blocks|key|897457|text|它不能，超出了B.cpp的作用域。编译器在每个编译单元的基础上操作，即它单独编译每个.cpp文件，所以如果它编译C.cpp，它将没有getA()的代码可用，并且需要执行函数调用并让链接器修复它(或者，如果它真的通过单词并尝试内联，它将以链接器错误结束。inline具有与static相似的特性)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|897458|唯一的例外是LTCG，即链接时代码生成，它在较新的编译器上可用。|897459|在这种情况下，一种方法是使用包含内联代码的另一个头文件(有时名为*.inl文件)。|897460|编辑:至于哪个内联是相关的-它是类定义中的内联，也就是头文件中的那个。请记住，许多编译器都有自己的想法，即什么可以内联，什么应该内联。例如，gcc可以完全禁用内联(-O0)，或者它可以内联任何它认为值得内联的东西(比如-O3)。|897461|entityMap^0|3I|6|3R|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|U|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|M|$]]

It can't, outside the scope of B.cpp. The compiler operates on a per-compile-unit base, i.e. it compiles each .cpp file individually, so if it compiles C.cpp, it won't have the code for getA() available and will need to perform a function call and have the linker fix it up (or, if it really took you by the word and tried to inline, it will have end up with a linker error. <code>inline</code> has similar qualities as <code>static</code>).

The only exception is LTCG, i.e. link-time code generation, which is available on newer compilers.

One approach in this case is to have another header file (sometimes named *.inl files) that contain the inlined code.

EDIT: As for which inline is relevant - it's the one in the class definition, i.e. in the header file. Keep in mind that many compilers have their own mind on what can and should be inlined. gcc for example can disable inlining completely (-O0), or it can inline anything that it deems worth inlining (like -O3).

blocks|key|897512|text|如今，大多数编译器都可以在链接时和编译时执行内联。如果您的函数可能从内联中受益，那么链接时间优化器很可能会这样做。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|897513|当链接器到达它的时候，编译器输出的内联状态就不多了，除了编译器将某些对象标记为可收集之外，例如，因为内联函数或类模板实例出现在多个编译单元中，或者当多个符号共享一个名称时，它应该引发错误，例如main函数被定义了两次。所有这些都不会影响它将生成的实际代码。|897514|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|$]]

These days, most compilers can perform inlining at link time, as well as compile time. If your function is likely to benefit from inlining, then the Link Time optimizer is likely to do just that.

By the time the linker gets to it, not much about the inline status of compiler output is available, except that the compiler will flag certain objects as being collectible, for instance because an inline function or class template instance appears in multiple compilation units, or it should raise an error when multiple symbols share a name, such as the main function being defined twice. None of this has influence on the actual code it will generate.

blocks|key|1112380|text|我会从相反的方向做这件事。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1112381|不要给你的函数添加内联声明(除非你也需要)。|1112382|只有在头文件中但在类声明之外定义函数时，才需要将内联声明添加到函数/方法中。|1112383|X.h|1112384|class+X
{
++++public:
++++++++int+getX()+++{+return+4;}+//+No+inline+because+it+is+part+of+the+class.
++++++++++++++++++++++++++++++++++//+The+compiler+knows+that+needs+an+inline+tag
++++++++int+getY();
++++++++int+getZ();
};

inline
int+X::getY()++{+return+5;}+++++++//+This+needs+to+be+explicitly+declared+inline.
++++++++++++++++++++++++++++++++++//+Otherwise+the+linker+will+complain+about
++++++++++++++++++++++++++++++++++//+multiple+definitions+in+compilation+units.|code-block|syntax|javascript|1112385|X.cpp|1112386|+//+Never+declare+anything+inline+in+the+cpp+file.

+int+X::getZ()+{+return+6;+}|1112387|给你更具体的例子。|1112388|删除所有内联规范。他们没有做你认为他们正在做的事情。|1112389|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Y|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|J|7|12|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|14|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

I would go about this from the opposite direction.
Don't add inline declarations to your function (unless you need too).
The only time you need to add the inline declaration to a function/method is if you define the function in a header file but outside the class declaration.
<h3>X.h</h3>
<pre><code>class X
{
 public:
 int getX() { return 4;} // No inline because it is part of the class.
 // The compiler knows that needs an inline tag
 int getY();
 int getZ();
};

inline
int X::getY() { return 5;} // This needs to be explicitly declared inline.
 // Otherwise the linker will complain about
 // multiple definitions in compilation units.
</code></pre>
<h3>X.cpp</h3>
<pre><code> // Never declare anything inline in the cpp file.

 int X::getZ() { return 6; }
</code></pre>
To you more specific case. 
Remove all the inline specifications. They are not doing what you think they are doing.

blocks|key|1112421|text|这是我做的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1112422|文件A.h|1112423|#pragma+once
#include+"B.h"

class+A+{
++++B+b;
};|code-block|syntax|javascript|1112424|文件B.h|1112425|#pragma+once

class+B+{
public:
++++template<class+T>+inline+T+getA()+{
++++++++assert(NULL);+//+Use+'getA<A>()'+template+specialization+only!
++++++++return+NULL;
++++}
};

class+A;+//+Forward+declaration
template<>+inline+A+B::getA<A>();|1112426|文件C.h|1112427|#pragma+once
#include+"A.h"
#include+"B.h"

//+Implement+template+specialization+here!
template<>+inline+A+B::getA<A>()+{+return+A();+}|1112428|只需包含"C.h“文件即可使用getA()方法。原始代码的唯一变化是必须将getA()方法定义为公共而不是私有。|1112429|然而，正如你们中的许多人解释的那样，这并不是真正有用的。|1112430|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|14|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

Here is the way I did it.

File A.h

<pre><code>#pragma once
#include "B.h"

class A {
 B b;
};
</code></pre>

File B.h

<pre><code>#pragma once

class B {
public:
 template&lt;class T&gt; inline T getA() {
 assert(NULL); // Use 'getA&lt;A&gt;()' template specialization only!
 return NULL;
 }
};

class A; // Forward declaration
template&lt;&gt; inline A B::getA&lt;A&gt;();
</code></pre>

File C.h

<pre><code>#pragma once
#include "A.h"
#include "B.h"

// Implement template specialization here!
template&lt;&gt; inline A B::getA&lt;A&gt;() { return A(); }
</code></pre>

Just include the "C.h" file to be able to use getA() method. The only change with the original code is that the getA() method must be defined as public instead of private.

However, as many of you explained it, this is not really useful.

I know that inline member functions by definition should go into the header. But what if it's not possible to put the implementation of the function into the header? Let's take this situation:

File A.h

<pre><code>#pragma once
#include "B.h"

class A{
 B b;
};
</code></pre>

File B.h

<pre><code>#pragma once

class A; //forward declaration

class B{
 inline A getA();
};
</code></pre>

Due to the circular include I have to put the implementation of <code>getA</code> into

B.cpp

<pre><code>#include "B.h"
#include "A.h"

inline A B::getA(){
 return A();
}
</code></pre>

Will the compiler inline <code>getA</code>? If so, which inline keyword is the significant one (the one in the header or the one in the .cpp file)? Is there another way to put the definition of an inline member function into its .cpp file?

C++ inline member function in .cpp file

编译器

我知道根据定义，内联成员函数应该放在头中。但是，如果无法将函数的实现放入头文件中，该怎么办？让我们来看看这种情况：文件A.h#pragma once#include "B.h"class A{    B b;};文件B.h#pragma onceclass A; //forward declarationclass B...

问.cpp文件中的C++内联成员函数
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