|GLib Reference Manual|
Running GLib Applications
Running GLib Applications — How to run and debug your GLib application
GLib inspects a few of environment variables in addition to standard
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.
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
Causes GLib to abort the program at the first call to g_critical(). This option is special in that it doesn't require GLib to be configured with debugging support.
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.
All modules loaded by GModule will be made resident. This can be useful for tracking memory leaks in modules which are later unloaded; but it can also hide bugs where code is accessed after the module would have normally been unloaded. This option is special in that it doesn't require GLib to be configured with debugging support.
All modules loaded by GModule will bind their symbols at load time, even when the code uses %G_MODULE_BIND_LAZY. This option is special in that it doesn't require GLib to be configured with debugging support.
The special value all can be used to turn on all debug options. The special value help can be used to print all available options.
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, allthough
Using this option (present since GLib-2.13) engages extra code
which performs sanity checks on the released memory slices.
Invalid slice adresses or slice sizes will be reported and lead to
a program halt.
This option is for debugging scenarios.
In particular, client packages sporting their own test suite should
always enable this option when running tests.
Global slice validation is ensured by storing size and address information
for each allocated chunk, and maintaining a global hash table of that data.
That way, multi-thread scalability is given up, and memory consumption is
increased. However, the resulting code usually performs acceptably well,
possibly better than with comparable memory checking carried out using
external tools. An example of a memory corruption scenario that cannot be
void *slist = g_slist_alloc(); /* void* gives up type-safety */ g_list_free (slist); /* corruption: sizeof (GSList) != sizeof (GList) */
The special value all can be used to turn on all options. The special value help can be used to print all available options.
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.
Allows to specify a nonstandard location for the
charset.aliases file that is used by the
character set conversion routines. The default location is the
libdir specified at compilation time.
A number of interfaces in GLib depend on the current locale in which
an application is running. Therefore, most GLib-using applications should
setlocale (LC_ALL, "") to set up the current
On Windows, in a C program there are several locale concepts that not necessarily are synchronized. On one hand, there is the system default ANSI code-page, which determines what encoding is used for file names handled by the C library's functions and the Win32 API. (We are talking about the "narrow" functions here that take character pointers, not the "wide" ones.)
On the other hand, there is the C library's current locale. The
character set (code-page) used by that is not necessarily the same as
the system default ANSI code-page. Strings in this character set are
returned by functions like
Some code portions contain trap variables that can be set during debugging
time if GLib has been configured with
Such traps lead to immediate code halts to examine the current program state
Currently, the following trap variables exist:
static volatile gulong g_trap_free_size; static volatile gulong g_trap_realloc_size; static volatile gulong g_trap_malloc_size;
If set to a size > 0, g_free(),
g_malloc() will be intercepted if the size
matches the size of the corresponding memory block. This will only work with
g_mem_set_vtable (glib_mem_profiler_table) upon startup
though, because memory profiling is required to match on the memory block sizes.
Note that many modern debuggers support conditional breakpoints, which achieve pretty much the same. E.g. in gdb, you can do
break g_malloc condition 1 n_bytes == 20
to break only on g_malloc() calls where the size of the allocated memory block is 20.
g_mem_profile() will output a summary g_malloc() memory usage, if memory
profiling has been enabled by calling
g_mem_set_vtable (glib_mem_profiler_table) upon startup.
If GLib has been configured with
then g_slice_debug_tree_statistics() can be called in a debugger to
output details about the memory usage of the slice allocator.