[Python-Dev] RE: [Python-checkins] python/dist/src/Objects unicodeobject.c,2.139,2.140 (original) (raw)

Martin v. Loewis martin@v.loewis.de
21 Apr 2002 11:45:34 +0200

Tim Peters <tim.one@comcast.net> writes:

I expect Martin checked in this change because of the unhappy hours he spent determining that the previous two versions of this function wrote beyond the memory they allocated. Since the most recent version still didn't bother to assert that it wasn't writing out of bounds, I can't blame Martin for checking in a version that does so assert; since I spent hours on this too, and this function has a repeated history of bad memory behavior, I viewed the version Martin replaced as unacceptable.

Exactly. I think the most recent version is worse than the one we had before.

However, the slowdown on large strings isn't attractive, and the previous version could easily enough have asserted its memory correctness.

I found the overallocations strategy that this code had just so embarrassing: a single three-byte character will cause an overallocation of three times the memory, which means that the final realloc will certainly truncate lots of bytes. As a result, we are at the mercy of the realloc implementation here: If realloc copies memory (such as Pymalloc might some day) when shrinking buffers, performance will get worse.

Since this appears to be religious, I'm backing the patch out.

Regards, Martin