Re: optimization/9015: bc segfaults when compiled with optimization

[Patrick Smith <patsmith at pobox dot com>]

bangerth@dealii.org wrote:
> Synopsis: bc segfaults when compiled with optimization
>
> State-Changed-From-To: open->feedback
> State-Changed-By: bangerth
> State-Changed-When: Fri Dec 20 19:20:49 2002
> State-Changed-Why:
>     It is very hard for us to reproduce a problem with such little
>     information, since we don't really know what we're looking
>     for. Sometimes such problems go away by moving to a different
>     platform, and then we would not be able to reproduce it.
>     Basically, a whole program is too large for us to find a
>     bug in.
>     
>     What you could do is the following: try to run bc under
>     a debugger and try to find out which function it crashes in
>     by looking at a stacktrace after the crash happens. Then
>     try to isolate the function in which this happens from
>     the rest of the program and see whether you can come up
>     with a small testcase from which we can work on. This
>     would ideally just include the one function in which things
>     happen, called from a dummy main function.
>     
>     Thanks
>       Wolfgang
>
> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9015
As mentioned in the original report, I think the problem is with the 
function load_code in the source file included in the bug report.  If 
that function is compiled without optimization and the rest of bc is 
optimized with -O2, the crash does not occur.

I've already been the debugger and trying to create a small test program 
route, without much luck.  The crash occurs in another function (addbyte 
in the same source file).

I'm currently reading up on PowerPC assembly, so I can look at the 
generated code for load_code and figure out if it's right or not.  If 
you want, I can send the .s file as well.
--
patsmith@pobox.com