physical memory

How can one find the physical memory of the system?
Recent xz utility <http://tukaani.org/xz/xz-4.999.8beta.tar.gz>
uses sysconf in src/common/physmem.h

May it's possible with getrlimit, setrlimit.
I don't know how glibc make this.

The next file shows that sysconf does not work in dietlibc.
The source of sysconf.c is obvious also :-)

Nikola
-------------------------------------------
#include <sys/param.h>
#include <sys/sysctl.h>

#include <unistd.h>
#include <stdio.h>

/*
  gcc -s -Wall -W phm.c;  ./a.out > phm_defs.h
  diet -Os gcc -s -Wall -W phm.c;  ./a.out

  Since this is a test file I used printf :(
 */

#ifdef __dietlibc__
#include "phm_defs.h"
#endif

int main() {
  const long pagesize = sysconf(_SC_PAGESIZE);
  const long pages = sysconf(_SC_PHYS_PAGES);

#ifndef __dietlibc__
  printf("#ifndef _SC_PAGESIZE\n");
  printf("#define _SC_PAGESIZE %d\n",   _SC_PAGESIZE);
  printf("#endif\n");
  printf("#ifndef _SC_PHYS_PAGES\n");
  printf("#define _SC_PHYS_PAGES %d\n", _SC_PHYS_PAGES);
  printf("#endif\n\n");
#endif

printf("/* pagesize=%ld  pages=%ld */\n", pagesize, pages);
  return 0;
}