I have this test program: ------------------------------------------- #include <iostream> #include <vector> #include class TestThread { size_t m_loopCount; int m_serverPort; public: TestThread (size_t loopCount) : m_loopCount (loopCount > 0 ? loopCount : 1) , m_serverPort (9090) { return; } void operator() (void) { for (size_t loopCount = 0; loopCount < m_loopCount; ++loopCount) { // Do the same thing the socket open code does char port[6]; sprintf(port, "%d", m_serverPort); char buf0[512]; sprintf (buf0, "%s %zd", "Our loop cont is: " , loopCount); char buf1[793]; sprintf (buf1, "Now the loop count is: %zd", loopCount); // boost::this_thread::yield(); } } }; int main (int argc, char * argv[]) { unsigned int threadLoopCount = 20000; unsigned int threadCount = 2500; // Thread storage std::vector threadVec; for (size_t i = 0; i < 1; ++i) { std::cout << i << ": Spawn " << threadCount << " threads with loop count = " << threadLoopCount << std::endl; for (size_t i = 0; i < threadCount; ++i) { TestThread theThread(threadLoopCount); threadVec.push_back (new boost::thread (theThread)); } while (false) <<<-----------------------------------------This block of code disabled { threadVec.at(0)->join(); delete threadVec.at(0); threadVec.erase(threadVec.begin()); TestThread theThread(threadLoopCount); threadVec.push_back (new boost::thread (theThread)); } for (size_t i = 0; i < threadVec.size(); ++i) { threadVec.at(i)->join(); <<<<-----------------------------Error location 1 delete threadVec.at(i); <<<<-----------------------------Error location 2 } threadVec.clear(); std::cout << "Done" << std::endl; } } ------------------------------------------- I haven't edited it to remove disabled code. Note the while(false) which disables the block of code that was starting a new thread as soon as one completed. What the thread code actually does is designed to reveal a different problem. The for loop that only executes once was a failed attempt to make the desired error happen more often. If I run this program enough times in the Xcode debugger, I eventually see the error: ./boost/thread/pthread/mutex.hpp:50: failed assertion `! pthread_mutex_lock(&m)' In the latest case, this happened at the line I have labeled as "Error location 1", but I have also seen this at the line labeled as "Error location 2". I have seen other threads regarding similar errors with boost threads, but nothing says that this was a bug that has been fixed, or that there is something I should do to avoid the error. I'm also wondering if I have misunderstood something about how to use the threads code. I am running Boost 1.36.0 on OSX 10.5.6 with Xcode 3.1.2. Does this look like pilot error, or is it a bug? - Rush