[Python-Dev] Before 2.5 - More signed integer overflows

Tim Peters tim.peters at gmail.com
Mon Sep 18 06:58:31 CEST 2006

[Armin Rigo]
>> There are more cases of signed integer overflows in the CPython source
>> code base...
>> That's on a 64-bits machine:
>>     [GCC 4.1.2 20060715 (prerelease) (Debian 4.1.1-9)] on linux2
>>     abs(-sys.maxint-1) == -sys.maxint-1
>> Humpf!  Looks like one person or two need to do a quick last-minute
>> review of all places trying to deal with -sys.maxint-1, and replace them
>> all with the "official" fix from Tim [SF 1545668].

[Anthony Baxter]
> Ick. We're now less than 24 hours from the scheduled release date for 2.5
> final. There seems to be a couple of approaches here:
> 1. Someone (it won't be me, I'm flat out with work and paperwriting today)
>    reviews the code and fixes it
> 2. We leave it for a 2.5.1. I'm expecting (based on the number of bugs found
>    and fixed during the release cycle) that we'll probably need a 2.5.1 in about
>    3 months.
> 3. We delay the release until it's fixed.
> I'm strongly leaning towards (2) at this point. (1) would probably require
> another release candidate, while (3) would result in another release
> candidate and massive amount of sobbing from a lot of people (including me).

I ignored this since I don't have a box where problems are visible (&
nobody responded to my request to check my last flying-blind "fix" on
a box where it mattered).

Given that these are weird, unlikely-in-real-life endcase bugs
specific to a single compiler, #2 is the natural choice.

BTW, did anyone try compiling Python with -fwrapv on a box where it
matters?  I doubt that Python's speed is affected one way or the
other, and if adding wrapv makes the problems go away, that would be
an easy last-second workaround for all possible such problems (which
of course could get fixed "for real" for 2.5.1, provided someone cares
enough to dig into it).

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