为什么kfifo.h充满#define语句 [英] Why is kfifo.h so full of #define statements

问题描述

kfifo。 ^ h 由几乎完全的#define 的。这是为什么？他们为什么没有宣布在H文件中像它的正常完成的功能。

kfifo.h is made up almost entirely of #define. Why is that? Why have they not declared the functions in the h file like its "normally" done.

好像我的问题是PTED作为实现的质疑轻易间$ P $，而不是我彪问，这是为什么实现好，从学习的角度来看。无论如何，因为我不知道我在看函数宏我投票关闭，因为它是obviosly重复。

It seems like my question is easily interpreted as a questioning of the implementation rather than what I ment to ask, why is this implementation better, from a learning standpoint. Anyway, since I didn't know I was looking at "Function-like macros" I am voting to close since it's obviosly a duplicate.

推荐答案

这是允许有很多的宏。为什么那麻烦你了？

It is permitted to have a lot of macros. Why does that trouble you?

像

 #define STRUCT_KFIFO_PTR(type) \
   struct __STRUCT_KFIFO_PTR(type, 0, type)

不是一个函数宏。

is not a function-like macro.

像

 #define kfifo_initialized(fifo) ((fifo)->kfifo.mask)

也可以用于某些任务（即使你可能不应该这样做）的左侧。它是短于相应的在线函数写

 static inline unsigned kfifo_initialezed_f(struct __kfifo *fifo) {
    return fifo->kfifo.mask;
 }

和更重要的是宏观 kfifo_initialized 将其 FIFO的几个不同的申报工作实际的参数（这是通用在一些有限的意义上）。

and more importantly the macro kfifo_initialized would work with several different declarations of its fifo actual argument (it is "generic" in some limited sense).

像

 #define __STRUCT_KFIFO(type, size, recsize, ptrtype) \
    { \
   __STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
        type    buf[((size < 2) || (size & (size - 1))) ? -1 : size]; \
    }

将扩大到申报相当于一个数组 BUF [-1] 如果给一个尺寸的 3 键，这将使编译器吆喝。 （最近的C ++标准2011还具有 static_assert 等用途）。

would expand to a declaration equivalent to an array buf[-1] if given a size of 3 and that would make the compiler yell. (The recent C++2011 standard also has static_assert for such purposes).

所以我不明白为什么你感到吃惊。在 C 的preprocessor是非常有用的（恕我直言，这甚至不够强大）。为什么要避免使用它？

So I don't understand why you are surprised. The C preprocessor is useful (IMHO it is even not powerful enough). Why avoid using it?

这是<强>免费软件;如果你不喜欢这样的源文件，你可以工作，提高它（这将需要时间）提出一个更好的解决方案。我不喜欢现在的这个。

This is free software; if you don't like that source file, you could work to improve it (and that would take time) to propose a better solution. I do like the current one.

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