C-可变参数宏，它扩展为每个参数上的一组宏调用 [英] C - Variadic macro which expands into set of macro calls on each argument

问题描述

我想要一个带有多个函数指针的宏调用，并且每个函数指针都由第二个宏调用，这是一个函数声明.

I want to have a single macro call which takes in multiple function pointers, and each function pointer is called by a second macro which is a function declaration.

我想要表格上的两个宏

#define FUNCTION_DEF(func) extern int func(void);
#define FUNCTION_DEFS(...) (???)

如此称呼

FUNCTION_DEFS(
    myFunc1,
    myFunc2,

    otherFunc1,
    otherFunc2,

    defaultFunc
)

扩展为

FUNCTION_DEF(myFunc1)
FUNCTION_DEF(myFunc2)

FUNCTION_DEF(otherFunc1)
FUNCTION_DEF(otherFunc2)

FUNCTION_DEF(defaultFunc)

换句话说，对FUNCTION_DEFS的单次调用扩展为所有可变参数的函数声明.

In other words, this single call to FUNCTION_DEFS expands into function declarations of all the variadic arguments.

当前，我只是跳过第一步，并在每个函数指针上调用FUNCTION_DEF，但是对此的解决方案将是不错的.

Currently I'm just skipping the first step and calling FUNCTION_DEF on each function pointer, however a solution to this would be great.

这可能吗?

感谢@Vality将我介绍给X-Macro.我发现这篇文章"在现实世界中使用X-Macros "正是我所需要的.

Thanks to @Vality for introducing me to X-Macro. I found this post "Real-world use of X-Macros" which was exactly what I needed.

推荐答案

我不相信使用标准C预处理程序可以实现您想要的精确功能.但是，使用X宏可以实现类似的解决方案.

I do not believe what you want precisely is possible using the standard C preprocessor. However a similar solution can be accomplished with X macros.

要使用它们等效于您的代码，您首先需要将函数列表定义为X宏:

To do the equivalent of your code using them you would first define the function list as an X macro:

#define FUNCTION_LIST_A \
    X(myFunc1) \
    X(myFunc2) \
    X(otherFunc1) \
    X(otherFunc2) \
    X(defaultFunc)

然后使用特定的宏实例化这些功能，然后定义要在每个功能上执行的宏:

Then to instantiate these functions with a specific macro you would then define the macro to perform on each function:

#define X(name) FUNCTION_DEF(name)
FUNCTION_LIST_A
#undef X

然后将其扩展为:

FUNCTION_DEF(myFunc1)
FUNCTION_DEF(myFunc2)
FUNCTION_DEF(otherFunc1)
FUNCTION_DEF(otherFunc2)
FUNCTION_DEF(defaultFunc)

希望这是有用的并且接近您想要的.诚然，语法有很大不同，但是如果您要完成的工作是将选定的函数或宏应用于整个数据列表(在这种情况下为函数指针)，这是我所知使用c预处理器的最惯用的方式

Hopefully this is useful and close to what you want. Admittedly the syntax is significantly different but if what you wish to accomplish is to apply a chosen function or macro to a whole list of data (in this case function pointers) this is the most idiomatic way I know of to do so using the c preprocessor.

这篇关于C-可变参数宏，它扩展为每个参数上的一组宏调用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！