[Python-Dev] r43041 - python/trunk/Modules/_ctypes/cfield.c

["Martin v. Löwis"]

Jim Jewett wrote:
>> It is possible to look at the changed APIs, see
> 
>> http://docs.python.org/dev/api/sequence.html
> 
> I think the problem is more with APIs that are not part of the
> sequence page.  For instance, in
> 
>     http://mail.python.org/pipermail/python-dev/2006-March/062679.html
> 
> M.-A. Lemburg mentioned
> 
>   PyAPI_FUNC(int) PyDict_Next(
>       PyObject *mp, Py_ssize_t *pos, PyObject **key, PyObject **value);
> 
> PyDict_Next  isn't on the sequence page, but if you call it, it could
> write a Py_ssize_t into pos, even though your pointer is only
> large enough for an int.

I gave the sequence page just as an example. The new signature of 
PyDict_Next is also documented, see

http://docs.python.org/dev/api/dictObjects.html#l2h-629

> To do things correctly, you really have to change your call to the
> new version (and add the #ifdef)
> 
>   #if PY_VERSION_HEX < 0x02050000
>   typedef int Py_ssize_t;
>   #endif
> 
> You can downcast if you aren't ready to support 64-bits, but ... setting
> up a possible buffer overflow is a bit worse than simply not supporting.

Sure. In that case, the compiler will give you a compiler warning, on
a 64-bit system. You certainly should react to that warning.

I personally doubt that somebody would go through the list of the 
100-something APIs that changed, memorize them, and then go to his
source code, to find out what to change; I know that I don't work
that way. That said, if somebody things it is worthwhile to create
such a list: contributions are welcome.

Regards,
Martin