C, variadic functions and stdarg.h

Question

I found this code on the codegolf.stackexchange site.

#include <stdio.h>
#define function int
#define var int
struct { int (*log)(const char *,...); } console = { printf };

/* From here on only JavaScript! */

function fac(x){
    if(x < 2) return 1;
    return x * fac(x - 1);
}

function main(){
    console.log("Hello world!\n");

    for(var i = 0; i < 10; i++){
        console.log("%i! = %i\n", i, fac(i));
    }

    return 0;
}

// *Should* we export the main function of this library??/
exports.main = main;

My question is, how is he able to run variadic function without including stdarg.h?

Joseph · Accepted Answer · 2014-03-25 22:06:07Z

4

Because he is not manipulating the ... parameter, but simply passing pointer to a function which internally manipulates the ... parameter, which in the case is printf:

int __cdecl printf(const char *_Format, ...);

Note: not all compilers support the __cdecl calling convention.

Aswell, the macros he has defined are pointless and should not be used under any circumstance, as it is not C.

edited Mar 25, 2014 at 22:06

answered Mar 25, 2014 at 22:00

Joseph

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