Function mi_free

3rd/mimalloc-2.0.9/src/alloc.c:534–562

Free a block fast path written carefully to prevent spilling on the stack

// Free a block
// fast path written carefully to prevent spilling on the stack
void mi_free(void* p) mi_attr_noexcept
{
  if mi_unlikely(p == NULL) return;
  mi_segment_t* const segment = mi_checked_ptr_segment(p,"mi_free");
  const bool          is_local= (_mi_thread_id() == mi_atomic_load_relaxed(&segment->thread_id));
  mi_page_t* const    page    = _mi_segment_page_of(segment, p);

  if mi_likely(is_local) {                       // thread-local free?
    if mi_likely(page->flags.full_aligned == 0)  // and it is not a full page (full pages need to move from the full bin), nor has aligned blocks (aligned blocks need to be unaligned)
    {
      mi_block_t* const block = (mi_block_t*)p;
      if mi_unlikely(mi_check_is_double_free(page, block)) return;
      mi_check_padding(page, block);
      mi_stat_free(page, block);
      #if (MI_DEBUG!=0) && !MI_TRACK_ENABLED
      memset(block, MI_DEBUG_FREED, mi_page_block_size(page));
      #endif
      mi_track_free(p);
      mi_block_set_next(page, block, page->local_free);
      page->local_free = block;
      if mi_unlikely(--page->used == 0) {   // using this expression generates better code than: page->used--; if (mi_page_all_free(page))
        _mi_page_retire(page);
      }
    }
    else {
      // page is full or contains (inner) aligned blocks; use generic path
      _mi_free_generic(segment, page, true, p);
    }
  }
  else {
    // not thread-local; use generic path
    _mi_free_generic(segment, page, false, p);