[Python-Dev] Modifying the PyUnicode_FromUnicode result

Currently, a number of routines assume that the result of PyUnicode_FromUnicode can be modified, i.e. they mutate the resulting unicode object. Look at unicodeobject.c:fixup for an example, and assume that fixfct is fixtitle (*). This is different from PyString_FromStringAndSize, whose result can be only modified if the str argument is NULL. These routines broke after I applied my caching patch, since now PyUnicode_FromUnicode may return an existing string. Is that difference intentional? My feeling is that it is an error to modify a unicode object, unless it is known not to be initialized. Regards, Martin P.S. This was actually the first failure case when running test_unicodedata under my patch.