Compiling the following code with -O2 produces an buggy excecutable:
(Using no optimization or -O1 produces an valid excecutable)
~~~ snip ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <iostream>
int main( void )
{
for ( int i = 1; i != 0; i = i + 1 )
{
if ( ! (i % 100000000) )
{
std::cout << i << std::endl;
if ( i == 0 )
{
std::cout << i << std::endl;
}
}
}
return 0;
}
~~~ snip ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Commands to build and execute:
~/c++work/multtest> g++ -O2 -o multtest main.cpp
~/c++work/multtest> ./multtest
100000000
200000000
:
-200000000
-100000000
0
100000000
200000000
: // and continues
== Environment =======================================
~/c++work/multtest> gcc --version
gcc (GCC) 4.1.1 (Gentoo 4.1.1)
Copyright (C) 2006 Free Software Foundation, Inc.
Dies ist freie Software; die Kopierbedingungen stehen in den Quellen. Es
gibt KEINE Garantie; auch nicht für MARKTGÄNGIGKEIT oder FÜR SPEZIELLE ZWECKE.
~/c++work/multtest> uname --all
Linux atlantis 2.6.17-gentoo-r5 #5 SMP PREEMPT Mon Aug 14 19:48:18 CEST 2006
i686 AMD Athlon(tm) XP 2500+ AuthenticAMD GNU/Linux
~/c++work/multtest> cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 6
model : 10
model name : AMD Athlon(tm) XP 2500+
stepping : 0
cpu MHz : 1837.783
cache size : 512 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow up ts
bogomips : 3679.34
--
Summary: Zerodetection (i != 0) compiled with -O2 don't work
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hgsawicki at web dot de
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28777
