mem_segments.c

/*************************************************************************\
*                  Copyright (C) Michael Kerrisk, 2014.                   *
*                                                                         *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU Affero General Public License as published   *
* by the Free Software Foundation, either version 3 or (at your option)   *
* any later version. This program is distributed without any warranty.    *
* See the file COPYING.agpl-v3 for details.                               *
\*************************************************************************/

/* Listing 6-1 */

/* mem_segments.c

   A program that does nothing in particular, but the comments indicate
   which memory segments each type of variable is allocated in.
*/
#define _BSD_SOURCE
#include <stdio.h>
#include <stdlib.h>

char globBuf[65536];            /* Uninitialized data segment */
int primes[] = { 2, 3, 5, 7 };  /* Initialized data segment */

static int
square(int x)                   /* Allocated in frame for square() */
{
    int result;                 /* Allocated in frame for square() */

    result = x * x;
    return result;              /* Return value passed via register */
}

static void
doCalc(int val)                 /* Allocated in frame for doCalc() */
{
    printf("The square of %d is %d\n", val, square(val));

    if (val < 1000) {
        int t;                  /* Allocated in frame for doCalc() */

        t = val * val * val;
        printf("The cube of %d is %d\n", val, t);
    }
}

int
main(int argc, char *argv[])    /* Allocated in frame for main() */
{
    static int key = 9973;      /* Initialized data segment */
    static char mbuf[10240000]; /* Uninitialized data segment */
    char *p;                    /* Allocated in frame for main() */

    p = malloc(1024);           /* Points to memory in heap segment */

    doCalc(key);

    exit(EXIT_SUCCESS);
}