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From: GLASGOW@NOSC-TECR.arpa
Newsgroups: comp.unix.wizards
Subject: Problems with pointers
Message-ID: <9519@brl-adm.ARPA>
Date: Mon, 28-Sep-87 14:54:16 EDT
Article-I.D.: brl-adm.9519
Posted: Mon Sep 28 14:54:16 1987
Date-Received: Tue, 29-Sep-87 06:24:46 EDT
Sender: news@brl-adm.ARPA
Lines: 32



     I am working ona a Sun 3/50 running SunOS V4.2.  I am trying to
use a generic pointer that I can use to point to one of several different
data structures.  I declare the pointer as:

typedef struct {
   /*  massive declarations  */
   ...
   } some_big_structure;

int    *p;

and by using:

p = (some_big_structure *)malloc(sizeof(some_big_structure));

I can get p pointing to a memory block of the correct size for the structre.

My problem arises when I try to release this memory back to the system. If
I use free(), will it assume that p points to an integer and release only
two bytes, or will it know that p is a larger structure and release the
proper number of bytes.  Also, if it releases only two bytes, is there a
way around this.  All of the different structures are large and memory is
tight, so this is definitely a problem.

All repsonses will be greatly appreciated.

michael

glasgow@marlin.nosc.mil
NOSC - San Diego