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📄 [c++对象模型][7]单继承与虚函数表 - itech's blog - 博客园.htm

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style="COLOR: #008000"><BR></SPAN><SPAN 
style="COLOR: #000000"><BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;f3(){cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #800000">B::f3</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;}&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">virtual</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;v3(){cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #800000">B::v3</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;}<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN 
style="COLOR: #000000">&nbsp;y;<BR>};<BR><BR></SPAN><SPAN 
style="COLOR: #0000ff">class</SPAN><SPAN 
style="COLOR: #000000">&nbsp;C&nbsp;:&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">public</SPAN><SPAN 
style="COLOR: #000000">&nbsp;B<BR>{<BR></SPAN><SPAN 
style="COLOR: #0000ff">public</SPAN><SPAN 
style="COLOR: #000000">:<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;f3(){cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #800000">C::f3</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;}&nbsp;</SPAN><SPAN 
style="COLOR: #008000">//</SPAN><SPAN 
style="COLOR: #008000">&nbsp;覆盖</SPAN><SPAN 
style="COLOR: #008000"><BR></SPAN><SPAN 
style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;v1(){cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #800000">C::v1</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;}&nbsp;</SPAN><SPAN 
style="COLOR: #008000">//</SPAN><SPAN 
style="COLOR: #008000">&nbsp;重写</SPAN><SPAN 
style="COLOR: #008000"><BR></SPAN><SPAN 
style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;v3(){cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #800000">C::v3</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;}&nbsp;</SPAN><SPAN 
style="COLOR: #008000">//</SPAN><SPAN 
style="COLOR: #008000">&nbsp;重写</SPAN><SPAN 
style="COLOR: #008000"><BR></SPAN><SPAN 
style="COLOR: #000000">&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN 
style="COLOR: #000000">&nbsp;z;<BR>};</SPAN><SPAN 
style="COLOR: #000000"></SPAN><SPAN style="COLOR: #0000ff"><BR></SPAN><SPAN 
style="COLOR: #000000"></SPAN></SPAN></DIV>
<P>&nbsp;</P>
<P>2）类图：</P>
<P><IMG 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/2009022722083661.png"></P>
<P>&nbsp;</P>
<P>3）VS2008的编译选项查看布局：</P>
<P><IMG 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/2009022722105825.png"></P>
<P>&nbsp;</P>
<P>4）可视化表示：</P>
<P><IMG height=287 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/2009022722240651.png" 
width=560></P>
<P>&nbsp;</P>
<P>5）代码验证：</P>
<DIV class=cnblogs_code><IMG id=Code_Closed_Image_221141 style="DISPLAY: none" 
onclick="this.style.display='none'; document.getElementById('Code_Closed_Text_221141').style.display='none'; document.getElementById('Code_Open_Image_221141').style.display='inline'; document.getElementById('Code_Open_Text_221141').style.display='inline';" 
height=16 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/ContractedBlock.gif" 
width=11 align=top><IMG id=Code_Open_Image_221141 
onclick="this.style.display='none'; document.getElementById('Code_Open_Text_221141').style.display='none'; getElementById('Code_Closed_Image_221141').style.display='inline'; getElementById('Code_Closed_Text_221141').style.display='inline';" 
height=16 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/ExpandedBlockStart.gif" 
width=11 align=top><SPAN class=cnblogs_code_Collapse 
id=Code_Closed_Text_221141>Code</SPAN><SPAN id=Code_Open_Text_221141><BR><!--<br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--><SPAN 
style="COLOR: #0000ff"></SPAN></SPAN><SPAN id=Code_Open_Text_220734><SPAN 
style="COLOR: #000000">typedef&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;(</SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">Fun)();<BR><BR></SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;PrintVTable(A&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">pA)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">pVT&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">&nbsp;(</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">)</SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">(</SPAN><SPAN style="COLOR: #0000ff">int</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">)(pA);<BR>&nbsp;&nbsp;&nbsp;&nbsp;Fun</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">&nbsp;pF&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;(Fun</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">)(pVT&nbsp;</SPAN><SPAN 
style="COLOR: #000000">+</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #800080">0</SPAN><SPAN 
style="COLOR: #000000">);<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN 
style="COLOR: #000000">&nbsp;iLength&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #800080">0</SPAN><SPAN 
style="COLOR: #000000">;<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">while</SPAN><SPAN style="COLOR: #000000">(</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000">pF&nbsp;</SPAN><SPAN 
style="COLOR: #000000">!=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;NULL)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">pF)();<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #000000">++</SPAN><SPAN 
