Hartmut, thanks for your help, but this issue is still alive ;) Just to be sure I did everything right, I took the entire head revision of boost and compiled it. I had no problems in the relevant libs. I also saw your changes in the cpp_context.hpp. The only problems I still get compiler errors using the flexi_string as described before. May usage scenario: token_type::string_type str("some string"); if(ctx.is_defined_macro(str)) { ... } There is still the iterator derefernece compiler error in the cpp_macromap.hpp: e:\boost\include\boost-1_35\boost\wave\util\cpp_macromap.hpp(396) : error C2228: left of '.get_value' must have class/struct/union type is 'const char' e:\boost\include\boost-1_35\boost\wave\cpp_context.hpp(198) : see reference to function template instantiation 'bool boost::wave::util::macromap<ContextT>::is_defined<const char*>(const IteratorT &,const IteratorT &)' being compiled with [ ContextT=boost::wave::context<token_groups::str_iter_type,token_groups::lex_iter_type>, IteratorT=const char * ] e:\projects\inpecting_wave\inpecting_wave\header_processor.cpp(178) : see reference to function template instantiation 'bool boost::wave::context<IteratorT,LexIteratorT>::is_defined_macro<boost::wave::cpplexer::lex_token<>::string_type>(const StringT &)' being compiled with [ IteratorT=token_groups::str_iter_type, LexIteratorT=token_groups::lex_iter_type, StringT=boost::wave::cpplexer::lex_token<>::string_type ] e:\boost\include\boost-1_35\boost\wave\util\cpp_macromap.hpp(396) : error C2228: left of '.c_str' must have class/struct/union the line: string_type name ((*it).get_value().c_str()); Still tries to call get_value on const char type. With Kind Regards, Ovanes