Christopher,
that sounds perfect.
When passing the line, i think, possible comments should be stripped to prevent problems when this line is stripped from the output. The on_illformed hook should also have a boolean return value signaling to pass the line to the output or to strip it (similar to other hooks).
Ok, I added the following preprocessing hook to Wave: /////////////////////////////////////////////////////////////////////////// // // The function 'found_unknown_directive' is called whenever an unknown // preprocessor directive was encountered. // // The parameter 'ctx' is a reference to the context object used for // instantiating the preprocessing iterators by the user. // // The parameter 'line' holds the tokens of the entire source line // containing the unknown directive. // // The parameter 'pending' may be used to push tokens back into the input // stream, which are to be used as the replacement text for the whole // line containing the unknown directive. // // The return value defines whether the given expression has been // properly interpreted by the hook function or not. If this function // returns 'false', the library will raise an 'ill_formed_directive' // preprocess_exception. Otherwise the tokens pushed back into 'pending' // are passed on to the user program. // /////////////////////////////////////////////////////////////////////////// template <typename Context, typename Container> bool found_unknown_directive(Context const& ctx, Container const& line, Container& pending) { return false; // by default we never interpret unknown directives } Depending on the settings comments are either retained or stripped _before_ invoking this hook function. For instance for a line: #version 150 core // some comment the parameter 'line' will contain the following tokens: T_POUND "#" T_IDENTIFIER "version" T_SPACE " " T_PP_NUMBER "150" T_SPACE " " T_IDENTIFIER "core" T_NEWLINE "\n" (if comments are to be stripped), or: T_POUND "#" T_IDENTIFIER "version" T_SPACE " " T_PP_NUMBER "150" T_SPACE " " T_IDENTIFIER "core" T_CPPCOMMENT "// some comment\n" if those are to be retained. A new example (custom_directives.cpp) demonstrates its usage. HTH Regards Hartmut --------------- Meet me at BoostCon www.boostcon.com