Re: Bug Report: Illegal Instruction

[Alexandre Oliva <aoliva at cygnus dot com>]

On May 23, 2000, Bill <billl@unm.edu> wrote:

>> Could it be a buffer overflow problem?
>> I do not consider myself a buffer-knowledgable person, but I don't
>> think its a buffer overflow problem.
   
>    Run it within a debugger and see how it crashes.  If it's a totally
>    strange address, odds are that you've inadvertently overwritten part
>    of the stack by overrunning a fixed-size buffer.

> Glad to take suggestions on how to solve this.  Really.

> I had previously ran it with a debugger (gdb 4.1.6).  Here's the
> result: 

> "Program received signal SIGILL, Illegal instruction.
> 0x0 in ?? () from /nfs/user/b/billl/test/notwork/TABLE
> (gdb)"

So it's very likely that you've somehow corrupted the stack, which was
already hinted at because moving part of the function into a separate
function altered the behavior.

I'd set a breakpoint in the method that fails to complete and run it
step-by-step, looking at the stack trace (`where') after each step.
When the stack trace breaks, you've found the culprit.

-- 
Alexandre Oliva    Enjoy Guaranį, see http://www.ic.unicamp.br/~oliva/
Cygnus Solutions, a Red Hat company        aoliva@{redhat, cygnus}.com
Free Software Developer and Evangelist    CS PhD student at IC-Unicamp
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