c++ - Cascaded macros in gcc C++14 vs msvc++ 2015 -

i have following code working under msvc 2015:

#define class_js_psg_property_ex(property, value) \ static bool get##property(/*irrelevant params here...*/) \ { \ ...  particular code ...     return true; \ }  #define class_js_psg_property(value) \ class_js_psg_property_ex(##value, value)  ...  #define kprop 1  class_js_psg_property_ex(version, kprop)  class_js_psg_property(kprop) 

this should define methods named getversion , getkprop.

now, gives following error under gcc c++14 (actually tdm-gcc-64):

pasting "(" , "kprop" not give valid preprocessing token

how should written in order compile under gcc c++14 , msvc 2015?

the trick - if don't want name expanded macro, must pass ## operator right away - result of concatenation must valid token. this:

#include <iostream>  #define class_js_psg_property_ex_helper(getname) \ static bool getname() { return true; }   #define class_js_psg_property_ex(property, value) \ class_js_psg_property_ex_helper(get##property)  #define class_js_psg_property(value) \ class_js_psg_property_ex_helper(get##value)   #define kprop 1  class_js_psg_property_ex(version, kprop)  class_js_psg_property(kprop)  int main() {     std::cout << getversion() + getkprop(); } 

works gcc , msvc

the reason original code appears work msvc because msvc preprocessor famously non-conforming - operates on stream of characters (wrong), rather stream of tokens (right). in class_js_psg_property_ex(##value, value), ## not unary operator suggest - it's binary operator glues ( , value single token (value. not valid preprocessing token, program ill-formed, gcc complains about. msvc preprocessor later breaks nonsensical token pieces (which conforming preprocessor never do).