I've run into a strange problem using shared_ptr which I've reduced to the following simple case. #include <tr1/memory> class X { public: typedef std::tr1::shared_ptr<X> Ptr; int x; }; int main(int argc, char *argv[]) { for (int i = 0; i < 100; i++) { X::Ptr pX(new X); } return EXIT_SUCCESS; } Compiling with g++ 4.0.1 on a Debian system with "-O0 -g -fno-inline -DDEBUG". When this program is run under Valgrind (MemCheck) repeated messages like the following occur. ==9950== Conditional jump or move depends on uninitialized value(s) ==9950== at 0x1BBB6D9A: pthread_mutex_lock (in /lib/tls/libpthread-2.3.5.so) ==9950== by 0x1BB56C75: pthread_mutex_lock (in /lib/tls/libc-2.3.5.so) ==9950== by 0x804BF29: __gthread_mutex_lock(pthread_mutex_t*) (gthr-default.h:510) ==9950== by 0x8057ACD: std::tr1::_Sp_counted_base::release() (boost_shared_ptr.h:148) ==9950== by 0x8057B14: std::tr1::shared_count::~shared_count() (boost_shared_ptr.h:266) ==9950== by 0x806B1F4: std::tr1::shared_ptr<X>::~shared_ptr() (boost_shared_ptr.h:474) ==9950== by 0x806B1C9: main (main.cpp:30) ==9950== In the real code this leads to either a hang or an assert in pthread_mutex_lock. If the created pointer is put in a container then this doesn't seem to happen although the problem may just be postponed (the program is never able to complete). I've tried Electric Fence and dmalloc but neither told me anything useful. The hang or assert occurs at the same point every time unless the program is changed or the environment changes (e.g., running under Valgrind). It seems consistent with uninitialized memory. But why? And more important, what can I do about it? Any help would be greatly appreciated! Kurt Kohler Alpha Omega Computer Systems Corvallis, OR