWORKPATH='#myframeworkdir')
-

will add
-

  ... -Fmyframeworkdir
-

to the compiler and linker command lines.
-
_FRAMEWORKPATH

On Mac OS X with gcc, an automatically-generated construction variable
-containing the linker command-line options corresponding to
-$FRAMEWORKPATH.
-
FRAMEWORKPATHPREFIX

On Mac OS X with gcc, the prefix to be used for the FRAMEWORKPATH entries.
-(see $FRAMEWORKPATH).
-The default value is
--F.
-
FRAMEWORKPREFIX

On Mac OS X with gcc,
-the prefix to be used for linking in frameworks
-(see $FRAMEWORKS).
-The default value is
--framework.
-
_FRAMEWORKS

On Mac OS X with gcc,
-an automatically-generated construction variable
-containing the linker command-line options
-for linking with FRAMEWORKS.
-
FRAMEWORKS

On Mac OS X with gcc, a list of the framework names to be linked into a
-program or shared library or bundle.
-The default value is the empty list.
-For example:
-

 env.AppendUnique(FRAMEWORKS=Split('System Cocoa SystemConfiguration'))
-

FRAMEWORKSFLAGS

On Mac OS X with gcc,
-general user-supplied frameworks options to be added at
-the end of a command
-line building a loadable module.
-(This has been largely superceded by
-the $FRAMEWORKPATH, $FRAMEWORKPATHPREFIX,
-$FRAMEWORKPREFIX and $FRAMEWORKS variables
-described above.)
-
GS

The Ghostscript program used to convert PostScript to PDF files.
-
GSCOM

The Ghostscript command line used to convert PostScript to PDF files.
-
GSCOMSTR

The string displayed when
-Ghostscript is used to convert
-a PostScript file to a PDF file.
-If this is not set, then $GSCOM (the command line) is displayed.
-
GSFLAGS

General options passed to the Ghostscript program
-when converting PostScript to PDF files.
-
IDLSUFFIXES

The list of suffixes of files that will be scanned
-for IDL implicit dependencies
-(#include or import lines).
-The default list is:
-

[".idl", ".IDL"]
-
IMPLICIT_COMMAND_DEPENDENCIES

Controls whether or not SCons will
-add implicit dependencies for the commands
-executed to build targets.
By default, SCons will add
-to each target
-an implicit dependency on the command
-represented by the first argument on any
-command line it executes.
-The specific file for the dependency is
-found by searching the
-PATH
-variable in the
-ENV
-environment used to execute the command.
If the construction variable
-$IMPLICIT_COMMAND_DEPENDENCIES
-is set to a false value
-(None,
-False,
-0,
-etc.),
-then the implicit dependency will
-not be added to the targets
-built with that construction environment.
-

env = Environment(IMPLICIT_COMMAND_DEPENDENCIES = 0)
-
INCPREFIX

The prefix used to specify an include directory on the C compiler command
-line.
-This will be appended to the beginning of each directory
-in the $CPPPATH and $FORTRANPATH construction variables
-when the $_CPPINCFLAGS and $_FORTRANINCFLAGS
-variables are automatically generated.
-
INCSUFFIX

The suffix used to specify an include directory on the C compiler command
-line.
-This will be appended to the end of each directory
-in the $CPPPATH and $FORTRANPATH construction variables
-when the $_CPPINCFLAGS and $_FORTRANINCFLAGS
-variables are automatically generated.
-
INSTALL

A function to be called to install a file into a
-destination file name.
-The default function copies the file into the destination
-(and sets the destination file's mode and permission bits
-to match the source file's).
-The function takes the following arguments:
-

def install(dest, source, env):
-

dest
-is the path name of the destination file.
-source
-is the path name of the source file.
-env
-is the construction environment
-(a dictionary of construction values)
-in force for this file installation.
-
INSTALLSTR

The string displayed when a file is
-installed into a destination file name.
-The default is:
-

Install file: "$SOURCE" as "$TARGET"
-
INTEL_C_COMPILER_VERSION

Set by the "intelc" Tool
-to the major version number of the Intel C compiler
-selected for use.
-
JAR

The Java archive tool.
-
JARCHDIR

The directory to which the Java archive tool should change
-(using the
--C
-option).
-
JARCOM

The command line used to call the Java archive tool.
-
JARCOMSTR

The string displayed when the Java archive tool
-is called
-If this is not set, then $JARCOM (the command line) is displayed.
-

env = Environment(JARCOMSTR = "JARchiving $SOURCES into $TARGET")
-
JARFLAGS

General options passed to the Java archive tool.
-By default this is set to
-cf
-to create the necessary
-jar
-file.
-
JARSUFFIX

The suffix for Java archives:
-.jar
-by default.
-
JAVABOOTCLASSPATH

Specifies the list of directories that
-will be added to the
-javac command line
-via the -bootclasspath option.
-The individual directory names will be
-separated by the operating system's path separate character
-(: on UNIX/Linux/POSIX,
-; on Windows).
-
JAVAC

The Java compiler.
-
JAVACCOM

The command line used to compile a directory tree containing
-Java source files to
-corresponding Java class files.
-Any options specified in the $JAVACFLAGS construction variable
-are included on this command line.
-
JAVACCOMSTR

The string displayed when compiling
-a directory tree of Java source files to
-corresponding Java class files.
-If this is not set, then $JAVACCOM (the command line) is displayed.
-

env = Environment(JAVACCOMSTR = "Compiling class files $TARGETS from $SOURCES")
-
JAVACFLAGS

General options that are passed to the Java compiler.
-
JAVACLASSDIR

The directory in which Java class files may be found.
-This is stripped from the beginning of any Java .class
-file names supplied to the
-JavaH
-builder.
-
JAVACLASSPATH

Specifies the list of directories that
-will be searched for Java
-.class file.
-The directories in this list will be added to the
-javac and javah command lines
-via the -classpath option.
-The individual directory names will be
-separated by the operating system's path separate character
-(: on UNIX/Linux/POSIX,
-; on Windows).
Note that this currently just adds the specified
-directory via the -classpath option.
-SCons does not currently search the
-$JAVACLASSPATH directories for dependency
-.class files.
-
JAVACLASSSUFFIX

The suffix for Java class files;
-.class
-by default.
-
JAVAH

The Java generator for C header and stub files.
-
JAVAHCOM

The command line used to generate C header and stub files
-from Java classes.
-Any options specified in the $JAVAHFLAGS construction variable
-are included on this command line.
-
JAVAHCOMSTR

The string displayed when C header and stub files
-are generated from Java classes.
-If this is not set, then $JAVAHCOM (the command line) is displayed.
-

env = Environment(JAVAHCOMSTR = "Generating header/stub file(s) $TARGETS from $SOURCES")
-
JAVAHFLAGS

General options passed to the C header and stub file generator
-for Java classes.
-
JAVASOURCEPATH

Specifies the list of directories that
-will be searched for input
-.java file.
-The directories in this list will be added to the
-javac command line
-via the -sourcepath option.
-The individual directory names will be
-separated by the operating system's path separate character
-(: on UNIX/Linux/POSIX,
-; on Windows).
Note that this currently just adds the specified
-directory via the -sourcepath option.
-SCons does not currently search the
-$JAVASOURCEPATH directories for dependency
-.java files.
-
JAVASUFFIX

The suffix for Java files;
-.java
-by default.
-
JAVAVERSION

Specifies the Java version being used by the Java builder.
-This is not currently used to select one
-version of the Java compiler vs. another.
-Instead, you should set this to specify the version of Java
-supported by your javac compiler.
-The default is 1.4.
This is sometimes necessary because
-Java 1.5 changed the file names that are created
-for nested anonymous inner classes,
-which can cause a mismatch with the files
-that SCons expects will be generated by the javac compiler.
-Setting $JAVAVERSION to 1.5
-(or 1.6, as appropriate)
-can make SCons realize that a Java 1.5 or 1.6
-build is actually up to date.
-
LATEX

The LaTeX structured formatter and typesetter.
-
LATEXCOM

The command line used to call the LaTeX structured formatter and typesetter.
-
LATEXCOMSTR

The string displayed when calling
-the LaTeX structured formatter and typesetter.
-If this is not set, then $LATEXCOM (the command line) is displayed.
-

env = Environment(LATEXCOMSTR = "Building $TARGET from LaTeX input $SOURCES")
-
LATEXFLAGS

General options passed to the LaTeX structured formatter and typesetter.
-
LATEXRETRIES

The maximum number of times that LaTeX
-will be re-run if the
-.log
-generated by the $LATEXCOM command
-indicates that there are undefined references.
-The default is to try to resolve undefined references
-by re-running LaTeX up to three times.
-
LATEXSUFFIXES

The list of suffixes of files that will be scanned
-for LaTeX implicit dependencies
-(\include or \import files).
-The default list is:
-

[".tex", ".ltx", ".latex"]
-
LDMODULE

The linker for building loadable modules.
-By default, this is the same as $SHLINK.
-
LDMODULECOM

The command line for building loadable modules.
-On Mac OS X, this uses the $LDMODULE,
-$LDMODULEFLAGS and
-$FRAMEWORKSFLAGS variables.
-On other systems, this is the same as $SHLINK.
-
LDMODULECOMSTR

The string displayed when building loadable modules.
-If this is not set, then $LDMODULECOM (the command line) is displayed.
-
LDMODULEFLAGS

General user options passed to the linker for building loadable modules.
-
LDMODULEPREFIX

The prefix used for loadable module file names.
-On Mac OS X, this is null;
-on other systems, this is
-the same as $SHLIBPREFIX.
-
LDMODULESUFFIX

The suffix used for loadable module file names.
-On Mac OS X, this is null;
-on other systems, this is
-the same as $SHLIBSUFFIX.
-
LEX

The lexical analyzer generator.
-
LEXCOM

The command line used to call the lexical analyzer generator
-to generate a source file.
-
LEXCOMSTR

The string displayed when generating a source file
-using the lexical analyzer generator.
-If this is not set, then $LEXCOM (the command line) is displayed.
-

env = Environment(LEXCOMSTR = "Lex'ing $TARGET from $SOURCES")
-
LEXFLAGS

General options passed to the lexical analyzer generator.
-
_LIBDIRFLAGS

An automatically-generated construction variable
-containing the linker command-line options
-for specifying directories to be searched for library.
-The value of $_LIBDIRFLAGS is created
-by appending $LIBDIRPREFIX and $LIBDIRSUFFIX
-to the beginning and end
-of each directory in $LIBPATH.
-
LIBDIRPREFIX

The prefix used to specify a library directory on the linker command line.
-This will be appended to the beginning of each directory
-in the $LIBPATH construction variable
-when the $_LIBDIRFLAGS variable is automatically generated.
-
LIBDIRSUFFIX

The suffix used to specify a library directory on the linker command line.
-This will be appended to the end of each directory
-in the $LIBPATH construction variable
-when the $_LIBDIRFLAGS variable is automatically generated.
-
_LIBFLAGS

An automatically-generated construction variable
-containing the linker command-line options
-for specifying libraries to be linked with the resulting target.
-The value of $_LIBFLAGS is created
-by appending $LIBLINKPREFIX and $LIBLINKSUFFIX
-to the beginning and end
-of each filename in $LIBS.
-
LIBLINKPREFIX

The prefix used to specify a library to link on the linker command line.
-This will be appended to the beginning of each library
-in the $LIBS construction variable
-when the $_LIBFLAGS variable is automatically generated.
-
LIBLINKSUFFIX

The suffix used to specify a library to link on the linker command line.
-This will be appended to the end of each library
-in the $LIBS construction variable
-when the $_LIBFLAGS variable is automatically generated.
-
LIBPATH

The list of directories that will be searched for libraries.
-The implicit dependency scanner will search these
-directories for include files. Don't explicitly put include directory
-arguments in $LINKFLAGS or $SHLINKFLAGS
-because the result will be non-portable
-and the directories will not be searched by the dependency scanner. Note:
-directory names in LIBPATH will be looked-up relative to the SConscript
-directory when they are used in a command. To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-

env = Environment(LIBPATH='#/libs')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

libs = Dir('libs')
-env = Environment(LIBPATH=libs)
-

The directory list will be added to command lines
-through the automatically-generated
-$_LIBDIRFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$LIBDIRPREFIX and $LIBDIRSUFFIX
-construction variables
-to the beginning and end
-of each directory in $LIBPATH.
-Any command lines you define that need
-the LIBPATH directory list should
-include $_LIBDIRFLAGS:
-

env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE")
-
LIBPREFIX

The prefix used for (static) library file names.
-A default value is set for each platform
-(posix, win32, os2, etc.),
-but the value is overridden by individual tools
-(ar, mslib, sgiar, sunar, tlib, etc.)
-to reflect the names of the libraries they create.
-
LIBPREFIXES

A list of all legal prefixes for library file names.
-When searching for library dependencies,
-SCons will look for files with these prefixes,
-the base library name,
-and suffixes in the $LIBSUFFIXES list.
-
LIBS

A list of one or more libraries
-that will be linked with
-any executable programs
-created by this environment.
The library list will be added to command lines
-through the automatically-generated
-$_LIBFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$LIBLINKPREFIX and $LIBLINKSUFFIX
-construction variables
-to the beginning and end
-of each filename in $LIBS.
-Any command lines you define that need
-the LIBS library list should
-include $_LIBFLAGS:
-

env = Environment(LINKCOM="my_linker $_LIBDIRFLAGS $_LIBFLAGS -o $TARGET $SOURCE")
-

If you add a
-File
-object to the
-$LIBS
-list, the name of that file will be added to
-$_LIBFLAGS,
-and thus the link line, as is, without
-$LIBLINKPREFIX
-or
-$LIBLINKSUFFIX.
-For example:
-

env.Append(LIBS=File('/tmp/mylib.so'))
-

In all cases, scons will add dependencies from the executable program to
-all the libraries in this list.
-
LIBSUFFIX

The suffix used for (static) library file names.
-A default value is set for each platform
-(posix, win32, os2, etc.),
-but the value is overridden by individual tools
-(ar, mslib, sgiar, sunar, tlib, etc.)
-to reflect the names of the libraries they create.
-
LIBSUFFIXES

A list of all legal suffixes for library file names.
-When searching for library dependencies,
-SCons will look for files with prefixes, in the $LIBPREFIXES list,
-the base library name,
-and these suffixes.
-
LICENSE

The abbreviated name of the license under which
-this project is released (gpl, lpgl, bsd etc.).
-See http://www.opensource.org/licenses/alphabetical
-for a list of license names.
-
LINK

The linker.
-
LINKCOM

The command line used to link object files into an executable.
-
LINKCOMSTR

The string displayed when object files
-are linked into an executable.
-If this is not set, then $LINKCOM (the command line) is displayed.
-

env = Environment(LINKCOMSTR = "Linking $TARGET")
-
LINKFLAGS

General user options passed to the linker.
-Note that this variable should
-not
-contain
--l
-(or similar) options for linking with the libraries listed in $LIBS,
-nor
--L
-(or similar) library search path options
-that scons generates automatically from $LIBPATH.
-See
-$_LIBFLAGS
-above,
-for the variable that expands to library-link options,
-and
-$_LIBDIRFLAGS
-above,
-for the variable that expands to library search path options.
-
M4

The M4 macro preprocessor.
-
M4COM

The command line used to pass files through the M4 macro preprocessor.
-
M4COMSTR

The string displayed when
-a file is passed through the M4 macro preprocessor.
-If this is not set, then $M4COM (the command line) is displayed.
-
M4FLAGS

