AC_CHECK_FUNCS(poll select listen bind shutdown close connect setsockopt)
AC_CHECK_FUNCS(setrlimit time ctime utime gettimeofday getrusage)
AC_CHECK_FUNCS(chmod fcntl stat fstat getenv putenv strerror)
-AC_CHECK_FUNCS(getpid getgid getsid getpgid getpgrp getuid)
+AC_CHECK_FUNCS(getpid getgid getsid getpgid getpgrp getuid sched_yield)
AC_CHECK_FUNCS(setgroups initgroups nl_langinfo nanosleep tzset)
AC_CHECK_FUNCS(strchr snprintf strstr strcpy strncpy memcpy memset memmove)