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<title>例6-6</title>
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<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">#include
<iostream.h></font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">class
A</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">public:</font></p>
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<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">virtual
~A( ) { cout<<"A::~A( ) Called.\n"; }</font></p>
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<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">};</font></p>
<font SIZE="1">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"> </p>
</font>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">class
B : public A</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">public:</font></p>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">B(int
i) { buf = new char[i]; }</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">virtual
~B( )</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">delete
[] buf;</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">cout<<"B::~B(
) Called.\n";</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
</blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">private:</font></p>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">char
* buf;</font></p>
</blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">};</font></p>
<font SIZE="1">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"> </p>
</font>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">void
fun(A *a)</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{</font></p>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">delete
a;</font></p>
</blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
<font SIZE="1">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"> </p>
</font>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">void
main( )</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">{</font></p>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">A
*a = new B(15);</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">fun(a);</font></p>
</blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">}</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font LANG="ZH-CN" size="2">执行该程序输出如下结果：</font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">B::~B(
) Called.</font></p>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">A::~A(
) Called.</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font LANG="ZH-CN">当说明基类的析构函数是虚函数时，调用</font>fun(a)<font LANG="ZH-CN">函数，执行下述语句：</font></font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">delete
a;</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font LANG="ZH-CN">由于执行</font>delete<font LANG="ZH-CN">语句时自动调用析构函数，采用动态联编，调用基类的析构函数，所以输出上述结果。</font></font></p>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font size="2"><font LANG="ZH-CN">当不说明基类的析构函数为虚函数时，</font>delete<font LANG="ZH-CN">隐含着对析构函数的调用，故产生</font></font></p>
<blockquote>
<blockquote>
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"><font size="2">A::~A(
) Called.</font></p>
</blockquote>
</blockquote>
<font SIZE="3">
<p ALIGN="justify" style="line-height: 100%; margin-top: 0; margin-bottom: 0"></font><font LANG="ZH-CN" size="2">的结果。</font></p>
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