macosx: Clean up single-shot timers correctly

QuLogic · QuLogic · commit 60c1d5ba7aba · 2024-03-07T03:41:07.000-05:00
The `NSTimer` docs state that a non-repeating (aka single-shot in our
terms) timer is invalidated after if fires. This means that we should
not do it ourselves, and in fact it appears that the pointer itself is
no longer valid, so we would be passing an `invalidate` message to a
random object or segfault.

I believe this is why `test_other_signal_before_sigint` is marked as
flaky as well, as it uses a single-shot timer and a segfault is recorded
in the XPASS log.
diff --git a/lib/matplotlib/tests/test_backends_interactive.py b/lib/matplotlib/tests/test_backends_interactive.py
@@ -764,8 +764,6 @@ def test_other_signal_before_sigint(env, target, kwargs, request):
     backend = env.get("MPLBACKEND")
     if not backend.startswith(("qt", "macosx")):
         pytest.skip("SIGINT currently only tested on qt and macosx")
-    if backend == "macosx":
-        request.node.add_marker(pytest.mark.xfail(reason="macosx backend is buggy"))
     proc = _WaitForStringPopen(
         [sys.executable, "-c",
          inspect.getsource(_test_other_signal_before_sigint_impl) +
diff --git a/src/_macosx.m b/src/_macosx.m
@@ -1741,6 +1741,11 @@ - (void)flagsChanged:(NSEvent *)event
                                          repeats: !single
                                            block: ^(NSTimer *timer) {
         gil_call_method((PyObject*)self, "_on_timer");
+        if (single) {
+            // A single-shot timer will be automatically invalidated when it fires, so
+            // we shouldn't do it ourselves when the object is deleted.
+            self->timer = NULL;
+        }
     }];
     // Schedule the timer on the main run loop which is needed
     // when updating the UI from a background thread
