stdarg宏的用法

#include 
#include 

int sum(int n_values, ...)
{
	va_list var_arg;
	int count;
	int sum = 0;

	va_start(var_arg, n_values);

	for (count = 0; count < n_values; ++count)
	{
		sum += va_arg(var_arg, int);
	}

	va_end(var_arg);

	return sum;
}

int main()
{
	printf("%d\n", sum(3, 1, 2, 3, 4, 5));
}

#include 
#include 

//求最大参数，以负数为结束标识
int max_para(int first_arg, ...)
{
	va_list var_arg;
	int max = 0;

	if (first_arg >= 0)
	{
		int this_arg = first_arg;
		max = first_arg;

		va_start(var_arg, first_arg);
		
		while ((this_arg = va_arg(var_arg, int)) >= 0)
			if (this_arg > max)
				max = this_arg;
		
		va_end(var_arg);
	}
	return max;
}

int main()
{
	printf("%d\n", max_para(10, 10, 20, 30, -1));
}

#include 
#include 

//实现printf函数，输出char和char *
void my_printf(char *format, ...)
{
	va_list arg;
	char ch;
	char *src;

	va_start(arg, format);

	while ((ch = *format++) != '\0')
	{
		if (ch != '%')
		{
			putchar(ch);
			continue;
		}

		switch(*format != '\0' ? *format++ : '\0')
		{
		/*
		case 'd':
			printf_integer(va_arg(arg, int));
			break;
		case 'f':
			printf_float(va_arg(arg, float));
			break;
		*/
		case 'c':
			putchar(va_arg(arg, char));
			break;
		case 's':
			src = va_arg(arg, char *);
			while (*src != '\0')
				putchar(*src++);
			break;
		}
	}
}

int main()
{
	my_printf("%c%c %c\n", 'A', 'B', 'C');
	my_printf("%s%s %s\n", "hello ", "world", "!");
}