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Date: Thu, 18 Jan 2007 07:55:41 -0500
From: Jeffrey Creem <jeff@thecreems.com>
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Subject: Re: GNAT Spitbol segmentation fault
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Date: 2007-01-18T07:55:41-05:00
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Alex R. Mosteo wrote:
> Hello,
> 
> before filing a bug report I'd like to hear your opinion to rule out a
> mistake on my part. I'm using the excellent Gnat.Spitbol.Patterns package
> to extract some patterns from large bodies of text. I'm doing it with this
> scheme:
> 
> declare
>    Text   : aliased Vstring := <initial text>;
>    Target : aliased Vstring;
>    
>    Patt   : constant Pattern := Some_Patterns ** Target;
> begin
>    while Match (Text, Target, "") loop
>       --  This extracts a Target string and removes it from the text.
>       --  It doesn't matter if the surrounding text causes new aftermatches.
>       Do_Something_With (Target);
>    end loop;
> end;
> 
> Very rarely I get a Storage_Error and segment violation that kills the
> program. Running inside gdb I get this backtrace:
> 
> #0  0xb7ddf37c in memcpy () from /lib/tls/i686/cmov/libc.so.6
> #1  0x081b7d8d in ada.strings.fixed.replace_slice ()
> #2  0x081bd6cf in ada.strings.unbounded.replace_slice ()
> #3  0x081d4f5e in gnat.spitbol.patterns.match ()
> 
> Unfortunately, address2line doesn't make any valid source lines from these
> addresses, I suppose because the gdb wrapping (but this is just a guess).
> 
> If you have used Gnat Spitbol before, could you comment if I'm doing
> something risky? This is with gnat gpl 2006 in linux x86
> 
> 

Any chance this is a simple matter of blowing the stack someplace? 
Compile with -fstack-check and/or try increasing the stack space of the 
task that is doing this work.