Variadic argument usage (C99)

[wispy spade]

I wish to implement the following functionality:

int main() {
    struct LeBigInt *x, *multiplicand, *addend;

    /* Pointers are allocated and used here */

    lbi_free(x, multiplicand, addend, result);
}

Looking at the varargs example on cppreference:

#include <stdio.h>
#include <stdarg.h>
 
int add_nums_C99(int count, ...)
{
    int result = 0;
    va_list args;
    va_start(args, count); // count can be omitted since C23
 
    for (int i = 0; i < count; ++i) {
        result += va_arg(args, int);
    }
 
    va_end(args);
    return result;
}
 
int main(void)
{
    printf("%d\n", add_nums_C99(4, 25, 25, 50, 50));
}

I'm having trouble figuring out how to use the va_* functions provided to write a function that does not require passing in the number of arguments as the first argument.

[solemn vine]

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[proper hinge]

pretty sure you cannot do it without knowing how many arguments you have

the whole point of variadic arguments is that the number of arguments is sorta unknown

you have to deduce it from the input somehow (e.g. for printf it just calls va_arg for every format specifier)

[pseudo sundial]

you just can't :(. you need a way to know how many arguments you have. you can use macros but its not gonna be any useful for your example

[proper hinge]

i saw some cursed variadic macro abuse to count arguments somewhere but its probably not ideal

[pseudo sundial]

yeah I was gonna suggest that

@wispy spade
I think this might help you

#include <stdio.h>
#include <stdarg.h>

#define add_nums(...) \
    _add_nums_C99(sizeof((int[]){__VA_ARGS__})/sizeof(int), __VA_ARGS__)

int _add_nums_C99(int count, ...)
{
    int result = 0;
    va_list args;
    va_start(args, count); // count can be omitted since C23, btw
 
    for (int i = 0; i < count; ++i) {
        result += va_arg(args, int);
    }
 
    va_end(args);
    return result;
}
 
int main(void)
{
    printf("%d\n", add_nums(25, 25, 50, 50));
}

you need to keep in mind that the argument that you're gonna pass to add_nums macros have to known at compile time

[proper hinge]

they're trying to use it for freeing multiple things

so not sure if that's gonna work

[pseudo sundial]

only if those pointers they are going to pass is is known at compile time

like just how many of them

[wispy spade]

Intriguing trick, thanks for the help

Though for the sake of clarity I've decided to just free the pointers one by one

instead of trying to be clever