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Date: Tue, 27 Mar 2001 17:35:31 -0500
From: Christopher Faylor <cgf AT redhat DOT com>
To: Cygwin <cygwin AT cygwin DOT com>
Cc: matts AT bluesguitar DOT org
Subject: Re: Debugging setup.exe
Message-ID: <20010327173531.A11821@redhat.com>
Reply-To: cygwin AT cygwin DOT com
Mail-Followup-To: Cygwin <cygwin AT cygwin DOT com>, matts AT bluesguitar DOT org
References: <BF35D9C143BCCC4EB63181B67C9320C804DD69 AT serv-075 DOT icon-germany DOT local> <02b701c0b707$7c30a230$3c5350d8 AT bluesguitar DOT org>
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In-Reply-To: <02b701c0b707$7c30a230$3c5350d8@bluesguitar.org>; from matts@bluesguitar.org on Tue, Mar 27, 2001 at 03:47:14PM -0600

On Tue, Mar 27, 2001 at 03:47:14PM -0600, Matthew Smith wrote:
>Changing 'int r' to 'volatile int r' seemed like a good idea, so I tried
>that, and it works well.  Now however, I've run into some stranger behavior
>still.  Take a look at this code snippet:
>
>  r = (y + ROW_MARGIN/2) / row_height;
>
>  if (r < 0 || r >= npackages)
>    return 0;
>
>  int p = package_indexes[r];
>
>  if (x >= headers[NEW_COL].x - HMARGIN/2 && x <= headers[NEW_COL+1].x -
>HMARGIN/2)
>    {
>        ...
>
>
>Ok, I step through and 'r' is set to a reasonable number.  'p' is then set
>to 0, which seems reasonable enough as well.  We hit the 'if' conditional,
>and get this....execution then goes BACKWARDS and executes the 'int p =
>package_indexes[r];' line again!  At that point, p is set to some gigantic
>negative number, so when we use it as an array index a short time later,
>everything blows up.  Is this related to the optimizer too?  Seems odd.

DJ has already indicated that what you are seeing is an artifact of
optimization.  Build setup.exe without the -O2 if you are having problems.

cgf

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