During my 'research' into different ways to implement thread specfic storage (tss) on Win32, I needed to implement custom cleanup handlers. The thread_dev branch allows for a custom cleanup handler on the basis of 'one cleanup handler per global object instance'. This is *not* the same as 'one cleanup handler per tss object instance' since with tss there is of course one object instance per thread. Consider: void no_cleanup(int*) { // do nothing } thread_specific_ptr p(no_cleanup); int main(int, char*[]) { int some_number = 42; // leaving aside why someone might want to do this, it's // the mechanincs that we're interested in! p.reset(&some_number); // fine p.reset(new int(0)); // leak - 'p' has no cleanup! return 0; } The theoretical alternative would be to allow (enforce?) a different cleanup handler per thread object, e.g.: void no_cleanup(int*) { // do nothing } void delete_cleanup(int* pd) { delete pd; } thread_specific_ptr p; int main(int, char*[]) { int some_number = 42; // this time call reset with a specfic handler for this thread //object instance p.reset(&some_number, no_cleanup); // fine p.reset(new int(0), delete_cleanup); // ok now, will call delete return 0; } My feeling is that boost::thread should only allow the first form and document that the use above leads to unspecified behaviour (it may not be a memory leak, we don't know what the cleanup handler may do). My only reason for this however is that allowing the latter case is probably not a frequent use and makes the implementation much complicated. Does anyone think the latter is required ? Malcolm Malcolm Noyes