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After gh-130704, the interpreter replaces some uses of `LOAD_FAST` with `LOAD_FAST_BORROW` which avoid incref/decrefs by "borrowing" references on the interpreter stack when the bytecode compiler can determine that it's safe. This change broke some checks in C API extensions that relied on `Py_REFCNT()` of `1` to determine if it's safe to modify an object in-place. Objects may have a reference count of one, but still be referenced further up the interpreter stack due to borrowing of references. This provides a replacement function for those checks. `PyUnstable_Object_IsUniqueReferencedTemporary` is more conservative: it checks that the object has a reference count of one and that it exists as a unique strong reference in the interpreter's stack of temporary variables in the top most frame. See also: * https://github.com/numpy/numpy/issues/28681 Co-authored-by: Pieter Eendebak <[email protected]> Co-authored-by: T. Wouters <[email protected]> Co-authored-by: mpage <[email protected]> Co-authored-by: Mark Shannon <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
The Python C API ================ The C API is divided into these sections: 1. ``Include/``: Limited API 2. ``Include/cpython/``: CPython implementation details 3. ``Include/cpython/``, names with the ``PyUnstable_`` prefix: API that can change between minor releases 4. ``Include/internal/``, and any name with ``_`` prefix: The internal API Information on changing the C API is available `in the developer guide`_ .. _in the developer guide: https://devguide.python.org/c-api/