Hi I have a win32 static library with a class like this : typedef boost::function TimerCallbackType; class TimerManager { public: int addTimer(int interval, TimerCallbackType callback); }; I use this lib in a Win32 exe, but it crashed on calling TimerManager::addTimer(), the error is: "Run-time check failure #0 - The value of ESP was not properly saved across a function call ... ". Both the exe and lib are compiled with "Struct Alignment" set to "4 Bytes". Finally, I find out a way make it work -- include the boost like this : #pragma pack(push,8) #include #pragma pop() But, I don't know why? Could anybody here help to clear this question? I'm using MS Viusal C++ 2005. Thanks! -- Neil.Fang.CN