Variable Arity in C?

Question

Does anyone knows how I might be able to implement variable arity for functions in C?

For example, a summing function:

Sum(1,2,3,4...); (Takes in a variable

Answer 1

If all aditional arguments are of the same type, you could also pass an array instead of using variadic macros.

With C99 compound literals and some macro magic, this can look quite nice:

#include 

#define sum(...) \
    sum_(sizeof ((int []){ __VA_ARGS__ }) / sizeof (int), (int []){ __VA_ARGS__ })

int sum_(size_t count, int values[])
{
    int s = 0;
    while(count--) s += values[count];
    return s;
}

int main(void)
{
    printf("%i", sum(1, 2, 3));
}