Re: Debug optimized code; Now: How many compiler bugs have you seen?

"Armel" <armelasselin@hotmail.com>
Wed, 24 Sep 2008 21:47:36 +0200

          From comp.compilers
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Was: Debug optimized code; Now: How many compiler bugs have you seen? cfc@shell01.TheWorld.com (Chris F Clark) (2008-09-24)
Re: Debug optimized code; Now: How many compiler bugs have you seen? armelasselin@hotmail.com (Armel) (2008-09-24)
Re: Debug optimized code; Now: How many compiler bugs have you seen? damian.thomas@unisys.com (Damian Thomas) (2008-09-25)
Re: Debug optimized code; Now: How many compiler bugs have you seen? jlforrest@berkeley.edu (Jon Forrest) (2008-09-25)
Re: Debug optimized code; Now: How many compiler bugs have you seen? marcov@stack.nl (Marco van de Voort) (2008-09-26)
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From: "Armel" <armelasselin@hotmail.com>
Newsgroups: comp.compilers
Date: Wed, 24 Sep 2008 21:47:36 +0200
Organization: les newsgroups par Orange
References: 08-09-076 08-09-105 08-09-110 08-09-115 08-09-119
Keywords: optimize, history
Posted-Date: 24 Sep 2008 15:59:55 EDT

"Chris F Clark" <cfc@shell01.TheWorld.com> a icrit
> So, I wonder, how many of you have experienced real compiler bugs,
> that you could verify was the compilers fault and not just "mysterious
> behavior" that could be fixed by changing the optimizer/debugger
> level?


Hum, it happened once to me for a C/C++ compiler for MIPS (used to be
delivered by M... for their PocketPC), was so clever that when
executing:


myfunc (astruc &a)


for (idx=0; idx<10; ++idx)
{
        mystruc.x = idx;
        myfunc (mystruc)
}


the compiler found intelligent to keep mystruc.x in a register and never
saved it into mystruc.
so an aliasing bug, but one incredibly easy to avoid by a good compiler, and
rather hard to workaround...


Armel


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