Hello, starting from line 66, I can find : #if defined(__GLIBCXX__) || (defined(__GLIBCPP__) && __GLIBCPP__>=20020514) // GCC >= 3.1.0 # define BOOST_STD_EXTENSION_NAMESPACE __gnu_cxx # define BOOST_HAS_SLIST # define BOOST_HAS_HASH # define BOOST_SLIST_HEADER <ext/slist> # if defined(__GLIBCXX__) && __GLIBCXX__ < 20071018 // GCC <= 4.3.0 # define BOOST_HASH_SET_HEADER <ext/hash_set> # define BOOST_HASH_MAP_HEADER <ext/hash_map> # else # define BOOST_HASH_SET_HEADER <backward/hash_set> # define BOOST_HASH_MAP_HEADER <backward/hash_map> # endif #endif on ubuntu 8.04 (64 bits) the 4.2.3 gcc version define __GLIBCXX__ as #define __GLIBCXX__ 20080329 so boost code prevents from using the ext headers when the backward headre do not exist (on my system)... Shouldn't the < be a > ? regards, Mathieu -- http://www.incub.net/