[Python-Dev] Bad interaction of index and sequence repeat (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Fri Jul 28 17:54:30 CEST 2006

Michael Hudson wrote:

David Hopwood <david.nospam.hopwood at blueyonder.co.uk> writes:

Armin Rigo wrote: Hi,

There is an oversight in the design of index() that only just surfaced :-( It is responsible for the following behavior, on a 32-bit machine with >= 2GB of RAM: >>> s = 'x' * (2**100) # works! >>> len(s) 2147483647 This is because PySequenceRepeat(v, w) works by applying w.index in order to call v->sqrepeat. However, index is defined to clip the result to fit in a Pyssizet. Clipping the result sounds like it would never be a good idea. What was the rationale for that? It should throw an exception. Why would you expect range(10)[:232-1] and range(10)[:232] to do different things?

In that case, I believe it is the slice object that should be suppressing the overflow error (via PyErr_Occurred and PyErr_Matches) when calculating the indices for a given length, rather than having silent clipping be part of the basic implementation of long.index().

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia

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