[RFC, PR68580] Handle pthread_create error in tsan testsuite

[Tom de Vries]

Hi,

Occasionally, I've been running into this failure while running the tsan 
testsuite:
...
FAIL: c-c++-common/tsan/pr65400-1.c -O0 execution test
...

I've also observed a potential similar occurrence here ( 
https://gcc.gnu.org/ml/gcc-regression/2015-08/msg00147.html ).

Initially, I couldn't reproduce it on the command line.

Then I tried mimicking heavy load situations that might arise while 
running the testsuite (I test with -j12 on a server), by running the 
test in parallel, and found that in that case pthread_create fails, and 
the test returns 0, which combined with the dg-shouldfail, makes the 
execution test fail.

So I suspect the failure I see while running the testsuite is the result 
of pthread_create failure.

The problem is that I can't be sure, given that in the testcase we do 
not distinguish between:
- return 0, case pthread_create failed, and
- return 0 at end of main, case -fsanitize=thread failed to catch the
   race condition.

Note also that it's possible that many other tsan tests are failing in 
pthread_create, but that this goes unnoticed because we don't test for 
the result of pthread_create in most tests.

This untested patch is an attempt at structurally testing and handling 
the result of pthread_create in the tsan testsuite, using this macro:
...
#define PTHREAD_CREATE(thread, attr, start_routine, arg)	\
   {								\
     int res = pthread_create (thread, attr, start_routine, arg);\
     if (res)							\
       {								\
	error (0, res, "pthread_create failed with");		\
	exit (0);						\
       }								\
   }
...

If this patch is committed, I should at least be able to find out if 
indeed the failure I observe is related to resource exhaustion.

Good idea? Any other comments?

Thanks,
- Tom

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