the remap testing program by a loop calling mremap memory increasing one page size

remap.c

// the remap testing program by a loop calling mremap memory increasing one page size
// till it failed, or be killed by OOM

// Compile by: gcc -Wall -D_GNU_SOURCE -o remap remap.c

#include <unistd.h>
#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

int main(void)
{
  const int PAGE_SIZE = sysconf(_SC_PAGESIZE);
  size_t mmap_sz = PAGE_SIZE;
  char *pp = mmap(NULL, mmap_sz, PROT_READ|PROT_WRITE,
           MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);

  if (pp == MAP_FAILED) {
    int saved = errno;
    perror("\nmremap failed");
    fprintf(stderr, "remap failed %s (%d).\n",
        strerror(saved), saved);
    return 1;
  }

  pp[mmap_sz-1] = '\0';
  printf("allocated one page @%p, (PAGE_SIZE: %d)\n",
     pp, PAGE_SIZE);

  while (1) {
    char *new_pp = mremap(pp, mmap_sz, mmap_sz+PAGE_SIZE, MREMAP_MAYMOVE);
    if (new_pp == MAP_FAILED) {
      int saved = errno;
      perror("\nmremap failed");
      fprintf(stderr, "remap failed %s (%d).\n",
          strerror(saved), saved);
      return 1;
    }
    if (new_pp != pp) {
      printf("\n");
      pp = new_pp;
    }

    mmap_sz += PAGE_SIZE;
    pp[mmap_sz-1] = '\0';

    printf("\rgrabbed %lu bytes of memory (%lu pages) @ %0*lx.",
       mmap_sz, mmap_sz / PAGE_SIZE,
       (int)sizeof(long)*2, (long)pp);
    fflush(stdout);
  }

  return 0;
}