General options passed to the M4 macro preprocessor.
-
MAKEINDEX

The makeindex generator for the TeX formatter and typesetter and the
-LaTeX structured formatter and typesetter.
-
MAKEINDEXCOM

The command line used to call the makeindex generator for the
-TeX formatter and typesetter and the LaTeX structured formatter and
-typesetter.
-
MAKEINDEXCOMSTR

The string displayed when calling the makeindex generator for the
-TeX formatter and typesetter
-and the LaTeX structured formatter and typesetter.
-If this is not set, then $MAKEINDEXCOM (the command line) is displayed.
-
MAKEINDEXFLAGS

General options passed to the makeindex generator for the TeX formatter
-and typesetter and the LaTeX structured formatter and typesetter.
-
MAXLINELENGTH

The maximum number of characters allowed on an external command line.
-On Win32 systems,
-link lines longer than this many characters
-are linked via a temporary file name.
-
MIDL

The Microsoft IDL compiler.
-
MIDLCOM

The command line used to pass files to the Microsoft IDL compiler.
-
MIDLCOMSTR

The string displayed when
-the Microsoft IDL copmiler is called.
-If this is not set, then $MIDLCOM (the command line) is displayed.
-
MIDLFLAGS

General options passed to the Microsoft IDL compiler.
-
MSVS

When the Microsoft Visual Studio tools are initialized, they set up
-this dictionary with the following keys:
VERSION:
-the version of MSVS being used (can be set via
-MSVS_VERSION)
VERSIONS:
-the available versions of MSVS installed
VCINSTALLDIR:
-installed directory of Visual C++
VSINSTALLDIR:
-installed directory of Visual Studio
FRAMEWORKDIR:
-installed directory of the .NET framework
FRAMEWORKVERSIONS:
-list of installed versions of the .NET framework, sorted latest to oldest.
FRAMEWORKVERSION:
-latest installed version of the .NET framework
FRAMEWORKSDKDIR:
-installed location of the .NET SDK.
PLATFORMSDKDIR:
-installed location of the Platform SDK.
PLATFORMSDK_MODULES:
-dictionary of installed Platform SDK modules,
-where the dictionary keys are keywords for the various modules, and
-the values are 2-tuples where the first is the release date, and the
-second is the version number.
If a value isn't set, it wasn't available in the registry.
-
MSVS_IGNORE_IDE_PATHS

Tells the MS Visual Studio tools to use minimal INCLUDE, LIB, and PATH settings,
-instead of the settings from the IDE.
For Visual Studio, SCons will (by default) automatically determine
-where MSVS is installed, and use the LIB, INCLUDE, and PATH variables
-set by the IDE.  You can override this behavior by setting these
-variables after Environment initialization, or by setting
-MSVS_IGNORE_IDE_PATHS = 1
-in the Environment initialization.
-Specifying this will not leave these unset, but will set them to a
-minimal set of paths needed to run the tools successfully.
For VS6, the mininimal set is:
-

   INCLUDE:'<VSDir>\VC98\ATL\include;<VSDir>\VC98\MFC\include;<VSDir>\VC98\include'
-   LIB:'<VSDir>\VC98\MFC\lib;<VSDir>\VC98\lib'
-   PATH:'<VSDir>\Common\MSDev98\bin;<VSDir>\VC98\bin'
-

For VS7, it is:
-

   INCLUDE:'<VSDir>\Vc7\atlmfc\include;<VSDir>\Vc7\include'
-   LIB:'<VSDir>\Vc7\atlmfc\lib;<VSDir>\Vc7\lib'
-   PATH:'<VSDir>\Common7\Tools\bin;<VSDir>\Common7\Tools;<VSDir>\Vc7\bin'
-

Where '<VSDir>' is the installed location of Visual Studio.
-
MSVS_PROJECT_BASE_PATH

The string
-placed in a generated Microsoft Visual Studio solution file
-as the value of the
-SccProjectFilePathRelativizedFromConnection0
-and
-SccProjectFilePathRelativizedFromConnection1
-attributes of the
-GlobalSection(SourceCodeControl)
-section.
-There is no default value.
-
MSVS_PROJECT_GUID

The string
-placed in a generated Microsoft Visual Studio project file
-as the value of the
-ProjectGUID
-attribute.
-The string is also placed in the
-SolutionUniqueID
-attribute of the
-GlobalSection(SourceCodeControl)
-section of the Microsoft Visual Studio solution file.
-There is no default value.
-
MSVS_SCC_AUX_PATH

The path name
-placed in a generated Microsoft Visual Studio project file
-as the value of the
-SccAuxPath
-attribute
-if the
-MSVS_SCC_PROVIDER
-construction variable is also set.
-There is no default value.
-
MSVS_SCC_LOCAL_PATH

The path name
-placed in a generated Microsoft Visual Studio project file
-as the value of the
-SccLocalPath
-attribute
-if the
-MSVS_SCC_PROVIDER
-construction variable is also set.
-The path name is also placed in the
-SccLocalPath0
-and
-SccLocalPath1
-attributes of the
-GlobalSection(SourceCodeControl)
-section of the Microsoft Visual Studio solution file.
-There is no default value.
-
MSVS_SCC_PROJECT_NAME

The project name
-placed in a generated Microsoft Visual Studio project file
-as the value of the
-SccProjectName
-attribute.
-There is no default value.
-
MSVS_SCC_PROVIDER

The string
-placed in a generated Microsoft Visual Studio project file
-as the value of the
-SccProvider
-attribute.
-The string is also placed in the
-SccProvider1
-attribute of the
-GlobalSection(SourceCodeControl)
-section of the Microsoft Visual Studio solution file.
-There is no default value.
-
MSVS_USE_MFC_DIRS

Tells the MS Visual Studio tool(s) to use
-the MFC directories in its default paths
-for compiling and linking.
-The $MSVS_USE_MFC_DIRS variable has no effect if the
-INCLUDE
-or
-LIB
-environment variables are set explictly.
Under Visual Studio version 6,
-setting
-$MSVS_USE_MFC_DIRS
-to a non-zero value
-adds the
-ATL\include
-and
-MFC\include
-directories to
-the default
-INCLUDE
-external environment variable,
-and adds the
-MFC\lib
-directory to
-the default
-LIB
-external environment variable.
Under Visual Studio version 7,
-setting
-$MSVS_USE_MFC_DIRS
-to a non-zero value
-adds the
-atlmfc\include
-directory to the default
-INCLUDE
-external environment variable,
-and adds the
-atlmfc\lib
-directory to the default
-LIB
-external environment variable.
Under Visual Studio version 8,
-setting
-$MSVS_USE_MFC_DIRS
-to a non-zero value will,
-by default,
-add the
-atlmfc\include
-directory to the default
-INCLUDE
-external environment variable,
-and the
-atlmfc\lib
-directory to the default
-LIB
-external environment variable.
-If, however, the
-['MSVS']['PLATFORMSDKDIR']
-variable is set,
-then the
-mfc
-and the
-atl
-subdirectories of the
-PLATFORMSDKDIR
-are added to the default value of the
-INCLUDE
-external environment variable,
-and the default value of the
-LIB
-external environment variable is left untouched.
-
MSVS_VERSION

Sets the preferred version of MSVS to use.
SCons will (by default) select the latest version of MSVS
-installed on your machine.
-So, if you have version 6 and version 7 (MSVS .NET) installed,
-it will prefer version 7.
-You can override this by
-specifying the
-MSVS_VERSION
-variable in the Environment initialization, setting it to the
-appropriate version ('6.0' or '7.0', for example).
-If the given version isn't installed, tool initialization will fail.
-
MSVSBUILDCOM

The build command line placed in
-a generated Microsoft Visual Studio project file.
-The default is to have Visual Studio invoke SCons with any specified
-build targets.
-
MSVSCLEANCOM

The clean command line placed in
-a generated Microsoft Visual Studio project file.
-The default is to have Visual Studio invoke SCons with the -c option
-to remove any specified targets.
-
MSVSENCODING

The encoding string placed in
-a generated Microsoft Visual Studio project file.
-The default is encoding
-Windows-1252.
-
MSVSPROJECTCOM

The action used to generate Microsoft Visual Studio project files.
-
MSVSPROJECTSUFFIX

The suffix used for Microsoft Visual Studio project (DSP) files.
-The default value is
-.vcproj
-when using Visual Studio version 7.x (.NET)
-or later version,
-and
-.dsp
-when using earlier versions of Visual Studio.
-
MSVSREBUILDCOM

The rebuild command line placed in
-a generated Microsoft Visual Studio project file.
-The default is to have Visual Studio invoke SCons with any specified
-rebuild targets.
-
MSVSSCONS

The SCons used in generated Microsoft Visual Studio project files.
-The default is the version of SCons being
-used to generate the project file.
-
MSVSSCONSCOM

The default SCons command used in generated Microsoft Visual Studio
-project files.
-
MSVSSCONSCRIPT

The sconscript file
-(that is,
-SConstruct
-or
-SConscript
-file)
-that will be invoked by Visual Studio
-project files
-(through the
-$MSVSSCONSCOM
-variable).
-The default is the same sconscript file
-that contains the call to
-MSVSProject
-to build the project file.
-
MSVSSCONSFLAGS

The SCons flags used in generated Microsoft Visual Studio
-project files.
-
MSVSSOLUTIONCOM

The action used to generate Microsoft Visual Studio solution files.
-
MSVSSOLUTIONSUFFIX

The suffix used for Microsoft Visual Studio solution (DSW) files.
-The default value is
-.sln
-when using Visual Studio version 7.x (.NET),
-and
-.dsw
-when using earlier versions of Visual Studio.
-
MWCW_VERSION

The version number of the MetroWerks CodeWarrior C compiler
-to be used.
-
MWCW_VERSIONS

A list of installed versions of the MetroWerks CodeWarrior C compiler
-on this system.
-
NAME

Specfies the name of the project to package.
-
no_import_lib

When set to non-zero,
-suppresses creation of a corresponding Windows static import lib by the
-SharedLibrary
-builder when used with
-MinGW, Microsoft Visual Studio or Metrowerks.
-This also suppresses creation
-of an export (.exp) file
-when using Microsoft Visual Studio.
-
OBJPREFIX

The prefix used for (static) object file names.
-
OBJSUFFIX

The suffix used for (static) object file names.
-
P4

The Perforce executable.
-
P4COM

The command line used to
-fetch source files from Perforce.
-
P4COMSTR

The string displayed when
-fetching a source file from Perforce.
-If this is not set, then $P4COM (the command line) is displayed.
-
P4FLAGS

General options that are passed to Perforce.
-
PACKAGEROOT

Specifies the directory where all files in resulting archive will be
-placed if applicable.  The default value is "$NAME-$VERSION".
-
PACKAGETYPE

Selects the package type to build.  Currently these are available:
 * msi - Microsoft Installer
- * rpm - Redhat Package Manger
- * ipkg - Itsy Package Management System
- * tarbz2 - compressed tar
- * targz - compressed tar
- * zip - zip file
- * src_tarbz2 - compressed tar source
- * src_targz - compressed tar source
- * src_zip - zip file source
This may be overridden with the "package_type" command line option.
-
PACKAGEVERSION

The version of the package (not the underlying project).
-This is currently only used by the rpm packager
-and should reflect changes in the packaging,
-not the underlying project code itself.
-
PCH

The Microsoft Visual C++ precompiled header that will be used when compiling
-object files. This variable is ignored by tools other than Microsoft Visual C++.
-When this variable is
-defined SCons will add options to the compiler command line to
-cause it to use the precompiled header, and will also set up the
-dependencies for the PCH file.
-Example:
-

env['PCH'] = 'StdAfx.pch'
-
PCHCOM

The command line used by the
-PCH
-builder to generated a precompiled header.
-
PCHCOMSTR

The string displayed when generating a precompiled header.
-If this is not set, then $PCHCOM (the command line) is displayed.
-
PCHPDBFLAGS

A construction variable that, when expanded,
-adds the /yD flag to the command line
-only if the $PDB construction variable is set.
-
PCHSTOP

This variable specifies how much of a source file is precompiled. This
-variable is ignored by tools other than Microsoft Visual C++, or when
-the PCH variable is not being used. When this variable is define it
-must be a string that is the name of the header that
-is included at the end of the precompiled portion of the source files, or
-the empty string if the "#pragma hrdstop" construct is being used:
-

env['PCHSTOP'] = 'StdAfx.h'
-
PDB

The Microsoft Visual C++ PDB file that will store debugging information for
-object files, shared libraries, and programs. This variable is ignored by
-tools other than Microsoft Visual C++.
-When this variable is
-defined SCons will add options to the compiler and linker command line to
-cause them to generate external debugging information, and will also set up the
-dependencies for the PDB file.
-Example:
-

env['PDB'] = 'hello.pdb'
-

The Visual C++ compiler switch that SCons uses by default
-to generate PDB information is /Z7.
-This works correctly with parallel (-j) builds
-because it embeds the debug information in the intermediate object files,
-as opposed to sharing a single PDB file between multiple object files.
-This is also the only way to get debug information
-embedded into a static library.
-Using the /Zi instead may yield improved
-link-time performance,
-although parallel builds will no longer work.
-You can generate PDB files with the /Zi
-switch by overriding the default $CCPDBFLAGS variable;
-see the entry for that variable for specific examples.
-
PDFCOM

A deprecated synonym for $DVIPDFCOM.
-
PDFLATEX

The pdflatex utility.
-
PDFLATEXCOM

The command line used to call the pdflatex utility.
-
PDFLATEXCOMSTR

The string displayed when calling the pdflatex utility.
-If this is not set, then $PDFLATEXCOM (the command line) is displayed.
-

env = Environment(PDFLATEX;COMSTR = "Building $TARGET from LaTeX input $SOURCES")
-
PDFLATEXFLAGS

General options passed to the pdflatex utility.
-
PDFPREFIX

The prefix used for PDF file names.
-
PDFSUFFIX

The suffix used for PDF file names.
-
PDFTEX

The pdftex utility.
-
PDFTEXCOM

The command line used to call the pdftex utility.
-
PDFTEXCOMSTR

The string displayed when calling the pdftex utility.
-If this is not set, then $PDFTEXCOM (the command line) is displayed.
-

env = Environment(PDFTEXCOMSTR = "Building $TARGET from TeX input $SOURCES")
-
PDFTEXFLAGS

General options passed to the pdftex utility.
-
PKGCHK

On Solaris systems,
-the package-checking program that will
-be used (along with $PKGINFO)
-to look for installed versions of
-the Sun PRO C++ compiler.
-The default is
-/usr/sbin/pgkchk.
-
PKGINFO

On Solaris systems,
-the package information program that will
-be used (along with $PKGCHK)
-to look for installed versions of
-the Sun PRO C++ compiler.
-The default is
-pkginfo.
-
PLATFORM

The name of the platform used to create the Environment.  If no platform is
-specified when the Environment is created,
-scons
-autodetects the platform.
-

env = Environment(tools = [])
-if env['PLATFORM'] == 'cygwin':
-    Tool('mingw')(env)
-else:
-    Tool('msvc')(env)
-
PRINT_CMD_LINE_FUNC

A Python function used to print the command lines as they are executed
-(assuming command printing is not disabled by the
--q
-or
--s
-options or their equivalents).
-The function should take four arguments:
-s,
-the command being executed (a string),
-target,
-the target being built (file node, list, or string name(s)),
-source,
-the source(s) used (file node, list, or string name(s)), and
-env,
-the environment being used.
The function must do the printing itself.  The default implementation,
-used if this variable is not set or is None, is:
-

def print_cmd_line(s, target, source, env):
-  sys.stdout.write(s + "\n")
-

Here's an example of a more interesting function:
-

def print_cmd_line(s, target, source, env):
-   sys.stdout.write("Building %s -> %s...\n" %
-    (' and '.join([str(x) for x in source]),
-     ' and '.join([str(x) for x in target])))
-env=Environment(PRINT_CMD_LINE_FUNC=print_cmd_line)
-env.Program('foo', 'foo.c')
-

