[Python-Dev] gcc 4.2 exposes signed integer overflows

Guido van Rossum guido at python.org
Sat Aug 26 23:01:18 CEST 2006

On 8/26/06, Jack Howarth <howarth at bromo.msbb.uc.edu> wrote:
>        I discovered that gcc 4.2 exposes a flaw with
> signed integer overflows in python. This bug and the
> necessary fix has been discussed in detail on the gcc
> mailing list. I have filed a detailed bug report and
> the recommended patch proposed by the gcc developers.
> This problem should be addressed BEFORE python 2.5 is
> released. The bug report is...
> [ 1545668 ] gcc trunk (4.2) exposes a signed integer overflows
> in the python sourceforge bug tracker. Thanks in advance
> for attempting to fix this before Python 2.5 is released.

I'm not sure I follow why this isn't considered a regression in GCC.
Clearly, on all current hardware, x == -x is also true for the most
negative int (0x80000000 on a 32-bit box). Why is GCC attempting to
break our code (and then blaming us for it!) by using the C standard's
weaselwords that signed integer overflow is undefined, despite that it
has had a traditional meaning on 2's complement hardware for many
decades? If GCC starts to enforce everything that the C standard says
is undefined then very few programs will still work...

--Guido van Rossum (home page: http://www.python.org/~guido/)

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