From:	"Mars" <mars AT homemail DOT com>
Sender:	"Mars" <marsj AT 195 DOT 158 DOT 64 DOT 19>
Reply-To:	"Mars" <mars AT homemail DOT com>
Subject:	Re: Crash in class when adding new variables
Newsgroups:	comp.os.msdos.djgpp
References:	<35eec1db DOT 0 AT 195 DOT 158 DOT 64 DOT 19> <35f0e017 DOT 37639438 AT news DOT Austria DOT EU DOT net> <35f01ace DOT 0 AT 195 DOT 158 DOT 64 DOT 19> <35fd5f72 DOT 48706033 AT news DOT Austria DOT EU DOT net>
MIME-Version:	1.0
NNTP-Posting-Host:	195.158.64.195
Message-ID:	<35f165f6.0@195.158.64.19>
Date:	5 Sep 1998 18:25:26 +0100
Lines:	201
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

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sparhawk AT eunet DOT at (Gerhard Gruber) wrote:
>Destination: "Mars" <mars AT homemail DOT com>
>=46rom: Gruber Gerhard
>Group: comp.os.msdos.djgpp
>Date: 4 Sep 1998 18:52:30 +0100:
>
>>It was not me.  This is another problem.
>
>Oh. Same subject line different problem. :)
>
>>This is the signiture of the class:
>
>Well, the calls is with 99.9% surity (is this the word?) not the problem.
>Rather your problem lies somewhere in your code. I'm pretty sure that you
>overwrite your stack somewhere and thats why changes in the class might
=
>crash
>your program. Because the stack layout is different with the new class =
>and it
>happens that the new values crash whereas the previous values went =
>unnoticed
>(but are still there). So check your code for parts where you use =
>automatic
>variables (specifically arrays) where you might go beyond array =
>boundaries.
>
>Something like that might cause your problem:
>
>foo()
>{
>   char s[5];
>
>   strcpy(s, "Very long string doesnt fit in this short array");
>}
>
>Another problem might be that you are shooting with wild pointers. :) Are=
> you
>sure you initialized all pointers prior to using them? Assigning a =
>default
>value of NULL often helps in detecting such errors. I'd recommend to do
=
>this
>on all pointers.
>
>--
>Bye,
>   Gerhard
>
>email: sparhawk AT eunet DOT at
>       g DOT gruber AT sis DOT co DOT at
>
>Spelling corrections are appreciated.

Thanks for your reply.
I tried as you said, to make the pointer point to NULL.  But it still crashed.
I'm attaching the source code so that you can try it.  As it is, it is runnable.
 But when you add another variable to either class GridMap or class GridMap2,
the program crashes.

To exit program, press 'x'.

Thanks again
Mars
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