optimization/9015: bc segfaults when compiled with optimization

[Wolfgang Bangerth]

The following reply was made to PR optimization/9015; it has been noted by GNATS.

From: Wolfgang Bangerth <bangerth@ticam.utexas.edu>
To: Patrick Smith <patsmith@pobox.com>
Cc: gcc-bugs@gcc.gnu.org, <gcc-gnats@gcc.gnu.org>
Subject: Re: optimization/9015: bc segfaults when compiled with optimization
Date: Fri, 20 Dec 2002 23:56:56 -0600 (CST)

 > >     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.
 > 
 > 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.
 
 Thanks for your effort. Basically, try to narrow it down as much as you 
 can, and the let us know as much of the information you have.
 
 You may also want to check out whether recent snapshots of the compiler 
 still show the same behavior -- maybe the bug was already fixed by 
 someone.
 
 Thanks anyway!
   Wolfgang
 
 -------------------------------------------------------------------------
 Wolfgang Bangerth              email:           bangerth@ticam.utexas.edu
                                www: http://www.ticam.utexas.edu/~bangerth