[Python-Dev] Removing tp_compare?

"Martin v. Löwis" martin at v.loewis.de
Sun Feb 1 19:03:58 CET 2009

Mark Dickinson wrote:
> On Sat, Jan 31, 2009 at 9:28 PM, "Martin v. Löwis" <martin at v.loewis.de> wrote:
>> tp_reserved sounds fine. In 3.0.1, filling it with a function pointer
>> should give no error, since that would be a binary-incompatible change.
> I'm not sure I understand you here.  Are you saying that in your
> opinion it is safe to change the type of tp_reserved
> from (cmpfunc *) to some other (dummy) function pointer?

No. I thought someone (you?) proposed that it should cause a runtime
error if a type definitions fills the tp_compare slot. I say that
3.0.1 must not produce such an error.

> I now realize (thanks to your message) that changing the type
> to (void *) isn't entirely safe, since sizeof(void*) may be
> different from sizeof(cmpfunc*) on some platforms.

Do you know of a platform where this is actually the case? I wouldn't
mind making that an #error (i.e. having it fail at compile time


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