Hi, I'm using pthreads on Fedora Core 1. I have compiled my entire project with -D_REENTRANT -D_MULTI_THREADED I get Segmentation faults for naive code that uses std::string's operator+, std::ostringstream's operator<< as a local variable in stack. std::string Formatter::format(const LogRecord& record) const { std::ostringstream ost; ost << record.getTime() << " " << record.getMessage(); //<--Crashes return ost.str(); } Do i have to do anything extra in order for my program to behave predictably in multi-threaded environment? Regards, L.Suresh.