fvwm3 may freeze when debugging applications

[jnse]

When debugging an application, fvwm3 may completely freeze when a breakpoint is triggered while handling an event.

It's kind of difficult for me to come up with a minimal example that triggers this problem, but I've had this happen when debugging qt applications in qt creator, but also SDL applications with regular gdb. Whenever a breakpoint triggers somewhere in my gui event loop, the entire wm will freeze up. And it's not rare, unfortunately - it's common enough to be very annoying.

When this happens, I have to vt-switch and kill -9 the debugged process, when vt-switching back to Xorg, fvwm3 resumes normally again.

Here's some debug output from fvwm when it's in this frozen state:

```#0  0x00007f6987003675 in select () at /lib64/libc.so.6
#1  0x00005585156a4bd7 in fvwmSelect (nfds=1024, readfds=0x7ffdc1e0ebf0, writefds=0x7ffdc1e0ec70, exceptfds=0x0, timeout=0x0)
    at fvwmsignal.c:208
#2  0x00005585155fb526 in My_XNextEvent (disp=0x55851763d590, event=0x7ffdc1e0ed10) at events.c:4405
#3  0x00005585155fb0d1 in HandleEvents () at events.c:4268
#4  0x0000558515626b04 in main (argc=2, argv=0x7ffdc1e0f1d8) at fvwm3.c:2526
#2  0x00005585155fb526 in My_XNextEvent (disp=0x55851763d590, event=0x7ffdc1e0ed10) at events.c:4405
4405			num_fd = fvwmSelect(
$1 = {tv_sec = 42, tv_usec = 0}
$2 = (struct timeval *) 0x0
$3 = -1
Single stepping until exit from function select,
which has no line number information.
fvwmSelect (nfds=1024, readfds=0x7ffdc1e0ebf0, writefds=0x7ffdc1e0ec70, exceptfds=0x0, timeout=0x0) at fvwmsignal.c:208
208				iRet = select(nfds,
221			canJump = false;
224		return iRet;
225	}
My_XNextEvent (disp=0x55851763d590, event=0x7ffdc1e0ed10) at events.c:4407
4407			if (is_waiting_for_scheduled_command)
4413			if (isTerminated)
4417		} while (num_fd < 0);
4419		if (num_fd > 0)
4422			module_list_itr_init(&moditr);
4423			while ( (module = module_list_itr_next(&moditr)) != NULL)
4425				if (FD_ISSET(MOD_READFD(module), &in_fdset))
4432					MOD_WRITEFD(module) >= 0 &&
4431				if (
4433					FD_ISSET(MOD_WRITEFD(module), &out_fdset))
4432					MOD_WRITEFD(module) >= 0 &&
4423			while ( (module = module_list_itr_next(&moditr)) != NULL)
4425				if (FD_ISSET(MOD_READFD(module), &in_fdset))
4432					MOD_WRITEFD(module) >= 0 &&
Continuing.
[Detaching after fork from child process 20022]

... etc (seems to be continuing the normal event loop)

Note that the timeout passed to the select() call is 0 (infinite) because of, what i think is a bug here:

````         	if (ms < 0)
		{
			timeout.tv_sec = 42;
			timeout.tv_usec = 0;
		}

timeout values are set but timeout is never assigned to timeoutP -

But obviously we /are/ returning from the select, so this has nothing to do with the problem -

Clarification - when i say 'freeze' - what i mean is, the WM, nor applications, will respond to keyboard input or mouse input. (no alt-tab, no titlebar-dragging, the currently focused window also won't receive key events) - rendering still works (my little wmcube keeps spinning) - so it's all input events that have gone dead in this scenario.