C语言 可变参数 （初始化OC数组最后的nil的由来）

////  main.m//  sentinel////  Created by Sinosoft on 9/17/13.//  Copyright (c) 2013 com.Sinosoft. All rights reserved.//#import <Foundation/Foundation.h>#import <stdarg.h>void printStrings(char *first,...) __attribute__((sentinel));void printString(char *first,...){    va_list args;    va_start(args, first);    char *string = first;    while (string != NULL) {        printf("%s",string);        string = va_arg(args, char *);    }    va_end(args);    printf("\n");}int addemUp(int firstNum,...){    va_list args;    int sum = firstNum;    int number;        va_start(args, firstNum);    while (1) {        number = va_arg(args, int);        sum += number;        if (number == 0) {            break;        }    }    va_end(args);    return sum;    }int main(int argc, const char * argv[]){    @autoreleasepool {                char* str = "";        if (str == NULL) {            NSLog(@"dashi");        }        else        {            NSLog(@"aaa");        }                int sumbody = addemUp(1,2,3,4,5,6,7,8,9,0);                printf("sum of 1-9 is %d\n",sumbody);        //        printStrings("spicy","pony","head", NULL);//        //        printString("machine","tool");            }    return 0;}