On Tue, May 25, 2010 at 08:14:05PM +0200, Iustin Pop wrote: > On Tue, May 25, 2010 at 08:05:11PM +0200, sean finney wrote: > > hi, > > > > On Tue, May 25, 2010 at 08:44:57AM +0200, Iustin Pop wrote: > > > I understand your point, and I'm fine with the bug being reopened. But > > > personally, I do not believe anymore this is a software bug, but simply a > > > compiler bug. > > > > I think i've already shown pretty clearly that there are signed overflow > > bugs in the code. I don't think this is up for debate. The build success > > by passing some syntatic sugar to the compiler lowers the severity of the > > bug (it's no longer RC, at least until it's shown that it is problematic > > in real life), but it doesn't make the overflows disappear. > > My point is that, if the behaviour is consistent, and upstream relies on it, > it's not buggy. Buggy is gcc that changes results between -O0 and -O2, and > *only* on arm. > > > did you try > > re-running the build with -ftrapv in the cmdline? i'm guessing not... > > Are you saying that overflows, under any conditions, are wrong?
Hmm… reading http://en.wikipedia.org/wiki/C_%28programming_language%29 and http://en.wikipedia.org/wiki/Integer_overflow, it indeed says that signed overflow is undefined/illegal in C. Then it means compiling -ftrapv should indeed pass. I retract my previous email :) iustin
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