[3.9] bpo-41498: Fix build on platforms without sigset_t (GH-29770) (GH-29774)

Co-authored-by: Christian Heimes <christian@python.org>

Author: tiran

Misc/NEWS.d/next/Build/2021-11-25-09-15-04.bpo-41498.qAk5eo.rst

@@ -0,0 +1,4 @@
+Python now compiles on platforms without ``sigset_t``. Several functions
+in :mod:`signal` are not available when ``sigset_t`` is missing.
+
+Based on patch by Roman Yurchak for pyodide.

Modules/clinic/signalmodule.c.h

@@ -5882,6 +5882,7 @@ parse_posix_spawn_flags(PyObject *module, const char *func_name, PyObject *setpg
 
     }
 
+#ifdef HAVE_SIGSET_T
    if (setsigmask) {
         sigset_t set;
         if (!_Py_Sigset_Converter(setsigmask, &set)) {
@@ -5907,6 +5908,13 @@ parse_posix_spawn_flags(PyObject *module, const char *func_name, PyObject *setpg
         }
         all_flags |= POSIX_SPAWN_SETSIGDEF;
     }
+#else
+    if (setsigmask || setsigdef) {
+        PyErr_SetString(PyExc_NotImplementedError,
+                        "sigset is not supported on this platform");
+        goto fail;
+    }
+#endif
 
     if (scheduler) {
 #ifdef POSIX_SPAWN_SETSCHEDULER

Modules/posixmodule.c

@@ -23,9 +23,7 @@ PyAPI_FUNC(int) _Py_Gid_Converter(PyObject *, gid_t *);
 # define HAVE_SIGSET_T
 #endif
 
-#ifdef HAVE_SIGSET_T
 PyAPI_FUNC(int) _Py_Sigset_Converter(PyObject *, void *);
-#endif /* HAVE_SIGSET_T */
 #endif /* Py_LIMITED_API */
 
 #ifdef __cplusplus

Modules/posixmodule.h

@@ -68,6 +68,8 @@ module signal
 [clinic start generated code]*/
 /*[clinic end generated code: output=da39a3ee5e6b4b0d input=b0301a3bde5fe9d3]*/
 
+#ifdef HAVE_SETSIG_T
+
 /*[python input]
 
 class sigset_t_converter(CConverter):
@@ -76,6 +78,7 @@ class sigset_t_converter(CConverter):
 
 [python start generated code]*/
 /*[python end generated code: output=da39a3ee5e6b4b0d input=b5689d14466b6823]*/
+#endif
 
 /*
    NOTES ON THE INTERACTION BETWEEN SIGNALS AND THREADS
@@ -880,6 +883,7 @@ signal_getitimer_impl(PyObject *module, int which)
 
 #endif
 
+#ifdef HAVE_SIGSET_T
 #if defined(PYPTHREAD_SIGMASK) || defined(HAVE_SIGPENDING)
 static PyObject*
 sigset_to_set(sigset_t mask)
@@ -1011,9 +1015,9 @@ signal_sigwait_impl(PyObject *module, sigset_t sigset)
 }
 
 #endif   /* #ifdef HAVE_SIGWAIT */
+#endif   /* #ifdef HAVE_SIGSET_T */
 
-
-#if defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS)
+#if (defined(HAVE_SIGFILLSET) && defined(HAVE_SIGSET_T)) || defined(MS_WINDOWS)
 
 /*[clinic input]
 signal.valid_signals
@@ -1051,7 +1055,8 @@ signal_valid_signals_impl(PyObject *module)
 #endif
 }
 
-#endif   /* #if defined(HAVE_SIGFILLSET) || defined(MS_WINDOWS) */
+#endif   /* #if (defined(HAVE_SIGFILLSET) && defined(HAVE_SIGSET_T)) || defined(MS_WINDOWS) */
+
 
 
 #if defined(HAVE_SIGWAITINFO) || defined(HAVE_SIGTIMEDWAIT)
@@ -1117,6 +1122,7 @@ fill_siginfo(siginfo_t *si)
 }
 #endif
 
+#ifdef HAVE_SIGSET_T
 #ifdef HAVE_SIGWAITINFO
 
 /*[clinic input]
@@ -1219,6 +1225,7 @@ signal_sigtimedwait_impl(PyObject *module, sigset_t sigset,
 }
 
 #endif   /* #ifdef HAVE_SIGTIMEDWAIT */
+#endif   /* #ifdef HAVE_SIGSET_T */
 
 
 #if defined(HAVE_PTHREAD_KILL)