core dumps in optimized case with gcc 3.0 and 3.0.1 (regression a

[Joe Buck]

> when compiling our software ( binary size approx. 40 MB) with gcc 3.0 and
> 3.0.1 with -O2 on
> 	Linux ia32, 
> 	RedHat 6.2 and SuSE 7.0 (i.e. glibc 2.1.3),
> 	kernel 2.2.19 and 2.4.4
> we find core dumps which do not appear when compiling with 2.95.[2,3] 
> (with or without optimization) or with gcc 3* without optimizations.

While a compiler bug is possible, it's also possible that there is a
problem with your source code: uninitialized variables, or constructs
with undefined behavior such as 

	a[i] = i++;

can result in optimized code functioning differently from unoptimized code.

> We suspect gcc bugs, since our software run on many 32 and 64 bit platforms,
> but - of course -
> we are not sure. We have no idea what is actually going on so we can not
> produce any testcase
> at the moment.

I suggest trying to isolate the function which is being miscompiled (if
your suspicion of a compiler bug is correct).  Try compiling some files
with -O2 and some with -O0, find the file that is being effected by
optimization level, then try to isolate the function.

Then you'll have a short test case you can send in as a bug report.