Store Py_MAX result in a variable.

It re-evaluates it, apparently.

Author: ZeroIntensity

Lib/threading.py

@@ -1557,8 +1557,9 @@ def _shutdown():
     # normally - that won't happen until the interpreter is nearly dead. So
     # mark it done here.
     if _main_thread._os_thread_handle.is_done() and _is_main_interpreter():
-        # _shutdown() was already called
-        return False
+        # _shutdown() was already called, but threads might have started
+        # in the meantime.
+        return _thread_shutdown()
 
     global _SHUTTING_DOWN
     _SHUTTING_DOWN = True

Python/pylifecycle.c

@@ -2013,10 +2013,12 @@ make_pre_finalization_calls(PyThreadState *tstate)
         int called = 0;
 
         // Wrap up existing "threading"-module-created, non-daemon threads.
-        called = Py_MAX(called, wait_for_thread_shutdown(tstate));
+        int threads_joined = wait_for_thread_shutdown(tstate);
+        called = Py_MAX(called, threads_joined);
 
         // Make any remaining pending calls.
-        called = Py_MAX(called, _Py_FinishPendingCalls(tstate));
+        int made_pending_calls = _Py_FinishPendingCalls(tstate);
+        called = Py_MAX(called, made_pending_calls);
 
         /* The interpreter is still entirely intact at this point, and the
         * exit funcs may be relying on that.  In particular, if some thread
@@ -2028,7 +2030,8 @@ make_pre_finalization_calls(PyThreadState *tstate)
         * the threads created via Threading.
         */
 
-        called = Py_MAX(called, _PyAtExit_Call(tstate->interp));
+        int called_atexit = _PyAtExit_Call(tstate->interp);
+        called = Py_MAX(called, called_atexit);
 
         if (called == 0) {
             break;