This just prints "Building targetname from sourcename..." instead
-of the actual commands.
-Such a function could also log the actual commands to a log file,
-for example.
-
PROGPREFIX

The prefix used for executable file names.
-
PROGSUFFIX

The suffix used for executable file names.
-
PSCOM

The command line used to convert TeX DVI files into a PostScript file.
-
PSCOMSTR

The string displayed when a TeX DVI file
-is converted into a PostScript file.
-If this is not set, then $PSCOM (the command line) is displayed.
-
PSPREFIX

The prefix used for PostScript file names.
-
PSSUFFIX

The prefix used for PostScript file names.
-
QT_AUTOSCAN

Turn off scanning for mocable files. Use the Moc Builder to explicitely
-specify files to run moc on.
-
QT_BINPATH

The path where the qt binaries are installed.
-The default value is '$QTDIR/bin'.
-
QT_CPPPATH

The path where the qt header files are installed.
-The default value is '$QTDIR/include'.
-Note: If you set this variable to None,
-the tool won't change the $CPPPATH
-construction variable.
-
QT_DEBUG

Prints lots of debugging information while scanning for moc files.
-
QT_LIB

Default value is 'qt'. You may want to set this to 'qt-mt'. Note: If you set
-this variable to None, the tool won't change the $LIBS variable.
-
QT_LIBPATH

The path where the qt libraries are installed.
-The default value is '$QTDIR/lib'.
-Note: If you set this variable to None,
-the tool won't change the $LIBPATH
-construction variable.
-
QT_MOC

Default value is '$QT_BINPATH/moc'.
-
QT_MOCCXXPREFIX

Default value is ''. Prefix for moc output files, when source is a cxx file.
-
QT_MOCCXXSUFFIX

Default value is '.moc'. Suffix for moc output files, when source is a cxx
-file.
-
QT_MOCFROMCXXCOM

Command to generate a moc file from a cpp file.
-
QT_MOCFROMCXXCOMSTR

The string displayed when generating a moc file from a cpp file.
-If this is not set, then $QT_MOCFROMCXXCOM (the command line) is displayed.
-
QT_MOCFROMCXXFLAGS

Default value is '-i'. These flags are passed to moc, when moccing a
-C++ file.
-
QT_MOCFROMHCOM

Command to generate a moc file from a header.
-
QT_MOCFROMHCOMSTR

The string displayed when generating a moc file from a cpp file.
-If this is not set, then $QT_MOCFROMHCOM (the command line) is displayed.
-
QT_MOCFROMHFLAGS

Default value is ''. These flags are passed to moc, when moccing a header
-file.
-
QT_MOCHPREFIX

Default value is 'moc_'. Prefix for moc output files, when source is a header.
-
QT_MOCHSUFFIX

Default value is '$CXXFILESUFFIX'. Suffix for moc output files, when source is
-a header.
-
QT_UIC

Default value is '$QT_BINPATH/uic'.
-
QT_UICCOM

Command to generate header files from .ui files.
-
QT_UICCOMSTR

The string displayed when generating header files from .ui files.
-If this is not set, then $QT_UICCOM (the command line) is displayed.
-
QT_UICDECLFLAGS

Default value is ''. These flags are passed to uic, when creating a a h
-file from a .ui file.
-
QT_UICDECLPREFIX

Default value is ''. Prefix for uic generated header files.
-
QT_UICDECLSUFFIX

Default value is '.h'. Suffix for uic generated header files.
-
QT_UICIMPLFLAGS

Default value is ''. These flags are passed to uic, when creating a cxx
-file from a .ui file.
-
QT_UICIMPLPREFIX

Default value is 'uic_'. Prefix for uic generated implementation files.
-
QT_UICIMPLSUFFIX

Default value is '$CXXFILESUFFIX'. Suffix for uic generated implementation
-files.
-
QT_UISUFFIX

Default value is '.ui'. Suffix of designer input files.
-
QTDIR

The qt tool tries to take this from os.environ.
-It also initializes all QT_*
-construction variables listed below.
-(Note that all paths are constructed
-with python's os.path.join() method,
-but are listed here with the '/' separator
-for easier reading.)
-In addition, the construction environment
-variables $CPPPATH,
-$LIBPATH and
-$LIBS may be modified
-and the variables
-PROGEMITTER, SHLIBEMITTER and LIBEMITTER
-are modified. Because the build-performance is affected when using this tool,
-you have to explicitly specify it at Environment creation:
-

Environment(tools=['default','qt'])
-

The qt tool supports the following operations:
Automatic moc file generation from header files.
-You do not have to specify moc files explicitly, the tool does it for you.
-However, there are a few preconditions to do so: Your header file must have
-the same filebase as your implementation file and must stay in the same
-directory. It must have one of the suffixes .h, .hpp, .H, .hxx, .hh. You
-can turn off automatic moc file generation by setting QT_AUTOSCAN to 0.
-See also the corresponding builder method
-.B Moc()
Automatic moc file generation from cxx files.
-As stated in the qt documentation, include the moc file at the end of
-the cxx file. Note that you have to include the file, which is generated
-by the transformation ${QT_MOCCXXPREFIX}<basename>${QT_MOCCXXSUFFIX}, by default
-<basename>.moc. A warning is generated after building the moc file, if you
-do not include the correct file. If you are using VariantDir, you may
-need to specify duplicate=1. You can turn off automatic moc file generation
-by setting QT_AUTOSCAN to 0. See also the corresponding
-Moc
-builder method.
Automatic handling of .ui files.
-The implementation files generated from .ui files are handled much the same
-as yacc or lex files. Each .ui file given as a source of Program, Library or
-SharedLibrary will generate three files, the declaration file, the
-implementation file and a moc file. Because there are also generated headers,
-you may need to specify duplicate=1 in calls to VariantDir.
-See also the corresponding
-Uic
-builder method.
-
RANLIB

The archive indexer.
-
RANLIBCOM

The command line used to index a static library archive.
-
RANLIBCOMSTR

The string displayed when a static library archive is indexed.
-If this is not set, then $RANLIBCOM (the command line) is displayed.
-

env = Environment(RANLIBCOMSTR = "Indexing $TARGET")
-
RANLIBFLAGS

General options passed to the archive indexer.
-
RC

The resource compiler used to build
-a Microsoft Visual C++ resource file.
-
RCCOM

The command line used to build
-a Microsoft Visual C++ resource file.
-
RCCOMSTR

The string displayed when invoking the resource compiler
-to build a Microsoft Visual C++ resource file.
-If this is not set, then $RCCOM (the command line) is displayed.
-
RCFLAGS

The flags passed to the resource compiler by the RES builder.
-
RCINCFLAGS

An automatically-generated construction variable
-containing the command-line options
-for specifying directories to be searched
-by the resource compiler.
-The value of $RCINCFLAGS is created
-by appending $RCINCPREFIX and $RCINCSUFFIX
-to the beginning and end
-of each directory in $CPPPATH.
-
RCINCPREFIX

The prefix (flag) used to specify an include directory
-on the resource compiler command line.
-This will be appended to the beginning of each directory
-in the $CPPPATH construction variable
-when the $RCINCFLAGS variable is expanded.
-
RCINCSUFFIX

The suffix used to specify an include directory
-on the resource compiler command line.
-This will be appended to the end of each directory
-in the $CPPPATH construction variable
-when the $RCINCFLAGS variable is expanded.
-
RCS

The RCS executable.
-Note that this variable is not actually used
-for the command to fetch source files from RCS;
-see the
-$RCS_CO
-construction variable, below.
-
RCS_CO

The RCS "checkout" executable,
-used to fetch source files from RCS.
-
RCS_COCOM

The command line used to
-fetch (checkout) source files from RCS.
-
RCS_COCOMSTR

The string displayed when fetching
-a source file from RCS.
-If this is not set, then $RCS_COCOM
-(the command line) is displayed.
-
RCS_COFLAGS

Options that are passed to the $RCS_CO command.
-
RDirs

A function that converts a string into a list of Dir instances by
-searching the repositories.
-
REGSVR

The program used on Windows systems
-to register a newly-built DLL library
-whenever the SharedLibrary builder
-is passed a keyword argument of register=1.
-
REGSVRCOM

The command line used on Windows systems
-to register a newly-built DLL library
-whenever the SharedLibrary builder
-is passed a keyword argument of register=1.
-
REGSVRCOMSTR

The string displayed when registering a newly-built DLL file.
-If this is not set, then $REGSVRCOM (the command line) is displayed.
-
REGSVRFLAGS

Flags passed to the DLL registration program
-on Windows systems when a newly-built DLL library is registered.
-By default,
-this includes the /s
-that prevents dialog boxes from popping up
-and requiring user attention.
-
RMIC

The Java RMI stub compiler.
-
RMICCOM

The command line used to compile stub
-and skeleton class files
-from Java classes that contain RMI implementations.
-Any options specified in the $RMICFLAGS construction variable
-are included on this command line.
-
RMICCOMSTR

The string displayed when compiling
-stub and skeleton class files
-from Java classes that contain RMI implementations.
-If this is not set, then $RMICCOM (the command line) is displayed.
-

env = Environment(RMICCOMSTR = "Generating stub/skeleton class files $TARGETS from $SOURCES")
-
RMICFLAGS

General options passed to the Java RMI stub compiler.
-
_RPATH

An automatically-generated construction variable
-containing the rpath flags to be used when linking
-a program with shared libraries.
-The value of $_RPATH is created
-by appending $RPATHPREFIX and $RPATHSUFFIX
-to the beginning and end
-of each directory in $RPATH.
-
RPATH

A list of paths to search for shared libraries when running programs.
-Currently only used in the GNU (gnulink),
-IRIX (sgilink) and Sun (sunlink) linkers.
-Ignored on platforms and toolchains that don't support it.
-Note that the paths added to RPATH
-are not transformed by
-scons
-in any way:  if you want an absolute
-path, you must make it absolute yourself.
-
RPATHPREFIX

The prefix used to specify a directory to be searched for
-shared libraries when running programs.
-This will be appended to the beginning of each directory
-in the $RPATH construction variable
-when the $_RPATH variable is automatically generated.
-
RPATHSUFFIX

The suffix used to specify a directory to be searched for
-shared libraries when running programs.
-This will be appended to the end of each directory
-in the $RPATH construction variable
-when the $_RPATH variable is automatically generated.
-
RPCGEN

The RPC protocol compiler.
-
RPCGENCLIENTFLAGS

Options passed to the RPC protocol compiler
-when generating client side stubs.
-These are in addition to any flags specified in the
-$RPCGENFLAGS
-construction variable.
-
RPCGENFLAGS

General options passed to the RPC protocol compiler.
-
RPCGENHEADERFLAGS

Options passed to the RPC protocol compiler
-when generating a header file.
-These are in addition to any flags specified in the
-$RPCGENFLAGS
-construction variable.
-
RPCGENSERVICEFLAGS

Options passed to the RPC protocol compiler
-when generating server side stubs.
-These are in addition to any flags specified in the
-$RPCGENFLAGS
-construction variable.
-
RPCGENXDRFLAGS

Options passed to the RPC protocol compiler
-when generating XDR routines.
-These are in addition to any flags specified in the
-$RPCGENFLAGS
-construction variable.
-
SCANNERS

A list of the available implicit dependency scanners.
-New file scanners may be added by
-appending to this list,
-although the more flexible approach
-is to associate scanners
-with a specific Builder.
-See the sections "Builder Objects"
-and "Scanner Objects,"
-below, for more information.
-
SCCS

The SCCS executable.
-
SCCSCOM

The command line used to
-fetch source files from SCCS.
-
SCCSCOMSTR

The string displayed when fetching
-a source file from a CVS repository.
-If this is not set, then $SCCSCOM
-(the command line) is displayed.
-
SCCSFLAGS

General options that are passed to SCCS.
-
SCCSGETFLAGS

Options that are passed specifically to the SCCS "get" subcommand.
-This can be set, for example, to
--e
-to check out editable files from SCCS.
-
SCONS_HOME

The (optional) path to the SCons library directory,
-initialized from the external environment.
-If set, this is used to construct a shorter and more
-efficient search path in the
-$MSVSSCONS
-command line executed
-from Microsoft Visual Studio project files.
-
SHCC

The C compiler used for generating shared-library objects.
-
SHCCCOM

The command line used to compile a C source file
-to a shared-library object file.
-Any options specified in the $SHCFLAGS,
-$SHCCFLAGS and
-$CPPFLAGS construction variables
-are included on this command line.
-
SHCCCOMSTR

The string displayed when a C source file
-is compiled to a shared object file.
-If this is not set, then $SHCCCOM (the command line) is displayed.
-

env = Environment(SHCCCOMSTR = "Compiling shared object $TARGET")
-
SHCCFLAGS

Options that are passed to the C and C++ compilers
-to generate shared-library objects.
-
SHCFLAGS

Options that are passed to the C compiler (only; not C++)
-to generate shared-library objects.
-
SHCXX

The C++ compiler used for generating shared-library objects.
-
SHCXXCOM

The command line used to compile a C++ source file
-to a shared-library object file.
-Any options specified in the $SHCXXFLAGS and
-$CPPFLAGS construction variables
-are included on this command line.
-
SHCXXCOMSTR

The string displayed when a C++ source file
-is compiled to a shared object file.
-If this is not set, then $SHCXXCOM (the command line) is displayed.
-

env = Environment(SHCXXCOMSTR = "Compiling shared object $TARGET")
-
SHCXXFLAGS

Options that are passed to the C++ compiler
-to generate shared-library objects.
-
SHELL

A string naming the shell program that will be passed to the
-$SPAWN
-function.
-See the
-$SPAWN
-construction variable for more information.
-
SHF77

The Fortran 77 compiler used for generating shared-library objects.
-You should normally set the $SHFORTRAN variable,
-which specifies the default Fortran compiler
-for all Fortran versions.
-You only need to set $SHF77 if you need to use a specific compiler
-or compiler version for Fortran 77 files.
-
SHF77COM

The command line used to compile a Fortran 77 source file
-to a shared-library object file.
-You only need to set $SHF77COM if you need to use a specific
-command line for Fortran 77 files.
-You should normally set the $SHFORTRANCOM variable,
-which specifies the default command line
-for all Fortran versions.
-
SHF77COMSTR

The string displayed when a Fortran 77 source file
-is compiled to a shared-library object file.
-If this is not set, then $SHF77COM or $SHFORTRANCOM
-(the command line) is displayed.
-
SHF77FLAGS

Options that are passed to the Fortran 77 compiler
-to generated shared-library objects.
-You only need to set $SHF77FLAGS if you need to define specific
-user options for Fortran 77 files.
-You should normally set the $SHFORTRANFLAGS variable,
-which specifies the user-specified options
-passed to the default Fortran compiler
-for all Fortran versions.
-
SHF77PPCOM

The command line used to compile a Fortran 77 source file to a
-shared-library object file
-after first running the file through the C preprocessor.
-Any options specified in the $SHF77FLAGS and $CPPFLAGS construction variables
-are included on this command line.
-You only need to set $SHF77PPCOM if you need to use a specific
-C-preprocessor command line for Fortran 77 files.
-You should normally set the $SHFORTRANPPCOM variable,
-which specifies the default C-preprocessor command line
-for all Fortran versions.
-
SHF77PPCOMSTR

