Jonathan Turkanis wrote:
When I compile the following simple program on VC6:
#include <boost/preprocessor/facilities/empty.hpp> #include <boost/preprocessor/punctuation/comma_if.hpp>
#define PARAM(has_param) BOOST_PP_IF(has_param, typename Param, BOOST_PP_EMPTY()) #define MACRO(has_param) \ template< PARAM(has_param) BOOST_PP_COMMA_IF(has_param) typename T> \ struct name { }; \ /**/
MACRO(0)
int main() { return 0; }
I get the following warnings:
warning C4003: not enough actual parameters for macro 'BOOST_PP_IIF' warning C4003: not enough actual parameters for macro 'BOOST_PP_IIF_I' warning C4003: not enough actual parameters for macro 'BOOST_PP_IIF_0'
It works fine on other compilers.
Am I missusing the preprocessor library, or is this a problem with VC6? If the latter, is there a workaround, or should I just turn off warning 4003?
BOOST_PP_EMPTY() evaluates to nothing, so I would think that VC6 is actually right. I'm probably wrong though, I'm no PP guru. ;) Anyway, I think you should do: #define PARAM(has_param) BOOST_PP_IF( \ has_param \ , BOOST_PP_IDENTITY(typename Param) \ , BOOST_PP_EMPTY)() HTH, -- Daniel Wallin