WebSVN – nexmon – Blame – Rev 1 – /utilities/glib/docs/reference/glib/running.xml

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<?xml version="1.0"?>

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"

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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [

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]>

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<refentry id="glib-running">

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<refmeta>

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<refentrytitle>Running GLib Applications</refentrytitle>

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<manvolnum>3</manvolnum>

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<refmiscinfo>GLib Library</refmiscinfo>

</refmeta>

<refnamediv>

<refname>Running GLib Applications</refname>

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<refpurpose>

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How to run and debug your GLib application

</refpurpose>

</refnamediv>

<refsect1>

<title>Running and debugging GLib Applications</title>

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<refsect2>

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<title>Environment variables</title>

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<para>

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The runtime behaviour of GLib applications can be influenced by a

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number of environment variables.

</para>

<formalpara>

<title>Standard variables</title>

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<para>

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GLib reads standard environment variables like <envar>LANG</envar>,

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<envar>PATH</envar>, <envar>HOME</envar>, <envar>TMPDIR</envar>,

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<envar>TZ</envar> and <envar>LOGNAME</envar>.

</para>

</formalpara>

<formalpara>

<title>XDG directories</title>

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<para>

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GLib consults the environment variables <envar>XDG_DATA_HOME</envar>,

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<envar>XDG_DATA_DIRS</envar>, <envar>XDG_CONFIG_HOME</envar>,

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<envar>XDG_CONFIG_DIRS</envar>, <envar>XDG_CACHE_HOME</envar> and

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<envar>XDG_RUNTIME_DIR</envar> for the various XDG directories.

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    For more information, see the <ulink url="http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html">XDG basedir spec</ulink>.

</para>

</formalpara>

<formalpara id="G_FILENAME_ENCODING">

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<title><envar>G_FILENAME_ENCODING</envar></title>

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<para>

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This environment variable can be set to a comma-separated list of character

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set names. GLib assumes that filenames are encoded in the first character

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set from that list rather than in UTF-8. The special token "@locale" can be

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used to specify the character set for the current locale.

</para>

</formalpara>

<formalpara id="G_BROKEN_FILENAMES">

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<title><envar>G_BROKEN_FILENAMES</envar></title>

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<para>

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If this environment variable is set, GLib assumes that filenames are in

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the locale encoding rather than in UTF-8. G_FILENAME_ENCODING takes

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priority over G_BROKEN_FILENAMES.

</para>

</formalpara>

<formalpara id="G_MESSAGES_PREFIXED">

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<title><envar>G_MESSAGES_PREFIXED</envar></title>

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<para>

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A list of log levels for which messages should be prefixed by the

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program name and PID of the application. The default is to prefix

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everything except <literal>G_LOG_LEVEL_MESSAGE</literal> and

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<literal>G_LOG_LEVEL_INFO</literal>.

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The possible values are

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<literal>error</literal>,

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<literal>warning</literal>,

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<literal>critical</literal>,

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<literal>message</literal>,

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<literal>info</literal> and

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<literal>debug</literal>.

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You can also use the special values

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<literal>all</literal> and

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<literal>help</literal>.

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</para>

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<para>

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This environment variable only affects the default log handler,

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g_log_default_handler().

</para>

</formalpara>

<formalpara id="G_MESSAGES_DEBUG">

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<title><envar>G_MESSAGES_DEBUG</envar></title>

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<para>

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A space-separated list of log domains for which informational

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and debug messages should be printed. By default, these

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messages are not printed.

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</para>

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<para>

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You can also use the special value <literal>all</literal>.

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</para>

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<para>

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This environment variable only affects the default log handler,

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g_log_default_handler().

</para>

</formalpara>

<formalpara id="G-DEBUG:CAPS">

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<title><envar>G_DEBUG</envar></title>

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<para>

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This environment variable can be set to a list of debug options,

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which cause GLib to print out different types of debugging information.

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<variablelist>

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<varlistentry>

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<term>fatal-warnings</term>

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<listitem><para>Causes GLib to abort the program at the first call

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to g_warning() or g_critical().</para>

</listitem>

</varlistentry>

<varlistentry>

<term>fatal-criticals</term>

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<listitem><para>Causes GLib to abort the program at the first call

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to g_critical().</para>

</listitem>

</varlistentry>

<varlistentry>

<term>gc-friendly</term>

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<listitem><para>Newly allocated memory that isn't directly initialized,

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as well as memory being freed will be reset to 0. The point here is

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to allow memory checkers and similar programs that use Boehm GC alike

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algorithms to produce more accurate results.</para>

</listitem>

</varlistentry>

<varlistentry>

<term>resident-modules</term>

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<listitem><para>All modules loaded by GModule will be made resident.

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This can be useful for tracking memory leaks in modules which are

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later unloaded; but it can also hide bugs where code is accessed

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after the module would have normally been unloaded.</para>

</listitem>

</varlistentry>

<varlistentry>

<term>bind-now-modules</term>

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<listitem><para>All modules loaded by GModule will bind their symbols

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at load time, even when the code uses %G_MODULE_BIND_LAZY.</para>

</listitem>

</varlistentry>

</variablelist>

The special value all can be used to turn on all debug options.

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The special value help can be used to print all available options.

</para>

</formalpara>

<formalpara id="G_SLICE">

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<title><envar>G_SLICE</envar></title>

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<para>

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This environment variable allows reconfiguration of the GSlice

memory allocator.

<variablelist>

<varlistentry>

<term>always-malloc</term>

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<listitem><para>This will cause all slices allocated through

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g_slice_alloc() and released by g_slice_free1() to be actually

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allocated via direct calls to g_malloc() and g_free().

