如何解决与&QUOT可变参数宏的相关问题;宏观超载"在MSVC ++(Microsoft Visual Studio)中?

问题描述

受这种解决方案的启发，我编写了下面的代码，用于模拟宏的重载" .

Inspired from this kind of solution, I have written below code, which simulates "overloading of macros".

#include<iostream>

#define CONCATE_(X,Y) X##Y
#define CONCATE(X,Y) CONCATE_(X,Y)
#define UNIQUE(NAME) CONCATE(NAME, __LINE__)

#define NUM_ARGS_(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, TOTAL, ...) TOTAL
#define NUM_ARGS(...) NUM_ARGS_(__VA_ARGS__, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1)
#define VA_MACRO(MACRO, ...) CONCATE(MACRO, NUM_ARGS(__VA_ARGS__))(__VA_ARGS__)

#define COUT(...) VA_MACRO(_COUT, __VA_ARGS__)
#define _COUT1(X) std::cout << "1 argument\n"
#define _COUT2(X, Y) std::cout << "2 arguments\n"
#define _COUT3(X, Y, Z) std::cout << "3 arguments\n"

int main ()
{
  COUT("A");
  COUT("A", 1);
  COUT("A", 1, 'a');
  return 0;
}

此工作正常以g ++/铛++编译器，给下面的输出:

This works fine in g++/clang++ compilers, giving below output:

1 argument
2 arguments
3 arguments

然而，它没有给出预期输出最新MSVC(2017)由于与已知的编译器故障:

However it doesn't give the expected output for latest MSVC (2017) due to known compiler bug related to __VA_ARGS__:

1 argument
1 argument
1 argument

我尝试过各种间接扩张"的组合，基于以下职位，但没有运气:点击视觉工作室__VA_ARGS__问题

I tried various "indirect expansions" combinations, based on below post, but no luck:
Visual studio __VA_ARGS__ issue

如何解决这个问题的MSVC?

How to fix this issue in MSVC?

推荐答案

我对MSVC错误的了解不是很丰富，除了知道它存在之外，但我能够在其他答案中应用替代方法如下:

I'm not very experienced with the MSVC bug other than knowing it exists, but I was able to apply the workaround in the other answer as follows:

#define MSVC_BUG(MACRO, ARGS) MACRO ARGS  // name to remind that bug fix is due to MSVC :-)

#define NUM_ARGS_2(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, TOTAL, ...) TOTAL
#define NUM_ARGS_1(...) MSVC_BUG(NUM_ARGS_2, (__VA_ARGS__))
#define NUM_ARGS(...) NUM_ARGS_1(__VA_ARGS__, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1)
#define VA_MACRO(MACRO, ...) MSVC_BUG(CONCATE, (MACRO, NUM_ARGS(__VA_ARGS__)))(__VA_ARGS__)

此也产生最新的GCC和锵适当预处理器输出.它不会让我感到吃惊地得知，有一种方法可以解决此而不调用宏间接扩张"两次，但我没有找到它.

This also produces appropriate preprocessor output on the latest GCC and Clang. It would not surprise me to learn that there's a way to work around this without calling MSVC_BUG macro for "indirect expansion" twice, but I didn't find it.

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