출처 : http://www.comeaucomputing.com/techtalk/c99/#variadicmacros

가변인자를 사용하는 매크로 함수를 만드는 방법...

Support for Variadic macros is now available. Consider:

#include <stdio.h>

// In C89/90, you need multiple macros with "funny" names to do this.
// Anyway, in this example, the arguments passed (those represented
// by the ...) replace the __VA_ARGS__ when the substitution occurs.
#define DoLogFile(...) fprintf(stderr, __VA_ARGS__)

// Variadic macros also help out if you want to effectively
// pass one argument  that contains commas
#define MakeName(...)  #__VA_ARGS__

// Of course, the macro can also take other args, so long as
// the ... is last
#define output(FILEptr, ...) fprintf(FILEptr, __VA_ARGS__)

// This is not right, since this is NOT a variadic macro
#define mac(arg) foo(arg, __VA_ARGS__)

int main()
{
    int bound = 99;
    int current_index = 88;
    int linenumber = 77;

    DoLogFile("Detected array out of bounds\n");
    DoLogFile("Bound = %d, current index =%d\n", bound, current_index);
    DoLogFile("Missing semicolon on line %d\n", linenumber);
    output(stderr, "Detected array out of bounds\n");

    char *p;
    p = MakeName(Mary);
    p = MakeName(Doe, John);
    p = MakeName(Martin Luther King, Jr.);
    // Combo two variadic macros
    DoLogFile("MakeName=%s\n", MakeName(This is a test, yes it is));
}

가변인자를 사용하는 매크로 함수를 이용하면, 손쉽게 디버깅용 함수를 만들어 사용할 수 있다.