[Python-Dev] Baffled by PyArg_ParseTupleAndKeywords modification

[Jeremy Hylton]

On 2/14/06, M.-A. Lemburg <mal at egenix.com> wrote:
> Martin v. Löwis wrote:
> > M.-A. Lemburg wrote:
> >>> It's the consequences:  nobody complains about tacking "const" on to a
> >>> former honest-to-God "char *" argument that was in fact not modified,
> >>> because that's not only helpful for C++ programmers, it's _harmless_
> >>> for all programmers.  For example, nobody could sanely object (and
> >>> nobody did :-)) to adding const to the attribute-name argument in
> >>> PyObject_SetAttrString().  Sticking to that creates no new problems
> >>> for anyone, so that's as far as I ever went.
> >>
> >> Well, it broke my C extensions... I now have this in my code:
> >>
> >> /* The keyword array changed to const char* in Python 2.5 */
> >> #if PY_VERSION_HEX >= 0x02050000
> >> # define Py_KEYWORDS_STRING_TYPE const char
> >> #else
> >> # define Py_KEYWORDS_STRING_TYPE char
> >> #endif
> >> ...
> >> static Py_KEYWORDS_STRING_TYPE *kwslist[] = {"yada", NULL};
> >> ...
> >
> > You did not read Tim's message carefully enough. He wasn't talking
> > about PyArg_ParseTupleAndKeywords *at all*. He only talked about
> > changing char* arguments to const char*, e.g. in
> > PyObject_SetAttrString. Did that break your C extensions also?
>
> I did read Tim's post: sorry for phrasing the reply the way I did.
>
> I was referring to his statement "nobody complains about tacking "const"
> on to a former honest-to-God "char *" argument that was in fact not
> modified".
>
> Also: it's not me complaining, it's the compilers !

Tim was talking about adding const to a char* not adding const to a
char** (note the two stars).  The subsequent discussion has been about
the different way those are handled in C and C++ and a general
agreement that the "const char**" has been a bother for people.

Jeremy