Function _mi_mem_alloc_aligned

3rd/mimalloc-2.0.9/src/region.c:349–384

Allocate `size` memory aligned at `alignment`. Return non NULL on success, with a given memory `id`. (`id` is abstract, but `id = idx*MI_REGION_MAP_BITS + bitidx`)

// Allocate `size` memory aligned at `alignment`. Return non NULL on success, with a given memory `id`.
// (`id` is abstract, but `id = idx*MI_REGION_MAP_BITS + bitidx`)
void* _mi_mem_alloc_aligned(size_t size, size_t alignment, size_t align_offset, bool* commit, bool* large, bool* is_pinned, bool* is_zero, size_t* memid, mi_os_tld_t* tld)
{
  mi_assert_internal(memid != NULL && tld != NULL);
  mi_assert_internal(size > 0);
  *memid = 0;
  *is_zero = false;
  *is_pinned = false;
  bool default_large = false;
  if (large==NULL) large = &default_large;  // ensure `large != NULL`
  if (size == 0) return NULL;
  size = _mi_align_up(size, _mi_os_page_size());

  // allocate from regions if possible
  void* p = NULL;
  size_t arena_memid;
  const size_t blocks = mi_region_block_count(size);
  if (blocks <= MI_REGION_MAX_OBJ_BLOCKS && alignment <= MI_SEGMENT_ALIGN && align_offset == 0) {
    p = mi_region_try_alloc(blocks, commit, large, is_pinned, is_zero, memid, tld);
    if (p == NULL) {
      _mi_warning_message("unable to allocate from region: size %zu\n", size);
    }
  }
  if (p == NULL) {
    // and otherwise fall back to the OS
    p = _mi_arena_alloc_aligned(size, alignment, align_offset, commit, large, is_pinned, is_zero, _mi_arena_id_none(),  & arena_memid, tld);
    *memid = mi_memid_create_from_arena(arena_memid);
  }

  if (p != NULL) {
    mi_assert_internal(((uintptr_t)p + align_offset) % alignment == 0);
    #if (MI_DEBUG>=2) && !MI_TRACK_ENABLED
    if (*commit) { ((uint8_t*)p)[0] = 0; } // ensure the memory is committed
    #endif
  }
  return p;
}