[Python-Dev] How to fix the buffer object's broken char buffer support (original) (raw)

Brett Cannon brett at python.org
Wed Jun 7 06:00:35 CEST 2006

On 6/6/06, Guido van Rossum <guido at python.org> wrote:

On 6/6/06, Brett Cannon <brett at python.org> wrote: > If you run import array; int(buffer(array.array('c'))) the > interpreter will segfault. While investigating this I discovered that > buffer objects, for their tpasbuffer->bfgetcharbuffer, return the > result by calling the wrapped object bfgetreadbuffer or > bfgetwritebuffer. This is wrong since it is essentially redirecting > the expected call to the wrong tpasbuffer slot for the wrapped > object. Plus it doesn't have PyTPFLAGSHAVEGETCHARBUFFER defined. > > I see two options here. One is to remove the bfgetcharbuffer slot > from the buffer object. The other option is to fix it so that it only > returns bfgetcharbuffer and doesn't redirect improperly (this also > brings up the issue if PyTPFLAGSHAVEGETCHARBUFFER should then also > be defined for buffer objects). > > Since I don't use buffer objects I don't know if it is better to fix > this or just rip it out.

How ironic. the charbuffer slot was added late in the game -- now we'd be ripping it out... I suspect that there's a reason for it; but in Py3k it will definitely be ripped out. Buffers will purely deal in byte then, never in characters; you won't be able to get a buffer from a (unicode) string at all. Unhelpfully,

I actually figured out a reasonable way to integrate it into the buffer object so that it won't be a huge issue. Just took a while to make sure there was not a ton of copy-and-paste and deciphering the docs (have a separate patch going for clarifying those).

So buffer objects will properly support charbuffer in 2.5 (won't backport since it is a semantic change). Hopefully it won't break too much stuff. =)

-Brett

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