The string displayed when a Fortran 77 source file
-is compiled to a shared-library object file
-after first running the file through the C preprocessor.
-If this is not set, then $SHF77PPCOM or $SHFORTRANPPCOM
-(the command line) is displayed.
-
SHF90

The Fortran 90 compiler used for generating shared-library objects.
-You should normally set the $SHFORTRAN variable,
-which specifies the default Fortran compiler
-for all Fortran versions.
-You only need to set $SHF90 if you need to use a specific compiler
-or compiler version for Fortran 90 files.
-
SHF90COM

The command line used to compile a Fortran 90 source file
-to a shared-library object file.
-You only need to set $SHF90COM if you need to use a specific
-command line for Fortran 90 files.
-You should normally set the $SHFORTRANCOM variable,
-which specifies the default command line
-for all Fortran versions.
-
SHF90COMSTR

The string displayed when a Fortran 90 source file
-is compiled to a shared-library object file.
-If this is not set, then $SHF90COM or $SHFORTRANCOM
-(the command line) is displayed.
-
SHF90FLAGS

Options that are passed to the Fortran 90 compiler
-to generated shared-library objects.
-You only need to set $SHF90FLAGS if you need to define specific
-user options for Fortran 90 files.
-You should normally set the $SHFORTRANFLAGS variable,
-which specifies the user-specified options
-passed to the default Fortran compiler
-for all Fortran versions.
-
SHF90PPCOM

The command line used to compile a Fortran 90 source file to a
-shared-library object file
-after first running the file through the C preprocessor.
-Any options specified in the $SHF90FLAGS and $CPPFLAGS construction variables
-are included on this command line.
-You only need to set $SHF90PPCOM if you need to use a specific
-C-preprocessor command line for Fortran 90 files.
-You should normally set the $SHFORTRANPPCOM variable,
-which specifies the default C-preprocessor command line
-for all Fortran versions.
-
SHF90PPCOMSTR

The string displayed when a Fortran 90 source file
-is compiled to a shared-library object file
-after first running the file through the C preprocessor.
-If this is not set, then $SHF90PPCOM or $SHFORTRANPPCOM
-(the command line) is displayed.
-
SHF95

The Fortran 95 compiler used for generating shared-library objects.
-You should normally set the $SHFORTRAN variable,
-which specifies the default Fortran compiler
-for all Fortran versions.
-You only need to set $SHF95 if you need to use a specific compiler
-or compiler version for Fortran 95 files.
-
SHF95COM

The command line used to compile a Fortran 95 source file
-to a shared-library object file.
-You only need to set $SHF95COM if you need to use a specific
-command line for Fortran 95 files.
-You should normally set the $SHFORTRANCOM variable,
-which specifies the default command line
-for all Fortran versions.
-
SHF95COMSTR

The string displayed when a Fortran 95 source file
-is compiled to a shared-library object file.
-If this is not set, then $SHF95COM or $SHFORTRANCOM
-(the command line) is displayed.
-
SHF95FLAGS

Options that are passed to the Fortran 95 compiler
-to generated shared-library objects.
-You only need to set $SHF95FLAGS if you need to define specific
-user options for Fortran 95 files.
-You should normally set the $SHFORTRANFLAGS variable,
-which specifies the user-specified options
-passed to the default Fortran compiler
-for all Fortran versions.
-
SHF95PPCOM

The command line used to compile a Fortran 95 source file to a
-shared-library object file
-after first running the file through the C preprocessor.
-Any options specified in the $SHF95FLAGS and $CPPFLAGS construction variables
-are included on this command line.
-You only need to set $SHF95PPCOM if you need to use a specific
-C-preprocessor command line for Fortran 95 files.
-You should normally set the $SHFORTRANPPCOM variable,
-which specifies the default C-preprocessor command line
-for all Fortran versions.
-
SHF95PPCOMSTR

The string displayed when a Fortran 95 source file
-is compiled to a shared-library object file
-after first running the file through the C preprocessor.
-If this is not set, then $SHF95PPCOM or $SHFORTRANPPCOM
-(the command line) is displayed.
-
SHFORTRAN

The default Fortran compiler used for generating shared-library objects.
-
SHFORTRANCOM

The command line used to compile a Fortran source file
-to a shared-library object file.
-
SHFORTRANCOMSTR

The string displayed when a Fortran source file
-is compiled to a shared-library object file.
-If this is not set, then $SHFORTRANCOM
-(the command line) is displayed.
-
SHFORTRANFLAGS

Options that are passed to the Fortran compiler
-to generate shared-library objects.
-
SHFORTRANPPCOM

The command line used to compile a Fortran source file to a
-shared-library object file
-after first running the file through the C preprocessor.
-Any options specified
-in the $SHFORTRANFLAGS and
-$CPPFLAGS construction variables
-are included on this command line.
-
SHFORTRANPPCOMSTR

The string displayed when a Fortran source file
-is compiled to a shared-library object file
-after first running the file throught the C preprocessor.
-If this is not set, then $SHFORTRANPPCOM
-(the command line) is displayed.
-
SHLIBPREFIX

The prefix used for shared library file names.
-
SHLIBSUFFIX

The suffix used for shared library file names.
-
SHLINK

The linker for programs that use shared libraries.
-
SHLINKCOM

The command line used to link programs using shared libaries.
-
SHLINKCOMSTR

The string displayed when programs using shared libraries are linked.
-If this is not set, then $SHLINKCOM (the command line) is displayed.
-

env = Environment(SHLINKCOMSTR = "Linking shared $TARGET")
-
SHLINKFLAGS

General user options passed to the linker for programs using shared libraries.
-Note that this variable should
-not
-contain
--l
-(or similar) options for linking with the libraries listed in $LIBS,
-nor
--L
-(or similar) include search path options
-that scons generates automatically from $LIBPATH.
-See
-$_LIBFLAGS
-above,
-for the variable that expands to library-link options,
-and
-$_LIBDIRFLAGS
-above,
-for the variable that expands to library search path options.
-
SHOBJPREFIX

The prefix used for shared object file names.
-
SHOBJSUFFIX

The suffix used for shared object file names.
-
SOURCE

A reserved variable name
-that may not be set or used in a construction environment.
-(See "Variable Substitution," below.)
-
SOURCE_URL

The URL
-(web address)
-of the location from which the project was retrieved.
-This is used to fill in the
-Source:
-field in the controlling information for Ipkg and RPM packages.
-
SOURCES

A reserved variable name
-that may not be set or used in a construction environment.
-(See "Variable Substitution," below.)
-
SPAWN

A command interpreter function that will be called to execute command line
-strings. The function must expect the following arguments:
-

def spawn(shell, escape, cmd, args, env):
-

sh
-is a string naming the shell program to use.
-escape
-is a function that can be called to escape shell special characters in
-the command line.
-cmd
-is the path to the command to be executed.
-args
-is the arguments to the command.
-env
-is a dictionary of the environment variables
-in which the command should be executed.
-
SUMMARY

A short summary of what the project is about.
-This is used to fill in the
-Summary:
-field in the controlling information for Ipkg and RPM packages,
-and as the
-Description:
-field in MSI packages.
-
SWIG

The scripting language wrapper and interface generator.
-
SWIGCFILESUFFIX

The suffix that will be used for intermediate C
-source files generated by
-the scripting language wrapper and interface generator.
-The default value is
-_wrap$CFILESUFFIX.
-By default, this value is used whenever the
--c++
-option is
-not
-specified as part of the
-$SWIGFLAGS
-construction variable.
-
SWIGCOM

The command line used to call
-the scripting language wrapper and interface generator.
-
SWIGCOMSTR

The string displayed when calling
-the scripting language wrapper and interface generator.
-If this is not set, then $SWIGCOM (the command line) is displayed.
-
SWIGCXXFILESUFFIX

The suffix that will be used for intermediate C++
-source files generated by
-the scripting language wrapper and interface generator.
-The default value is
-_wrap$CFILESUFFIX.
-By default, this value is used whenever the
--c++
-option is specified as part of the
-$SWIGFLAGS
-construction variable.
-
SWIGFLAGS

General options passed to
-the scripting language wrapper and interface generator.
-This is where you should set
--python,
--perl5,
--tcl,
-or whatever other options you want to specify to SWIG.
-If you set the
--c++
-option in this variable,
-scons
-will, by default,
-generate a C++ intermediate source file
-with the extension that is specified as the
-$CXXFILESUFFIX
-variable.
-
_SWIGINCFLAGS

An automatically-generated construction variable
-containing the SWIG command-line options
-for specifying directories to be searched for included files.
-The value of $_SWIGINCFLAGS is created
-by appending $SWIGINCPREFIX and $SWIGINCSUFFIX
-to the beginning and end
-of each directory in $SWIGPATH.
-
SWIGINCPREFIX

The prefix used to specify an include directory on the SWIG command line.
-This will be appended to the beginning of each directory
-in the $SWIGPATH construction variable
-when the $_SWIGINCFLAGS variable is automatically generated.
-
SWIGINCSUFFIX

The suffix used to specify an include directory on the SWIG command line.
-This will be appended to the end of each directory
-in the $SWIGPATH construction variable
-when the $_SWIGINCFLAGS variable is automatically generated.
-
SWIGOUTDIR

Specifies the output directory in which
-the scripting language wrapper and interface generator
-should place generated language-specific files.
-This will be used by SCons to identify
-the files that will be generated by the swig call,
-and translated into the
-swig -outdir option on the command line.
-
SWIGPATH

The list of directories that the scripting language wrapper
-and interface generate will search for included files.
-The SWIG implicit dependency scanner will search these
-directories for include files.
-The default is to use the same path
-specified as $CPPPATH.
Don't explicitly put include directory
-arguments in SWIGFLAGS;
-the result will be non-portable
-and the directories will not be searched by the dependency scanner.
-Note: directory names in SWIGPATH will be looked-up relative to the SConscript
-directory when they are used in a command.
-To force
-scons
-to look-up a directory relative to the root of the source tree use #:
-

env = Environment(SWIGPATH='#/include')
-

The directory look-up can also be forced using the
-Dir()
-function:
-

include = Dir('include')
-env = Environment(SWIGPATH=include)
-

The directory list will be added to command lines
-through the automatically-generated
-$_SWIGINCFLAGS
-construction variable,
-which is constructed by
-appending the values of the
-$SWIGINCPREFIX and $SWIGINCSUFFIX
-construction variables
-to the beginning and end
-of each directory in $SWIGPATH.
-Any command lines you define that need
-the SWIGPATH directory list should
-include $_SWIGINCFLAGS:
-

env = Environment(SWIGCOM="my_swig -o $TARGET $_SWIGINCFLAGS $SORUCES")
-
TAR

The tar archiver.
-
TARCOM

The command line used to call the tar archiver.
-
TARCOMSTR

The string displayed when archiving files
-using the tar archiver.
-If this is not set, then $TARCOM (the command line) is displayed.
-

env = Environment(TARCOMSTR = "Archiving $TARGET")
-
TARFLAGS

General options passed to the tar archiver.
-
TARGET

A reserved variable name
-that may not be set or used in a construction environment.
-(See "Variable Substitution," below.)
-
TARGETS

A reserved variable name
-that may not be set or used in a construction environment.
-(See "Variable Substitution," below.)
-
TARSUFFIX

The suffix used for tar file names.
-
TEMPFILEPREFIX

The prefix for a temporary file used
-to execute lines longer than $MAXLINELENGTH.
-The default is '@'.
-This may be set for toolchains that use other values,
-such as '-@' for the diab compiler
-or '-via' for ARM toolchain.
-
TEX

The TeX formatter and typesetter.
-
TEXCOM

The command line used to call the TeX formatter and typesetter.
-
TEXCOMSTR

The string displayed when calling
-the TeX formatter and typesetter.
-If this is not set, then $TEXCOM (the command line) is displayed.
-

env = Environment(TEXCOMSTR = "Building $TARGET from TeX input $SOURCES")
-
TEXFLAGS

General options passed to the TeX formatter and typesetter.
-
TEXINPUTS

List of directories that the LaTeX programm will search
-for include directories.
-The LaTeX implicit dependency scanner will search these
-directories for \include and \import files.
-
TOOLS

A list of the names of the Tool specifications
-that are part of this construction environment.
-
VENDOR

The person or organization who supply the packaged software.
-This is used to fill in the
-Vendor:
-field in the controlling information for RPM packages,
-and the
-Manufacturer:
-field in the controlling information for MSI packages.
-
VERSION

The version of the project, specified as a string.
-
WIN32_INSERT_DEF

A deprecated synonym for $WINDOWS_INSERT_DEF.
-
WIN32DEFPREFIX

A deprecated synonym for $WINDOWSDEFPREFIX.
-
WIN32DEFSUFFIX

A deprecated synonym for $WINDOWSDEFSUFFIX.
-
WIN32EXPPREFIX

A deprecated synonym for $WINDOWSEXPSUFFIX.
-
WIN32EXPSUFFIX

A deprecated synonym for $WINDOWSEXPSUFFIX.
-
WINDOWS_INSERT_DEF

When this is set to true,
-a library build of a Windows shared library
-(.dllfile)
-will also build a corresponding .def file
-at the same time,
-if a .def file
-is not already listed as a build target.
-The default is 0 (do not build a .def file).
-
WINDOWS_INSERT_MANIFEST

When this is set to true,
-scons
-will be aware of the
-.manifest
-files generated by Microsoft Visua C/C++ 8.
-
WINDOWSDEFPREFIX

The prefix used for Windows .deffile names.
-
WINDOWSDEFSUFFIX

The suffix used for Windows .def file names.
-
WINDOWSEXPPREFIX

The prefix used for Windows .exp file names.
-
WINDOWSEXPSUFFIX

The suffix used for Windows .exp file names.
-
WINDOWSPROGMANIFESTPREFIX

The prefix used for executable program .manifest files
-generated by Microsoft Visual C/C++.
-
WINDOWSPROGMANIFESTSUFFIX

The suffix used for executable program .manifest files
-generated by Microsoft Visual C/C++.
-
WINDOWSSHLIBMANIFESTPREFIX

The prefix used for shared library .manifest files
-generated by Microsoft Visual C/C++.
-
WINDOWSSHLIBMANIFESTSUFFIX

The suffix used for shared library .manifest files
-generated by Microsoft Visual C/C++.
-
X_IPK_DEPENDS

This is used to fill in the
-Depends:
-field in the controlling information for Ipkg packages.
-
X_IPK_DESCRIPTION

This is used to fill in the
-Description:
-field in the controlling information for Ipkg packages.
-The default value is
-$SUMMARY\n$DESCRIPTION
-
X_IPK_MAINTAINER

This is used to fill in the
-Maintainer:
-field in the controlling information for Ipkg packages.
-
X_IPK_PRIORITY

This is used to fill in the
-Priority:
-field in the controlling information for Ipkg packages.
-
X_IPK_SECTION

This is used to fill in the
-Section:
-field in the controlling information for Ipkg packages.
-
X_MSI_LANGUAGE

This is used to fill in the
-Language:
-attribute in the controlling information for MSI packages.
-
X_MSI_LICENSE_TEXT

The text of the software license in RTF format.
-Carriage return characters will be
-replaced with the RTF equivalent \\par.
-
X_MSI_UPGRADE_CODE

TODO
-
X_RPM_AUTOREQPROV

This is used to fill in the
-AutoReqProv:
-field in the RPM
-.spec file.
-
X_RPM_BUILD

internal, but overridable
-
X_RPM_BUILDREQUIRES

This is used to fill in the
-BuildRequires:
-field in the RPM
-.spec file.
-
X_RPM_BUILDROOT

internal, but overridable
-
X_RPM_CLEAN

internal, but overridable
-
X_RPM_CONFLICTS

This is used to fill in the
-Conflicts:
-field in the RPM
-.spec file.
-
X_RPM_DEFATTR

