Function mi_os_mem_alloc

3rd/mimalloc-2.0.9/src/os.c:708–743

Note: the `try_alignment` is just a hint and the returned pointer is not guaranteed to be aligned.

// Note: the `try_alignment` is just a hint and the returned pointer is not guaranteed to be aligned.
static void* mi_os_mem_alloc(size_t size, size_t try_alignment, bool commit, bool allow_large, bool* is_large, mi_stats_t* stats) {
  mi_assert_internal(size > 0 && (size % _mi_os_page_size()) == 0);
  if (size == 0) return NULL;
  if (!commit) allow_large = false;
  if (try_alignment == 0) try_alignment = 1; // avoid 0 to ensure there will be no divide by zero when aligning

  void* p = NULL;
  /*
  if (commit && allow_large) {
    p = _mi_os_try_alloc_from_huge_reserved(size, try_alignment);
    if (p != NULL) {
      *is_large = true;
      return p;
    }
  }
  */

  #if defined(_WIN32)
    int flags = MEM_RESERVE;
    if (commit) { flags |= MEM_COMMIT; }
    p = mi_win_virtual_alloc(NULL, size, try_alignment, flags, false, allow_large, is_large);
  #elif defined(MI_USE_SBRK) || defined(__wasi__)
    MI_UNUSED(allow_large);
    *is_large = false;
    p = mi_heap_grow(size, try_alignment);
  #else
    int protect_flags = (commit ? (PROT_WRITE | PROT_READ) : PROT_NONE);
    p = mi_unix_mmap(NULL, size, try_alignment, protect_flags, false, allow_large, is_large);
  #endif
  mi_stat_counter_increase(stats->mmap_calls, 1);
  if (p != NULL) {
    _mi_stat_increase(&stats->reserved, size);
    if (commit) { _mi_stat_increase(&stats->committed, size); }
  }
  return p;
}


// Primitive aligned allocation from the OS.