check_c_source_compiles (
                                 "#include <unistd.h>
                                  #include <pthread.h>
                                  #include <sched.h>

                                 int main () {
                                        #if ${PLIBSYS_SCHED_CHECK}
                                          sched_get_priority_min (0);
                                          sched_get_priority_max (0);
                                        #else
                                          stop_compile_here
                                        #endif
                                        return 0;
                                 }"
                                 PLIBSYS_HAS_POSIX_SCHEDULING
                                )