This value is used as the default attributes
-for the files in the RPM package.
-The default value is
-(-,root,root).
-
X_RPM_DISTRIBUTION

This is used to fill in the
-Distribution:
-field in the RPM
-.spec file.
-
X_RPM_EPOCH

This is used to fill in the
-Epoch:
-field in the controlling information for RPM packages.
-
X_RPM_EXCLUDEARCH

This is used to fill in the
-ExcludeArch:
-field in the RPM
-.spec file.
-
X_RPM_EXLUSIVEARCH

This is used to fill in the
-ExclusiveArch:
-field in the RPM
-.spec file.
-
X_RPM_GROUP

This is used to fill in the
-Group:
-field in the RPM
-.spec file.
-
X_RPM_GROUP_lang

This is used to fill in the
-Group(lang):
-field in the RPM
-.spec file.
-Note that
-lang
-is not literal
-and should be replaced by
-the appropriate language code.
-
X_RPM_ICON

This is used to fill in the
-Icon:
-field in the RPM
-.spec file.
-
X_RPM_INSTALL

internal, but overridable
-
X_RPM_PACKAGER

This is used to fill in the
-Packager:
-field in the RPM
-.spec file.
-
X_RPM_POSTINSTALL

This is used to fill in the
-%post:
-section in the RPM
-.spec file.
-
X_RPM_POSTUNINSTALL

This is used to fill in the
-%postun:
-section in the RPM
-.spec file.
-
X_RPM_PREFIX

This is used to fill in the
-Prefix:
-field in the RPM
-.spec file.
-
X_RPM_PREINSTALL

This is used to fill in the
-%pre:
-section in the RPM
-.spec file.
-
X_RPM_PREP

internal, but overridable
-
X_RPM_PREUNINSTALL

This is used to fill in the
-%preun:
-section in the RPM
-.spec file.
-
X_RPM_PROVIDES

This is used to fill in the
-Provides:
-field in the RPM
-.spec file.
-
X_RPM_REQUIRES

This is used to fill in the
-Requires:
-field in the RPM
-.spec file.
-
X_RPM_SERIAL

This is used to fill in the
-Serial:
-field in the RPM
-.spec file.
-
X_RPM_URL

This is used to fill in the
-Url:
-field in the RPM
-.spec file.
-
YACC

The parser generator.
-
YACCCOM

The command line used to call the parser generator
-to generate a source file.
-
YACCCOMSTR

The string displayed when generating a source file
-using the parser generator.
-If this is not set, then $YACCCOM (the command line) is displayed.
-

env = Environment(YACCCOMSTR = "Yacc'ing $TARGET from $SOURCES")
-
YACCFLAGS

General options passed to the parser generator.
-If $YACCFLAGS contains a -d option,
-SCons assumes that the call will also create a .h file
-(if the yacc source file ends in a .y suffix)
-or a .hpp file
-(if the yacc source file ends in a .yy suffix)
-
YACCHFILESUFFIX

The suffix of the C
-header file generated by the parser generator
-when the
--d
-option is used.
-Note that setting this variable does not cause
-the parser generator to generate a header
-file with the specified suffix,
-it exists to allow you to specify
-what suffix the parser generator will use of its own accord.
-The default value is
-.h.
-
YACCHXXFILESUFFIX

The suffix of the C++
-header file generated by the parser generator
-when the
--d
-option is used.
-Note that setting this variable does not cause
-the parser generator to generate a header
-file with the specified suffix,
-it exists to allow you to specify
-what suffix the parser generator will use of its own accord.
-The default value is
-.hpp,
-except on Mac OS X,
-where the default is
-${TARGET.suffix}.h.
-because the default bison parser generator just
-appends .h
-to the name of the generated C++ file.
-
YACCVCGFILESUFFIX

The suffix of the file
-containing the VCG grammar automaton definition
-when the
---graph=
-option is used.
-Note that setting this variable does not cause
-the parser generator to generate a VCG
-file with the specified suffix,
-it exists to allow you to specify
-what suffix the parser generator will use of its own accord.
-The default value is
-.vcg.
-
ZIP

The zip compression and file packaging utility.
-
ZIPCOM

The command line used to call the zip utility,
-or the internal Python function used to create a
-zip archive.
-
ZIPCOMPRESSION

The
-compression
-flag
-from the Python
-zipfile
-module used by the internal Python function
-to control whether the zip archive
-is compressed or not.
-The default value is
-zipfile.ZIP_DEFLATED,
-which creates a compressed zip archive.
-This value has no effect when using Python 1.5.2
-or if the
-zipfile
-module is otherwise unavailable.
-
ZIPCOMSTR

The string displayed when archiving files
-using the zip utility.
-If this is not set, then $ZIPCOM
-(the command line or internal Python function) is displayed.
-

env = Environment(ZIPCOMSTR = "Zipping $TARGET")
-
ZIPFLAGS

General options passed to the zip utility.
-
ZIPSUFFIX

The suffix used for zip file names.
-
Appendix B. Builders

-This appendix contains descriptions of all of the
-Builders that are potentially
-available "out of the box" in this version of SCons.
-
-
CFile(), env.CFile()

Builds a C source file given a lex (.l)
-or yacc (.y) input file.
-The suffix specified by the $CFILESUFFIX construction variable
-(.c by default)
-is automatically added to the target
-if it is not already present.
-Example:
-

# builds foo.c
-env.CFile(target = 'foo.c', source = 'foo.l')
-# builds bar.c
-env.CFile(target = 'bar', source = 'bar.y')
-
CXXFile(), env.CXXFile()

Builds a C++ source file given a lex (.ll)
-or yacc (.yy)
-input file.
-The suffix specified by the $CXXFILESUFFIX construction variable
-(.cc by default)
-is automatically added to the target
-if it is not already present.
-Example:
-

# builds foo.cc
-env.CXXFile(target = 'foo.cc', source = 'foo.ll')
-# builds bar.cc
-env.CXXFile(target = 'bar', source = 'bar.yy')
-
DVI(), env.DVI()

Builds a .dvi file
-from a .tex,
-.ltx or .latex input file.
-If the source file suffix is .tex,
-scons
-will examine the contents of the file;
-if the string
-\documentclass
-or
-\documentstyle
-is found, the file is assumed to be a LaTeX file and
-the target is built by invoking the $LATEXCOM command line;
-otherwise, the $TEXCOM command line is used.
-If the file is a LaTeX file,
-the
-DVI
-builder method will also examine the contents
-of the
-.aux
-file and invoke the $BIBTEX command line
-if the string
-bibdata
-is found,
-start $MAKEINDEX to generate an index if a
-.ind
-file is found
-and will examine the contents
-.log
-file and re-run the $LATEXCOM command
-if the log file says it is necessary.
The suffix .dvi
-(hard-coded within TeX itself)
-is automatically added to the target
-if it is not already present.
-Examples:
-

# builds from aaa.tex
-env.DVI(target = 'aaa.dvi', source = 'aaa.tex')
-# builds bbb.dvi
-env.DVI(target = 'bbb', source = 'bbb.ltx')
-# builds from ccc.latex
-env.DVI(target = 'ccc.dvi', source = 'ccc.latex')
-
Install(), env.Install()

Installs one or more source files or directories
-in the specified target,
-which must be a directory.
-The names of the specified source files or directories
-remain the same within the destination directory.
-

env.Install('/usr/local/bin', source = ['foo', 'bar'])
-
InstallAs(), env.InstallAs()

Installs one or more source files or directories
-to specific names,
-allowing changing a file or directory name
-as part of the installation.
-It is an error if the
-target
-and
-source
-arguments list different numbers of files or directories.
-

env.InstallAs(target = '/usr/local/bin/foo',
-              source = 'foo_debug')
-env.InstallAs(target = ['../lib/libfoo.a', '../lib/libbar.a'],
-              source = ['libFOO.a', 'libBAR.a'])
-
Jar(), env.Jar()

Builds a Java archive (.jar) file
-from the specified list of sources.
-Any directories in the source list
-will be searched for .class files).
-Any .java files in the source list
-will be compiled  to .class files
-by calling the Java Builder.
If the $JARCHDIR value is set, the
-jar
-command will change to the specified directory using the
--C
-option.
-If $JARCHDIR is not set explicitly,
-SCons will use the top of any subdirectory tree
-in which Java .class
-were built by the Java Builder.
If the contents any of the source files begin with the string
-Manifest-Version,
-the file is assumed to be a manifest
-and is passed to the
-jar
-command with the
-m
-option set.
-

env.Jar(target = 'foo.jar', source = 'classes')
-
-env.Jar(target = 'bar.jar',
-        source = ['bar1.java', 'bar2.java'])
-
Java(), env.Java()

Builds one or more Java class files.
-The sources may be any combination of explicit
-.java files,
-or directory trees which will be scanned
-for .java files.
SCons will parse each source .java file
-to find the classes
-(including inner classes)
-defined within that file,
-and from that figure out the
-target .class files that will be created.
-The class files will be placed underneath
-the specified target directory.
SCons will also search each Java file
-for the Java package name,
-which it assumes can be found on a line
-beginning with the string
-package
-in the first column;
-the resulting .class files
-will be placed in a directory reflecting
-the specified package name.
-For example,
-the file
-Foo.java
-defining a single public
-Foo
-class and
-containing a package name of
-sub.dir
-will generate a corresponding
-sub/dir/Foo.class
-class file.
Examples:
-

env.Java(target = 'classes', source = 'src')
-env.Java(target = 'classes', source = ['src1', 'src2'])
-env.Java(target = 'classes', source = ['File1.java', 'File2.java'])
-

Java source files can use the native encoding for the underlying OS.
-Since SCons compiles in simple ASCII mode by default,
-the compiler will generate warnings about unmappable characters,
-which may lead to errors as the file is processed further.
-In this case, the user must specify the LANG
-environment variable to tell the compiler what encoding is uesd.
-For portibility, it's best if the encoding is hard-coded
-so that the compile will work if it is done on a system
-with a different encoding.
-

env = Environment()
-env['ENV']['LANG'] = 'en_GB.UTF-8'
-
JavaH(), env.JavaH()

Builds C header and source files for
-implementing Java native methods.
-The target can be either a directory
-in which the header files will be written,
-or a header file name which
-will contain all of the definitions.
-The source can be the names of .class files,
-the names of .java files
-to be compiled into .class files
-by calling the Java builder method,
-or the objects returned from the
-Java
-builder method.
If the construction variable
-$JAVACLASSDIR
-is set, either in the environment
-or in the call to the
-JavaH
-builder method itself,
-then the value of the variable
-will be stripped from the
-beginning of any .class file names.
Examples:
-

# builds java_native.h
-classes = env.Java(target = 'classdir', source = 'src')
-env.JavaH(target = 'java_native.h', source = classes)
-
-# builds include/package_foo.h and include/package_bar.h
-env.JavaH(target = 'include',
-          source = ['package/foo.class', 'package/bar.class'])
-
-# builds export/foo.h and export/bar.h
-env.JavaH(target = 'export',
-          source = ['classes/foo.class', 'classes/bar.class'],
-          JAVACLASSDIR = 'classes')
-
Library(), env.Library()

A synonym for the
-StaticLibrary
-builder method.
-
LoadableModule(), env.LoadableModule()

On most systems,
-this is the same as
-SharedLibrary.
-On Mac OS X (Darwin) platforms,
-this creates a loadable module bundle.
-
M4(), env.M4()

Builds an output file from an M4 input file.
-This uses a default $M4FLAGS value of
--E,
-which considers all warnings to be fatal
-and stops on the first warning
-when using the GNU version of m4.
-Example:
-

env.M4(target = 'foo.c', source = 'foo.c.m4')
-
Moc(), env.Moc()

Builds an output file from a moc input file. Moc input files are either
-header files or cxx files. This builder is only available after using the
-tool 'qt'. See the $QTDIR variable for more information.
-Example:
-

env.Moc('foo.h') # generates moc_foo.cc
-env.Moc('foo.cpp') # generates foo.moc
-
MSVSProject(), env.MSVSProject()

Builds a Microsoft Visual Studio project file,
-and by default builds a solution file as well.
This builds a Visual Studio project file, based on the version of
-Visual Studio that is configured (either the latest installed version,
-or the version specified by
-$MSVS_VERSION
-in the Environment constructor).
-For Visual Studio 6, it will generate a
-.dsp
-file.
-For Visual Studio 7 (.NET) and later versions, it will generate a
-.vcproj
-file.
By default,
-this also generates a solution file
-for the specified project,
-a
-.dsw
-file for Visual Studio 6
-or a
-.sln
-file for Visual Studio 7 (.NET).
-This behavior may be disabled by specifying
-auto_build_solution=0
-when you call
-MSVSProject,
-in which case you presumably want to
-build the solution file(s)
-by calling the
-MSVSSolution
-Builder (see below).
The MSVSProject builder
-takes several lists of filenames
-to be placed into the project file.
-These are currently limited to
-srcs,
-incs,
-localincs,
-resources,
-and
-misc.
-These are pretty self-explanatory, but it should be noted that these
-lists are added to the $SOURCES construction variable as strings,
-NOT as SCons File Nodes.  This is because they represent file
-names to be added to the project file, not the source files used to
-build the project file.
The above filename lists are all optional,
-although at least one must be specified
-for the resulting project file to be non-empty.
In addition to the above lists of values,
-the following values may be specified:
target:
-The name of the target
-.dsp
-or
-.vcproj
-file.
-The correct
-suffix for the version of Visual Studio must be used,
-but the
-$MSVSPROJECTSUFFIX
-construction variable
-will be defined to the correct value (see example below).
variant:
-The name of this particular variant.
-For Visual Studio 7 projects,
-this can also be a list of variant names.
-These are typically things like "Debug" or "Release", but really
-can be anything you want.
-For Visual Studio 7 projects,
-they may also specify a target platform
-separated from the variant name by a
-|
-(vertical pipe)
-character:
-Debug|Xbox.
-The default target platform is Win32.
-Multiple calls to
-MSVSProject
-with different variants are allowed;
-all variants will be added to the project file with their appropriate
-build targets and sources.
buildtarget:
-An optional string, node, or list of strings or nodes
-(one per build variant), to tell the Visual Studio debugger
-what output target to use in what build variant.
-The number of
-buildtarget
-entries must match the number of
-variant
-entries.
runfile:
-The name of the file that Visual Studio 7 and later
-will run and debug.
-This appears as the value of the
-Output
-field in the resutling Visual Studio project file.
-If this is not specified,
-the default is the same as the specified
-buildtarget
-value.
Note that because SCons always executes its build commands
-from the directory in which the SConstruct file is located,
-if you generate a project file in a different directory
-than the SConstruct directory,
-users will not be able to double-click
-on the file name in compilation error messages
-displayed in the Visual Studio console output window.
-This can be remedied by adding the
-Visual C/C++
-.B /FC
-compiler option to the $CCFLAGS  variable
-so that the compiler will print
-the full path name of any
-files that cause compilation errors.
Example usage:
-

barsrcs = ['bar.cpp'],
-barincs = ['bar.h'],
-barlocalincs = ['StdAfx.h']
-barresources = ['bar.rc','resource.h']
-barmisc = ['bar_readme.txt']
-
-dll = env.SharedLibrary(target = 'bar.dll',
-                        source = barsrcs)
-
-env.MSVSProject(target = 'Bar' + env['MSVSPROJECTSUFFIX'],
-                srcs = barsrcs,
-                incs = barincs,
-                localincs = barlocalincs,
-                resources = barresources,
-                misc = barmisc,
-                buildtarget = dll,
-                variant = 'Release')
-
MSVSSolution(), env.MSVSSolution()

