[New-bugs-announce] [issue12701] Apple's clang 2.1 (xcode 4.1, OSX 10.7) optimizer miscompiles intobject.c

[deadshort]

New submission from deadshort <cploomis at gmail.com>:

Apple Radar ticket 9908625 has been filed. The clang 2.1 optimizer causes overflows in Object/intobject.c:int_pow() to be missed, so 2**63 turns into a negative integer. The attached test program narrows it down. llvm-gcc is fine, so this ticket is mostly an FYI.

idiotbox:Python-2.7.2 cloomis$ ./seqpoint-OK 4000000000 4000000000
a=4000000000, b=4000000000, c(a*b)=-2446744073709551616, c/b=-611686018
overflow detected: 1

  to turn into:

idiotbox:Python-2.7.2 cloomis$ ./seqpoint 4294967296 4200000000
a=4294967296, b=4200000000, c(a*b)=-407881430509551616, c/b=4294967296
overflow detected: 0

----------
components: Interpreter Core
files: seqpoint.c
messages: 141701
nosy: deadshort
priority: normal
severity: normal
status: open
title: Apple's clang 2.1 (xcode 4.1, OSX 10.7) optimizer miscompiles intobject.c
versions: Python 2.7
Added file: http://bugs.python.org/file22845/seqpoint.c

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<http://bugs.python.org/issue12701>
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