Files
Neil SchemenauerandGitHub be5386f03f [3.14] gh-159136: Avoid stop-the-world when setting function name attributes (gh-159269) (gh-159726)
Setting __name__, __qualname__, __doc__ or __module__ on a function
stopped the world in the free-threaded build since gh-154826 and
gh-154851, making functools.wraps() orders of magnitude slower with
multiple threads.

Use the per-object critical section and _PyObject_XSetRefDelayed()
instead, as gen_set_name() already does.  Use acquire loads in the
readers and hold strong references across error reporting, tracing, and
eval-frame recording that may execute Python or detach the thread.  The
__code__, __defaults__, __kwdefaults__ and __closure__ setters still
stop the world to clear func_version.

Document synchronization requirements for direct field access and the
lifetime of borrowed function attributes.

(cherry picked from commit 010bebbf9f)
2026-10-30 11:03:31 -07:00
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Tests in this directory are compiled into the _testcapi extension.
The main file for the extension is Modules/_testcapimodule.c, which
calls `_PyTestCapi_Init_*` from these functions.

General guideline when writing test code for C API.
* Use Argument Clinic to minimise the amount of boilerplate code.
* Add a newline between the argument spec and the docstring.
* If a test description is needed, make sure the added docstring clearly and succinctly describes purpose of the function.
* DRY, use the clone feature of Argument Clinic.
* Try to avoid adding new interned strings; reuse existing parameter names if possible. Use the `as` feature of Argument Clinic to override the C variable name, if needed.