mremap3.c revision 663860b1408516d02ebfcb3a9999a134e6cfb223 
1#define _GNU_SOURCE 1
2#include <sys/mman.h>
3#include <stdio.h>
4#include <stdlib.h>
5#include <string.h>
6#include <unistd.h>
7
8int main(void)
9{
10   /* first  find free segment of 40K, then unmap it */
11   void *initial_area = mmap((void *)0x10000000, 40960, PROT_READ|PROT_WRITE,
12                             MAP_ANONYMOUS|MAP_PRIVATE,0,0);
13
14   if (initial_area == MAP_FAILED)
15      perror ("initial area");
16   printf("initial_area= %p\n", initial_area);
17   if (munmap(initial_area, 40960) != 0)
18      perror ("munmap initial_area");
19
20   /* remap the same segment, but with 4K size */
21   void *area = mmap(initial_area, 4096, PROT_READ|PROT_WRITE,
22                     MAP_ANONYMOUS|MAP_PRIVATE,0,0);
23   if (area == MAP_FAILED)
24      perror ("area");
25   if (area != initial_area)
26      printf("FAILED : was expecting to get back the initial_area\n");
27   printf("area= %p\n", area);
28   strcpy(area, "Hello World");
29
30   /* extend it to 40K */
31   void *a2 = mremap(area, 4096, 40960, 0);
32   if (a2 == MAP_FAILED) {
33      perror("mremap");
34   }
35   if (a2 != initial_area)
36      printf("FAILED : was expecting to get back the same area increased\n");
37   printf("increased area= %p\n", a2);
38   printf("%s\n", (char *)a2);
39   return 0;
40}
41