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Date: Fri, 24 Feb 2012 13:02:00 +0000
From: Dave Korn <dave DOT korn DOT cygwin AT gmail DOT com>
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Subject: Re: strange bug that doesn't occur in Linux, OpenBSD or ITS
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On 18/02/2012 18:32, Jeremiah Bishop wrote:
> the  bash commands used are: 1) gcc "cygwin puzzle.c"
> 
> 2) ./a.out a b
> Now either version used on a file with a shorter set of lines, works just
> fine but strangely, that single digit difference aborts the program without
> throwing any error on the sample input or text files with similarly long
> lines.

  Your program is overflowing the stack.  The default amount of stack space
allocated by windows for a program is 2MB, but you can increase it using the
"-Wl,--stack,<SIZE>" option (GCC passes -Wl options through to the linker, see
'man ld' for details of the --stack option).  I found your program could run
to completion when I compiled it with "-Wl,--stack,10000000" for a ~10MB stack.

  However the better fix would not to be to nest forty-three thousand
recursive stack calls.  Your code is very slow because it starts at the
beginning of the list every time and recursively works its way to the end,
costing a function call and stack frame for every node along the way.  Iterate
if you really have to do it that way, or even better, keep a pointer to the
end node of the list and just go straight there.

    cheers,
      DaveK






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