main.c

#include <sys/mman.h>
#include <stdio.h>

int main(void)
{
    int *map = mmap(
        0,
        4096,
        PROT_READ|PROT_WRITE|PROT_EXEC,
        MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS,
        -1,
        0);
    *map = 42;
    printf("%p %d %d\n", map, *map, *(int *)0);
    return 0;
}