The GIL must be held when calling any Python C API functions. In multithreaded applications that use callbacks this requirement can easily be violated by accident. A general tool to ensure GIL health is not available, but patching Python Py_INCREF to add an assert provides a basic health check:
```
+int PyGILState_Check(void); /* Include/internal/pystate.h */
+
#define Py_INCREF(op) ( \
+ assert(PyGILState_Check()), \
_Py_INC_REFTOTAL _Py_REF_DEBUG_COMMA \
((PyObject *)(op))->ob_refcnt++)
#define Py_DECREF(op) \
do { \
+ assert(PyGILState_Check()); \
PyObject *_py_decref_tmp = (PyObject *)(op); \
if (_Py_DEC_REFTOTAL _Py_REF_DEBUG_COMMA \
--(_py_decref_tmp)->ob_refcnt != 0) \
```
Adding this assertion causes around 50 test failures in LLDB. Adjusting the scope of things guarded by `py_lock` fixes them.
More background: https://docs.python.org/3/glossary.html#term-global-interpreter-lock
Patch by Ralf Grosse-Kunstleve
Differential Revision: https://reviews.llvm.org/D114722
a6598575f4