[Python-Dev] Re: [snake-farm] test test_slice failed -- [9, 7, 5, 3, 1] == [0]

[Guido van Rossum]

> It is a 64-bit problem, but doesn't have to do with the checkin to
> sliceobject.  The new test (below) broke with old code too.
> 
>         vereq(range(10)[::sys.maxint - 1], [0])
> 
> The problem is that sizeof(int) != sizeof(long).  The parameters for
> PySlice_GetIndices() and PySlice_GetIndicesEx() take ints, not longs.
> So the code is doing:
> 
>         range(10)[::-2]
> 
> since the high 32 bits are lost.
> 
> The only solution I can think of is to have 2 interfaces:
>   - the old API which takes int/int*, PySlice_GetIndices()
>     deprecate this API and raise overflow exception
>     if (int)value != (long)value
>   - the new API which takes long/long*, PySlice_GetIndicesEx()
> 
> PySlice_GetIndicesEx() was added in 2.3.

You meant "must be added" right?

> Otherwise, we are stuck with slices only being able to support
> 32 bits even on 64 bit architectures.

But *everything* having to do with sequences only supports 32 bits:
ob_size, PySequence_Length() the arguments to PySequence_GetItem(),
etc.

Unless you want to fix all those (breaking backwards compatibility),
I'm not sure why you'd want to fix PySlice_GetIndices()...

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