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;
}