Question

I want to include the result of a macro expansion. It seems include only knows <> “”?

This fails:

#define audio sinwave

#ifdef audio
#include audio".c"
/*#include "sinwave.c"*/
#endif

But this works:

#ifdef audio
        if(i==0){set_audio((char *)audio);return;}
#endif

Answer 1

You could do something like this:

#define audio audio

#define FF(X) #X
#define F(X) FF(X.c)

#ifdef audio
#include F(audio)
#endif

that is you’d have to append the .c before you place everything into a string. The usual concatenation "audio" ".c" -> "audio.c" of adjacent strings happens in a later compilation phase than preprocessing, so an #include directive cannot deal with this.