csdn_文档中心_c++中的内部连接与外部连接(二).htm
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</SPAN><SPAN style="mso-spacerun: yes">
</SPAN><SPAN
style="mso-tab-count: 1">
</SPAN>int k;<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 1">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>};<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 1">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN><o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 1">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>struct D<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 1">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>{<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 1">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN><SPAN
style="mso-tab-count: 1">
</SPAN>int d;<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 1">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>};<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在这个例子中，</SPAN><SPAN
lang=EN-US>main.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">与</SPAN><SPAN
lang=EN-US>a.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中都有</SPAN><SPAN
lang=EN-US>class B</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和</SPAN><SPAN
lang=EN-US>class D</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">的定义，但在编译这两个</SPAN><SPAN
lang=EN-US>cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">文件时并不发生</SPAN><SPAN
lang=EN-US>link</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">错误。</SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN: 0cm 0cm 0pt; tab-stops: 45.0pt"><FONT size=3><SPAN
lang=EN-US><SPAN
style="mso-tab-count: 1">
</SPAN>2.</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类的非</SPAN><SPAN
lang=EN-US>inline</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">成员函数</SPAN><SPAN
lang=EN-US>(</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">一般，静态，虚拟都是</SPAN><SPAN
lang=EN-US>)</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">总有外部连接，这样当你</SPAN><SPAN
lang=EN-US>include</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">了某个类的头文件，使用这个类的函数时，就能连接到正确的类成员函数上，继续以上面为例子，如果把</SPAN><SPAN
lang=EN-US>a.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中的</SPAN><SPAN
lang=EN-US>struct D</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">改为</SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes"> </SPAN><SPAN
style="COLOR: green"><SPAN
style="mso-spacerun: yes"> </SPAN>struct D<SPAN
style="mso-tab-count: 2">
</SPAN><SPAN
style="mso-tab-count: 2">
</SPAN>//</SPAN></SPAN><SPAN
style="COLOR: green; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类定义</SPAN><SPAN
lang=EN-US style="COLOR: green"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>{<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes"> </SPAN>int
d;<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US style="COLOR: green"><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>void foo();<SPAN
style="mso-tab-count: 1"> </SPAN><SPAN
style="mso-tab-count: 2">
</SPAN>//</SPAN><SPAN
style="COLOR: green; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类成员函数声明</SPAN><SPAN
lang=EN-US style="COLOR: green"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>};<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US style="COLOR: green"><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes"> </SPAN>void
D::foo()<SPAN
style="mso-tab-count: 2">
</SPAN><SPAN
style="mso-tab-count: 1">
</SPAN>//</SPAN><SPAN
style="COLOR: green; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类成员函数定义，外部连接</SPAN><SPAN
lang=EN-US style="COLOR: green"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>{<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>cout << " D::foo in a.cpp"
<<endl;<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN>}<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN
lang=EN-US><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US><SPAN
style="mso-tab-count: 1">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">这时</SPAN><SPAN
lang=EN-US>main.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">与</SPAN><SPAN
lang=EN-US>a.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中的</SPAN><SPAN
lang=EN-US>D::foo</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">都有外部连接，在连接就会出现</SPAN><SPAN
lang=EN-US>multiply defined symbols</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">错。</SPAN>
</FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>3.</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类的静态数据成员有外部连接，如上例的</SPAN><SPAN
lang=EN-US>B::s_i,</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">这样当你在</SPAN><SPAN
lang=EN-US>main.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">中定义了类静态数据成员，其它编译单元若使用了</SPAN><SPAN
lang=EN-US>B::s_i,</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">就会连接到</SPAN><SPAN
lang=EN-US>main.cpp</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">对应编译单元的</SPAN><SPAN
lang=EN-US>s_i</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。</SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN
lang=EN-US><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="mso-spacerun: yes">
</SPAN></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US><SPAN
style="mso-tab-count: 1">
</SPAN><B>d)inline</B></SPAN><B><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">函数总有内部连接，不论这个函数是什么函数</SPAN><SPAN
lang=EN-US><o:p></o:p></SPAN></B></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN
lang=EN-US><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><SPAN style="COLOR: green">//
main.cpp<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN><o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US style="COLOR: green"><SPAN
style="mso-tab-count: 2">
</SPAN>inline int foo() { return 1;}<SPAN
style="mso-tab-count: 2">
</SPAN>//inline</SPAN><SPAN
style="COLOR: green; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">全局函数，内部连接</SPAN><SPAN
lang=EN-US style="COLOR: green"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US style="COLOR: green"><SPAN
style="mso-tab-count: 2">
</SPAN>class Bar<SPAN
style="mso-tab-count: 3">
</SPAN><SPAN
style="mso-tab-count: 3">
</SPAN>//</SPAN><SPAN
style="COLOR: green; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">类定义，内部连接</SPAN><SPAN
lang=EN-US style="COLOR: green"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN>{<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-US
style="COLOR: green"><FONT size=3><SPAN
style="mso-tab-count: 2">
</SPAN>public:<o:p></o:p></FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><FONT size=3><SPAN
lang=EN-US style="COLOR: green"><SPAN
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