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.)

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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

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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.