[Bug sanitizer/68580] FAIL: c-c++-common/tsan/pr65400-1.c -O0 execution test

["vries at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68580

--- Comment #8 from vries at gcc dot gnu.org ---
I managed to trigger the test returning 0 from the command line, by running it
in parallel:
...
$ ( export LD_LIBRARY_PATH=$(pwd -P)/install/lib64; for cnt in $(seq 1 400); do
(./a.out ; echo $? ) > log.$cnt 2>&1 & done )
$ egrep  '^0$' log.* | wc -l
54
...

I can't be sure if that is the reason that the test is failing (by returning 0)
during running the testsuite, but it's certainly possible (I'm running it with
-j12).

So, I suspect that the test fails because pthread_create fails with EAGAIN due
to insufficient resources:
...
int
main ()
{
  pthread_t th;
  barrier_init (&barrier, 2);
  if (pthread_create (&th, NULL, tf, NULL))
    return 0;
...

Indeed in the testcase we do not distinguish between:
- return 0, case pthread_create failed, and
- return 0 at end of main, -fsanitize=thread failed to catch the race
condition.

It would probably be good to print an error message when pthread_create fails,
such that when looking at the fail in the testlog, we can easily see that that
is the reason it failed, and not expect it to reproduce otherwise.