glib/docs/reference/glib/running.sgml
Matthias Clasen 5cb432b56c Mention g_trap_object_ref
2006-01-26  Matthias Clasen  <mclasen@redhat.com>

	* gobject/tut_tools.xml: Mention g_trap_object_ref

	* glib/running.sgml: Add g_trap variables to the index.
	Mention conditional breakpoints as an alternative.
2006-01-26 19:28:33 +00:00

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<refentry id="glib-running" revision="17 Jan 2002">
<refmeta>
<refentrytitle>Running GLib Applications</refentrytitle>
<manvolnum>3</manvolnum>
<refmiscinfo>GLib Library</refmiscinfo>
</refmeta>
<refnamediv>
<refname>Running GLib Applications</refname>
<refpurpose>
How to run and debug your GLib application
</refpurpose>
</refnamediv>
<refsect1>
<title>Running and debugging GLib Applications</title>
<refsect2>
<title>Environment variables</title>
<para>
GLib inspects a few of environment variables in addition to standard
variables like <envar>LANG</envar>, <envar>PATH</envar> or <envar>HOME</envar>.
</para>
<formalpara id="G_FILENAME_ENCODING">
<title><envar>G_FILENAME_ENCODING</envar></title>
<para>
This environment variable can be set to a comma-separated list of character
set names. GLib assumes that filenames are encoded in the first character
set from that list rather than in UTF-8. The special token "@locale" can be
used to specify the character set for the current locale.
</para>
</formalpara>
<formalpara id="G_BROKEN_FILENAMES">
<title><envar>G_BROKEN_FILENAMES</envar></title>
<para>
If this environment variable is set, GLib assumes that filenames are in
the locale encoding rather than in UTF-8. G_FILENAME_ENCODING takes
priority over G_BROKEN_FILENAMES.
</para>
</formalpara>
<formalpara id="G_MESSAGES_PREFIXED">
<title><envar>G_MESSAGES_PREFIXED</envar></title>
<para>
A list of log levels for which messages should be prefixed by the
program name and PID of the application. The default is to prefix
everything except <literal>G_LOG_LEVEL_MESSAGE</literal> and <literal>G_LOG_LEVEL_INFO</literal>.
</para>
</formalpara>
<formalpara id="G_DEBUG">
<title><envar>G_DEBUG</envar></title>
<para>
If GLib has been configured with <option>--enable-debug=yes</option>,
this variable can be set to a list of debug options, which cause GLib
to print out different types of debugging information.
<variablelist>
<varlistentry>
<term>fatal_warnings</term>
<listitem><para>Causes GLib to abort the program at the first call
to <link linkend="g-warning">g_warning</link>() or
<link linkend="g-critical">g_critical</link>(). This option is
special in that it doesn't require GLib to be configured with
debugging support.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>fatal_criticals</term>
<listitem><para>Causes GLib to abort the program at the first call
to <link linkend="g-critical">g_critical</link>(). This option is
special in that it doesn't require GLib to be configured with
debugging support.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>gc-friendly</term>
<listitem>
<para>
Newly allocated memory that isn't directly initialized, as well
as memory being freed will be reset to 0. The point here is to
allow memory checkers and similar programs that use bohem GC alike
algorithms to produce more accurate results.
This option is special in that it doesn't require GLib to be
configured with debugging support.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</formalpara>
<formalpara id="G_SLICE">
<title><envar>G_SLICE</envar></title>
<para>
This environment variable allows reconfiguration of the #GSlice
memory allocator.
<variablelist>
<varlistentry>
<term>always-malloc</term>
<listitem>
<para>
This will cause all slices allocated through g_slice_alloc() and
released by g_slice_free1() to be actually allocated via direct
calls to g_malloc() and g_free().
This is most useful for memory checkers and similar programs that
use bohem GC alike algorithms to produce more accurate results.
It can also be in conjunction with debugging features of the system's
malloc implementation such as glibc's MALLOC_CHECK_=2 to debug
erroneous slice allocation code.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</formalpara>
<formalpara id="G_RANDOM_VERSION">
<title><envar>G_RANDOM_VERSION</envar></title>
<para>
If this environment variable is set to '2.0', the outdated
pseudo-random number seeding and generation algorithms from
GLib-2.0 are used instead of the new better ones. Use the GLib-2.0
algorithms only if you have sequences of numbers generated with
Glib-2.0 that you need to reproduce exactly.
</para>
</formalpara>
<formalpara id="LIBCHARSET_ALIAS_DIR">
<title><envar>LIBCHARSET_ALIAS_DIR</envar></title>
<para>
Allows to specify a nonstandard location for the
<filename>charset.aliases</filename> file that is used by the
character set conversion routines. The default location is the
<replaceable>libdir</replaceable> specified at compilation time.
</para>
</formalpara>
<formalpara id="G_WIN32_PRETEND_WIN9X">
<title><envar>G_WIN32_PRETEND_WIN9X</envar></title>
<para>
Setting this variable to any value forces g_win32_get_windows_version()
to return a version code for Windows 9x. This is mainly an internal
debugging aid for GTK+ and GLib developers, to be able to check the
code paths for Windows 9x.
</para>
</formalpara>
</refsect2>
<refsect2>
<title>Traps and traces</title>
<para>
<indexterm><primary>g_trap_free_size</primary></indexterm>
<indexterm><primary>g_trap_realloc_size</primary></indexterm>
<indexterm><primary>g_trap_malloc_size</primary></indexterm>
Some code portions contain trap variables that can be set during debugging
time if GLib has been configured with <option>--enable-debug=yes</option>.
Such traps lead to immediate code halts to examine the current program state
and backtrace.
</para>
<para>
Currently, the following trap variables exist:
<programlisting>
static volatile gulong g_trap_free_size;
static volatile gulong g_trap_realloc_size;
static volatile gulong g_trap_malloc_size;
</programlisting>
If set to a size > 0, <link linkend="g-free">g_free</link>(),
<link linkend="g-realloc">g_realloc</link>() and
<link linkend="g-malloc">g_malloc</link>() will be intercepted if the size
matches the size of the corresponding memory block. This will only work with
<literal>g_mem_set_vtable (glib_mem_profiler_table)</literal> upon startup
though, because memory profiling is required to match on the memory block sizes.
</para>
<para>
Note that many modern debuggers support conditional breakpoints, which achieve
pretty much the same. E.g. in gdb, you can do
<programlisting>
break g_malloc
condition 1 n_bytes == 20
</programlisting>
to break only on g_malloc() calls where the size of the allocated memory block
is 20.
</para>
</refsect2>
</refsect1>
</refentry>