[Boost-users] boost::thread Destructor being called multiple times

I was just curious as to why the class destructor are (apparently) being called multiple times. I have tried searching the archives to no avail (which prompted me to register and post to the mailinglist). #include struct TestingClass { TestingClass() { std::cout << "constructor called" << std::endl; } ~TestingClass() { std::cout << "destructor called" << std::endl; } void operator()() { std::cout << "operator() called" << std::endl; } } testclass; void testBoostThread() { boost::thread thrd (testclass); thrd.join(); } int main () { testBoostThread(); return 0; } The output: constructor called destructor called destructor called destructor called destructor called operator() called destructor called I would appreciate if someone can enlighten me on this. Will having the destructor called multiple times be a cause of concern? Will it cause some undefined symptoms? Is there a way to completely avoid this situation?