From b06d1f4d8d7199746063b1ef0d1a1c37ccf48188 Mon Sep 17 00:00:00 2001 From: chrisjbillington Date: Thu, 26 Jun 2025 12:38:33 +1000 Subject: [PATCH] Clean up Qt socket notifier to avoid spurious interrupt handler calls Closes #29688 Objects without a parent are not necessarily cleaned up in `PyQt5/6` when their reference count reaches zero, and must be explicitly cleaned up with `deleteLater()` This prevents the notifier firing after the signal handling was supposed to have been reset to its previous state. Rather than have both `bakend_bases._allow_interrupt()` and `backend_qt._allow_interrupt_qt()` hold a reference to the notifier, we pass it to the backend-specific `handle_signint()` function for cleanup. Note the approach to cleaning up the notifier with `.deleteLater()` followed by `sendPostedEvents()` is the documented workaround for when immediate deletion is desired: https://doc.qt.io/qt-6/qobject.html#deleteLater This ensures the object is still deleted up even if the same event loop does not run again. --- lib/matplotlib/backend_bases.py | 10 ++++++---- lib/matplotlib/backends/backend_qt.py | 11 ++++++++--- src/_macosx.m | 4 ++-- 3 files changed, 16 insertions(+), 9 deletions(-) diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py index 527d8c010710..626852f2aa34 100644 --- a/lib/matplotlib/backend_bases.py +++ b/lib/matplotlib/backend_bases.py @@ -1619,7 +1619,8 @@ def _allow_interrupt(prepare_notifier, handle_sigint): If SIGINT was indeed caught, after exiting the on_signal() function the interpreter reacts to the signal according to the handler function which had been set up by a signal.signal() call; here, we arrange to call the - backend-specific *handle_sigint* function. Finally, we call the old SIGINT + backend-specific *handle_sigint* function, passing the notifier object + as returned by prepare_notifier(). Finally, we call the old SIGINT handler with the same arguments that were given to our custom handler. We do this only if the old handler for SIGINT was not None, which means @@ -1629,7 +1630,7 @@ def _allow_interrupt(prepare_notifier, handle_sigint): Parameters ---------- prepare_notifier : Callable[[socket.socket], object] - handle_sigint : Callable[[], object] + handle_sigint : Callable[[object], object] """ old_sigint_handler = signal.getsignal(signal.SIGINT) @@ -1645,9 +1646,10 @@ def _allow_interrupt(prepare_notifier, handle_sigint): notifier = prepare_notifier(rsock) def save_args_and_handle_sigint(*args): - nonlocal handler_args + nonlocal handler_args, notifier handler_args = args - handle_sigint() + handle_sigint(notifier) + notifier = None signal.signal(signal.SIGINT, save_args_and_handle_sigint) try: diff --git a/lib/matplotlib/backends/backend_qt.py b/lib/matplotlib/backends/backend_qt.py index 5cde4866cad7..9089e982cea6 100644 --- a/lib/matplotlib/backends/backend_qt.py +++ b/lib/matplotlib/backends/backend_qt.py @@ -169,9 +169,14 @@ def _may_clear_sock(): # be forgiving about reading an empty socket. pass - return sn # Actually keep the notifier alive. - - def handle_sigint(): + # We return the QSocketNotifier so that the caller holds a reference, and we + # also explicitly clean it up in handle_sigint(). Without doing both, deletion + # of the socket notifier can happen prematurely or not at all. + return sn + + def handle_sigint(sn): + sn.deleteLater() + QtCore.QCoreApplication.sendPostedEvents(sn, QtCore.QEvent.Type.DeferredDelete) if hasattr(qapp_or_eventloop, 'closeAllWindows'): qapp_or_eventloop.closeAllWindows() qapp_or_eventloop.quit() diff --git a/src/_macosx.m b/src/_macosx.m index aa2a6e68cda5..1372157bc80d 100755 --- a/src/_macosx.m +++ b/src/_macosx.m @@ -258,7 +258,7 @@ static void lazy_init(void) { } static PyObject* -stop(PyObject* self) +stop(PyObject* self, PyObject* _ /* ignored */) { stopWithEvent(); Py_RETURN_NONE; @@ -1863,7 +1863,7 @@ - (void)flagsChanged:(NSEvent *)event "written on the file descriptor given as argument.")}, {"stop", (PyCFunction)stop, - METH_NOARGS, + METH_VARARGS, PyDoc_STR("Stop the NSApp.")}, {"show", (PyCFunction)show,