2020年NT Insider：开放系统资源的最新计算机科学专刊

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《NT Insider》是由OSR Open Systems Resources, Inc.出版的一份专业计算机科学期刊，专注于操作系统研究和资源分享。这份月刊在2020年9月至10月期间发行，版权属于OSR公司，地址位于美国新罕布什尔州曼彻斯特市。联系可以通过电话+1.603.595.6500或邮件NtInsider@osr.com进行交流。该期刊的编辑团队由Peter G. Viscarola（咨询合伙人）、Scott Noone（工程合伙人）和Daniel D. Root（执行编辑）组成，同时OSR员工也作为贡献编辑参与内容创作。单期订阅价格为15美元，强调所有内容受2020年OSR版权保护，未经书面许可，不得复制或使用其中任何部分。《NT Insider》欢迎读者的评论和未公开的手稿提交，但保留编辑权，并拥有独家发表的权利。对于刊载的内容，杂志明确表示，所有提及的商标均为其各自所有者的所有物，例如"OSR"、"OSR Online"以及OSR公司的企业标识都是注册商标。该期刊旨在提供最新的技术规格、论文、设计图纸和手册等资源，确保信息的准确性和可靠性，以满足IT专业人士的需求。读者可以在www.osr.com网站上获取更多关于最新技术和趋势的深度分析和讨论。在阅读过程中，如果遇到法律规定的限制或有任何疑问，应遵循OSR的指导原则。整体而言，《NT Insider》是IT领域内一个重要的学习和交流平台，对于那些追求深入理解和行业动态的读者来说，它是一份不可或缺的资源。

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The NT Insider Sep - Oct 2020 © OSR Open Systems Resources, Inc.

have long held that C++ sucks, and that it sucks really, really, badly. I have been so very vocal about this over the past 20 or so

years, that almost anyone who’s been involved in Windows driver development and has read NTDEV even a lile has seen me

hold forth on this topic.

I am not alone in this belief. In fact, no lesser beings than Mr. Penguin Pants and Elon Musk agree with me. Ken Thompson and

Rob Pike apparently also agree.

But… I like to think that I’ve changed some over the years.

And over me C++ has very much changed. Versions of C++

before C++ 11 are very dierent from versions of C++ since.

We now have a type of C++ that’s generally referred to as

“Modern C++” – If you’re new to this concept, there’s quite a

nice descripon on MSDN.

I have, somewhat reluctantly due to the extreme level of my

previous vociferousness, concluded that maybe there are

some features of Modern C++ that aren’t so bad. In fact, I

think there are some features that even the most

enthusiasc C Language programmer might nd both useful

and (more importantly) helpful in building quality into

Windows drivers.

In this arcle, I’ll describe a few of the C++ features that we

regularly use at OSR in driver development. You’ll see we’re not enrely “bought in” to the world of C++; But, as C++ has evolved

and we’ve evolved, we’ve come a long way from our previous posion which was “If you put any C++ code in one of our drivers,

you will be hanged, drawn and quartered.”

Limitaons on C++ in Windows Drivers

Before we begin, I should probably note that there are many good and useful things in Modern C++ that cannot be used in kernel-

mode. This is because in Windows kernel-mode does not support C++ excepon handling. C++ excepon handling is enrely

dierent from our customary kernel-mode Structured Excepon Handling. As a result of this limitaon, most parts of the C++

Standard Library (std) are o limits, including some of the most pleasant and useful features such as Containers (std::vector, for

example) and string handling. This also means that you can’t use ATL or STL – both of which are prey much superseded by std

anyhow. Unless, that is, you’re using ATL for wring COM programs. And if you are, well… I’m sorry.

So, having menoned some cool stu that we can’t use, let’s have a look at ve of our favorite C++ constructs that do work in

Windows kernel-mode drivers.

#1: Strong Type Checking

Yes, I realize that this isn’t a Modern C++ innovaon. But it’s sll a massive advantage of C++ over plain old C. There can be lile

disagreement that strong type checking, which is inherent in C++, is a good thing. Over the past million or so years that I’ve been

in this business, I’ve inherited numerous drivers that were inially wrien (usually by clients) in “pure” C. And I can truthfully say

that I have never, not once, failed to nd a meaningful type error when I’ve renamed those les with CPP extensions and rebuilt

them. I think that’s a good enough argument for strong type checking’s value.

#2: constexpr instead of #dene

I hope there’s nobody le in the world who doesn’t think that the use of preprocessor macros in C/C++ is, at best, “problemac.”

By way of review: Good old #dene performs a textual substuon at compile me. This can lead to all sorts of unintenonal

problems, given that there’s no type safety in a #dene, arguments passed into the #dene can get evaluated mulple mes, and

more. I’m not saying you should never use #dene. I’m just saying you should use it when no other tool in your toolbox will do.

(CONTINUED ON PAGE 7)

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Usually constexpr can be used as a direct replacement for “simple”

#denes, such as when you dene bitmasks and register bit paerns.

The primary dierence in this case is that constexpr has a type. Visual

Studio will even suggest that you change your basic #denes to

constexpr and will oer to do the conversion for you (Figure 1).

The only disadvantage I see to leng VS have its way with your code

here, is that it uses auto for the type… which may not be what you want

(Figure 2).

I, personally, much prefer to specify the type myself. Aer all, I know

how/when/where I’m going to use the denion (Figure 3).

You can/should also use constexpr in place of many of your “funcon

like” #dene macros. For example, the classic macro shown in Figure 4,

is quite easily converted to a constexpr. This lets you replace the macro

with the equivalent of a funcon, the result of which is available at

compile me. Though VS won’t suggest this conversion with cute lile

dots, it will do the conversion for you if you ask it to. It will go out of its

way to use type auto, including templang the data types of any

arguments – picture me rolling my eyes here. I say just assign the

arguments a specic type and be done with it (Figure 5). Let’s agree to

delay our argument about whether and when auto is a good or bad

thing unl later in this arcle.

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(CONTINUED ON PAGE 8)

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Figure 1—Visual Studio Suggests

Figure 2—VS Fixes… with auto as the type

Figure 3—I’m not a fan of auto in this case

Figure 4—Ripe for conversion to constexpr

Figure 5—Now constant at compile me

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