宏和 Visual C++

发布于 2024-07-14 17:38:03 字数 1265 浏览 4 评论 0原文

我试图更好地了解宏在现代 C++ 和 Visual C++ 中的位置（如果有），同时参考 Windows 编程库：宏在解决什么问题（如果有）这些情况如果不使用它们就无法解决？

我记得从这篇博文，它们也用在 MFC 中 - 这是该博客文章中的宏示例，如果可能的话，我想详细解释一下：

// CWindowImpl
BEGIN_MSG_MAP(Edit)
  MSG_WM_CHAR(OnChar)
  MSG_WM_CONTEXTMENU(OnContextMenu)
  MSG_WM_COPY(OnCopy)
  MSG_WM_CUT(OnCut)
  MESSAGE_HANDLER_EX(WM_IME_COMPOSITION, OnImeComposition)
  MSG_WM_KEYDOWN(OnKeyDown)
  MSG_WM_LBUTTONDBLCLK(OnLButtonDblClk)
  MSG_WM_LBUTTONDOWN(OnLButtonDown)
  MSG_WM_LBUTTONUP(OnLButtonUp)
  MSG_WM_MBUTTONDOWN(OnNonLButtonDown)
  MSG_WM_MOUSEMOVE(OnMouseMove)
  MSG_WM_MOUSELEAVE(OnMouseLeave)
  MSG_WM_NCCALCSIZE(OnNCCalcSize)
  MSG_WM_NCPAINT(OnNCPaint)
  MSG_WM_RBUTTONDOWN(OnNonLButtonDown)
  MSG_WM_PASTE(OnPaste)
  MSG_WM_SYSCHAR(OnSysChar)  // WM_SYSxxx == WM_xxx with ALT down
  MSG_WM_SYSKEYDOWN(OnKeyDown)
END_MSG_MAP()

我已阅读这些 MSDN 上与宏有关的文章，但我也尝试获取编写或避免宏以及在何处/何时使用宏的最佳实践他们。

原文

I'm trying to get a better understanding of what place (if any) Macros have in modern C++ and Visual C++, also with reference to Windows programming libraries: What problem (if any) do Macros solve in these situations that cannot be solved without using them?

I remember reading about Google Chrome's use of WTL for Macros (amonst other things) from this blog post, and they are also used in MFC - here is an example of a Macro from that blog post I'd like explained in a superb amount of detail if possible:

// CWindowImpl
BEGIN_MSG_MAP(Edit)
  MSG_WM_CHAR(OnChar)
  MSG_WM_CONTEXTMENU(OnContextMenu)
  MSG_WM_COPY(OnCopy)
  MSG_WM_CUT(OnCut)
  MESSAGE_HANDLER_EX(WM_IME_COMPOSITION, OnImeComposition)
  MSG_WM_KEYDOWN(OnKeyDown)
  MSG_WM_LBUTTONDBLCLK(OnLButtonDblClk)
  MSG_WM_LBUTTONDOWN(OnLButtonDown)
  MSG_WM_LBUTTONUP(OnLButtonUp)
  MSG_WM_MBUTTONDOWN(OnNonLButtonDown)
  MSG_WM_MOUSEMOVE(OnMouseMove)
  MSG_WM_MOUSELEAVE(OnMouseLeave)
  MSG_WM_NCCALCSIZE(OnNCCalcSize)
  MSG_WM_NCPAINT(OnNCPaint)
  MSG_WM_RBUTTONDOWN(OnNonLButtonDown)
  MSG_WM_PASTE(OnPaste)
  MSG_WM_SYSCHAR(OnSysChar)  // WM_SYSxxx == WM_xxx with ALT down
  MSG_WM_SYSKEYDOWN(OnKeyDown)
END_MSG_MAP()

I've read these articles to do with Macros on MSDN but am trying to also pick up best practices for writing or avoiding Macros and where/when to use them.

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夜空下最亮的亮点 2024-07-21 17:38:03

所有这些宏都在公共 sdk 头文件中定义，因此您可以根据需要自行阅读它们的作用。基本上，这里发生的是使用宏生成 WndProc 函数。每个 MSG_WM_* 条目都是一个 case 语句，它通过将其参数从 wParam 和 lParam 转换为其原始类型并调用将这些类型作为参数的辅助函数（然后您可以实现）来处理给定的窗口消息（如果合适的话 -有些窗口消息有 0 或 1 个参数）。

在我看来，这一切都是垃圾。您需要权衡必须预先编写一堆样板，但作为交换，您会使以后的调试变得更加困难。宏在我的现代编程世界中没有太多地位，除了检查它们是否已定义之外。进行流量控制的宏，或者假设总是定义特定的局部变量等，让我很不高兴。特别是当我必须调试它们时。

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╰◇生如夏花灿烂 2024-07-21 17:38:03

Peter，你不妨问 vi 还是 EMACS 是更好的编辑器。（顺便说一句，EMACS。）很多人认为 C 预处理器是一个可怕的想法；事实上，C 预处理器是一个非常糟糕的想法。斯特鲁斯特鲁普和吉姆·高斯林就是其中之一。这就是为什么 Java 没有预处理器，并且 Stroustrup 在 C++ 中放入了无数的东西，从 const 到模板，以避免使用预处理器。

还有其他人发现添加新语言很方便，就像在该代码中一样。

如果您阅读原始的 Bourne shell 代码，您会发现它看起来像

IF a == b THEN
   do_something();
   do_more();
ELSE
   do_less();
FI

Steve Bourne 基本上使用宏来赋予它类似 Algol68 的外观（当时这就是真正酷的语言。）对于任何人来说，使用它都可能非常困难，但史蒂夫·伯恩。

然后看一下混淆 C 竞赛，其中一些最令人惊奇的混淆利用了 #define。

就我个人而言，我不太介意，尽管这个例子有点令人畏惧（你如何调试它？）但是做这种事情是在没有网络的情况下进行的；那里没有多少瓦伦达。

Peter, you might as well ask if vi or EMACS is the better editor. (EMACS, by the way.) There are a lot of people who think the C preprocessor is a horrible idea; Stroustrup and Jim Gosling among them. That's why Java has no preprocessor, and there are innumerable things Stroustrup put into C++, from const to templates, to avoid using the preprocessor.

There are other people who find it convenient to be able to add a new language, as in that code.

If you read the original Bourne shell code, you'll find it looks like

IF a == b THEN
   do_something();
   do_more();
ELSE
   do_less();
FI

Steve Bourne basically used macros to give it an Algol68-like look (that being the Really Cool Language then.) It could be very difficult to work with for anyone but Steve Bourne.

Then have a look at the Obfuscated C contest, where some of the most amazing obfuscations take advantage of the #define.

Personally, I don't mind too much, although that example is a little daunting (how do you debug that?) But doing that kind of thing is working without a net; there aren't many Wallendas out there.

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