Builds a Microsoft Visual Studio solution file.
This builds a Visual Studio solution file,
-based on the version of Visual Studio that is configured
-(either the latest installed version,
-or the version specified by
-$MSVS_VERSION
-in the construction environment).
-For Visual Studio 6, it will generate a
-.dsw
-file.
-For Visual Studio 7 (.NET), it will
-generate a
-.sln
-file.
The following values must be specified:
target:
-The name of the target .dsw or .sln file.  The correct
-suffix for the version of Visual Studio must be used, but the value
-$MSVSSOLUTIONSUFFIX
-will be defined to the correct value (see example below).
variant:
-The name of this particular variant, or a list of variant
-names (the latter is only supported for MSVS 7 solutions). These are
-typically things like "Debug" or "Release", but really can be anything
-you want. For MSVS 7 they may also specify target platform, like this
-"Debug|Xbox". Default platform is Win32.
projects:
-A list of project file names, or Project nodes returned by calls to the
-MSVSProject
-Builder,
-to be placed into the solution file.
-It should be noted that these file names are NOT added to the $SOURCES
-environment variable in form of files, but rather as strings.   This
-is because they represent file names to be added to the solution file,
-not the source files used to build the solution file.
(NOTE: Currently only one project is supported per solution.)
Example Usage:
-

env.MSVSSolution(target = 'Bar' + env['MSVSSOLUTIONSUFFIX'],
-                 projects = ['bar' + env['MSVSPROJECTSUFFIX']],
-                 variant = 'Release')
-
Object(), env.Object()

A synonym for the
-StaticObject
-builder method.
-
Package(), env.Package()

Builds software distribution packages.
-Packages consist of files to install and packaging information.
-The former may be specified with the source parameter and may be left out,
-in which case the FindInstalledFiles function will collect
-all files that have an Install or InstallAs Builder attached.
-If the target is not specified
-it will be deduced from additional information given to this Builder.
The packaging information is specified
-with the help of construction variables documented below.
-This information is called a tag to stress that
-some of them can also be attached to files with the Tag function.
-The mandatory ones will complain if they were not specified.
-They vary depending on chosen target packager.
The target packager may be selected with the "PACKAGETYPE" command line
-option or with the $PACKAGETYPE construction variable. Currently
-the following packagers available:
 * msi - Microsoft Installer
- * rpm - Redhat Package Manger
- * ipkg - Itsy Package Management System
- * tarbz2 - compressed tar
- * targz - compressed tar
- * zip - zip file
- * src_tarbz2 - compressed tar source
- * src_targz - compressed tar source
- * src_zip - zip file source
An updated list is always available under the "package_type" option when
-running "scons --help" on a project that has packaging activated.
-

env = Environment(tools=['default', 'packaging'])
-env.Install('/bin/', 'my_program')
-env.Package( NAME           = 'foo',
-             VERSION        = '1.2.3',
-             PACKAGEVERSION = 0,
-             PACKAGETYPE    = 'rpm',
-             LICENSE        = 'gpl',
-             SUMMARY        = 'balalalalal',
-             DESCRIPTION    = 'this should be really really long',
-             X_RPM_GROUP    = 'Application/fu',
-             SOURCE_URL     = 'http://foo.org/foo-1.2.3.tar.gz'
-        )
-
PCH(), env.PCH()

Builds a Microsoft Visual C++ precompiled header.
-Calling this builder method
-returns a list of two targets: the PCH as the first element, and the object
-file as the second element. Normally the object file is ignored.
-This builder method is only
-provided when Microsoft Visual C++ is being used as the compiler.
-The PCH builder method is generally used in
-conjuction with the PCH construction variable to force object files to use
-the precompiled header:
-

env['PCH'] = env.PCH('StdAfx.cpp')[0]
-
PDF(), env.PDF()

Builds a .pdf file
-from a .dvi input file
-(or, by extension, a .tex,
-.ltx,
-or
-.latex input file).
-The suffix specified by the $PDFSUFFIX construction variable
-(.pdf by default)
-is added automatically to the target
-if it is not already present.  Example:
-

# builds from aaa.tex
-env.PDF(target = 'aaa.pdf', source = 'aaa.tex')
-# builds bbb.pdf from bbb.dvi
-env.PDF(target = 'bbb', source = 'bbb.dvi')
-
PostScript(), env.PostScript()

Builds a .ps file
-from a .dvi input file
-(or, by extension, a .tex,
-.ltx,
-or
-.latex input file).
-The suffix specified by the $PSSUFFIX construction variable
-(.ps by default)
-is added automatically to the target
-if it is not already present.  Example:
-

# builds from aaa.tex
-env.PostScript(target = 'aaa.ps', source = 'aaa.tex')
-# builds bbb.ps from bbb.dvi
-env.PostScript(target = 'bbb', source = 'bbb.dvi')
-
Program(), env.Program()

Builds an executable given one or more object files
-or C, C++, D, or Fortran source files.
-If any C, C++, D or Fortran source files are specified,
-then they will be automatically
-compiled to object files using the
-Object
-builder method;
-see that builder method's description for
-a list of legal source file suffixes
-and how they are interpreted.
-The target executable file prefix
-(specified by the $PROGPREFIX construction variable; nothing by default)
-and suffix
-(specified by the $PROGSUFFIX construction variable;
-by default, .exe on Windows systems,
-nothing on POSIX systems)
-are automatically added to the target if not already present.
-Example:
-

env.Program(target = 'foo', source = ['foo.o', 'bar.c', 'baz.f'])
-
RES(), env.RES()

Builds a Microsoft Visual C++ resource file.
-This builder method is only provided
-when Microsoft Visual C++ or MinGW is being used as the compiler. The
-.res
-(or
-.o
-for MinGW) suffix is added to the target name if no other suffix is given.
-The source
-file is scanned for implicit dependencies as though it were a C file.
-Example:
-

env.RES('resource.rc')
-
RMIC(), env.RMIC()

Builds stub and skeleton class files
-for remote objects
-from Java .class files.
-The target is a directory
-relative to which the stub
-and skeleton class files will be written.
-The source can be the names of .class files,
-or the objects return from the
-Java
-builder method.
If the construction variable
-$JAVACLASSDIR
-is set, either in the environment
-or in the call to the
-RMIC
-builder method itself,
-then the value of the variable
-will be stripped from the
-beginning of any .class 
-file names.
-

classes = env.Java(target = 'classdir', source = 'src')
-env.RMIC(target = 'outdir1', source = classes)
-
-env.RMIC(target = 'outdir2',
-         source = ['package/foo.class', 'package/bar.class'])
-
-env.RMIC(target = 'outdir3',
-         source = ['classes/foo.class', 'classes/bar.class'],
-         JAVACLASSDIR = 'classes')
-
RPCGenClient(), env.RPCGenClient()

Generates an RPC client stub (_clnt.c) file
-from a specified RPC (.x) source file.
-Because rpcgen only builds output files
-in the local directory,
-the command will be executed
-in the source file's directory by default.
-

# Builds src/rpcif_clnt.c
-env.RPCGenClient('src/rpcif.x')
-
RPCGenHeader(), env.RPCGenHeader()

Generates an RPC header (.h) file
-from a specified RPC (.x) source file.
-Because rpcgen only builds output files
-in the local directory,
-the command will be executed
-in the source file's directory by default.
-

# Builds src/rpcif.h
-env.RPCGenHeader('src/rpcif.x')
-
RPCGenService(), env.RPCGenService()

Generates an RPC server-skeleton (_svc.c) file
-from a specified RPC (.x) source file.
-Because rpcgen only builds output files
-in the local directory,
-the command will be executed
-in the source file's directory by default.
-

# Builds src/rpcif_svc.c
-env.RPCGenClient('src/rpcif.x')
-
RPCGenXDR(), env.RPCGenXDR()

Generates an RPC XDR routine (_xdr.c) file
-from a specified RPC (.x) source file.
-Because rpcgen only builds output files
-in the local directory,
-the command will be executed
-in the source file's directory by default.
-

# Builds src/rpcif_xdr.c
-env.RPCGenClient('src/rpcif.x')
-
SharedLibrary(), env.SharedLibrary()

Builds a shared library
-(.so on a POSIX system,
-.dll on Windows)
-given one or more object files
-or C, C++, D or Fortran source files.
-If any source files are given,
-then they will be automatically
-compiled to object files.
-The static library prefix and suffix (if any)
-are automatically added to the target.
-The target library file prefix
-(specified by the $SHLIBPREFIX construction variable;
-by default, lib on POSIX systems,
-nothing on Windows systems)
-and suffix
-(specified by the $SHLIBSUFFIX construction variable;
-by default, .dll on Windows systems,
-.so on POSIX systems)
-are automatically added to the target if not already present.
-Example:
-

env.SharedLibrary(target = 'bar', source = ['bar.c', 'foo.o'])
-

On Windows systems, the
-SharedLibrary
-builder method will always build an import
-(.lib) library
-in addition to the shared (.dll) library,
-adding a .lib library with the same basename
-if there is not already a .lib file explicitly
-listed in the targets.
Any object files listed in the
-source
-must have been built for a shared library
-(that is, using the
-SharedObject
-builder method).
-scons
-will raise an error if there is any mismatch.
On Windows systems, specifying
-register=1
-will cause the .dll to be
-registered after it is built using REGSVR32.
-The command that is run
-("regsvr32" by default) is determined by $REGSVR construction
-variable, and the flags passed are determined by $REGSVRFLAGS.  By
-default, $REGSVRFLAGS includes the /s option,
-to prevent dialogs from popping
-up and requiring user attention when it is run.  If you change
-$REGSVRFLAGS, be sure to include the /s option.
-For example,
-

env.SharedLibrary(target = 'bar',
-                  source = ['bar.cxx', 'foo.obj'],
-                  register=1)
-

will register bar.dll as a COM object
-when it is done linking it.
-
SharedObject(), env.SharedObject()

Builds an object file for
-inclusion in a shared library.
-Source files must have one of the same set of extensions
-specified above for the
-StaticObject
-builder method.
-On some platforms building a shared object requires additional
-compiler option
-(e.g. -fPIC for gcc)
-in addition to those needed to build a
-normal (static) object, but on some platforms there is no difference between a
-shared object and a normal (static) one. When there is a difference, SCons
-will only allow shared objects to be linked into a shared library, and will
-use a different suffix for shared objects. On platforms where there is no
-difference, SCons will allow both normal (static)
-and shared objects to be linked into a
-shared library, and will use the same suffix for shared and normal
-(static) objects.
-The target object file prefix
-(specified by the $SHOBJPREFIX construction variable;
-by default, the same as $OBJPREFIX)
-and suffix
-(specified by the $SHOBJSUFFIX construction variable)
-are automatically added to the target if not already present.
-Examples:
-

env.SharedObject(target = 'ddd', source = 'ddd.c')
-env.SharedObject(target = 'eee.o', source = 'eee.cpp')
-env.SharedObject(target = 'fff.obj', source = 'fff.for')
-

Note that the source files will be scanned
-according to the suffix mappings in the
-SourceFileScanner
-object.
-See the section "Scanner Objects,"
-below, for a more information.
-
StaticLibrary(), env.StaticLibrary()

Builds a static library given one or more object files
-or C, C++, D or Fortran source files.
-If any source files are given,
-then they will be automatically
-compiled to object files.
-The static library prefix and suffix (if any)
-are automatically added to the target.
-The target library file prefix
-(specified by the $LIBPREFIX construction variable;
-by default, lib on POSIX systems,
-nothing on Windows systems)
-and suffix
-(specified by the $LIBSUFFIX construction variable;
-by default, .lib on Windows systems,
-.a on POSIX systems)
-are automatically added to the target if not already present.
-Example:
-

env.StaticLibrary(target = 'bar', source = ['bar.c', 'foo.o'])
-

Any object files listed in the
-source
-must have been built for a static library
-(that is, using the
-StaticObject
-builder method).
-scons
-will raise an error if there is any mismatch.
-
StaticObject(), env.StaticObject()

Builds a static object file
-from one or more C, C++, D, or Fortran source files.
-Source files must have one of the following extensions:
-

  .asm    assembly language file
-  .ASM    assembly language file
-  .c      C file
-  .C      Windows:  C file
-          POSIX:  C++ file
-  .cc     C++ file
-  .cpp    C++ file
-  .cxx    C++ file
-  .cxx    C++ file
-  .c++    C++ file
-  .C++    C++ file
-  .d      D file
-  .f      Fortran file
-  .F      Windows:  Fortran file
-          POSIX:  Fortran file + C pre-processor
-  .for    Fortran file
-  .FOR    Fortran file
-  .fpp    Fortran file + C pre-processor
-  .FPP    Fortran file + C pre-processor
-  .m      Object C file
-  .mm     Object C++ file
-  .s      assembly language file
-  .S      Windows:  assembly language file
-          POSIX:  assembly language file + C pre-processor
-  .spp    assembly language file + C pre-processor
-  .SPP    assembly language file + C pre-processor
-

The target object file prefix
-(specified by the $OBJPREFIX construction variable; nothing by default)
-and suffix
-(specified by the $OBJSUFFIX construction variable;
-.obj on Windows systems,
-.o on POSIX systems)
-are automatically added to the target if not already present.
-Examples:
-

env.StaticObject(target = 'aaa', source = 'aaa.c')
-env.StaticObject(target = 'bbb.o', source = 'bbb.c++')
-env.StaticObject(target = 'ccc.obj', source = 'ccc.f')
-

Note that the source files will be scanned
-according to the suffix mappings in
-SourceFileScanner
-object.
-See the section "Scanner Objects,"
-below, for a more information.
-
Tar(), env.Tar()

Builds a tar archive of the specified files
-and/or directories.
-Unlike most builder methods,
-the
-Tar
-builder method may be called multiple times
-for a given target;
-each additional call
-adds to the list of entries
-that will be built into the archive.
-Any source directories will
-be scanned for changes to
-any on-disk files,
-regardless of whether or not
-scons
-knows about them from other Builder or function calls.
-

env.Tar('src.tar', 'src')
-
-# Create the stuff.tar file.
-env.Tar('stuff', ['subdir1', 'subdir2'])
-# Also add "another" to the stuff.tar file.
-env.Tar('stuff', 'another')
-
-# Set TARFLAGS to create a gzip-filtered archive.
-env = Environment(TARFLAGS = '-c -z')
-env.Tar('foo.tar.gz', 'foo')
-
-# Also set the suffix to .tgz.
-env = Environment(TARFLAGS = '-c -z',
-                  TARSUFFIX = '.tgz')
-env.Tar('foo')
-
TypeLibrary(), env.TypeLibrary()

Builds a Windows type library (.tlb)
-file from an input IDL file (.idl).
-In addition, it will build the associated inteface stub and
-proxy source files,
-naming them according to the base name of the .idl file.
-For example,
-

env.TypeLibrary(source="foo.idl")
-

Will create foo.tlb,
-foo.h,
-foo_i.c,
-foo_p.c
-and
-foo_data.c
-files.
-
Uic(), env.Uic()

