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fix: make gil_safe_call_once thread-safe in free-threaded CPython #5246

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Merged
merged 3 commits into from
Jul 16, 2024
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fix: make gil_safe_call_once thread-safe in free-threaded CPython #5246

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fix: Make gil_safe_call_once thread-safe in free-threaded CPython
colesbury Jul 16, 2024
49179c6
style: pre-commit fixes
pre-commit-ci[bot] Jul 16, 2024
2e2b323
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colesbury Jul 16, 2024
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11 changes: 10 additions & 1 deletion include/pybind11/gil_safe_call_once.h
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,10 @@
#include <cassert>
#include <mutex>

#ifdef Py_GIL_DISABLED
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Slight preference for an empty line before the #ifdef.

# include <atomic>
#endif

PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)

// Use the `gil_safe_call_once_and_store` class below instead of the naive
Expand Down Expand Up @@ -82,7 +86,12 @@ class gil_safe_call_once_and_store {
private:
alignas(T) char storage_[sizeof(T)] = {};
std::once_flag once_flag_ = {};
bool is_initialized_ = false;
#ifdef Py_GIL_DISABLED
std::atomic_bool
#else
bool
#endif
is_initialized_{false};
// The `is_initialized_`-`storage_` pair is very similar to `std::optional`,
// but the latter does not have the triviality properties of former,
// therefore `std::optional` is not a viable alternative here.
Expand Down