STINNER Victor <vstin...@python.org> added the comment:
> For any sane design of tagged pointers, `x == y` (in C) will work fine. I wrote a proof-of-concept for using tagged pointners in CPython: https://github.com/vstinner/cpython/pull/6 "The PR is large because of the first changes which add Py_IS_NONE(), Py_IS_TRUE() and Py_IS_FALSE() macros." For backward compatibility, I added a function to get a concrete Python object from a tagged pointer: the True as a tagged pointer becomes (PyObject *)&_Py_TrueStruct concrete object. Py_IS_TRUE() has to check for both values: tagged pointer or &_Py_TrueStruct (don't look at my exact implementation, it's wrong ;-)). In a perfect world, there would be no backward compatibility and you would never have to create Python objects from a tagged pointer. The other problem is that the stable ABI exposes "Py_True" as "&_Py_TrueStruct" and so C extensions built with the stable ABI uses "&_Py_TrueStruct", not the tagged pointer. See also bpo-39511 which discuss solutions for these problems. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue43753> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
