Traps (G_BREAKPOINT) and traces for the debuging

================================================

Some code portions contain trap variables that can be set during

debugging time if G_ENABLE_DEBUG has been defined upon compilation

(use the --enable-debug=yes option to configure for this, macros.txt

covers more details).

Such traps lead to immediate code halts to examine the current

program state and backtrace.

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_realloc() and g_malloc()

	respectively, will be intercepted if the size matches the

	size of the corresponding memory block to free/reallocate/allocate.

	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.

static volatile GObject *g_trap_object_ref;

	If set to a valid object pointer, ref/unref will be intercepted

	with G_BREAKPOINT ();

static volatile gpointer *g_trap_instance_signals;

static volatile gpointer *g_trace_instance_signals;

       If set to a valid instance pointer, debugging messages

       will be spewed about emissions of signals on this instance.

       For g_trap_instance_signals matches, the emissions will

       also be intercepted with G_BREAKPOINT ();

Environment variables for debugging

===================================

When G_ENABLE_DEBUG was defined upon compilation, the GObject library 

supports an environment variable GOBJECT_DEBUG that can be set to a

combination of the flags passed in to g_type_init() (currently

"objects" and "signals") to trigger debugging messages about

object bookkeeping and signal emissions during runtime.

2000/02/04	Tim Janik