可變參數宏__VA_ARGS__

宏定義使用可變參數，使用起來方便多了。具體看msdn例子：

Support for variadic macros was introduced in Visual C++ 2005.

// variadic_macros.cpp
#include <stdio.h>
#define EMPTY

#define CHECK1(x, ...) if (!(x)) { printf(__VA_ARGS__); }
#define CHECK2(x, ...) if ((x)) { printf(__VA_ARGS__); }
#define CHECK3(...) { printf(__VA_ARGS__); }
#define MACRO(s, ...) printf(s, __VA_ARGS__)

int main() {
   CHECK1(0, "here %s %s %s", "are", "some", "varargs1(1)\n");
   CHECK1(1, "here %s %s %s", "are", "some", "varargs1(2)\n");   // won't print

   CHECK2(0, "here %s %s %s", "are", "some", "varargs2(3)\n");   // won't print
   CHECK2(1, "here %s %s %s", "are", "some", "varargs2(4)\n");

   // always invokes printf in the macro
   CHECK3("here %s %s %s", "are", "some", "varargs3(5)\n");

   MACRO("hello, world\n");
   // MACRO("error\n", EMPTY);   would cause C2059
}
  
here are some varargs1(1)
here are some varargs2(4)
here are some varargs3(5)
hello, world