Macro with function parameter which calls the function

Question

I need a macro which simply calls the function which is passed as parameter to that macro. The function is void type with no parameter.

For example, if I have the following function:

void function(void) {
//doSomething
}

I need a macro, APPLY_FUNCTION which is called with the function parameter and simply calls that function:

APPLY_FUNCTION(function);

I've tried to define the macro like:

#define APPLY_FUNCTION(function)    (function)

But it does not work, when I try to call the macro I am getting a "statement with no effect" error.

The question is how should I define that macro?

What's the point of having this macro? Why not simply call the function? — Jabberwocky
This might be an XY problem. Indeed, such a macro would be completely useless. But "Apply" rings a bell, are you trying to implement the Apply HOF? This won't work with a macro. — user2371524

Jabberwocky Jabberwocky · Accepted Answer · 2018-05-02T13:39:42

You probably want this:

#include <stdio.h>

#define APPLY_FUNCTION(functionname) functionname()

void function(void) {
  printf("Function called\n");
}

int main()
{
  APPLY_FUNCTION(function);
}

Output:

Function called

With your definition:

#define APPLY_FUNCTION(function)   (function)

The preprocessor generates following line:

(function);

This is syntaxically correct, but it doesn't call the function, hence the warning.

BTW: you should call the macro rather CALL_FUNCTION. You don't apply a function, you call it.

Macro with function parameter which calls the function

2 Answers