Date:	Wed, 18 Mar 1998 21:55:13 -0800 (PST)
Message-Id:	<199803190555.VAA19201@adit.ap.net>
Mime-Version:	1.0
To:	rpinnell AT characato DOT ucsm DOT edu DOT pe, djgpp AT delorie DOT com
From:	Nate Eldredge <eldredge AT ap DOT net>
Subject:	Re: Pointers and DJGPP

At 04:42  3/18/1998 -0500, rpinnell AT characato DOT ucsm DOT edu DOT pe wrote:
>Hi I have been trying to teach myself C for the last few months or so
>and have been using DJGPP.  I seem to be having a lot of problems
>whenever I use pointers with DJGPP.  Take the following example a simple
>strcat.
>
>#include <stdio.h>
>
>void mstrcat(char *s,char *t);
>
>int main()
>{
>char ms1[]="Hello";
>char ms2[]=" World";
>mstrcat(ms1,ms2);

You have not left any space in `ms1' to add the characters from `ms2'. This
is a bug in your code.

[snipped]
>The program compiles fine and does what I want it to when it runs but
>exits with the following error message.
>Exiting due to signal SIGSEGV
[snipped]
>Which is all Greek to me!  

SIGSEGV = SIGnal SEGmentation Violation. Basically, it means your program
has accessed memory in an illegal way. In this case, you have written past
the end of an array.

>It isnīt just this simple program that I have
>problems with I seem to get similar error messages whenever I pass
>pointers to a function.  The same things work ok if I just use arrays
>rather than pointers. 

These, too, are with 99.9% certainty bugs in your code.

> Any advice would be aprreciated.  My apologies if
>this is the wrong place to ask this question  but it seems to me it is
>more a DGJPP/DOS question that a general C one.

It isn't. Many system will report illegal operations like this. These are
general C questions and should be asked on a comp.lang.c newsgroup.

Nate Eldredge
eldredge AT ap DOT net

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