double side effects in args of Py_CLEAR/Py_SETREF

[iritkatriel]

See python/cpython#98724.

[serhiy-storchaka]

Py_CLEAR and Py_SETREF are macros (they cannot be functions). I think that we should simply document that the first argument should not have a side effect. It is the same as for Py_MAX, nobody expect that they work with arguments with a side effect.

[vstinner]

double side effects in args of Py_CLEAR/Py_SETREF

Maybe the scope of this issue can be broader, like: some functions are implemented as macros with macro pitfalls, whereas some others are implemented as function calls or macros without macro pitfalls. Or in short: macro with macro pitfalls are considered harmful :-)