Issue #12871: sched_get_priority_(min|max) might not be defined even though

<sched.h> is available (most notably on OpenBSD when built without pthread):
add an explicit configure check.

Lib/test/test_posix.py

@@ -840,6 +840,8 @@ def test_sched_yield(self):
         posix.sched_yield()
 
     @requires_sched_h
+    @unittest.skipUnless(hasattr(posix, 'sched_get_priority_max'),
+                         "requires sched_get_priority_max()")
     def test_sched_priority(self):
         # Round-robin usually has interesting priorities.
         pol = posix.SCHED_RR

Modules/posixmodule.c

@@ -4555,6 +4555,8 @@ posix_fork(PyObject *self, PyObject *noargs)
 
 #ifdef HAVE_SCHED_H
 
+#ifdef HAVE_SCHED_GET_PRIORITY_MAX
+
 PyDoc_STRVAR(posix_sched_get_priority_max__doc__,
 "sched_get_priority_max(policy)\n\n\
 Get the maximum scheduling priority for *policy*.");
@@ -4589,6 +4591,8 @@ posix_sched_get_priority_min(PyObject *self, PyObject *args)
     return PyLong_FromLong(min);
 }
 
+#endif /* HAVE_SCHED_GET_PRIORITY_MAX */
+
 #ifdef HAVE_SCHED_SETSCHEDULER
 
 PyDoc_STRVAR(posix_sched_getscheduler__doc__,
@@ -10452,8 +10456,10 @@ static PyMethodDef posix_methods[] = {
     {"fork",            posix_fork, METH_NOARGS, posix_fork__doc__},
 #endif /* HAVE_FORK */
 #ifdef HAVE_SCHED_H
+#ifdef HAVE_SCHED_GET_PRIORITY_MAX
     {"sched_get_priority_max", posix_sched_get_priority_max, METH_VARARGS, posix_sched_get_priority_max__doc__},
     {"sched_get_priority_min", posix_sched_get_priority_min, METH_VARARGS, posix_sched_get_priority_min__doc__},
+#endif
 #ifdef HAVE_SCHED_SETPARAM
     {"sched_getparam", posix_sched_getparam, METH_VARARGS, posix_sched_getparam__doc__},
 #endif
@@ -10474,7 +10480,7 @@ static PyMethodDef posix_methods[] = {
     {"sched_setaffinity", posix_sched_setaffinity, METH_VARARGS, posix_sched_setaffinity__doc__},
     {"sched_getaffinity", posix_sched_getaffinity, METH_VARARGS, posix_sched_getaffinity__doc__},
 #endif
-#endif
+#endif /* HAVE_SCHED_H */
 #if defined(HAVE_OPENPTY) || defined(HAVE__GETPTY) || defined(HAVE_DEV_PTMX)
     {"openpty",         posix_openpty, METH_NOARGS, posix_openpty__doc__},
 #endif /* HAVE_OPENPTY || HAVE__GETPTY || HAVE_DEV_PTMX */

configure.in

@@ -2538,7 +2538,8 @@ AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  select sem_open sem_timedwait sem_getvalue sem_unlink sendfile setegid seteuid \
  setgid sethostname \
  setlocale setregid setreuid setresuid setresgid setsid setpgid setpgrp setpriority setuid setvbuf \
- sched_setaffinity sched_setscheduler sched_setparam sched_rr_get_interval \
+ sched_get_priority_max sched_setaffinity sched_setscheduler sched_setparam \
+ sched_rr_get_interval \
  sigaction sigaltstack siginterrupt sigpending sigrelse \
  sigtimedwait sigwait sigwaitinfo snprintf strftime strlcpy symlinkat sync \
  sysconf tcgetpgrp tcsetpgrp tempnam timegm times tmpfile tmpnam tmpnam_r \

pyconfig.h.in

@@ -653,6 +653,9 @@
 /* Define to 1 if you have the `round' function. */
 #undef HAVE_ROUND
 
+/* Define to 1 if you have the `sched_get_priority_max' function. */
+#undef HAVE_SCHED_GET_PRIORITY_MAX
+
 /* Define to 1 if you have the <sched.h> header file. */
 #undef HAVE_SCHED_H