[ python-Bugs-1521947 ] possible bug in mystrtol.c with recent gcc

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Bugs item #1521947, was opened at 2006-07-13 10:39
Message generated for change (Comment added) made by nnorwitz
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Category: Python Interpreter Core
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Marien Zwart (marienz)
Assigned to: Nobody/Anonymous (nobody)
Summary: possible bug in mystrtol.c with recent gcc

Initial Comment:
python 2.5b2 compiled with gentoo's gcc 4.1.1 and -O2
fails test_unary_minus in test_compile.py. Some
investigating showed that the -ftree-vrp pass of that
gcc (implied by -O2) optimizes out the "result ==
-result" test on line 215 of PyOS_strtol, meaning
PyOS_strtol of the most negative long will incorrectly
overflow. 

Python deals with this in this case by constructing a
python long object instead of a python int object, so
at least in this case the problem is not serious. I
have no idea if there is a case where this is a "real"
problem.

At first I reported this as a gentoo compiler bug, but
got the reply that:

"""
I'm pretty sure it's broken. -LONG_MIN overflows when
LONG_MIN < -LONG_MAX, and in standard C as well as "GNU
C", behaviour after overflow on signed integer
operations is undefined.
"""

(see https://bugs.gentoo.org/show_bug.cgi?id=140133)

So now I'm reporting this here. There seems to be a
LONG_MIN constant in limits.h here that could checked
against instead, but I have absolutely no idea how
standard that is. Or this could be a compiler bug after
all, in which case I would appreciate information I Can
use to back that up :)

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>Comment By: Neal Norwitz (nnorwitz)
Date: 2006-07-16 18:13

Message:
Logged In: YES 
user_id=33168

Is this a duplicate of 1521726?

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