[Python-Dev] Changing ob_size to [s]size_t

[Guido van Rossum]

> Besides "breaks binary compatibility", the only other objection was:
> 
> > Also could cause lots of compilation warnings when user code stores
> > the result into an int.
> 
> True; this would be a migration issue. To be safe, we probably would
> define Py_size_t (or Py_ssize_t). People on 32-bit platforms would not
> notice the problems; people on 64-bit platforms would soon provide
> patches to use Py_ssize_t in the core.
> 
> That is a lot of work, so it requires careful planning, but I believe
> this needs to be done sooner or later. Given MAL's and your response,
> I already accepted that it would likely be done rather later than
> sooner.

Perhaps we could introduce a new signed type in 2.3 that's implemented
as an int, and switch it to something of the same size as size_t in
a later revision.

> I don't agree with MAL's objection
> 
> > Wouldn't it be easier to solve this particular problem in
> > the type used for mmapping files ?
> 
> Sure, it would be faster and easier, but that is the dark side of the
> force. People will find that they cannot have string objects with more
> than 2Gib one day, too, and, perhaps somewhat later, that they cannot
> have more than 2 milliard objects in a list.

What's a milliard? <US-parochial wink>

Seriously, I think the problem for this "solution" would be that you
can't use index notation on an mmap object, because
PySequence_GetSlice takes two int args.

I'm not very concerned about strings or lists with more than 2GB
items, but I am concerned about other memory buffers.

> It is unlikely that the problem will go away, so at some point, all
> the problems will become pressing. It is perfectly reasonable to defer
> the binary breakage to that later point, except that probably more
> users will be affected in the future than would be affected now
> (because of the current rareness of 64-bit Python installations).

So we should be planning now.

--Guido van Rossum (home page: http://www.python.org/~guido/)