Boost.Python's sources only deal with GCC's "-fvisibility=hidden" option for versions [3.5 - 3.9]. It should also work properly when built with GCC 4 and higher. The attached patches to boost/python/detail/config.hpp and boost/python/module_init.hpp enable it to do so. Tested with GCC 4.0 (XCode 2.2) on OSX 10.4.3 (Tiger). -- Jason Kankiewicz Advanced Publishing Technology, Inc. Index: boost/python/detail/config.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/python/detail/config.hpp,v retrieving revision 1.37 diff -u -r1.37 config.hpp --- boost/python/detail/config.hpp 29 Nov 2004 21:32:14 -0000 1.37 +++ boost/python/detail/config.hpp 29 Nov 2005 20:29:13 -0000 @@ -67,9 +67,8 @@ #endif #if defined(BOOST_PYTHON_DYNAMIC_LIB) - -# if !defined(_WIN32) && !defined(__CYGWIN__) \ - && defined(__GNUC__) && __GNUC__ >= 3 && __GNUC_MINOR__ >=5 \ +# if !defined(_WIN32) && !defined(__CYGWIN__) \ + && defined(__GNUC__) && ((__GNUC__ >= 3 && __GNUC_MINOR__ >=5) || __GNUC__ >= 4) \ && !defined(BOOST_PYTHON_GCC_SYMBOL_VISIBILITY) # define BOOST_PYTHON_USE_GCC_SYMBOL_VISIBILITY # endif Index: boost/python/module_init.hpp =================================================================== RCS file: /cvsroot/boost/boost/boost/python/module_init.hpp,v retrieving revision 1.6 diff -u -r1.6 module_init.hpp --- boost/python/module_init.hpp 20 Sep 2004 12:47:31 -0000 1.6 +++ boost/python/module_init.hpp 29 Nov 2005 20:29:13 -0000 @@ -42,7 +42,7 @@ } \ void init_module_##name() -# elif (defined(__GNUC__) && __GNUC__ >= 3 && __GNUC_MINOR__ >=5) +# elif (defined(__GNUC__) && ((__GNUC__ >= 3 && __GNUC_MINOR__ >=5) || __GNUC__ >= 4)) # define BOOST_PYTHON_MODULE_INIT(name) \ void init_module_##name(); \