Builds a header file, an implementation file and a moc file from an ui file.
-and returns the corresponding nodes in the above order.
-This builder is only available after using the tool 'qt'. Note: you can
-specify .ui files directly as source
-files to the Program,
-Library and SharedLibrary builders
-without using this builder. Using this builder lets you override the standard
-naming conventions (be careful: prefixes are always prepended to names of
-built files; if you don't want prefixes, you may set them to ``).
-See the $QTDIR variable for more information.
-Example:
-

env.Uic('foo.ui') # -> ['foo.h', 'uic_foo.cc', 'moc_foo.cc']
-env.Uic(target = Split('include/foo.h gen/uicfoo.cc gen/mocfoo.cc'),
-        source = 'foo.ui') # -> ['include/foo.h', 'gen/uicfoo.cc', 'gen/mocfoo.cc']
-
Zip(), env.Zip()

Builds a zip archive of the specified files
-and/or directories.
-Unlike most builder methods,
-the
-Zip
-builder method may be called multiple times
-for a given target;
-each additional call
-adds to the list of entries
-that will be built into the archive.
-Any source directories will
-be scanned for changes to
-any on-disk files,
-regardless of whether or not
-scons
-knows about them from other Builder or function calls.
-

env.Zip('src.zip', 'src')
-
-# Create the stuff.zip file.
-env.Zip('stuff', ['subdir1', 'subdir2'])
-# Also add "another" to the stuff.tar file.
-env.Zip('stuff', 'another')
-
Appendix C. Tools

-This appendix contains descriptions of all of the
-Tools modules that are
-available "out of the box" in this version of SCons.
-
-
386asm

Sets construction variables for the 386ASM assembler
-for the Phar Lap ETS embedded operating system.
-

Sets:  $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.
-

Uses:  $CC, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.
-
aixc++

Sets construction variables for the IMB xlc / Visual Age C++ compiler.
-

Sets:  $CXX, $CXXVERSION, $SHCXX, $SHOBJSUFFIX.
-
aixcc

Sets construction variables for the IBM xlc / Visual Age C compiler.
-

Sets:  $CC, $CCVERSION, $SHCC.
-
aixf77

Sets construction variables for the IBM Visual Age f77 Fortran compiler.
-

Sets:  $F77, $SHF77.
-
aixlink

Sets construction variables for the IBM Visual Age linker.
-

Sets:  $LINKFLAGS, $SHLIBSUFFIX, $SHLINKFLAGS.
-
applelink

Sets construction variables for the Apple linker
-(similar to the GNU linker).
-

Sets:  $FRAMEWORKPATHPREFIX, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULEPREFIX, $LDMODULESUFFIX, $LINKCOM, $SHLINKCOM, $SHLINKFLAGS, $_FRAMEWORKPATH, $_FRAMEWORKS.
-

Uses:  $FRAMEWORKSFLAGS.
-
ar

Sets construction variables for the ar library archiver.
-

Sets:  $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $RANLIB, $RANLIBCOM, $RANLIBFLAGS.
-
as

Sets construction variables for the as assembler.
-

Sets:  $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.
-

Uses:  $CC, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.
-
bcc32

Sets construction variables for the bcc32 compiler.
-

Sets:  $CC, $CCCOM, $CCFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX, $CPPDEFSUFFIX, $INCPREFIX, $INCSUFFIX, $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHOBJSUFFIX.
-

Uses:  $_CPPDEFFLAGS, $_CPPINCFLAGS.
-
BitKeeper

Sets construction variables for the BitKeeper
-source code control system.
-

Sets:  $BITKEEPER, $BITKEEPERCOM, $BITKEEPERGET, $BITKEEPERGETFLAGS.
-

Uses:  $BITKEEPERCOMSTR.
-
cc

Sets construction variables for generic POSIX C copmilers.
-

Sets:  $CC, $CCCOM, $CCFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX, $CPPDEFSUFFIX, $FRAMEWORKPATH, $FRAMEWORKS, $INCPREFIX, $INCSUFFIX, $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHOBJSUFFIX.
-

Uses:  $PLATFORM.
-
cvf

Sets construction variables for the Compaq Visual Fortran compiler.
-

Sets:  $FORTRAN, $FORTRANCOM, $FORTRANMODDIR, $FORTRANMODDIRPREFIX, $FORTRANMODDIRSUFFIX, $FORTRANPPCOM, $OBJSUFFIX, $SHFORTRANCOM, $SHFORTRANPPCOM.
-

Uses:  $CPPFLAGS, $FORTRANFLAGS, $SHFORTRANFLAGS, $_CPPDEFFLAGS, $_FORTRANINCFLAGS, $_FORTRANMODFLAG.
-
CVS

Sets construction variables for the CVS source code
-management system.
-

Sets:  $CVS, $CVSCOFLAGS, $CVSCOM, $CVSFLAGS.
-

Uses:  $CVSCOMSTR.
-
cXX

Sets construction variables for generic POSIX C++ compilers.
-

Sets:  $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM, $CXXFILESUFFIX, $CXXFLAGS, $INCPREFIX, $INCSUFFIX, $OBJSUFFIX, $SHCXX, $SHCXXCOM, $SHCXXFLAGS, $SHOBJSUFFIX.
-

Uses:  $CXXCOMSTR.
-
default

Sets variables by calling a default list of Tool modules
-for the platform on which SCons is running.
-
dmd

Sets construction variables for D language compilers
-(the Digital Mars D compiler, or GDC).
-
dvi

Attaches the DVI builder to the
-construction environment.
-
dvipdf

Sets construction variables for the dvipdf utility.
-

Sets:  $DVIPDF, $DVIPDFCOM, $DVIPDFFLAGS.
-

Uses:  $DVIPDFCOMSTR.
-
dvips

Sets construction variables for the dvips utility.
-

Sets:  $DVIPS, $DVIPSFLAGS, $PSCOM, $PSPREFIX, $PSSUFFIX.
-

Uses:  $PSCOMSTR.
-
f77

Set construction variables for generic POSIX Fortran 77 compilers.
-

Sets:  $F77, $F77COM, $F77FILESUFFIXES, $F77FLAGS, $F77PPCOM, $F77PPFILESUFFIXES, $FORTRAN, $FORTRANCOM, $FORTRANFLAGS, $SHF77, $SHF77COM, $SHF77FLAGS, $SHF77PPCOM, $SHFORTRAN, $SHFORTRANCOM, $SHFORTRANFLAGS, $SHFORTRANPPCOM, $_F77INCFLAGS.
-

Uses:  $F77COMSTR, $F77PPCOMSTR, $FORTRANCOMSTR, $FORTRANPPCOMSTR, $SHF77COMSTR, $SHF77PPCOMSTR, $SHFORTRANCOMSTR, $SHFORTRANPPCOMSTR.
-
f90

Set construction variables for generic POSIX Fortran 90 compilers.
-

Sets:  $F90, $F90COM, $F90FLAGS, $F90PPCOM, $SHF90, $SHF90COM, $SHF90FLAGS, $SHF90PPCOM, $_F90INCFLAGS.
-

Uses:  $F90COMSTR, $F90PPCOMSTR, $SHF90COMSTR, $SHF90PPCOMSTR.
-
f95

Set construction variables for generic POSIX Fortran 95 compilers.
-

Sets:  $F95, $F95COM, $F95FLAGS, $F95PPCOM, $SHF95, $SHF95COM, $SHF95FLAGS, $SHF95PPCOM, $_F95INCFLAGS.
-

Uses:  $F95COMSTR, $F95PPCOMSTR, $SHF95COMSTR, $SHF95PPCOMSTR.
-
fortran

Set construction variables for generic POSIX Fortran compilers.
-

Sets:  $FORTRAN, $FORTRANCOM, $FORTRANFLAGS, $SHFORTRAN, $SHFORTRANCOM, $SHFORTRANFLAGS, $SHFORTRANPPCOM.
-

Uses:  $FORTRANCOMSTR, $FORTRANPPCOMSTR, $SHFORTRANCOMSTR, $SHFORTRANPPCOMSTR.
-
g++

Set construction variables for the gXX C++ compiler.
-

Sets:  $CXX, $CXXVERSION, $SHCXXFLAGS, $SHOBJSUFFIX.
-
g77

Set construction variables for the g77 Fortran compiler.
-Calls the f77 Tool module
-to set variables.
-
gas

Sets construction variables for the gas assembler.
-Calls the as module.
-

Sets:  $AS.
-
gcc

Set construction variables for the gcc C compiler.
-

Sets:  $CC, $CCVERSION, $SHCCFLAGS.
-
gnulink

Set construction variables for GNU linker/loader.
-

Sets:  $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.
-
gs

Set construction variables for Ghostscript.
-

Sets:  $GS, $GSCOM, $GSFLAGS.
-

Uses:  $GSCOMSTR.
-
hpc++

Set construction variables for the compilers aCC on HP/UX systems.
-
hpcc

Set construction variables for the
-aCC on HP/UX systems.
-Calls the cXX tool for additional variables.
-

Sets:  $CXX, $CXXVERSION, $SHCXXFLAGS.
-
hplink

Sets construction variables for the linker on HP/UX systems.
-

Sets:  $LINKFLAGS, $SHLIBSUFFIX, $SHLINKFLAGS.
-
icc

Sets construction variables for the
-icc compiler on OS/2 systems.
-

Sets:  $CC, $CCCOM, $CFILESUFFIX, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXXCOM, $CXXFILESUFFIX, $INCPREFIX, $INCSUFFIX.
-

Uses:  $CCFLAGS, $CFLAGS, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.
-
icl

Sets construction variables for the Intel C/C++ compiler.
-Calls the intelc Tool module to set its variables.
-
ifl

Sets construction variables for the Intel Fortran compiler.
-

Sets:  $FORTRAN, $FORTRANCOM, $FORTRANPPCOM, $SHFORTRANCOM, $SHFORTRANPPCOM.
-

Uses:  $CPPFLAGS, $FORTRANFLAGS, $_CPPDEFFLAGS, $_FORTRANINCFLAGS.
-
ifort

Sets construction variables for newer versions
-of the Intel Fortran compiler for Linux.
-

Sets:  $F77, $F90, $F95, $FORTRAN, $SHF77, $SHF77FLAGS, $SHF90, $SHF90FLAGS, $SHF95, $SHF95FLAGS, $SHFORTRAN, $SHFORTRANFLAGS.
-
ilink

Sets construction variables for the
-ilink linker on OS/2 systems.
-

Sets:  $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM, $LINKFLAGS.
-
ilink32

Sets construction variables for the Borland
-ilink32 linker.
-

Sets:  $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM, $LINKFLAGS.
-
install

Sets construction variables for file
-and directory installation.
-

Sets:  $INSTALL, $INSTALLSTR.
-
intelc

Sets construction variables for the Intel C/C++ compiler
-(Linux and Windows, version 7 and later).
-Calls the gcc or msvc
-(on Linux and Windows, respectively)
-to set underlying variables.
-

Sets:  $AR, $CC, $CXX, $INTEL_C_COMPILER_VERSION, $LINK.
-
jar

Sets construction variables for the jar utility.
-

Sets:  $JAR, $JARCOM, $JARFLAGS, $JARSUFFIX.
-

Uses:  $JARCOMSTR.
-
javac

Sets construction variables for the javac compiler.
-

Sets:  $JAVABOOTCLASSPATH, $JAVAC, $JAVACCOM, $JAVACFLAGS, $JAVACLASSPATH, $JAVACLASSSUFFIX, $JAVASOURCEPATH, $JAVASUFFIX.
-

Uses:  $JAVACCOMSTR.
-
javah

Sets construction variables for the javah tool.
-

Sets:  $JAVACLASSSUFFIX, $JAVAH, $JAVAHCOM, $JAVAHFLAGS.
-

Uses:  $JAVACLASSPATH, $JAVAHCOMSTR.
-
latex

Sets construction variables for the latex utility.
-

Sets:  $LATEX, $LATEXCOM, $LATEXFLAGS.
-

Uses:  $LATEXCOMSTR.
-
lex

Sets construction variables for the lex lexical analyser.
-

Sets:  $LEX, $LEXCOM, $LEXFLAGS.
-

Uses:  $LEXCOMSTR.
-
link

Sets construction variables for generic POSIX linkers.
-

Sets:  $LDMODULE, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULEPREFIX, $LDMODULESUFFIX, $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM, $LINKFLAGS, $SHLIBSUFFIX, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.
-

Uses:  $LDMODULECOMSTR, $LINKCOMSTR, $SHLINKCOMSTR.
-
linkloc

Sets construction variables for the
-LinkLoc
-linker for the Phar Lap ETS embedded operating system.
-

Sets:  $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM, $LINKFLAGS, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.
-

Uses:  $LINKCOMSTR, $SHLINKCOMSTR.
-
m4

Sets construction variables for the m4 macro processor.
-

Sets:  $M4, $M4COM, $M4FLAGS.
-

Uses:  $M4COMSTR.
-
masm

Sets construction variables for the Microsoft assembler.
-

Sets:  $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.
-

Uses:  $ASCOMSTR, $ASPPCOMSTR, $CPPFLAGS, $_CPPDEFFLAGS, $_CPPINCFLAGS.
-
midl

Sets construction variables for the Microsoft IDL compiler.
-

Sets:  $MIDL, $MIDLCOM, $MIDLFLAGS.
-

Uses:  $MIDLCOMSTR.
-
mingw

Sets construction variables for MinGW (Minimal Gnu on Windows).
-

Sets:  $AS, $CC, $CXX, $LDMODULECOM, $LIBPREFIX, $LIBSUFFIX, $OBJSUFFIX, $RC, $RCCOM, $RCFLAGS, $RCINCFLAGS, $RCINCPREFIX, $RCINCSUFFIX, $SHCCFLAGS, $SHCXXFLAGS, $SHLINKCOM, $SHLINKFLAGS, $SHOBJSUFFIX, $WINDOWSDEFPREFIX, $WINDOWSDEFSUFFIX.
-

Uses:  $RCCOMSTR, $SHLINKCOMSTR.
-
mslib

Sets construction variables for the Microsoft
-mslib
-library archiver.
-

Sets:  $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.
-

Uses:  $ARCOMSTR.
-
mslink

Sets construction variables for the Microsoft linker.
-

Sets:  $LDMODULE, $LDMODULECOM, $LDMODULEFLAGS, $LDMODULEPREFIX, $LDMODULESUFFIX, $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM, $LINKFLAGS, $REGSVR, $REGSVRCOM, $REGSVRFLAGS, $SHLINK, $SHLINKCOM, $SHLINKFLAGS, $WIN32DEFPREFIX, $WIN32DEFSUFFIX, $WIN32EXPPREFIX, $WIN32EXPSUFFIX, $WINDOWSDEFPREFIX, $WINDOWSDEFSUFFIX, $WINDOWSEXPPREFIX, $WINDOWSEXPSUFFIX, $WINDOWSPROGMANIFESTPREFIX, $WINDOWSPROGMANIFESTSUFFIX, $WINDOWSSHLIBMANIFESTPREFIX, $WINDOWSSHLIBMANIFESTSUFFIX, $WINDOWS_INSERT_DEF.
-

Uses:  $LDMODULECOMSTR, $LINKCOMSTR, $MSVS_IGNORE_IDE_PATHS, $REGSVRCOMSTR, $SHLINKCOMSTR.
-
msvc

Sets construction variables for the Microsoft Visual C/C++ compiler.
-

Sets:  $BUILDERS, $CC, $CCCOM, $CCFLAGS, $CCPCHFLAGS, $CCPDBFLAGS, $CFILESUFFIX, $CFLAGS, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM, $CXXFILESUFFIX, $CXXFLAGS, $INCPREFIX, $INCSUFFIX, $OBJPREFIX, $OBJSUFFIX, $PCHCOM, $PCHPDBFLAGS, $RC, $RCCOM, $RCFLAGS, $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHCXX, $SHCXXCOM, $SHCXXFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.
-

