/* bigdata.c - how much can one malloc take, and where does it land. C89.
   usage: bigdata MB */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
int main(int argc, char **argv)
{
    long mb = argc > 1 ? atol(argv[1]) : 300, i, pg = sysconf(_SC_PAGESIZE);
    char *p = malloc(mb << 20);
    if (!p) { printf("malloc %ld MB: NULL, errno %d (%s)\n", mb, errno, strerror(errno)); return 1; }
    for (i = 0; i < (mb << 20); i += pg) p[i] = 1;
    printf("malloc %ld MB: %p .. %p, touched\n", mb, (void *)p, (void *)(p + (mb << 20) - 1));
    return 0;
}