style="COLOR: #000000">iLength;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;pF&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;(Fun</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">)(pVT&nbsp;</SPAN><SPAN 
style="COLOR: #000000">+</SPAN><SPAN 
style="COLOR: #000000">&nbsp;iLength);<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR>}<BR></SPAN><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;PrintMembers(A&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">pA)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000">p&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">&nbsp;(</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">)(pA);<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">int</SPAN><SPAN 
style="COLOR: #000000">&nbsp;i&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #800080">1</SPAN><SPAN 
style="COLOR: #000000">;<BR>&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">while</SPAN><SPAN 
style="COLOR: #000000">(i&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800080">3</SPAN><SPAN 
style="COLOR: #000000">)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN 
style="COLOR: #000000">(p</SPAN><SPAN style="COLOR: #000000">+</SPAN><SPAN 
style="COLOR: #000000">i)&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;i</SPAN><SPAN 
style="COLOR: #000000">++</SPAN><SPAN 
style="COLOR: #000000">;<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR>}<BR></SPAN></SPAN><SPAN 
id=Code_Open_Text_221141><SPAN style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;TestVT()<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;A&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000">pA&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">new</SPAN><SPAN 
style="COLOR: #000000">&nbsp;C();<BR>&nbsp;&nbsp;&nbsp;&nbsp;C&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000">pC&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;dynamic_cast</SPAN><SPAN 
style="COLOR: #000000">&lt;</SPAN><SPAN style="COLOR: #000000">C</SPAN><SPAN 
style="COLOR: #000000">*&gt;</SPAN><SPAN 
style="COLOR: #000000">(pA);<BR>&nbsp;&nbsp;&nbsp;&nbsp;pC</SPAN><SPAN 
style="COLOR: #000000">-&gt;</SPAN><SPAN 
style="COLOR: #000000">x&nbsp;</SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800080">10</SPAN><SPAN 
style="COLOR: #000000">;<BR>&nbsp;&nbsp;&nbsp;&nbsp;pC</SPAN><SPAN 
style="COLOR: #000000">-&gt;</SPAN><SPAN 
style="COLOR: #000000">y&nbsp;</SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800080">20</SPAN><SPAN 
style="COLOR: #000000">;<BR>&nbsp;&nbsp;&nbsp;&nbsp;pC</SPAN><SPAN 
style="COLOR: #000000">-&gt;</SPAN><SPAN 
style="COLOR: #000000">z&nbsp;</SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800080">30</SPAN><SPAN 
style="COLOR: #000000">;<BR>&nbsp;&nbsp;&nbsp;&nbsp;PrintVTable(pA);<BR>&nbsp;&nbsp;&nbsp;&nbsp;PrintMembers(pA);<BR>&nbsp;&nbsp;&nbsp;&nbsp;delete&nbsp;pA;<BR>}</SPAN></SPAN></DIV>
<P>&nbsp;</P>
<P>6）验证代码运行结果：</P>
<P><IMG 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/2009022722265758.png"></P>
<P>&nbsp;</P>
<P>7）总结：</P>
<P><SPAN style="COLOR: #ff0000">单继承的对象的布局，第一个为虚函数表指针vtbl，</SPAN><SPAN 
style="COLOR: #ff0000">其后为成员且先基类后子类，</SPAN><SPAN 
style="COLOR: #ff0000">虚函数表里包含了所有的虚函数的地址，</SPAN><SPAN 
style="COLOR: #ff0000">以NULL结束。</SPAN><SPAN 
style="COLOR: #ff0000">虚函数如果子类有重写，就由子类的重新的代替。</SPAN></P>
<P>二 单继承运行时类型转化</P>
<P>1）代码验证：</P>
<DIV class=cnblogs_code><IMG id=Code_Closed_Image_093106 style="DISPLAY: none" 
onclick="this.style.display='none'; document.getElementById('Code_Closed_Text_093106').style.display='none'; document.getElementById('Code_Open_Image_093106').style.display='inline'; document.getElementById('Code_Open_Text_093106').style.display='inline';" 
height=16 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/ContractedBlock.gif" 
width=11 align=top><IMG id=Code_Open_Image_093106 
onclick="this.style.display='none'; document.getElementById('Code_Open_Text_093106').style.display='none'; getElementById('Code_Closed_Image_093106').style.display='inline'; getElementById('Code_Closed_Text_093106').style.display='inline';" 
height=16 
src="[C++对象模型][7]单继承与虚函数表 - iTech's Blog - 博客园.files/ExpandedBlockStart.gif" 
width=11 align=top><SPAN class=cnblogs_code_Collapse 
id=Code_Closed_Text_093106>Code</SPAN><SPAN id=Code_Open_Text_093106><BR><!--<br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--><SPAN 
style="COLOR: #0000ff">void</SPAN><SPAN 
style="COLOR: #000000">&nbsp;TestDynamicCast()<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;A&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000">pA&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #0000ff">new</SPAN><SPAN 
style="COLOR: #000000">&nbsp;C();<BR>&nbsp;&nbsp;&nbsp;&nbsp;cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #800000">A:</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;pA&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;endl;<BR>&nbsp;&nbsp;&nbsp;&nbsp;B&nbsp;</SPAN><SPAN 
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000">pB&nbsp;</SPAN><SPAN 
style="COLOR: #000000">=</SPAN><SPAN 
style="COLOR: #000000">&nbsp;dynamic_cast</SPAN><SPAN 
style="COLOR: #000000">&lt;</SPAN><SPAN style="COLOR: #000000">B</SPAN><SPAN 
style="COLOR: #000000">*&gt;</SPAN><SPAN 
style="COLOR: #000000">(pA);<BR>&nbsp;&nbsp;&nbsp;&nbsp;cout&nbsp;</SPAN><SPAN 
style="COLOR: #000000">&lt;&lt;</SPAN><SPAN 
style="COLOR: #000000">&nbsp;</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
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