Merge pull request #414 from samschlegel/fix-411

Check if interpreter is finalizing in ~ThreadStateCreator

Author: jamadden

src/greenlet/TThreadStateDestroy.cpp

@@ -96,6 +96,23 @@ struct ThreadState_DestroyNoGIL
     // Python < 3.8 or >= 3.9
     static int AddPendingCall(int (*func)(void*), void* arg)
     {
+        // If the interpreter is in the middle of finalizing, we can't add a
+        // pending call. Trying to do so will end up in a SIGSEGV, as
+        // Py_AddPendingCall will not be able to get the interpreter and will
+        // try to dereference a NULL pointer. It's possible this can still
+        // segfault if we happen to get context switched, and maybe we should
+        // just always implement our own AddPendingCall, but I'd like to see if
+        // this works first
+#if GREENLET_PY313
+        if (Py_IsFinalizing()) {
+#else
+        if (_Py_IsFinalizing()) {
+#endif
+            fprintf(stderr,
+                    "greenlet: WARNING: Interpreter is finalizing. Ignoring "
+                    "call to Py_AddPendingCall; \n");
+            return 0;
+        }
         return Py_AddPendingCall(func, arg);
     }
 #endif