应该preprocessor指令是某一行的开始？ [英] Should preprocessor instructions be on the beginning of a line?

问题描述

前段时间我发现一个（而古）C编译器，它扫描宏这样（伪code）：

A while ago I have discovered an (rather ancient) C Compiler, which scanned macros this way (Pseudo code):

 if line.startswith("#include") or line.startswith("#define"):
     ...

..哪位好心的提出，其中宏应该被放置在一行的开始，像这样对我的问题是：

.. Which kind of raised the question for me where macros should really be placed, at the beginning of a line, like so:

void stuff()
{
#if defined(WIN32) || defined(_WIN32)
    ...
#else
#if defined(__GNUC__)
    ...
#else
    ...
#endif
#endif
}

或者说像这样（因为这是我做的，为了提高可读性的方式）：

Or rather like so (as that's the way I do it, for improved readability):

void stuff()
{
    #if defined(WIN32) || defined(_WIN32)
    ...
    #else
    #   if defined(__GNUC__)
    ...
    #   else
    ...
    #   endif
    #endif
}

是一个缩进preprocessor ​​code标准化的方式，那就是，无论我怎么缩进它，它总是会以同样的方式？

Is the way one indents the Preprocessor code standardized, that is, no matter how i indent it, it will always work the same way?

推荐答案

需要一些旧的C编译器的的#define （例如）与左边距齐平：

Some old C compilers required that the #define (for example) be flush with the left margin:

#define FOO bar

规定的其他C编译器只有在＃处于左边距，所以，你可以：

Other C compilers required only that the # be at the left margin, so you could:

#    define FOO bar

较新的C编译器倾向于接受＃任何前导空格后：

    #define FOO bar

如果你想用这种老的编译器的兼容性，你至少应该把你的＃中的第一列。如果兼容性并不重要，那么它给你。

If you want compatibility with such older compilers, you should at least put your # in the first column. If compatibility doesn't matter, then it's up to you.

我通常会尽量不嵌入 #IFDEF 块内部的功能，所以是否应缩进大多是整个问题就会消失。

I would usually try not to embed #ifdef blocks inside functions, so the whole question of whether they should be indented mostly goes away.

这篇关于应该preprocessor指令是某一行的开始？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！