Function mi_heap_absorb

3rd/mimalloc-2.0.9/src/heap.c:370–401

Transfer the pages from one heap to the other

// Transfer the pages from one heap to the other
static void mi_heap_absorb(mi_heap_t* heap, mi_heap_t* from) {
  mi_assert_internal(heap!=NULL);
  if (from==NULL || from->page_count == 0) return;

  // reduce the size of the delayed frees
  _mi_heap_delayed_free_partial(from);

  // transfer all pages by appending the queues; this will set a new heap field
  // so threads may do delayed frees in either heap for a while.
  // note: appending waits for each page to not be in the `MI_DELAYED_FREEING` state
  // so after this only the new heap will get delayed frees
  for (size_t i = 0; i <= MI_BIN_FULL; i++) {
    mi_page_queue_t* pq = &heap->pages[i];
    mi_page_queue_t* append = &from->pages[i];
    size_t pcount = _mi_page_queue_append(heap, pq, append);
    heap->page_count += pcount;
    from->page_count -= pcount;
  }
  mi_assert_internal(from->page_count == 0);

  // and do outstanding delayed frees in the `from` heap
  // note: be careful here as the `heap` field in all those pages no longer point to `from`,
  // turns out to be ok as `_mi_heap_delayed_free` only visits the list and calls a
  // the regular `_mi_free_delayed_block` which is safe.
  _mi_heap_delayed_free_all(from);
  #if !defined(_MSC_VER) || (_MSC_VER > 1900) // somehow the following line gives an error in VS2015, issue #353
  mi_assert_internal(mi_atomic_load_ptr_relaxed(mi_block_t,&from->thread_delayed_free) == NULL);
  #endif

  // and reset the `from` heap
  mi_heap_reset_pages(from);
}

// Safe delete a heap without freeing any still allocated blocks in that heap.
void mi_heap_delete(mi_heap_t* heap)