C/C++ #define Macro inside macro?

Question

I would like something like:

#define C_OR_CPP(C__, CPP__) #ifdef __cplusplus\\
CPP__\\
#else\\
C__\\
#endif

Is it possible? Maybe some dirt

Answer 1

Not in C++. But you can

#ifdef __cplusplus
# define CPP
#else
# define C
#endif

I assume this is just a pathological example by you. Note also that double underscore is reserved to library implementors (see 17.6.4.3.2 Global names).

vector, but in C i want it to simply be void, you know.

So, what speaks against a solution like

struct Foo {
  #ifdef __cplusplus
  ...
  #else
  ...
  #endif
};

or what speaks against providing different APIs for different programming languages?