From: hipermar AT mail2 DOT esoterica DOT pt (Hiper M.A.R.)
Newsgroups: comp.os.msdos.djgpp
Subject: Malloc and realloc problems
Date: Mon, 18 Sep 2000 10:29:56 GMT
Organization: Esoterica, Portugal
Lines: 115
Message-ID: <969276437.311068@osiris.esoterica.pt>
NNTP-Posting-Host: osiris-ip.esoterica.pt
X-Trace: news.interpacket.net 969272975 88134 209.198.242.35 (18 Sep 2000 10:29:35 GMT)
X-Complaints-To: usenet AT news DOT interpacket DOT net
NNTP-Posting-Date: 18 Sep 2000 10:29:35 GMT
X-Newsreader: Forte Free Agent 1.0.82
Cache-Post-Path: osiris.esoterica.pt!unknown AT por411 DOT esoterica DOT pt
X-Cache: nntpcache 2.3.3 (see http://www.nntpcache.org/)
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

Incoerent results are given deppending on how memory is malloc or
realloc:
a)Using a straight foward malloc
b)Trying to malloc in 1MB step
c)Trying to realloc in 1 to 10 MB steps.

Using the programs listen at the bottom, i came the the following
results, using a computer with 128 MB ram and win98 1st edition:

      Step   Success     Fail
a)                124        125
b)                   95         96
c)      1           35         36
         2           42         44
         3           45         48
         4           48         52
         5           45         50
         6           54         60
         7           63         70
         8           48         56
         9           54         63
        10          60         70

What on earth this means...???
Can someone help...?
Thanks.

//--------------------------------------------------------------------
// a) Straight malloc

#include <stdlib.h>
#include <stdio.h>

int main(void)
{
    void *ptr;
    int step;

    step=124;  //change this value; recompile to find max. available

    ptr = malloc(1048576*step);
    if (!ptr) {
        printf("Fail to allocate %d MB of memory!\n", step);
        return 0;
    }
    else {
        printf("Successfuly allocated %d MB\n", step);
	free(ptr);
    }
    return 0;
}

//---------------------------------------------------------------------
// b) Trying to malloc in 1MB step

#include <stdlib.h>
#include <stdio.h>

int main(void)
{
    void *ptr;
    int step, i;

    step=1;  //in 1MB step

    for(i=1;i<257;i++) {
        ptr = malloc(1048576*step*i);
        if (!ptr) {
            printf("Fail to malloc %d MB of memory!\n", step*i);
            return 0;
        }
        else {
            printf("Successfuly malloc %d MB\n", step*i);
            free(ptr);
        }
    }
    return 0;
}

//---------------------------------------------------------------------
// c)Trying to realloc in 1 to 10 MB step.

#include <stdlib.h>
#include <stdio.h>

int main(void)
{
    void *ptr;
    int step, i;

    ptr = malloc(1048576*1);
    if (!ptr) {
        printf("Fail to malloc 1 MB of memory!\n");
        return 0;
    }
    else {
        printf("Successfuly malloc 1 MB\n");
    }

    step=1;  //change the setp from 1 to 10, and recompile

    for(i=1;i<257;i++) {
        ptr = realloc(ptr, 1048576*step*i);
        if (!ptr) {
            printf("Fail to realloc %d MB of memory!\n", step*i);
            return 0;
        }
        else {
            printf("Successfuly realloc %d MB\n", step*i);
        }
    }
    return 0;
}