From:	"Michael Schuster" <Schuster AT eev DOT e-technik DOT uni-erlangen DOT de>
Organization:	LS f. Elektr. Energieversorgung
To:	djgpp AT delorie DOT com
Date:	Mon, 8 Jul 1996 16:58:42 MEZ
Subject:	Pointer-Allocation
Message-Id:	<52C767D10EA@merlin2.e-technik.uni-erlangen.de>

Gruess Euch!

I've written some programs with pointers and dynamic arrays, which 
might not be very exiting, but I came to a very interesting point, 
when using the realloc -function of libc.a.
I defined a pointer int* p, malloc'ed and then realloc'ed some more 
space.(see source below)
When using  p[a]= a for initialising the pointerposition a , everything worked fine.
I've never had an error. But when using   *p=a; p=p+1;
there was an error. (I did realloc the pointer before p+1 of course)-
My super C- book (C-Grundlagen, Data Becker) told that this should 
cause no error. 
Somehow I had the idea to run it in a DOS Box (Win3.11) and there it 
works now (see source-code). My conclusion is, that this must be the 
DPMI server.
My question: 
Which one behaves correctely? Or is a known thing which I' ve nerver 
heard of?

Michi
-------------------------------------------- 
/* Dyn.c 
   Works fine in a DOS Box (Win 3.11) but doesnot work with native DOS
*/
#include <stdio.h>
#include <stdlib.h>
int main(void)
     {
        int *p;
        int a;
        p=(int*) malloc(sizeof(int));
        for (a=0;a<20;a++) {
           p=(int*) realloc(p,sizeof(int)*(a+1));  /* resizing p*/

           *p=a;  /* init the pointer */
           printf(" Nummer: %d \t %d \n", a,*p);  /* debug info */

        /* The crucial statement */  
           if (!(p==NULL)) p=p+1; 

         
            };
     }











**********************************************
Michael Schuster
E-mail: Schuster AT eev DOT e-technik DOT uni-erlangen DOT de

Universitaet Erlangen/Nuernberg
Lehrstuhl fuer Elektrische Energieversorgung
Cauerstrasse 4
91058 Erlangen

http://www.eev.e-technik.uni-erlangen.de/
**********************************************

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