[Python-Dev] New PEP: Using ssize_t as the index type

[M.-A. Lemburg]

Neal Norwitz wrote:
> On 1/10/06, M.-A. Lemburg <mal at egenix.com> wrote:
>> We'd also have to make sure that old extensions don't
>> just import with a warning, since the change will introduce
>> buffer overflows and seg faults in extensions that are not
>> aware of the change.
> 
> I agree that on 64-bit platforms we should prevent the import.  In the
> past we only provided a warning and the users were on their own.  This
> is different.
> 
> If you read my massive checkin to check the return results of
> Py_InitModule*(), you'll realize this isn't as simple as just failing
> in Py_InitMethod*().  I was hoping to just modify Py_InitModule4() in
> Python/modsupport.c to fail and return NULL.  That doesn't seem
> practical given that we didn't check return results.  We will just
> crash the interpreter with standard python 2.4 modules.
> 
> ISTM we need to modify _PyImport_LoadDynamicModule() in
> Python/importdl.c before calling the init function (line 56, (*p)())
> to check for some magic symbol that is defined only when compiling 2.5
> and above.  For example we could add a static int  _64_bit_clean = 1;
> in modsupport.h.  Without some trickery we will get this defined in
> every .o file though, not just modules.
> 
> Other ideas?

We could explicitly break binary compatibility for Python 2.5
on 64-bit platforms, by changing the name of an often used
API, e.g. the Py_InitModule*() APIs.

This is how Unicode does it - we map the various APIs to
either ...UCS2 or ...UCS4, so that you cannot import an
extension compiled for e.g. UCS2 into a Python interpreter
compiled for UCS4. If we didn't, you'd get seg faults and
buffer overflows the same way you would with the ssize_t
change on 64-bit platforms.

-- 
Marc-Andre Lemburg
eGenix.com

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