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<div class=Section1>
<h3><span lang=EN-US>92. </span><span style='font-family:宋体;mso-ascii-font-family:
Arial;mso-hansi-font-family:Arial'>避免使用</span><span class=SpellE><span
lang=EN-US>reinterpret_cast</span></span><span style='font-family:宋体;
mso-ascii-font-family:Arial;mso-hansi-font-family:Arial'>。</span></h3>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><b style='mso-bidi-font-weight:
normal'><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>摘要</span><span lang=EN-US><o:p></o:p></span></b></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>谎言不会持久（德国和罗马尼亚谚语）：不要用</span><span
class=SpellE><span lang=EN-US>reinterpret_cast</span></span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>来强制编译器把某种类型的对象解释成另一种不同类型的对象。这和维持类型安全性是对立的，尤其是对</span><span
class=SpellE><span lang=EN-US>reinterpret_cast</span></span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>到底能做什么甚至都无法保证。</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><b style='mso-bidi-font-weight:
normal'><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>讨论</span><span lang=EN-US><o:p></o:p></span></b></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>再次提醒：如果你对编译器撒谎，那么编译器会报复你的。——</span><span
lang=EN-US>Henry Spencer</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span class=SpellE><span
lang=EN-US>reinterpret_cast</span></span><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>反映了程序员对对象的数据表示方式所能做出的最强的假定，也就是说程序员比编译器知道得更清楚，并打定主意不使用编译器精心维护的类型信息。如果你让编译器闭嘴，那么它就会闭嘴，但是强行这么做应该只是不得已的手段。应该避免对数据的表示方式做任何的假设，因为这样的假设在极大程度上影响了代码的安全性和可靠性。</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>除此之外，事实上</span><span
class=SpellE><span lang=EN-US>reinterpret_cast</span></span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>的结果比重新解释对象的位模式（这已经够糟糕的了）更糟糕。除了一些一定可逆的转换，</span><span
class=SpellE><span lang=EN-US>reinterpret_cast</span></span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>的结果是由编译器的实现来定义的，因此你没法知道编译器到底会不会这样做。它是不可靠也是不可移植的。</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><b style='mso-bidi-font-weight:
normal'><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>例外</span><span lang=EN-US><o:p></o:p></span></b></p>
<p class=MsoNormal style='tab-stops:162.0pt'><b style='mso-bidi-font-weight:
normal'><span lang=EN-US><o:p> </o:p></span></b></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>在一些与系统相关的底层编程中，你可能被迫用</span><span
class=SpellE><span lang=EN-US>reinterpret_cast</span></span><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>在端口输入和输出数据，或者把整数转换为地址。尽量少用不安全的强制类型转换，把它们抽象出来，只在一些隐藏得比较好的函数中使用，这样只需很少的改动，代码就能够移植到其它平台。如果需要在不相关的指针类型间进行强制类型转换，尽量对</span><span
lang=EN-US>void*</span><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>进行强制转换而不要直接用</span><span class=SpellE><span
lang=EN-US>reinterpret_cast</span></span><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>。也就是说，用下面的代码</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:36.0pt;tab-stops:162.0pt'><span
lang=EN-US>T1* p1 = <span class=GramE>... ;</span></span></p>
<p class=MsoNormal style='margin-left:36.0pt;tab-stops:162.0pt'><span
class=GramE><span lang=EN-US>void</span></span><span lang=EN-US>* <span
class=SpellE>pV</span> = p1;</span></p>
<p class=MsoNormal style='margin-left:36.0pt;tab-stops:162.0pt'><span
lang=EN-US>T2* p2 = <span class=SpellE>static_cast</span><T2*<span
class=GramE>>(</span> <span class=SpellE>pV</span> );</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span style='font-family:宋体;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>代替</span></p>
<p class=MsoNormal style='tab-stops:162.0pt'><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:36.0pt;tab-stops:162.0pt'><span
lang=EN-US>T1* p1 = <span class=GramE>... ;</span></span></p>
<p class=MsoNormal style='margin-left:36.0pt;tab-stops:162.0pt'><span
lang=EN-US>T2* p2 = <span class=SpellE>reinterpret_cast</span><T2*<span
class=GramE>>(</span> p1 );</span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
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