自定义sprintf

char *my_sprintf(int length,const char *fmt, ...)
{
	char *str = (char*)malloc(length);
	memset(str,0,length);
	va_list args; 
	va_start(args, fmt);
	_vsnprintf(str, length, fmt, args); 
	va_end(args); 
	return str;
}

//使用
char *a = my_sprintf(1000,"haha:%d",10);
if(a)
{
	printf("%s\n",a);
	free(a);
}

简单改造下也可以改成自定义printf