#include <stdio.h>
#include <sys/resource.h>
#include <sys/mman.h>
#include <unistd.h>
#include <stdint.h>
#include <x86intrin.h>

void * alloc_page(uint64_t flags) {
  return mmap(NULL, 4096, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | flags, 0, 0);

}
uint64_t get_vmem_limit(void) {
  void *  p = alloc_page(0);munmap(p, 4096);
  return (p - sbrk(0));
}

int main(void) {
  uint64_t lim = get_vmem_limit();
  fprintf(stderr, "limit: %luMB - its %ubit\n", lim/(1024*1024), __bsrq(lim));
}