Can I instruct gdb to run commands in response to SIGTRAP?

I'm debugging a reference leak in a GObject-based application. GObject has a simple built-in mechanism to help with such matters: you can set the g_trap_object_ref variable in gobject.c to the object that you care about, and then every ref or unref of that object will hit a breakpoint instruction (via G_BREAKPOINT()).

So sure enough, the program does get stopped, with gdb reporting:

Program received signal SIGTRAP, Trace/breakpoint trap.
g_object_ref (_object=0x65f090) at gobject.c:2606
2606      old_val = g_atomic_int_exchange_and_add ((int *)&object->ref_count, 1);
(gdb) _

which is a great start. Now, normally I'd script some commands to be run at a breakpoint I manually set using commands 3 (for breakpoint 3, say). But the equivalent for SIGTRAP, namely handle SIGTRAP, doesn't give me the option of doing anything particularly interesting. Is there a good way to do this?

(I'm aware that there are other ways to debug reference leaks, such as setting watchpoints on the object's ref_count field, refdbg, scripting regular breakpoints on g_object_ref() and g_object_unref(). I'm about to go try of those now. I'm looking specifically开发者_如何学编程 for a way to script a response to SIGTRAP. It might come in useful in other situations, too, and I'd be surprised if gdb doesn't support this.)

Do you want to show some values and continue execution of the program? In that case, just define a macro that displays the values you're interested in, continues execution and calls itself recursively:

 define c
 echo do stuff\n
 continue
 c
 end

GDB doesn't support it.

In general, attaching a command script to signal makes little sense -- your program could be receiving SIGTRAP in any number of places, and the command will not know whether a particular SIGTRAP came in in expected context or not.