Invokes gdb, which attaches to the current process and shows a
stack trace. Called by
g_on_error_query() when the “[S]tack trace”
option is selected. You can get the current process’s program name
with g_get_prgname(), assuming that you have called
gtk_init() or gdk_init().
This function may cause different actions on non-UNIX platforms.
When running on Windows, this function is not called by
g_on_error_query(). If called directly, it will raise an
exception, which will crash the program. If the
variable is set, a debugger will be invoked to attach and
handle that exception (see Running GLib Applications).