Cheers! The code in question is this: // boost/thread/exceptions.hpp class thread_exception { ... const char* message() const; }; // libs/thread/src/exceptions.cpp std::string system_message(int sys_err_code){..} const char* thread_exception::message() const { if (m_sys_err != 0) return system_message(m_sys_err).c_str(); return what(); } If message() is called and m_sys_err is set, it will return a pointer to storage of a temporary, which is bad, as we all know. I did some research on that, and I think this whole method can be removed completely because: - it is not decumented - it is not used - it never worked (probably, at least not with 1.32) Further, one could then remove <string> from the includes in the header and some more includes in the sourcefile. An alternative approach would be to change the returntype to std::string, of course, or (and I think that's an interesting alternative!) derive all those classes from std::runtime_error, which can hold a std::string natively. Uli