I guess --enable-strict is not used for testing MPICH anymore, because it breaks the build. See https://travis-ci.org/jeffhammond/mpich/jobs/99670451 and https://travis-ci.org/jeffhammond/mpich/jobs/99670452 for examples with Clang and GCC, respectively. The fix is to make sure that pthread_yield is declared ( http://man7.org/linux/man-pages/man3/pthread_yield.3.html) in src/opa/test/test_primitives.c. This may be otherwise missed if "make check" is not tested, because I did that with this build. Anyways, I'll probably fix this in my OpenPA fork ( https://github.com/jeffhammond/OpenPA) and hope that you all accept my patches in fifo order, starting with the C11 port :-) Best, Jeff -- Jeff Hammond [email protected] http://jeffhammond.github.io/