glib/docs/reference/gobject/glib-mkenums.xml

<refentry id="glib-mkenums" lang="en">

<refentryinfo>
  <title>gdbus</title>
  <productname>GObject</productname>
  <authorgroup>
    <author>
      <contrib>Developer</contrib>
      <firstname>Owen</firstname>
      <surname>Taylor</surname>
    </author>
  </authorgroup>
</refentryinfo>

<refmeta>
<refentrytitle>glib-mkenums</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo class="manual">User Commands</refmiscinfo>
</refmeta>

<refnamediv>
<refname>glib-mkenums</refname>
<refpurpose>C language enum description generation utility</refpurpose>
</refnamediv>

<refsynopsisdiv>
<cmdsynopsis>
<command>glib-mkenums</command>
<arg choice="opt" rep="repeat">OPTION</arg>
<arg choice="opt" rep="repeat">FILE</arg>
</cmdsynopsis>
</refsynopsisdiv>

<refsect1><title>Description</title>
<para><command>glib-mkenums</command> is a small utility that parses C code to
extract enum definitions and produces enum descriptions based on text templates
specified by the user. Typically, you can use this tool to generate enumeration
types for the GType type system, for GObject properties and signal marshalling;
additionally, you can use it to generate enumeration values of GSettings schemas.
</para>

<para><command>glib-mkenums</command> takes a list of valid C code files as
input. The options specified control the text that generated, substituting various
keywords enclosed in <literal>@</literal> characters in the templates.
</para>

<para>Since version 2.74, GLib provides the <literal>G_DEFINE_ENUM_TYPE</literal>
and <literal>G_DEFINE_FLAGS_TYPE</literal> C pre-processor macros. These macros
can be used to define a GType for projects that have few, small enumeration
types without going through the complexities of generating code at build
time.</para>

<refsect2><title>Production text substitutions</title>
<para>
Certain keywords enclosed in <literal>@</literal> characters will be substituted in the
emitted text. For the substitution examples of the keywords below,
the following example enum definition is assumed:
</para>
<informalexample><programlisting>
typedef enum
{
  PREFIX_THE_XVALUE    = 1 &lt;&lt; 3,
  PREFIX_ANOTHER_VALUE = 1 &lt;&lt; 4
} PrefixTheXEnum;
</programlisting></informalexample>
<variablelist>
<varlistentry>
<term><literal>@EnumName@</literal>></term>
<listitem><para>
The name of the enum currently being processed, enum names are assumed to be
properly namespaced and to use mixed capitalization to separate
words (e.g. <literal>PrefixTheXEnum</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@enum_name@</literal></term>
<listitem><para>
The enum name with words lowercase and word-separated by underscores
(e.g. <literal>prefix_the_xenum</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@ENUMNAME@</literal></term>
<listitem><para>
The enum name with words uppercase and word-separated by underscores
(e.g. <literal>PREFIX_THE_XENUM</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@ENUMSHORT@</literal></term>
<listitem><para>
The enum name with words uppercase and word-separated by underscores,
prefix stripped (e.g. <literal>THE_XENUM</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@ENUMPREFIX@</literal></term>
<listitem><para>
The prefix of the enum name (e.g. <literal>PREFIX</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@VALUENAME@</literal></term>
<listitem><para>
The enum value name currently being processed with words uppercase and
word-separated by underscores,
this is the assumed literal notation of enum values in the C sources
(e.g. <literal>PREFIX_THE_XVALUE</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@valuenick@</literal></term>
<listitem><para>
A nick name for the enum value currently being processed, this is usually
generated by stripping common prefix words of all the enum values of the
current enum, the words are lowercase and underscores are substituted by a
minus (e.g. <literal>the-xvalue</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@valuenum@</literal></term>
<listitem><para>
The integer value for the enum value currently being processed. If the
evaluation fails then <command>glib-mkenums</command> will exit with an
error status, but this only happens if <literal>@valuenum@</literal>
appears in your value production template. (Since: 2.26)
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@type@</literal></term>
<listitem><para>
This is substituted either by "enum" or "flags", depending on whether the
enum value definitions contained bit-shift operators or not (e.g. <literal>flags</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@Type@</literal></term>
<listitem><para>
The same as <literal>@type@</literal> with the first letter capitalized (e.g. <literal>Flags</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@TYPE@</literal></term>
<listitem><para>
The same as <literal>@type@</literal> with all letters uppercased (e.g. <literal>FLAGS</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@filename@</literal></term>
<listitem><para>
The full path of the input file currently being processed (e.g. <literal>/build/environment/project/src/foo.h</literal>).
</para></listitem>
</varlistentry>

