There is a design flaw in PyModule_AddObject(). It steals reference of its value only if the result is success. To avoid leaks it should be used in the following form:

    PyObject *tmp = <new reference>;
    if (PyModule_AddObject(name, name, tmp) < 0) {
        Py_XDECREF(tmp);
        goto error;
    }

It is inconvenient and many code forgot to use a temporary variable and call Py_XDECREF().

It was not intention, but it is too late to change this behavior now, because some code calls Py_XDECREF() if PyModule_AddObject() fails. Fixing PyModule_AddObject() now will break hard such code.

There was an idea to make the change gradual, controlled by a special macro (see issue26871). But it still has significant risk.

I propose to add new function PyModule_Add() which always steals reference to its argument. It is more convenient and allows to get rid of temporary variable:

    if (PyModule_Add(name, name, <new reference>) < 0) {
        goto error;
    }

I choose name PyModule_Add because it is short, and allow to write the call in one line with moderately long expression <new reference> (like PyFloat_FromDouble(...) or PyLong_FromUnsignedLong(...)).