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From: wlp@calmasd.Prime.COM (Walter L. Peterson, Jr.)
Newsgroups: comp.lang.c
Subject: Turbo-C Debugger Oddity
Keywords: Turbo-C Debugger, Floating Point Errors
Message-ID: <210@calmasd.Prime.COM>
Date: 6 Feb 89 18:50:14 GMT
Organization: Prime-Calma, San Diego R&D, Object and Data Management Group
Lines: 36

I have recently encountered an odd situation with the Turbo-C V2.0
Integrated Debugger.  I am in the process of making some modifications
to some neural net software (Rumelhart & McClelland's PDP book &
disks) and I'm compiling it with Turbo-C V2.0.  Everything compiles
and links OK, but when I run the EXE from the DOS prompt I get the
error:
         Floating Point Error: Domain

This occurs soon after the program starts computing the weights in the
network, but I'm not certain exactly where ( the software is
extensive, and is loaded with floating point computations ).

The upshot of all of this is that, in order to find the floating point
error, I tried running it in the integrated debugger.  Well, Murphy's
Law was in effect and so naturally it WORKED!  I have tried repeatedly
to get the silly thing to fail while in the debugger ( or just running
out of the integrated environment at all for that matter ) and it runs
perfectly. ( I have checked the results against an unmodified version
and the results ARE correct, too ). EVERY time I run the program from
the DOS prompt, it fails with the same floating point error at
( apparently ) the same place; EVERY time I run the program from the
Turbo-C environment, it works !!

While I have seen similar situations with VAX/VMS and occasionally on
UNIX ( that is, something that fails when run normally, but works in
the debugger ), this is the first time I have seen it in Turbo-C.

Has anyone out there ever encountered this type of situation with the
Turbo-C environment and if so is there a solution ?


-- 
Walt Peterson.  Prime - Calma San Diego R&D (Object and Data Management Group)
"The opinions expressed here are my own and do not necessarily reflect those
Prime, Calma nor anyone else.
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