From:	Michal Mertl <xmerm05 AT manes DOT vse DOT cz>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Bug caused by ____crtl_startup+138
Date:	Wed, 22 Apr 1998 18:08:25 +0200
Organization:	Prague University of Economics
Lines:	51
Message-ID:	<Pine.ULT.3.95.980422174530.6504B-100000@manes.vse.cz>
References:	<3537BABA DOT 7D4D AT cableol DOT co DOT uk>
NNTP-Posting-Host:	manes.vse.cz
Mime-Version:	1.0
In-Reply-To:	<3537BABA.7D4D@cableol.co.uk>
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

On Fri, 17 Apr 1998, Allen's wrote:
> When I run some programs, I get a crash, when symify-ied I get
> ____crtl_startup+138.  What does this do, and how can I stop it?
> 
> Source for one of the programs used to compile it:
<- snipp ->
> int col=0;
> int ma,mat,n,y=50,x=50,start,loop,div,k,go;
> char map [100][100],row[80][160],drawhat;
> 
>  
>    allegro_init();
>    install_keyboard(); 
>      set_gfx_mode(GFX_VGA, 320, 200, 0, 0); 
A good habit is to always check for results of functions which may fail.
Set_gfx_mode is definitely one of them eventhough GFX_VGA can be set probably
on every computer.
> set_pallete(desktop_pallete);
> for (loop = 0; loop < 500; loop++){
> for (start = 80; start > 0; start=start-2){
> 
> for (n = - (start-2); n < (start/2); n++)
> {
You can yourself find that values at first iteration are 
start==80,
col==0,
x==50,
y==50,
n==-78
so you are accessing places in memory out of the array bounds, this results in
unexpected behaviour of everything :)

                          !!130!! !!-28!! 
> row [start][col] = map [y+start][x+n];
              !!240!!       !!-28!! !!-30!!         
> row [start][col+240] = map [y+n][x-start];

There are some more out of arrays accesses in your code.

<- snip the rest of code ->

Hope this helps

One question: I don't know what _stklen is, but assume it changes
stack size of the executable. If so you wouldn't need to enlarge it if you
move the array definitions (or declarations ? - never know which is which)
out of main and they won't eat the stack. 

Michal "MiMe" Mertl
  xmerm05 AT vse DOT cz

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