From: DavMac AT iname DOT com (Davin McCall)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: URGENT!!! Please (A Little Long)
Date: Mon, 25 Oct 1999 11:44:03 GMT
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To: djgpp AT delorie DOT com
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On Mon, 25 Oct 1999 05:31:39 GMT, kezman AT nOsPaMbigfoot DOT com (Kieran
Farrell) wrote:

>Heya peeps,
>
>I need a liitle help, I am doing a complex flat file database using
>linked lists and I can't think for some reason. Please look at the
>following segment.

[snipped]

>OK this is the sort of thing I'm trying to do, however when I allocate
>memory and leave the function it destroys the memory and Start in main
>is still NULL. This suggests to me that I'm passing by value and not
>by reference right?
>
>So how would I pass the pointer to the structure by refference. As a
>quick fix I have done the following.

[snipped again]

To pass a pointer by reference, you pass a pointer to the pointer. For
eg (and this isn't tested):

--- begin
#include <stdio.h>

void AllocInt( int **x )
{
  *x = malloc(sizeof(int));  /* allocate space for an int */
  **x = 5;			/* set the value to 5 */
}

int main()
{
  int *a;

  AllocInt(&a);

  printf( "*a is: %d\n", *a );
  return 0;
}
--- end

Hope this helps. Structures are a little more complex as you have to
do stuff like (*myvar)->member = ....

Davin.

__________________________________________________________
       *** davmac - sharkin'!! davmac AT iname DOT com ***
my programming page: http://yoyo.cc.monash.edu.au/~davmac/