Hi. I have posted a new gc implementation in the boost vault here: http://www.boostpro.com/vault/index.php?action=downloadfile&filename=gc1.zip&directory=Memory& The code included in the file is a garbage collector with the following differences from the previous one: 1) finalization order that respects destructor semantics, except when there are cycles. In the previous collector, the order of finalization was random. In the new collector, an unreachable object A that is pointed to by another unreachable object B will be finalized after B is finalized. This allows the use of gc ptrs within destructors. 2) O(1) detection of member ptrs: pointers registers themselves to the appropriate ptr list as they are created. In the previous collector, pointers where discovered in the collection phase by look-up on the sorted blocks. The code is not completed or polished, but it is published for discussing possible implementation ideas. The main bottleneck right now is how to locate blocks from pointers. The current solution is to sort the blocks by address at collection time, then use std::upper_bound to locate the blocks. This has O(log2(N)) complexity, where N is the number of blocks.