I've been seeing a problem in building MinGW version of he serializationalization library. This is related to auto-link. Now I notice that in config/compiler/gcc.hpp we've got: #if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2)) && defined(__GXX_EXPERIMENTAL_CXX0X__) # define BOOST_HAS_DECLTYPE ... # define BOOST_NO_DECLTYPE Also in another part of the same file I find: #if __GNUC__ >= 4 # if defined(_WIN32) || defined(__WIN32__) || defined(WIN32) // All Win32 development environments, including 64-bit Windows and MinGW, define // _WIN32 or one of its variant spellings. Note that Cygwin is a POSIX environment, // so does not define _WIN32 or its variants. # define BOOST_HAS_DECLSPEC In my code I use BOOST_HAS_DECLSPEC but I'm having problems with mingw. I'm not sure it has anything to do with this, but it's not at clear to me what the differing meanings are of BOOST_HAS_DECLTYPE and BOOST_HAS_DECLSPEC. Robert Ramey