From: flux AT stack DOT nl (Mark van der Aalst)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Re-Mallocing an array...
Date: 21 May 1998 09:15:05 +0200
Organization: MCGV Stack, Eindhoven University of Technology, the Netherlands.
Lines: 54
Message-ID: <6k0k9p$aof@toad.stack.nl>
References: <6jv6s8$kn1 AT nnrp4 DOT farm DOT idt DOT net> <35635D05 DOT 69D AT cs DOT com>
NNTP-Posting-Host: toad.stack.nl
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

John M. Aldrich (fighteer AT cs DOT com) wrote:
> Chia wrote:
> > 
> >   foo = (int *)malloc( sizeof(int) * 10);
> > 
> > And then I want to change it to hold 20 ints.  So, I figured I'd free it and
> > then remalloc it.
> > 
> >   free(foo);
> >   foo = (int *)malloc( sizeof(int) * 20);
> > 
> > but this crashes.  How do I do this, then?

This can't crash (assuming your machine has at least 80 bytes of memory :)
*if* you included <stdlib.h> as a header file. If you didn't the program
results in undefined behaviour and might indeed, among other things, crash.
Another hint ; lose the int * casts, they don't buy you anything, worse
they hide possible proto type mismatches. E.g. if you don't have stdlib.h
and use a cast malloc() will return an int wich will be cast to a pointer
... nasty stuff, anyway this should do it ;

#include <stdio.h>
#include <stdlib.h> /* aha ! */

int main(void)
{
  int *foo = malloc(sizeof *foo * 10);

  if(foo) /* we malloced okay */
   {
     free(foo);

     foo = malloc(sizeof *foo * 20);

     /* or just (even if foo == NULL) 

     foo = realloc(foo, sizeof *foo * 20);

     */

     if(!foo)
      puts("damn");
     else
      free(foo);
   }
  else
   puts("darn");

  return 0; 
}

If you manage to crash this program I'll eat my hat.

Cheers, flux.