,Hi Carl, Le ven. 26 juin 2020 à 07:36, Carl Shapiro <carl.shap...@gmail.com> a écrit : > It would be very helpful to broaden the objective of avoiding functions > returning PyObject** to other types of pointers. I have in mind several > functions in the C-API that return a char* pointer to the contents of an > object. While these functions are easy to implement on top of the CPython > object model they are challenging for alternative Python implementations. > > Consider PyBytes_AsString: it returns a mutable char* pointing to the > contents of a byte instance. This presents several obvious problems. For > starters, it burdens a relocating garbage collector to pin objects or create > a temporary copy of an object's contents in non-moving memory. It also has > implications for treating PyObejct* as a handle, using tagged pointers (and > tagged immediates), and multi-threading. > > To eliminate C-API functions such as PyBytes_AsString, PyUnicode_AsUTF8, > etc., new functions should be added to the C-API that copy the contents of > objects out into a buffer, similar to PyUnicode_AsUCS4 or to return the > contents in an dynamically allocated buffer like PyUnicode_AsUCS4Copy.
Well, the general problem is to track when the caller ends using a resource. Borrowed references are a variant of this problem, PySequence_Fast_ITEMS() is another variant. For PyUnicode_AsUTF8, INADA-san added PyUnicode_GetUTF8Buffer() which should be used wit PyBuffer_Release(): * https://github.com/python/cpython/commit/c7ad974d341d3edb6b9d2a2dcae4d3d4794ada6b * https://github.com/python/cpython/pull/17659 * https://discuss.python.org/t/better-api-for-encoding-unicode-objects-with-utf-8/2909 ... but it was reverted soon after its addition: * https://github.com/python/cpython/commit/3a8c56295d6272ad2177d2de8af4c3f824f3ef92 * https://github.com/python/cpython/pull/18985 * https://bugs.python.org/issue39087 See also the "(PEP 620) C API for efficient loop iterating on a sequence of PyObject** or other C types" thread. Victor -- Night gathers, and now my watch begins. It shall not end until my death. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/PGXUHWZDDP3M27SAP4XR6YSI3D2Q6TWS/ Code of Conduct: http://python.org/psf/codeofconduct/
