Re: [Qemu-devel] [PATCH v2 for-3.0] tests/libqtest: Improve kill_qemu()

[Eric Blake <eblake@redhat.com>]

On 07/24/2018 01:36 AM, Markus Armbruster wrote:
> Eric Blake <eblake@redhat.com> writes:
> 
>> In kill_qemu() we have an assert that checks that the QEMU process
>> didn't dump core:
>>              assert(!WCOREDUMP(wstatus));
>>
>> Unfortunately the WCOREDUMP macro here means the resulting message
>> is not very easy to comprehend on at least some systems:
>>

>> -        if (pid == s->qemu_pid && WIFSIGNALED(wstatus)) {
>> -            assert(!WCOREDUMP(wstatus));

>> +            } else if (WIFSIGNALED(wstatus)) {
>> +                int sig = WTERMSIG(wstatus);
>> +                const char *signame = strsignal(sig) ?: "unknown ???";
>> +
>> +                if (!WCOREDUMP(wstatus)) {
>> +                    die = false;
> 
> Does WCOREDUMP(wstatus) depend on the user's ulimit -c?

'man waitpid' on Linux mentions that WCOREDUMP is nonportable, but does 
not mention any interaction with setrlimit.  But a quick test shows:

$ ulimit -S -c 0
$ cat foo.c
int main(int argc, char **argv) {
   return *argv[1];
}
$ gcc -o foo -Wall foo.c
$ ./foo 1
$ ./foo
Segmentation fault (core dumped)
$

the output was produced by bash, which uses waitpid() - and therefore 
the fact that bash reports the core dump even when no core file is 
created is promising.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org