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From: xwang@gmuvax2.gmu.edu (Xiang-Min Wang)
Newsgroups: comp.lang.c
Subject: Re: Simple ptr passing question
Message-ID: <1991May22.204153.3967@gmuvax2.gmu.edu>
Date: 22 May 91 20:41:53 GMT
References: <24268@unix.SRI.COM>
Organization: George Mason University, Fairfax, Va.
Lines: 49

In article <24268@unix.SRI.COM> ric@ace.sri.com (Richard Steinberger) writes:
>
>	I am a bit rusty with C.  Could someone help me with this simple
>pointer passing problem.  I wanted to pass a ptr to a function and
>have the function allocate some space and pass back the address in the ptr.
>Here's what I tried:
>
>#include <stdio.h>
>main()
>{
>  extern void zip();
>  int *ip;
>
>  zip(ip);
>
>  printf("*ip is %d\n",*ip);
>}
>
>void zip (iptr)
>int *iptr;
>{
>  int * jptr;
>  jptr = (int *) malloc(sizeof (int) );
>  *jptr = 12;
>  iptr = jptr;
>}
>
>	I know I could have passed back the pointer in a return statement,
>I wanted to get this done correctly for now.  In the main program,
>ip is <nil> on return, instead of pointing to jptr as I had hoped.
>
>	Can someone explain what I should have done to get the desired
>effect?  Thanks in advance for replies and suggestions.
>
>regards,
>
>	ric steinberger
>	ric@ace.sri.com

Hi, ric steinberger. if you knew "all parameters passed by value" in c,then
you could easily figure out where your code went wrong. your problem is a
typical c programming problem. I would suggest you to pass the address of 'ip'
and the rest of your code should be changed accordingly.

good luck, ric.

xwang

xwang@gmuvax2.gmu.edu