Philip Martin wrote on Mon, Feb 08, 2016 at 10:33:05 +0000:
> When there are two different signals I don't think there is a 'correct'
> signal with which to exit, all that matters is that we exit with one of
> the signals.
Agreed.
> So how about:
>
> int saved_signum = signum_cancelled;
> apr_signal(saved_signum, SIG_DFL);
> kill(getpid(), saved_signum);
This fixes the race I mentioned, but I think we have another problem
here: signum_cancelled is accessed by the signal handler so it must be
of type 'static volatile sig_atomic_t' (C89 §4.7.1.1)... but I don't
think anything guarantees that signal numbers are representable as
a sig_atomic_t. On Linux/amd64 and FreeBSD they are, but that need not
be the case everywhere.
If we can't assume sig_atomic_t is at least as large as an int, I think
we have to use the following roundabout method:
static volatile sig_atomic_t signum_cancelled[4] = {0, 0, 0, 0};
static void signal_handler(int signum)
{
⋮
if (signum == SIGINT)
signum_cancelled[0] = TRUE;
#ifdef SIGHUP
if (signum == SIGHUP)
signum_cancelled[1] = TRUE;
#endif
#ifdef SIGTERM
if (signum == SIGTERM)
signum_cancelled[2] = TRUE;
#endif
#ifdef SIGBREAK
if (signum == SIGBREAK)
signum_cancelled[3] = TRUE;
#endif
}
and then check which element(s) of the array are set to know which
signal to send to self.
Cheers,
Daniel
