Date: Tue, 9 May 1995 09:50:45 +0300
From: eliz AT is DOT elta DOT co DOT il (Eli Zaretskii)
To: sjagordo AT FLASH DOT LakeheadU DOT CA
Subject: Re: exception 14 runtime error
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu

> My modified version compiles with Borland C++ (version 4.5) and with
> djgpp (from the archive gcc263bn.zip), but the djgpp version always
> crashes at runtime with the message:
>
>	 Segmentation violation in pointer 0x00000000 at ...
>
>
>	exception 14 (0xe) occurred, error code=0
>
> I have traced this in at least two cases.  The first occurs when the 
> string argument to atof() is NULL.  The second occurs when a NULL pointer 
> is dereferenced.  (Ultimately, these two errors are the same, since atof()
> attempts to dereference the NULL argument to read the string).
>
> When compiled with the Borland compiler, the program just runs right
> through these sections.  In fact, atof((char *) NULL) returns 0.0
> when compiled with Borland C++ 4.5.

Borland C generates real-mode programs, where you don't have almost ANY
protection against dereferncing a null pointer (or even against loading
your registers with garbage and jumping into the blue, for that matter).
DJGPP just did you a great service in that it found a severe bug in the
program that somebody trusts to produce meaningful results.  How can
anybody ask for a facility to turn this great feature off??  How can you
trust the results of a simulation program after you learn that it uses
garbled data (produced by dereferencing a null pointer) from time to time???
I worked with simulations for several years.  I remember that any suspicion
about the program(s) I used, even a compile-time warning, would immediately
invalidate its output until such time as that problem is resolved.

I say you should hunt the bug in the program which causes a null pointer
to be passed, and eliminate it.  If I were you, I won't be satisfied with
a wrapper function solution, as suggested by Aaron Ucko, but would try very
hard to understand why that null pointer is born in the first place.

P.S.  I apologize for somewhat steamy style, I just couldn't believe my eyes
when I've read your posting.