Uses:  $CCCOMSTR, $CXXCOMSTR, $SHCCCOMSTR, $SHCXXCOMSTR.
-
msvs

Sets construction variables for Microsoft Visual Studio.
-

Sets:  $MSVSBUILDCOM, $MSVSCLEANCOM, $MSVSENCODING, $MSVSPROJECTCOM, $MSVSREBUILDCOM, $MSVSSCONS, $MSVSSCONSCOM, $MSVSSCONSCRIPT, $MSVSSCONSFLAGS, $MSVSSOLUTIONCOM.
-
mwcc

Sets construction variables for the Metrowerks CodeWarrior compiler.
-

Sets:  $CC, $CCCOM, $CFILESUFFIX, $CPPDEFPREFIX, $CPPDEFSUFFIX, $CXX, $CXXCOM, $CXXFILESUFFIX, $INCPREFIX, $INCSUFFIX, $MWCW_VERSION, $MWCW_VERSIONS, $SHCC, $SHCCCOM, $SHCCFLAGS, $SHCFLAGS, $SHCXX, $SHCXXCOM, $SHCXXFLAGS.
-

Uses:  $CCCOMSTR, $CXXCOMSTR, $SHCCCOMSTR, $SHCXXCOMSTR.
-
mwld

Sets construction variables for the Metrowerks CodeWarrior linker.
-

Sets:  $AR, $ARCOM, $LIBDIRPREFIX, $LIBDIRSUFFIX, $LIBLINKPREFIX, $LIBLINKSUFFIX, $LINK, $LINKCOM, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.
-
nasm

Sets construction variables for the
-nasm Netwide Assembler.
-

Sets:  $AS, $ASCOM, $ASFLAGS, $ASPPCOM, $ASPPFLAGS.
-

Uses:  $ASCOMSTR, $ASPPCOMSTR.
-
packaging

A framework for building binary and source packages.
-
Packaging

Sets construction variables for the Package Builder.
-
pdf

Sets construction variables for the Portable Document Format builder.
-

Sets:  $PDFPREFIX, $PDFSUFFIX.
-
pdflatex

Sets construction variables for the pdflatex utility.
-

Sets:  $LATEXRETRIES, $PDFLATEX, $PDFLATEXCOM, $PDFLATEXFLAGS.
-

Uses:  $PDFLATEXCOMSTR.
-
pdftex

Sets construction variables for the pdftex utility.
-

Sets:  $LATEXRETRIES, $PDFLATEX, $PDFLATEXCOM, $PDFLATEXFLAGS, $PDFTEX, $PDFTEXCOM, $PDFTEXFLAGS.
-

Uses:  $PDFLATEXCOMSTR, $PDFTEXCOMSTR.
-
Perforce

Sets construction variables for interacting with the
-Perforce source code management system.
-

Sets:  $P4, $P4COM, $P4FLAGS.
-

Uses:  $P4COMSTR.
-
qt

Sets construction variables for building Qt applications.
-

Sets:  $QTDIR, $QT_AUTOSCAN, $QT_BINPATH, $QT_CPPPATH, $QT_LIB, $QT_LIBPATH, $QT_MOC, $QT_MOCCXXPREFIX, $QT_MOCCXXSUFFIX, $QT_MOCFROMCXXCOM, $QT_MOCFROMCXXFLAGS, $QT_MOCFROMHCOM, $QT_MOCFROMHFLAGS, $QT_MOCHPREFIX, $QT_MOCHSUFFIX, $QT_UIC, $QT_UICCOM, $QT_UICDECLFLAGS, $QT_UICDECLPREFIX, $QT_UICDECLSUFFIX, $QT_UICIMPLFLAGS, $QT_UICIMPLPREFIX, $QT_UICIMPLSUFFIX, $QT_UISUFFIX.
-
RCS

Sets construction variables for the interaction
-with the Revision Control System.
-

Sets:  $RCS, $RCS_CO, $RCS_COCOM, $RCS_COFLAGS.
-

Uses:  $RCS_COCOMSTR.
-
rmic

Sets construction variables for the rmic utility.
-

Sets:  $JAVACLASSSUFFIX, $RMIC, $RMICCOM, $RMICFLAGS.
-

Uses:  $RMICCOMSTR.
-
rpcgen

Sets construction variables for building with RPCGEN.
-

Sets:  $RPCGEN, $RPCGENCLIENTFLAGS, $RPCGENFLAGS, $RPCGENHEADERFLAGS, $RPCGENSERVICEFLAGS, $RPCGENXDRFLAGS.
-
SCCS

Sets construction variables for interacting with the
-Source Code Control System.
-

Sets:  $SCCS, $SCCSCOM, $SCCSFLAGS, $SCCSGETFLAGS.
-

Uses:  $SCCSCOMSTR.
-
sgiar

Sets construction variables for the SGI library archiver.
-

Sets:  $AR, $ARCOMSTR, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $SHLINK, $SHLINKFLAGS.
-

Uses:  $ARCOMSTR, $SHLINKCOMSTR.
-
sgic++

Sets construction variables for the SGI C++ compiler.
-

Sets:  $CXX, $CXXFLAGS, $SHCXX, $SHOBJSUFFIX.
-
sgicc

Sets construction variables for the SGI C compiler.
-

Sets:  $CXX, $SHOBJSUFFIX.
-
sgilink

Sets construction variables for the SGI linker.
-

Sets:  $LINK, $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.
-
sunar

Sets construction variables for the Sun library archiver.
-

Sets:  $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX, $SHLINK, $SHLINKCOM, $SHLINKFLAGS.
-

Uses:  $ARCOMSTR, $SHLINKCOMSTR.
-
sunc++

Sets construction variables for the Sun C++ compiler.
-

Sets:  $CXX, $CXXVERSION, $SHCXX, $SHCXXFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.
-
suncc

Sets construction variables for the Sun C compiler.
-

Sets:  $CXX, $SHCCFLAGS, $SHOBJPREFIX, $SHOBJSUFFIX.
-
sunlink

Sets construction variables for the Sun linker.
-

Sets:  $RPATHPREFIX, $RPATHSUFFIX, $SHLINKFLAGS.
-
swig

Sets construction variables for the SWIG interface generator.
-

Sets:  $SWIG, $SWIGCFILESUFFIX, $SWIGCOM, $SWIGCXXFILESUFFIX, $SWIGFLAGS, $SWIGINCPREFIX, $SWIGINCSUFFIX, $SWIGPATH, $_SWIGINCFLAGS.
-

Uses:  $SWIGCOMSTR.
-
tar

Sets construction variables for the tar archiver.
-

Sets:  $TAR, $TARCOM, $TARFLAGS, $TARSUFFIX.
-

Uses:  $TARCOMSTR.
-
tex

Sets construction variables for the TeX formatter and typesetter.
-

Sets:  $BIBTEX, $BIBTEXCOM, $BIBTEXFLAGS, $LATEX, $LATEXCOM, $LATEXFLAGS, $MAKEINDEX, $MAKEINDEXCOM, $MAKEINDEXFLAGS, $TEX, $TEXCOM, $TEXFLAGS.
-

Uses:  $BIBTEXCOMSTR, $LATEXCOMSTR, $MAKEINDEXCOMSTR, $TEXCOMSTR.
-
tlib

Sets construction variables for the Borlan
-tib library archiver.
-

Sets:  $AR, $ARCOM, $ARFLAGS, $LIBPREFIX, $LIBSUFFIX.
-

Uses:  $ARCOMSTR.
-
yacc

Sets construction variables for the yacc parse generator.
-

Sets:  $YACC, $YACCCOM, $YACCFLAGS, $YACCHFILESUFFIX, $YACCHXXFILESUFFIX, $YACCVCGFILESUFFIX.
-

Uses:  $YACCCOMSTR.
-
zip

Sets construction variables for the zip archiver.
-

Sets:  $ZIP, $ZIPCOM, $ZIPCOMPRESSION, $ZIPFLAGS, $ZIPSUFFIX.
-

Uses:  $ZIPCOMSTR.
-
Appendix D. Handling Common Tasks

There is a common set of simple tasks that many build configurations rely
-on as they become more complex. Most build tools have special
-purpose constructs for performing these tasks, but since SConscript
-files are Python scripts, you can use more flexible built-in Python
-services to perform these tasks. This appendix lists a number of these
-tasks and how to implement them in Python.
-
Example D-1. Wildcard globbing to create a list of filenames

import glob
-files = glob.glob(wildcard)
-
Example D-2. Filename extension substitution

import os.path
-filename = os.path.splitext(filename)[0]+extension
-
Example D-3. Appending a path prefix to a list of filenames

import os.path
-filenames = [os.path.join(prefix, x) for x in filenames]
-
or in Python 1.5.2:

import os.path
-new_filenames = [] 
-for x in filenames:
-    new_filenames.append(os.path.join(prefix, x))
-
Example D-4. Substituting a path prefix with another one

if filename.find(old_prefix) == 0:
-    filename = filename.replace(old_prefix, new_prefix)
-
or in Python 1.5.2:

import string
-if string.find(filename, old_prefix) == 0:
-    filename = string.replace(filename, old_prefix, new_prefix)      
-
Example D-5. Filtering a filename list to exclude/retain only a specific set
-of extensions

import os.path
-filenames = [x for x in filenames if os.path.splitext(x)[1] in extensions]
-
or in Python 1.5.2:

import os.path
-new_filenames = []
-for x in filenames:
-    if os.path.splitext(x)[1] in extensions:
-        new_filenames.append(x)
-
Example D-6. The "backtick function": run a shell command and capture the
-output
import os
-output = os.popen(command).read()
-
Notes
[1]
In programming parlance,
-     the SConstruct file is
-     declarative,
-     meaning you tell SCons what you want done
-     and let it figure out the order in which to do it,
-     rather than strictly imperative,
-     where you specify explicitly the order in
-     which to do things.
-     
[2]

      This easily-overlooked distinction between
-      how SCons decides if the target itself must be rebuilt
-      and how the target is then used to decide if a different
-      target must be rebuilt is one of the confusing
-      things that has led to the TargetSignatures
-      and SourceSignatures functions being
-      replaced by the simpler Decider function.
-      
[3]

      The AddOption function is,
-      in fact, implemented using a subclass
-      of the optparse.OptionParser.
-      
[4]

    Unfortunately, in the early days of SCons design,
-    we used the name Copy for the function that
-    returns a copy of the environment,
-    otherwise that would be the logical choice for
-    a Builder that copies a file or directory tree
-    to a target location.
-    
[5]

      Actually, the MD5 signature is used as the name of the file
-      in the shared cache directory in which the contents are stored.
-      

\ No newline at end of file
diff --git a/scons-user.html-2.3.0.tar.bz2 b/scons-user.html-2.3.0.tar.bz2
new file mode 100644
index 0000000..361a68f
--- /dev/null
+++ b/scons-user.html-2.3.0.tar.bz2
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:df7bcf2ff8b2eaa8849b8024770136bb4db6e03f4020db494ba32843390963dc
+size 141714
diff --git a/scons.changes b/scons.changes
index 87a279f..7fdbf93 100644
--- a/scons.changes
+++ b/scons.changes
@@ -1,3 +1,51 @@
+-------------------------------------------------------------------
+Sun Jul 21 09:19:19 UTC 2013 - andreas.stieger@gmx.de
+
+- update to 2.3.0
+  - Added ability to run scripts/scons.py directly from source checkout
+  - Hide deprecated --debug={dtree,stree,tree} from --help output
+  - Error messages from option parser now include hints about valid choices
+  - Cleaned up some Python 1.5 and pre-2.3 code, so don't expect SCons
+    to run on anything less than Python 2.4 anymore
+  - Several fixes for runtest.py:
+     * exit with an error if no tests were found
+     * removed --noqmtest option - this behavior is by default
+     * replaced `-o FILE --xml` combination with `--xml FILE`
+     * changed `-o, --output FILE` option to capture stdout/stderr output
+       from runtest.py
+   - Remove os_spawnv_fix.diff patch required to enable parallel builds
+     support prior to Python 2.2
+   - Fix WiX Tool to use .wixobj rather than .wxiobj for compiler output
+   - Support building with WiX releases after 2.0
+   - Fix nested LIBPATH expansion by flattening sequences in subst_path.
+   - Print target name with command execution time with --debug=time
+   - Updated test framework to support dir and file fixtures and
+     added ability to test external (out-of-tree) tools
+   - Fixed several errors in the test suite (Java paths, MSVS version
+     detection, Tool import), additionally
+     * provided MinGW command-line support for the CXX, AS and
+       Fortran tests,
+     * refactored the detection of the gcc version and the according
+       Fortran startup library,
+     * provided a new module rpmutils.py, wrapping the RPM naming rules
+       for target files and further hardware-dependent info (compatibility,
+       compiler flags, ...),
+     * added new test methods must_exist_one_of() and
+       must_not_exist_any_of() and
+     * removed Aegis support from runtest.py. (#2872)
+   - Add -jN support to runtest.py to run tests in parallel
+   - Updated the TeX builder to support the \newglossary command
+     in LaTeX's glossaries package and the files it creates.
+   - Improve support for new versions of biblatex in the TeX builder
+     so biber is called automatically if biblatex requires it.
+   - Add SHLIBVERSION as an option that tells SharedLibrary to build
+     a versioned shared library and create the required symlinks.
+     Add builder InstallVersionedLib to create the required symlinks
+     installing a versioned shared library.
+- packaging changes
+  * update to current (and compressed) user guide
+  * make noarch package
+
 -------------------------------------------------------------------
 Sat Sep 22 20:20:39 UTC 2012 - i@marguerite.su
 
diff --git a/scons.spec b/scons.spec
index f494ac4..caa8434 100644
--- a/scons.spec
+++ b/scons.spec
@@ -1,7 +1,7 @@
 #
 # spec file for package scons
 #
-# Copyright (c) 2012 SUSE LINUX Products GmbH, Nuernberg, Germany.
+# Copyright (c) 2013 SUSE LINUX Products GmbH, Nuernberg, Germany.
 #
 # All modifications and additions to the file contributed by third parties
 # remain the property of their copyright owners, unless otherwise agreed
@@ -26,10 +26,11 @@ Name:           scons
 Summary:        Replacement for Make
 License:        MIT
 Group:          Development/Tools/Building
-Version:        2.2.0
+Version:        2.3.0
 Release:        0
-Source0:        http://freefr.dl.sourceforge.net/project/scons/scons/%{version}/%{name}-%{version}.tar.gz
-Source1:        scons-user.html
+Source0:        http://prdownloads.sourceforge.net/scons/%{name}-%{version}.tar.gz
+#http://www.scons.org/doc/%%{version}/HTML/scons-user.html
+Source1:        scons-user.html-%{version}.tar.bz2
 # rpmlintrc
 Source99:       %{name}-rpmlintrc
 # Sets _mandir to _datadir/man instead of _prefix/man
@@ -38,7 +39,10 @@ Patch1:         %{name}-1.2.0-noenv.patch
 Url:            http://www.scons.org/
 BuildRoot:      %{_tmppath}/%{name}-%{version}-build
 BuildRequires:  fdupes
-BuildRequires:  python-devel
+BuildRequires:  python-devel >= 2.4
+%if 0%{?suse_version} > 1110
+BuildArch:      noarch
+%endif
 %{py_requires}
 
 %description
@@ -49,7 +53,7 @@ provides itself as well as the features. SCons allows you to use the
 full power of Python to control compilation.
 
 %prep
-%setup -q
+%setup -q -a1
 %patch0
 %patch1
 # fix libdir for qt
@@ -60,23 +64,23 @@ patch -p0 <