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

[Neal Norwitz]

On Tue, Nov 05, 2002 at 10:38:18PM +0100, Anders Qvist wrote:
> Between 1036491804 and 1036522446 (should be GMT 2002-11-05, 10:20 and
> 2002-11-05, 18:54 respectively), test_slice started failing with the
> following message:
> 
>   test test_slice failed -- [9, 7, 5, 3, 1] == [0]
> 
> om moghedien; linux/alpha. There has been some changes containing
> pointer arithmetic around line 160 of sliceobjects.c, which might be
> guilty (just a shot in the dark; 64-bit clean?):

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.

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

Other ideas?

Neal