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

int sum(int, ...);

int main(void)
{
   printf("Sum of 10, 20 and 30 = %d\n",  sum(3, 10, 20, 30) );
   printf("Sum of 4, 20, 25 and 30 = %d\n",  sum(4, 4, 20, 25, 30) );

   return 0;
}

int sum(int num_args, ...)
{
   int val = 0;
   va_list ap; //指向参数的指针
   int i;

   va_start(ap, num_args);  //将指针ap指向最后一个确定的参数
   for(i = 0; i < num_args; i++)
   {
      val += va_arg(ap, int); //va_arg(),将指针ap指向可变参数的首地址
   }
   va_end(ap); //将指针ap赋值为NULL
 
   return val;
}