Hi All, I've just realized weak_ptr::lock is not thread safe. Is it expected behavior? Following sample reproduced this conclusion. #include <iostream> #include <boost/shared_ptr.hpp> #include <boost/thread.hpp> #include <boost/weak_ptr.hpp> #include <boost/interprocess/detail/atomic.hpp> #include <boost/interprocess/sync/interprocess_semaphore.hpp> static volatile int v = 0; boost::interprocess::interprocess_semaphore s1(0); boost::interprocess::interprocess_semaphore s2(0); boost::interprocess::interprocess_semaphore s3(0); class SomeClass{ public: boost::shared_ptr<SomeClass> s_this_; boost::weak_ptr<SomeClass> w_this_; SomeClass() { s_this_.reset( this ); w_this_ = s_this_; v = 1; } void release() { s_this_.reset(); } ~SomeClass() { v = 0; } }; SomeClass *c; void worker() { int counter = 0; for( ;; ) { s1.wait(); // wait for created object boost::weak_ptr<SomeClass> w = c->w_this_; // make weak ptr s2.post(); // let main thread go ahead boost::shared_ptr<SomeClass> s = w.lock(); // create shared_ptr from weak_ptr if( s ) // test for valid shared_ptr { if( 0 == v ) // if 0, object is destroyed { std::cout << "!!!!!!!! : " << counter << std::endl; exit(1); } } s3.post(); // notify main thread about test completion ++counter; } } int main() { boost::thread t = boost::thread( &worker ); for( ;; ) { c = new SomeClass(); // create object s1.post(); // notify thread about new object s2.wait(); // wait for thread to make weak_ptr c->release(); // destroy object s3.wait(); // wait for thread complete } return 0; } Best regards. Dima -- Dmytro Ovdiienko