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This is most useful for memory checkers and similar programs that

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use Boehm GC alike algorithms to produce more accurate results.

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It can also be in conjunction with debugging features of the system's

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malloc() implementation such as glibc's MALLOC_CHECK_=2 to debug

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erroneous slice allocation code, although

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<literal>debug-blocks</literal> is usually a better suited debugging

tool.</para>

</listitem>

</varlistentry>

<varlistentry>

<term>debug-blocks</term>

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<listitem><para>Using this option (present since GLib 2.13) engages

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extra code which performs sanity checks on the released memory

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slices. Invalid slice addresses or slice sizes will be reported and

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lead to a program halt. This option is for debugging scenarios.

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In particular, client packages sporting their own test suite should

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<emphasis>always enable this option when running tests</emphasis>.

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Global slice validation is ensured by storing size and address

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information for each allocated chunk, and maintaining a global

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hash table of that data. That way, multi-thread scalability is

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given up, and memory consumption is increased. However, the

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resulting code usually performs acceptably well, possibly better

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than with comparable memory checking carried out using external

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tools.</para>

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<para>An example of a memory corruption scenario that cannot be

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reproduced with <literal>G_SLICE=always-malloc</literal>, but will

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be caught by <literal>G_SLICE=debug-blocks</literal> is as follows:

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<programlisting>

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void *slist = g_slist_alloc (); /* void* gives up type-safety */

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g_list_free (slist); /* corruption: sizeof (GSList) != sizeof (GList) */

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</programlisting></para>

</listitem>

</varlistentry>

</variablelist>

The special value all can be used to turn on all options.

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The special value help can be used to print all available options.

</para>

</formalpara>

<formalpara id="G_RANDOM_VERSION">

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<title><envar>G_RANDOM_VERSION</envar></title>

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<para>

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If this environment variable is set to '2.0', the outdated

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pseudo-random number seeding and generation algorithms from

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GLib 2.0 are used instead of the newer, better ones. You should

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only set this variable if you have sequences of numbers that were

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generated with Glib 2.0 that you need to reproduce exactly.

</para>

</formalpara>

<formalpara id="LIBCHARSET_ALIAS_DIR">

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<title><envar>LIBCHARSET_ALIAS_DIR</envar></title>

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<para>

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Allows to specify a nonstandard location for the

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<filename>charset.aliases</filename> file that is used by the

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character set conversion routines. The default location is the

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<replaceable>libdir</replaceable> specified at compilation time.

</para>

</formalpara>

<formalpara id="TZDIR">

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<title><envar>TZDIR</envar></title>

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<para>

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Allows to specify a nonstandard location for the timezone data files

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that are used by the #GDateTime API. The default location is under

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<filename>/usr/share/zoneinfo</filename>. For more information,

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also look at the <command>tzset</command> manual page.

</para>

</formalpara>

</refsect2>

<refsect2 id="setlocale">

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<title>Locale</title>

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<para>

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A number of interfaces in GLib depend on the current locale in which

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an application is running. Therefore, most GLib-using applications should

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call <function>setlocale (LC_ALL, "")</function> to set up the current

locale.

</para>

<para>

On Windows, in a C program there are several locale concepts

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that not necessarily are synchronized. On one hand, there is the

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system default ANSI code-page, which determines what encoding is used

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for file names handled by the C library's functions and the Win32

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API. (We are talking about the "narrow" functions here that take

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character pointers, not the "wide" ones.)

</para>

<para>

On the other hand, there is the C library's current locale. The

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character set (code-page) used by that is not necessarily the same as

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the system default ANSI code-page. Strings in this character set are

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returned by functions like <function>strftime()</function>.

</para>

</refsect2>

<para>

glib ships with a set of python macros for the gdb debugger. These includes pretty

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printers for lists, hashtables and gobject types. It also has a backtrace filter

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that makes backtraces with signal emissions easier to read.

</para>

<para>

To use this you need a recent enough gdb that supports python scripting. Gdb 7.0

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should be recent enough, but branches of the "archer" gdb tree as used in Fedora 11

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and Fedora 12 should work too. You then need to install glib in the same prefix as

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gdb so that the python gdb autoloaded files get installed in the right place for

gdb to pick up.

</para>

<para>

General pretty printing should just happen without having to do anything special.

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To get the signal emission filtered backtrace you must use the "new-backtrace" command

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instead of the standard one.

</para>

<para>

There is also a new command called gforeach that can be used to apply a command

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on each item in a list. E.g. you can do

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<programlisting>

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gforeach i in some_list_variable: print *(GtkWidget *)l

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</programlisting>

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Which would print the contents of each widget in a list of widgets.

</para>

<refsect2>

<title>SystemTap</title>

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<para>

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<ulink url="http://sourceware.org/systemtap/">SystemTap</ulink> is a dynamic whole-system

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analysis toolkit. GLib ships with a file <filename>glib.stp</filename> which defines a

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set of probe points, which you can hook into with custom SystemTap scripts.

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See the files <filename>glib.stp</filename> and <filename>gobject.stp</filename> which

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are in your shared SystemTap scripts directory.

</para>

</refsect2>

<refsect2>

<title>Memory statistics</title>

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<para>

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g_mem_profile() will output a summary g_malloc() memory usage, if memory

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profiling has been enabled by calling

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<literal>g_mem_set_vtable (glib_mem_profiler_table)</literal> upon startup.

</para>

<para>

If GLib has been configured with <option>--enable-debug=yes</option>,

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then g_slice_debug_tree_statistics() can be called in a debugger to

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output details about the memory usage of the slice allocator.

</para>

</refsect2>

</refsect1>

</refentry>

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