<varlistentry>
<term><literal>@basename@</literal></term>
<listitem><para>
The base name of the input file currently being processed (e.g. <literal>foo.h</literal>).
Typically you want to use <literal>@basename@</literal> in place of <literal>@filename@</literal>
in your templates, to improve the reproducibility of the build. (Since: 2.22)
</para></listitem>
</varlistentry>
</variablelist>
</refsect2>
<refsect2><title>Trigraph extensions</title>
<para>
Some C comments are treated specially in the parsed enum definitions,
such comments start out with the trigraph sequence <literal>/*&lt;</literal>
and end with the trigraph sequence <literal>&gt;*/</literal>.
</para>

<para>The following options can be specified per enum definition:</para>
<variablelist>
<varlistentry>
<term><literal>skip</literal></term>
<listitem><para>
Indicates this enum definition should  be skipped.
</para></listitem>
</varlistentry>
<varlistentry>
<term><literal>flags</literal></term>
<listitem><para>
Indicates this enum should be treated as a flags definition.
</para></listitem>
</varlistentry>
<varlistentry>
<term><literal>underscore_name</literal></term>
<listitem><para>
Specifies the word separation used in the <function>*_get_type()</function>
function. For instance, <literal>/*&lt; underscore_name=gnome_vfs_uri_hide_options &gt;*/</literal>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><literal>since</literal></term>
<listitem><para>
Specifies the version tag that will be used to substitute the <literal>@enumsince@</literal>
keyword in the template, useful when documenting methods generated from the enums
(e.g. <literal>Since: @enumsince@</literal>). (Since: 2.66)
</para></listitem>
</varlistentry>
</variablelist>

<para>The following options can be specified per value definition:</para>
<variablelist>
<varlistentry>
<term><literal>skip</literal></term>
<listitem><para>
Indicates the value should be skipped.
</para></listitem>
</varlistentry>
<varlistentry>
<term><literal>nick</literal></term>
<listitem><para>
Specifies the otherwise auto-generated nickname.
</para></listitem>
</varlistentry>
</variablelist>

<para>Examples:</para>
<informalexample><programlisting>
typedef enum /*&lt; skip &gt;*/
{
  PREFIX_FOO
} PrefixThisEnumWillBeSkipped;
typedef enum /*&lt; flags,prefix=PREFIX,since=1.0 &gt;*/
{
  PREFIX_THE_ZEROTH_VALUE,	/*&lt; skip &gt;*/
  PREFIX_THE_FIRST_VALUE,
  PREFIX_THE_SECOND_VALUE,
  PREFIX_THE_THIRD_VALUE,	/*&lt; nick=the-last-value &gt;*/
} PrefixTheFlagsEnum;
</programlisting></informalexample>
</refsect2>
</refsect1>

