c - How to pass a macro's result to another macro? -

i have 2 macros in c code helps me compose name of variables. example, consider following:

#define macroa(name) a_##name #define macrob(name) b_##name  void *macrob(macroa(object)); 

so, i'm trying declare variable called b_a_object. however, doesn't work , compiler throws me message:

object.c:27:21: error: parameter list without types allowed in function definition void *macrob(macroa(object));                     ^ object.c:26:26: note: expanded macro 'macrob' #define macrob(name) b_##name                          ^ 

so, seems preprocessor not taking result of macroa(object), considering expression tries make b_macroa(object). so, have make preprocessor consider result of macro passed macro?

the concatenation operator acts weird. concatenates first , evaluates later:

void *macrob(macroa(object));  // original line void *b_macroa(object);       // becomes this, nothing more expand 

you can solve way:

#define conc(a,b) ## b #define macroa(name) conc(a_, name) #define macrob(name) conc(b_, name)