1<refentry id="glib-running" revision="17 Jan 2002"> 2<refmeta> 3<refentrytitle>Running GLib Applications</refentrytitle> 4<manvolnum>3</manvolnum> 5<refmiscinfo>GLib Library</refmiscinfo> 6</refmeta> 7 8<refnamediv> 9<refname>Running GLib Applications</refname> 10<refpurpose> 11How to run and debug your GLib application 12</refpurpose> 13</refnamediv> 14 15<refsect1> 16<title>Running and debugging GLib Applications</title> 17 18<refsect2> 19<title>Environment variables</title> 20 21<para> 22GLib inspects a few of environment variables in addition to standard 23variables like <envar>LANG</envar>, <envar>PATH</envar> or <envar>HOME</envar>. 24</para> 25 26<formalpara id="G_FILENAME_ENCODING"> 27 <title><envar>G_FILENAME_ENCODING</envar></title> 28 29 <para> 30 This environment variable can be set to a comma-separated list of character 31 set names. GLib assumes that filenames are encoded in the first character 32 set from that list rather than in UTF-8. The special token "@locale" can be 33 used to specify the character set for the current locale. 34 </para> 35</formalpara> 36 37<formalpara id="G_BROKEN_FILENAMES"> 38 <title><envar>G_BROKEN_FILENAMES</envar></title> 39 40 <para> 41 If this environment variable is set, GLib assumes that filenames are in 42 the locale encoding rather than in UTF-8. G_FILENAME_ENCODING takes 43 priority over G_BROKEN_FILENAMES. 44 </para> 45</formalpara> 46 47<formalpara id="G_MESSAGES_PREFIXED"> 48 <title><envar>G_MESSAGES_PREFIXED</envar></title> 49 50 <para> 51 A list of log levels for which messages should be prefixed by the 52 program name and PID of the application. The default is to prefix 53 everything except <literal>G_LOG_LEVEL_MESSAGE</literal> and <literal>G_LOG_LEVEL_INFO</literal>. 54 </para> 55</formalpara> 56 57<formalpara id="G_DEBUG"> 58 <title><envar>G_DEBUG</envar></title> 59 <para> 60 If GLib has been configured with <option>--enable-debug=yes</option>, 61 this variable can be set to a list of debug options, which cause GLib 62 to print out different types of debugging information. 63 <variablelist> 64 <varlistentry> 65 <term>fatal_warnings</term> 66 <listitem><para>Causes GLib to abort the program at the first call 67 to <link linkend="g-warning">g_warning</link>() or 68 <link linkend="g-critical">g_critical</link>(). This option is 69 special in that it doesn't require GLib to be configured with 70 debugging support.</para> 71 </listitem> 72 </varlistentry> 73 <varlistentry> 74 <term>fatal_criticals</term> 75 <listitem><para>Causes GLib to abort the program at the first call 76 to <link linkend="g-critical">g_critical</link>(). This option is 77 special in that it doesn't require GLib to be configured with 78 debugging support.</para> 79 </listitem> 80 </varlistentry> 81 <varlistentry> 82 <term>gc-friendly</term> 83 <listitem> 84 <para> 85 Newly allocated memory that isn't directly initialized, as well 86 as memory being freed will be reset to 0. The point here is to 87 allow memory checkers and similar programs that use bohem GC alike 88 algorithms to produce more accurate results. 89 This option is special in that it doesn't require GLib to be 90 configured with debugging support. 91 </para> 92 </listitem> 93 </varlistentry> 94 <varlistentry> 95 <term>resident-modules</term> 96 <listitem> 97 <para> 98 All modules loaded by GModule will be made resident. This can be useful 99 for tracking memory leaks in modules which are later unloaded; but it can 100 also hide bugs where code is accessed after the module would have normally 101 been unloaded. 102 This option is special in that it doesn't require GLib to be 103 configured with debugging support. 104 </para> 105 </listitem> 106 </varlistentry> 107 <varlistentry> 108 <term>bind-now-modules</term> 109 <listitem> 110 <para> 111 All modules loaded by GModule will bind their symbols at load time, even 112 when the code uses %G_MODULE_BIND_LAZY. 113 This option is special in that it doesn't require GLib to be 114 configured with debugging support. 115 </para> 116 </listitem> 117 </varlistentry> 118 </variablelist> 119 The special value all can be used to turn on all debug options. 120 The special value help can be used to print all available options. 121 </para> 122</formalpara> 123 124<formalpara id="G_SLICE"> 125 <title><envar>G_SLICE</envar></title> 126 <para> 127 This environment variable allows reconfiguration of the GSlice 128 memory allocator. 129 <variablelist> 130 <varlistentry> 131 <term>always-malloc</term> 132 <listitem> 133 <para> 134 This will cause all slices allocated through g_slice_alloc() and 135 released by g_slice_free1() to be actually allocated via direct 136 calls to g_malloc() and g_free(). 137 This is most useful for memory checkers and similar programs that 138 use Bohem GC alike algorithms to produce more accurate results. 139 It can also be in conjunction with debugging features of the system's 140 malloc implementation such as glibc's MALLOC_CHECK_=2 to debug 141 erroneous slice allocation code, allthough <literal>debug-blocks</literal> 142 usually is a better suited debugging tool. 143 </para> 144 </listitem> 145 </varlistentry> 146 <varlistentry> 147 <term>debug-blocks</term> 148 <listitem> 149 <para> 150 Using this option (present since GLib-2.13) engages extra code 151 which performs sanity checks on the released memory slices. 