<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 standardvariables 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 achievepretty much the same. E.g. in gdb, you can do<programlisting>break g_malloccondition 1 n_bytes == 20</programlisting>to break only on g_malloc() calls where the size of the allocated memory blockis 20. </para></refsect2></refsect1></refentry>