有没有办法在可变参数宏参数上使用 C++ 预处理器字符串化? [英] Is there a way to use C++ preprocessor stringification on variadic macro arguments?

问题描述

我猜这个问题的答案是否定的，但如果有办法就太好了.为了澄清，假设我有以下宏:

My guess is the answer to this question is no, but it would be awesome if there was a way. To clarify, assume I have the following macro:

#define MY_VARIADIC_MACRO(X...) // Does some stuff here in the macro definition

我想做的是在将 X 的所有变量传递给可变参数函数之前以某种方式对其进行字符串化；这里的关键字是之前.我意识到无法从宏定义中真正访问各个参数，但是有没有办法将所有参数字符串化，可能类似于以下内容?

What I would like to do is somehow perform stringification on all the variables of X before passing it to a variadic function; the keyword here is before. I realize there's no way to really access the individual arguments from within the macro definition, but is there a way to stringify all the arguments, with maybe something like the following?

#define MY_VARIADIC_MACRO(X...) some_variadic_function("some string", #X)

推荐答案

好吧，我不是想在这里回答我自己的问题，但我想出了一个不错的解决方案，有点像 Mark Wilkins 的组合答案和我在问题中给出的例子.

Okay, I didn't mean to answer my own question here, but I've come up with a decent solution that is somewhat of a combination of Mark Wilkins answer and the example I gave in the question.

可以对整个可变参数集进行字符串化，然后在字符串中包含分隔逗号.这是一个简单的例子:

It is possible to stringify the entire set variadic set, which then includes the delimiting commas in the string. Here's a quick example:

#define MY_VARIADIC_MACRO(X...) printf(#X)

使用上面的宏表明传递给宏的整个参数集都被字符串化了.

Using the above macro shows you that the entire set of arguments passed to the macro gets stringified.

然后您可以定义一个函数来使用分隔逗号对这些参数进行标记，从而通过使用可变参数宏获得一组标记的字符串:

Then you can then define a function to tokenize these arguments using the delimiting comma, thereby getting the set of tokenized strings by using the variadic macro:

#define MY_VARIADIC_MACRO(X...) tokenize_my_arguments(#X)

然后实际上不再依赖于让可变参数宏调用可变参数函数，我可以很好地遍历我的常量 C 字符串数组，而不是遍历 va_arg.

Then there's actually no longer the dependency of having the variadic macro call a variadic function and I can iterate nicely through my array of constant C strings rather than iterating through va_arg.

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根据 Tim 的评论，这里是解决方案的详细信息.请原谅任何错误，因为它是匆忙完成的，我不得不从我正在做的事情中移植过来.此外，它并不意味着是复制/粘贴解决方案，因为它只输出参数的字符串化来演示 POC，但应该足以演示功能.

Per Tim's comment, here's the details of the solution. Please forgive any errors since it was done in haste and I had to port from what I'm working on. Also, it's not meant to be copy/paste solution since it only outputs the stringification of the arguments to demonstrate POC, but should be sufficient enough to demonstrate the functionality.

虽然这个解决方案需要一些运行时计算，可变参数宏经常调用可变参数函数并且需要通过 va_args 进行迭代，因此迭代发生在寻找令牌的过程中，尽管可能会牺牲一些性能.然而，为了可维护性、通用性和易于实施，这似乎是目前最好的选择:

Although this solution requires some run time computation, variadic macros often times call variadic functions and requires iterating through va_args, so the iteration takes place in finding the tokens, although a bit of performance is probably sacrificed. However, for maintainability, versatility, and ease of implementation, this seems to be the best option at the moment:

#define VARIADIC_STRINGIFY(_ARGUMENTS_TO_STRINGIFY...) Variadic_Stringification_Without_Variadic_Function(#_ARGUMENTS_TO_STRINGIFY)

void Variadic_Stringification_Without_Variadic_Function (const char* _stringified_arguments)
{
    strcpy(converted_arguments, _stringified_arguments);

    for(char* token = strtok(converted_arguments, ","); token != 0x0; token = strtok(0x0, ","))
        std::cout << token << std::endl;
}

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