On Tue, May 26, 2020 at 1:17 PM Ken Moffat <[email protected]> wrote:
> I'm trying to discover why two tests in the testsuite for 'check'
> always fail for me. I've now got a response that the tests raise
> SIGFPE but do not receive it. The example is
>
> ken@plexi ~/check-debug $cat test.c
> #include <stdio.h>
>
> #include <signal.h>
>
>
> int main() {
>
> printf("Before\n");
>
> raise(SIGFPE);
>
> printf("After\n");
>
> return 0;
>
> }
>
> followed by gcc test.c ; ./a.out
>
> That should terminate on the signal, but for me it doesn't:
>
> ken@plexi ~/check-debug $./a.out
> Before
> After
>
>
> However, if I try a division by zero I do get the exception:
>
> ken@plexi ~/check-debug $cat divbyzero.c
> #include <stdio.h>
>
> #include <signal.h>
>
>
> int main() {
>
> int a = 1000;
> int z = 0;
> int result;
>
> printf("Before\n");
>
> //raise(SIGFPE);
> result = a / z;
>
> printf("After\n");
>
> return result;
>
> }
>
> gcc -o divbyzero divbyzero.c
>
> ken@plexi ~/check-debug $./divbyzero
> Before
> Floating point exception
>
>
> Any clues to how I can find what is causing this breakage, please ?
> It seems to happen on all my machines.
>
> ĸen
>
>
Hi Ken,
That is weird. The test works as expected on my Debian machine. Can you
try running "strace" on your test program? Here's what mine looks like
(edited for brevity):
strace ./a.out
#--- edited ---
write(1, "Before\n", 7Before
) = 7
rt_sigprocmask(SIG_BLOCK, ~[RTMIN RT_1], [], 8) = 0
getpid() = 27404
gettid() = 27404
tgkill(27404, 27404, SIGFPE) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGFPE {si_signo=SIGFPE, si_code=SI_TKILL, si_pid=27404, si_uid=1000}
---
+++ killed by SIGFPE +++
Floating point exception
>From "man raise" you can go down the rabbit hole and see that it ends up
calling tgkill(). It would be interesting to see what's happening on your
system.
You can also try printing the integer return value of raise(). It is
supposed to return 0 on success, nonzero on failure. That might be a clue
too...
printf("%d\n", raise(SIGFPE));
Don
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