<refsect1><title>Options</title>
<variablelist>

<varlistentry>
<term><option>--fhead</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> prior to processing input files.
</para>
<para>
You can specify this option multiple times, and the <replaceable>TEXT</replaceable>
will be concatenated.
</para>
<para>
When used along with a template file, <replaceable>TEXT</replaceable>
will be prepended to the template's <literal>file-header</literal> section.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--fprod</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> every time a new input file
is being processed.
</para>
<para>
You can specify this option multiple times, and the <replaceable>TEXT</replaceable>
will be concatenated.
</para>
<para>
When used along with a template file, <replaceable>TEXT</replaceable>
will be appended to the template's <literal>file-production</literal> section.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--ftail</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> after all input files have been
processed.
</para>
<para>
You can specify this option multiple times, and the <replaceable>TEXT</replaceable>
will be concatenated.
</para>
<para>
When used along with a template file, <replaceable>TEXT</replaceable>
will be appended to the template's <literal>file-tail</literal> section.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--eprod</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> every time an enum is encountered
in the input files.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--vhead</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> before iterating over the set of
values of an enum.
</para>
<para>
You can specify this option multiple times, and the <replaceable>TEXT</replaceable>
will be concatenated.
</para>
<para>
When used along with a template file, <replaceable>TEXT</replaceable>
will be prepended to the template's <literal>value-header</literal> section.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--vprod</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> for every value of an enum.
</para>
<para>
You can specify this option multiple times, and the <replaceable>TEXT</replaceable>
will be concatenated.
</para>
<para>
When used along with a template file, <replaceable>TEXT</replaceable>
will be appended to the template's <literal>value-production</literal> section.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--vtail</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Emits <replaceable>TEXT</replaceable> after iterating over all values
of an enum.
</para>
<para>
You can specify this option multiple times, and the <replaceable>TEXT</replaceable>
will be concatenated.
</para>
<para>
When used along with a template file, <replaceable>TEXT</replaceable>
will be appended to the template's <literal>value-tail</literal> section.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--comments</option> <replaceable>TEXT</replaceable></term>
<listitem><para>
Template for auto-generated comments, the default (for C code generations) is
<literal>"/* @comment@ */"</literal>.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--template</option> <replaceable>FILE</replaceable></term>
<listitem><para>
Read templates from the given file. The templates are enclosed in
specially-formatted C comments:
</para>
<informalexample><programlisting>
/*** BEGIN section ***/
/*** END section ***/
</programlisting></informalexample>
<para>
<replaceable>section</replaceable> may be <literal>file-header</literal>,
<literal>file-production</literal>, <literal>file-tail</literal>,
<literal>enumeration-production</literal>, <literal>value-header</literal>,
<literal>value-production</literal>, <literal>value-tail</literal> or
<literal>comment</literal>.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--identifier-prefix</option> <replaceable>PREFIX</replaceable></term>
<listitem><para>
Indicates what portion of the enum name should be interpreted as the
prefix (eg, the "<literal>Gtk</literal>" in
"<literal>GtkDirectionType</literal>"). Normally this will be figured
out automatically, but you may need to override the default if your
namespace is capitalized oddly.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--symbol-prefix</option> <replaceable>PREFIX</replaceable></term>
<listitem><para>
Indicates what prefix should be used to correspond to the identifier
prefix in related C function names (eg, the "<literal>gtk</literal>"
in "<literal>gtk_direction_type_get_type</literal>". Equivalently,
this is the lowercase version of the prefix component of the enum
value names (eg, the "<literal>GTK</literal>" in
"<literal>GTK_DIR_UP</literal>". The default value is the identifier
prefix, converted to lowercase.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--help</option></term>
<listitem><para>
Print brief help and exit.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--version</option></term>
<listitem><para>
Print version and exit.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>--output=FILE</option></term>
<listitem><para>
Write output to FILE instead of stdout.
</para></listitem>
</varlistentry>

<varlistentry>
<term><option>@RSPFILE</option></term>
<listitem><para>
When passed as the sole argument, read and parse the actual arguments from
<literal>RSPFILE</literal>. Useful on systems with a low command-line length
limit. For example, Windows has a limit of 8191 characters.
</para></listitem>
</varlistentry>

</variablelist>
</refsect1>

<refsect1><title>Using templates</title>
<para>
Instead of passing the various sections of the generated file to the command
line of <command>glib-mkenums</command>, it's strongly recommended to use a
template file, especially for generating C sources.
</para>

<para>
A C header template file will typically look like this:
</para>
<informalexample><programlisting>
/*** BEGIN file-header ***/
#pragma once

/* Include the main project header */
#include "project.h"

G_BEGIN_DECLS
/*** END file-header ***/

/*** BEGIN file-production ***/

/* enumerations from "@basename@" */
/*** END file-production ***/

/*** BEGIN value-header ***/
GType @enum_name@_get_type (void) G_GNUC_CONST;
#define @ENUMPREFIX@_TYPE_@ENUMSHORT@ (@enum_name@_get_type ())
/*** END value-header ***/

/*** BEGIN file-tail ***/
G_END_DECLS
/*** END file-tail ***/
</programlisting></informalexample>

<para>
A C source template file will typically look like this:
</para>
<informalexample><programlisting>
/*** BEGIN file-header ***/
#include "config.h"
#include "enum-types.h"

/*** END file-header ***/

/*** BEGIN file-production ***/
/* enumerations from "@basename@" */
/*** END file-production ***/

/*** BEGIN value-header ***/
GType
@enum_name@_get_type (void)
{
  static gsize static_g_@type@_type_id;

  if (g_once_init_enter (&amp;static_g_@type@_type_id))
    {
      static const G@Type@Value values[] = {
/*** END value-header ***/

/*** BEGIN value-production ***/
            { @VALUENAME@, "@VALUENAME@", "@valuenick@" },
/*** END value-production ***/

/*** BEGIN value-tail ***/
            { 0, NULL, NULL }
      };

      GType g_@type@_type_id =
        g_@type@_register_static (g_intern_static_string ("@EnumName@"), values);

      g_once_init_leave (&amp;static_g_@type@_type_id, g_@type@_type_id);
    }
  return static_g_@type@_type_id;
}

/*** END value-tail ***/
</programlisting></informalexample>

<para>
Template files are easier to modify and update, and can be used
to generate various types of outputs using the same command line
or tools during the build.
</para>
</refsect1>

