Date: Mon, 7 Jul 1997 08:19:46 -0700 (PDT)
Message-Id: <199707071519.IAA23833@adit.ap.net>
Mime-Version: 1.0
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To: 080970 AT bud DOT cc DOT swin DOT edu DOT au
From: Nate Eldredge <eldredge AT ap DOT net>
Subject: Re: Pseudo bugs?
Cc: djgpp AT delorie DOT com
Precedence: bulk

>Im working on a ray tracer, using djgpp, and its mostly working, but i 
>kept getting sigfpe errors telling me that a co-processor wasn't found, 
>which is fine, cos im using a 486SX.  But having/not having a 
>co-processor shouldn't make a differnce to the program, just make it 
>slower.  So i ran symify, and narrowed it down to a particular function, 
>intsphere().  The respoonse from symify was something like: intsphere+219 
>(BTW is the +219 number of characters? or something else)
It's bytes in the executable, I think. The crash happened 219 bytes into
intsphere. A debugger might be able to do something with this.
>  This wasn't 
>much help, so i recompiled using the -g switch, so symify would give me a 
>valid number. But it didn't give me a vaild dumpfile, the program 
>actually stop giving me the error!! It now seems to work ok, just by 
>placing -g into the compile line.
Odd. What happens when you strip it?
I would suggest you look through the offending function with a debugger, and
see what (if any) floating-point instructions get used. Then look again
without -g and compare. AFAIK, -g isn't supposed to generate any different
code, just add the debugging info. Are you sure you didn't use any other
switches differently?
>
>This is my 2nd weird experience with my program, the 1st being that some 
>variables wouldn't initialize properly (they read from the command line) 
>and i could do nothing about it, but then i placed the variable 
>declaration the next line down in the source code, and it worked.
>(eg i had: int x,y,flag; and x and y wouldn't work, but i changed it to
>int flag;
>int x,y; 
>and it worked fine)

Now *that's* weird. I'd like to see a fragment of that. Maybe looking at the
assembly the compiler makes would be enlightening.

Nate Eldredge
eldredge AT ap DOT net