https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63783
Bug ID: 63783
Summary: gcc-4.9: Miscompilation of boolean negation on SH4
using -O2
Product: gcc
Version: 4.9.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: glaubitz at physik dot fu-berlin.de
Hello!
Recently we ran into linker issues on our SH4 buildds in Debian [1]. We
initially blamed the linker for the problem, but after some more investigation,
Michael Karcher was eventually able to track down the problem being a
regression in gcc [2].
When compiling the following code snippet with optimization -O2 enabled, the
assertation will fail but succeed without:
#include <assert.h>
int decision_result;
int truecount = 0;
int val;
void buggy(int flag)
{
int condition;
if(flag == 0)
condition = val != 0;
else
condition = !decision_result;
if (condition)
{
truecount++;
}
}
int main(void)
{
decision_result = 1;
buggy(1);
assert(truecount == 0);
}
The issue did not arise with gcc-4.6, for example, so it appears to be a
regression with one of the later versions of gcc.
Cheers,
Adrian
> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=17553
> [2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=768574
