in ffi/primitives/primitives_library/primitives.c [47:58]
int multi_sum(int nr_count, ...)
{
va_list nums;
va_start(nums, nr_count);
int sum = 0;
for (int i = 0; i < nr_count; i++)
{
sum += va_arg(nums, int);
}
va_end(nums);
return sum;
}