blocks|key|1110279|text|这是微软对C%2B%2B语言的一个特定扩展，它允许您使用存储类信息对类型或函数进行属性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1110280|文档|1110281|__declspec+(C%2B%2B)|offset|length|1110282|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.microsoft.com/en-us/cpp/cpp/declspec^0|0|0|0|G|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

This is a Microsoft specific extension to the C++ language which allows you to attribute a type or function with storage class information. 

Documentation

<a href="https://docs.microsoft.com/en-us/cpp/cpp/declspec" rel="noreferrer">__declspec (C++)</a>

blocks|key|1325504|text|典型的例子是__declspec(dllimport)和__declspec(dllexport)，它们分别指示链接器从DLL导入符号或将符号导出到DLL。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1325505|//+header
__declspec(dllimport)+void+foo();


//+code+-+this+calls+foo()+somewhere+in+a+DLL
foo();|code-block|syntax|javascript|1325506|(__declspec(..)只是包装了微软的特定内容-为了实现兼容性，人们通常会用宏将其包装起来)|1325507|entityMap^0|6|L|S|L|0|0|1|E|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

The canonical examples are <code>__declspec(dllimport)</code> and <code>__declspec(dllexport)</code>, which instruct the linker to import and export (respectively) a symbol from or to a DLL.

<pre><code>// header
__declspec(dllimport) void foo();


// code - this calls foo() somewhere in a DLL
foo();
</code></pre>

(<code>__declspec(..)</code> just wraps up Microsoft's specific stuff - to achieve compatibility, one would usually wrap it away with macros)

blocks|key|1325573|text|本质上，这是微软引入其C%2B%2B扩展的方式，这样它们就不会与标准C%2B%2B的未来扩展冲突。使用__declspec，您可以给函数或类赋予属性；确切的含义因__declspec的性质而异。例如，线程(__declspec)(裸体)抑制prolog/epilog生成(用于中断处理程序、可嵌入代码等)，__declspec(线程)使变量成为线程本地变量，等等。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1325574|__declspec属性的完整列表在MSDN上可用，并因编译器版本和平台而异。|1325575|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Essentially, it's the way Microsoft introduces its C++ extensions so that they won't conflict with future extensions of standard C++. With __declspec, you can attribute a function or class; the exact meaning varies depending on the nature of __declspec. __declspec(naked), for example, suppresses prolog/epilog generation (for interrupt handlers, embeddable code, etc), __declspec(thread) makes a variable thread-local, and so on.

The full list of __declspec attributes is available on MSDN, and varies by compiler version and platform.

blocks|key|1325616|text|它主要用于从共享库(DLL)导入元件/将元件导出到共享库(DLL)。Visual+C%2B%2B和GCC编译器都支持__declspec(dllimport)和__declspec(dllexport)。其他用途(一些仅限微软的)是in+the+MSDN文档。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1325617|entityMap|0|LINK|mutability|MUTABLE|url|https://msdn.microsoft.com/en-us/library/dabb5z75(v=vs.140).aspx)^0|1I|L|24|L|34|B|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

It is mostly used for importing symbols from / exporting symbols to a shared library (DLL). Both Visual C++ and GCC compilers support <code>__declspec(dllimport)</code> and <code>__declspec(dllexport)</code>. Other uses (some Microsoft-only) are documented <a href="https://msdn.microsoft.com/en-us/library/dabb5z75(v=vs.140).aspx" rel="noreferrer">in the MSDN</a>.

blocks|key|1110483|text|我知道已经八年了，但我想分享在MRuby中找到的这段代码，它展示了如何在与export+keyword相同的级别上使用__declspec()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1110484|/**+Declare+a+public+MRuby+API+function.+*/
#if+defined(MRB_BUILD_AS_DLL)
#if+defined(MRB_CORE)+%7C%7C+defined(MRB_LIB)
#+define+MRB_API+__declspec(dllexport)
#else
#+define+MRB_API+__declspec(dllimport)
#endif
#else
#+define+MRB_API+extern
#endif|code-block|syntax|javascript|1110485|entityMap^0|11|E|1N|C|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

I know it's been eight years but I wanted to share this piece of code found in MRuby that shows how <code>__declspec()</code> can bee used at the same level as the <code>export keyword</code>.

<pre><code>/** Declare a public MRuby API function. */
#if defined(MRB_BUILD_AS_DLL)
#if defined(MRB_CORE) || defined(MRB_LIB)
# define MRB_API __declspec(dllexport)
#else
# define MRB_API __declspec(dllimport)
#endif
#else
# define MRB_API extern
#endif
</code></pre>

I have seen instances of <code>__declspec</code> in the code that I am reading. What is it? And when would I need to use this construct?

What is __declspec and when do I need to use it?

编译器

我在我正在阅读的代码中看到过__declspec的实例。那是什么？我什么时候需要使用这个结构呢？

问什么是__declspec ?我什么时候需要使用它？
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问什么是__declspec ?我什么时候需要使用它？
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