hi, i want to do the following in a win32 project, which generates a dlls. commonly there is a macro defined like this: #ifdef DLL_BUILD #define __scm_export __declspec(dllexport) #else #define __scm_export __declspec(dllimport) #endif now i have several projects which generate dlls and depend on each other like: core_lib <- graphics_lib now to do this it is needed to differenciate between dll builds. lets say with a macro CORE_DLL_BUILD and GFX_DLL_BUILD. BUT i think this is hell ;) and thought of something like this: i would like to have one macro __scm_export(lib) which decides by the lib parameter which lib is build. i tried it the following way: (code broken out of context) #include <boost/preprocessor.hpp> #include <boost/preprocessor/detail/is_nullary.hpp> #if SCM_COMPILER == SCM_COMPILER_MSVC #define __scm_export(lib) export_(BOOST_PP_EXPAND(BOOST_PP_CAT(SCM_BUILD_LIBRARY_, lib))) #define export_(lib) BOOST_PP_IF(BOOST_PP_IS_NULLARY(lib), __declspec(dllexport), __declspec(dllimport)) #define __scm_private(lib) #else #pragma error "unsupported compiler" #endif this way i only have to define something like /DSCM_BUILD_LIBRARY_core=() for the core project and /DSCM_BUILD_LIBRARY_ogl=() for the graphics library and use __scm_export(ogl) and __scm_export(core) in the particular libraries. this works perfectly, BUT i am searching for a more elegant way to do this, because i do not like the definition of a unary macro for the projects. i would like more to define it this way: /DSCM_BUILD_LIBRARY=core and /DSCM_BUILD_LIBRARY=ogl for the libs. i experimented with BOOST_PP_IIF and so on, but the problem is if these macros are presented with an undefined macro (like when i use the one lib in the other) they do not use the false alternative and insert a lengthy macro. after a long night i came up with the BOOST_PP_IS_NULLARY workaround, but as is said i do not think is is a very good solution. dies anyone have suggestions how to solve this on a more elegant way? Thanks -chris -- Christopher Lux | | Bauhaus University Weimar | Faculty of Media - Virtual Reality Systems Group