<refsect1><title>Using glib-mkenums with Meson</title>
<para>
Meson supports generating enumeration types using <command>glib-mkenums</command>
out of the box in its "gnome" module.
</para>

<para>
In your <filename>meson.build</filename> file you will typically call the
<literal>gnome.mkenums_simple()</literal> method to generate idiomatic enumeration
types from a list of headers to inspect:
</para>
<informalexample><programlisting>
project_headers = [
  'project-foo.h',
  'project-bar.h',
  'project-baz.h',
]

gnome = import('gnome')
enum_files = gnome.mkenums_simple('enum-types',
  sources: project_headers,
)
</programlisting></informalexample>

<para>
The <literal>enum_files</literal> variable will contain an array of two elements
in the following order:
</para>
<itemizedlist>
  <listitem><para>a build target for the source file</para></listitem>
  <listitem><para>a build target for the header file</para></listitem>
</itemizedlist>
<para>
You should use the returned objects to provide a dependency on every other
build target that references the source or header file; for instance, if you
are using the source to build a library:
</para>
<informalexample><programlisting>
mainlib = library('project',
  sources: project_sources + enum_files,
  ...
)
</programlisting></informalexample>
<para>
Additionally, if you are including the generated header file inside a build
target that depends on the library you just built, you must ensure that the
internal dependency includes the generated header as a required source file:
</para>
<informalexample><programlisting>
mainlib_dep = declare_dependency(sources: enum_files[1], link_with: mainlib)
</programlisting></informalexample>
<para>
You should not include the generated source file as well, otherwise it will
be built separately for every target that depends on it, causing build
failures. To know more about why all this is required, please refer to the
<ulink url="https://mesonbuild.com/FAQ.html#how-do-i-tell-meson-that-my-sources-use-generated-headers">
corresponding Meson FAQ entry</ulink>.
</para>

<para>
If you are generating C header and source files that require special
templates, you can use <literal>gnome.mkenums()</literal> to provide those
headers, for instance:
</para>
<informalexample><programlisting>
enum_files = gnome.mkenums('enum-types',
  sources: project_headers,
  h_template: 'enum-types.h.in',
  c_template: 'enum-types.c.in',
  install_header: true,
)
</programlisting></informalexample>
<para>
For more information, see the <ulink url="https://mesonbuild.com/Gnome-module.html#gnomegenmarshal">Meson
documentation for <literal>gnome.mkenums()</literal></ulink>.
</para>
</refsect1>

<refsect1><title>Using glib-mkenums with Autotools</title>
<para>
In order to use <command>glib-mkenums</command> in your project when using
Autotools as the build system, you will first need to modify your
<filename>configure.ac</filename> file to ensure you find the appropriate
command using <command>pkg-config</command>, similarly as to how you discover
the compiler and linker flags for GLib.
</para>
<informalexample><programlisting>
PKG_PROG_PKG_CONFIG([0.28])

PKG_CHECK_VAR([GLIB_MKENUMS], [glib-2.0], [glib_mkenums])
</programlisting></informalexample>
<para>
In your <filename>Makefile.am</filename> file you will typically use rules
like these:
</para>
<informalexample><programlisting>
# A list of headers to inspect
project_headers = \
        project-foo.h \
        project-bar.h \
        project-baz.h

enum-types.h: $(project_headers) enum-types.h.in
        $(AM_V_GEN)$(GLIB_MKENUMS) \
                --template=enum-types.h.in \
                --output=$@ \
                $(project_headers)

enum-types.c: $(project_headers) enum-types.c.in enum-types.h
        $(AM_V_GEN)$(GLIB_MKENUMS) \
                --template=enum-types.c.in \
                --output=$@ \
                $(project_headers)

# Build the enum types files before every other target
BUILT_SOURCES += enum-types.h enum-types.c
CLEANFILES += enum-types.h enum-types.c
EXTRA_DIST += enum-types.h.in enum-types.c.in
</programlisting></informalexample>
<para>
In the example above, we have a variable called <literal>project_headers</literal>
where we reference all header files we want to inspect for generating enumeration
GTypes. In the <filename>enum-types.h</filename> rule we use <command>glib-mkenums</command>
with a template called <filename>enum-types.h.in</filename> in order to generate the
header file; similarly, in the <filename>enum-types.c</filename> rule we use a
template called <filename>enum-types.c.in</filename>.
</para>
</refsect1>

<refsect1><title>See also</title>
<para>
<citerefentry>
<refentrytitle>glib-genmarshal</refentrytitle>
<manvolnum>1</manvolnum>
</citerefentry>
</para>
</refsect1>
</refentry>