Bug#289884: Problem with compiler optimization (now with a patch)

[Niko Tyni]

On Thu, May 27, 2010 at 08:29:14AM +0200, Marc Pignat wrote:
> Only the -O0 fails... the compiler seems to have optimized away most of our test!!!
> 
> My proposed solution is to use the 'volatile' keyword to make sure the compiler
> will really do the job.
> 
> Please note that it does not work with -O3, but the configure script compile with
> -O2, so this should be fine.

I'd love to have a fix that works with -O3 too, but that may be better to
resolve upstream. Making the test program depend on its input (arguments,
stdin or whatever) should help, but as Configure is actually a generated
file, I assume some things are easier to implement than others.

Meanwhile, I'll use the 'volatile' solution and hope that gcc -O2 doesn't
become more aggressive soon.

I wonder if this should be considered a gcc optimization bug.

> At this time I've only tested the Configure scripts, which now detects the
> align problem on ARM. I'm compiling the whole thing to check if the md5 bug
> goes away!

All my tests indicate that your solution works, so I intend to include
it in the next upload soon and notify upstream when we've verified the
bug is actually fixed with the new packages.

Thanks for your work on this,
-- 
Niko Tyni   ntyni at debian.org