152 Invalid slice adresses or slice sizes will be reported and lead to 153 a program halt. 154 This option is for debugging scenarios. 155 In particular, client packages sporting their own test suite should 156 <emphasis>always enable this option when running tests</emphasis>. 157 Global slice validation is ensured by storing size and address information 158 for each allocated chunk, and maintaining a global hash table of that data. 159 That way, multi-thread scalability is given up, and memory consumption is 160 increased. However, the resulting code usually performs acceptably well, 161 possibly better than with comparable memory checking carried out using 162 external tools. An example of a memory corruption scenario that cannot be 163 reproduced with <literal>G_SLICE=always-malloc</literal>, but will be caught 164 by <literal>G_SLICE=debug-blocks</literal> is as follows: 165 <programlisting> 166 void *slist = g_slist_alloc(); /* void* gives up type-safety */ 167 g_list_free (slist); /* corruption: sizeof (GSList) != sizeof (GList) */ 168 </programlisting> 169 </para> 170 </listitem> 171 </varlistentry> 172 </variablelist> 173 The special value all can be used to turn on all options. 174 The special value help can be used to print all available options. 175 </para> 176</formalpara> 177 178<formalpara id="G_RANDOM_VERSION"> 179 <title><envar>G_RANDOM_VERSION</envar></title> 180 181 <para> 182 If this environment variable is set to '2.0', the outdated 183 pseudo-random number seeding and generation algorithms from 184 GLib-2.0 are used instead of the new better ones. Use the GLib-2.0 185 algorithms only if you have sequences of numbers generated with 186 Glib-2.0 that you need to reproduce exactly. 187 </para> 188</formalpara> 189 190<formalpara id="LIBCHARSET_ALIAS_DIR"> 191 <title><envar>LIBCHARSET_ALIAS_DIR</envar></title> 192 193 <para> 194 Allows to specify a nonstandard location for the 195 <filename>charset.aliases</filename> file that is used by the 196 character set conversion routines. The default location is the 197 <replaceable>libdir</replaceable> specified at compilation time. 198 </para> 199</formalpara> 200 201</refsect2> 202 203<refsect2 id="setlocale"> 204<title>Locale</title> 205 206<para> 207A number of interfaces in GLib depend on the current locale in which 208an application is running. Therefore, most GLib-using applications should 209call <function>setlocale (LC_ALL, "")</function> to set up the current 210locale. 211</para> 212 213<para> 214On Windows, in a C program there are several locale concepts 215that not necessarily are synchronized. On one hand, there is the 216system default ANSI code-page, which determines what encoding is used 217for file names handled by the C library's functions and the Win32 218API. (We are talking about the "narrow" functions here that take 219character pointers, not the "wide" ones.) 220</para> 221 222<para> 223On the other hand, there is the C library's current locale. The 224character set (code-page) used by that is not necessarily the same as 225the system default ANSI code-page. Strings in this character set are 226returned by functions like <function>strftime()</function>. 227</para> 228 229</refsect2> 230 231<refsect2> 232<title>Traps and traces</title> 233 234<para> 235<indexterm><primary>g_trap_free_size</primary></indexterm> 236<indexterm><primary>g_trap_realloc_size</primary></indexterm> 237<indexterm><primary>g_trap_malloc_size</primary></indexterm> 238Some code portions contain trap variables that can be set during debugging 239time if GLib has been configured with <option>--enable-debug=yes</option>. 240Such traps lead to immediate code halts to examine the current program state 241and backtrace. 242</para> 243 244<para> 245Currently, the following trap variables exist: 246<programlisting> 247static volatile gulong g_trap_free_size; 248static volatile gulong g_trap_realloc_size; 249static volatile gulong g_trap_malloc_size; 250</programlisting> 251If set to a size > 0, <link linkend="g-free">g_free</link>(), 252<link linkend="g-realloc">g_realloc</link>() and 253<link linkend="g-malloc">g_malloc</link>() will be intercepted if the size 254matches the size of the corresponding memory block. This will only work with 255<literal>g_mem_set_vtable (glib_mem_profiler_table)</literal> upon startup 256though, because memory profiling is required to match on the memory block sizes. 257</para> 258<para> 259Note that many modern debuggers support conditional breakpoints, which achieve 260pretty much the same. E.g. in gdb, you can do 261<programlisting> 262break g_malloc 263condition 1 n_bytes == 20 264</programlisting> 265to break only on g_malloc() calls where the size of the allocated memory block 266is 20. 267</para> 268</refsect2> 269 270<refsect2> 271<title>Memory statistics</title> 272 273<para> 274g_mem_profile() will output a summary g_malloc() memory usage, if memory 275profiling has been enabled by calling 276<literal>g_mem_set_vtable (glib_mem_profiler_table)</literal> upon startup. 277</para> 278 279<para> 280If GLib has been configured with <option>--enable-debug=yes</option>, 281then g_slice_debug_tree_statistics() can be called in a debugger to 282output details about the memory usage of the slice allocator. 283</para> 284 285</refsect2> 286</refsect1> 287</refentry> 288