Empty function macros

Question

If I define a function macro with no actual body, is it like an empty string with the compiler (i.e. It doesn't generate any extra instructions at compile time)?

Example:

#define SomeMacro(a)  SomeMacro("hello"); // This line doesn't add any instructions, does it? 

Answer 1

You're absolutely correct, the empty macro doesn't generate any code.

I've seen two places where this is useful. The first is to eliminate warnings when a function parameter isn't used:

#define UNUSED(x)  int foo(int UNUSED(value)) {     return 42; } 

The second is when you use conditionals to determine if there should be code or not.

#ifdef LOGGING_ENABLED #define LOG(x) log_message(x) #else #define LOG(x) #endif