Henry Schreiner 085b66068a fix: data race on last_storage_ptr_ cache in gil_safe_call_once_and_store (#6087) ...

Under free-threaded CPython (Py_GIL_DISABLED) the GIL provides no mutual
exclusion, so the plain pointer last_storage_ptr_ was read and written
concurrently without synchronization, a C++ data race. Make it a
std::atomic<T *>.

Also reorder get_stored() to check is_last_storage_valid() before loading
the cached pointer. The writer publishes the pointer before setting the
validity flag, so the flag must be observed first for correct
acquire/release ordering.

Assisted-by: ClaudeCode:claude-fable-5

2026-06-23 21:48:26 -04:00

..

pybind11

fix: data race on last_storage_ptr_ cache in gil_safe_call_once_and_store (#6087)

2026-06-23 21:48:26 -04:00