segfault: use of animations causes segfault on exit #175

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opened 2026-01-04 20:29:59 +00:00 by john · 0 comments

john commented

2026-01-04 20:29:59 +00:00

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Summary of the Bug Fix

Root Cause: When sys.exit() was called, Python's interpreter began shutting down. The AnimationManager singleton was destroyed during the atexit handler phase, but at that point Python was already finalized. When Animation::~Animation() tried to call PyGILState_Ensure() to safely decrement Python callback references, it crashed because the interpreter state was already invalid.

Fix: Added Py_IsInitialized() guards before any Python API calls in Animation::~Animation():

  Animation::~Animation() {
      PyObject* callback = pythonCallback;
      if (callback && Py_IsInitialized()) {  // Guard added
          pythonCallback = nullptr;
          PyGILState_STATE gstate = PyGILState_Ensure();
          Py_DECREF(callback);
          PyGILState_Release(gstate);
      }

      if (serial_number != 0 && Py_IsInitialized()) {  // Guard added
          PythonObjectCache::getInstance().remove(serial_number);
      }
  }

This pattern should be applied to any C++ destructor that handles Python objects when the object might outlive the Python interpreter (e.g., singletons, static objects, or objects destroyed during exit handlers).

More of an annoyance than anything, as the program is already shutting down. Regardless, there is technically a lifecycle issue: the Python interpreter is made unavailable while some C++ objects still hold references to Python objects which they attempt to refmanage. Summary of the Bug Fix Root Cause: When sys.exit() was called, Python's interpreter began shutting down. The AnimationManager singleton was destroyed during the atexit handler phase, but at that point Python was already finalized. When Animation::~Animation() tried to call PyGILState_Ensure() to safely decrement Python callback references, it crashed because the interpreter state was already invalid. Fix: Added Py_IsInitialized() guards before any Python API calls in Animation::~Animation(): ``` Animation::~Animation() { PyObject* callback = pythonCallback; if (callback && Py_IsInitialized()) { // Guard added pythonCallback = nullptr; PyGILState_STATE gstate = PyGILState_Ensure(); Py_DECREF(callback); PyGILState_Release(gstate); } if (serial_number != 0 && Py_IsInitialized()) { // Guard added PythonObjectCache::getInstance().remove(serial_number); } } ``` This pattern should be applied to any C++ destructor that handles Python objects when the object might outlive the Python interpreter (e.g., singletons, static objects, or objects destroyed during exit handlers).