C/C++学习----第四章内存分配及其管理

偏执的太偏执、 2022-09-17 15:29 36阅读 0赞

**第四章 内存分配及其管理**

**4.1 存储**

在C和C++中，有三种基本的存储使用区：

**4.1.1静态存储区（Static Memory）**

在静态存储区中，连接器（ linker）根据程序的需求为对象分配空间。 **全局变量、静态类成员以及函数中的静态变量都被分配在该区域中**。一个在该区域中分配的对象只被构造一次，其生存期一直维持到程序结束。在程序运行的时候其中的地址是固定不变的。在使用线程（thread,共享地址空间的并发物）的程序里，静态对象可能会引起一些问题，因为这时的静态对象是被共享的，要对其正常访问就需要进行锁定操作。

**4.1.2自动存储区（Automatic Memory）**

**函数的参数和局部变量**被分配在此。对同一个函数或区块的每一处调用，其在该区域内都有自己单独的位置。这种存储被自动创建和销毁；因而才叫做“自动存储区”。自动存储区也被称为是“在 **栈**上的（ be on the stack）”。

**4.1.3自由存储区（Free Store）**

在该区域中， **程序必须明确的为对象申请空间，并可以在使用完毕之后释放申请到的空间**（使用 new和delete运算符）。当程序需要其中更多的空间时，就使用new向操作系统提出申请。通常情况下，自由存储区（也被称作动态存储区或者 **堆**（heap））在一个程序的生存期内是不断增大的，因为其间被其它程序占用的空间从来都不被归还给操作系统。例如：

**4.2 new和delete的使用**

在C/C++中，允许在用户程序执行时动态的为对象分配存储。在C中，使用malloc（）或calloc（）、realloc()、free（）来动态的分配、释放存储空间；在C++中，使用new()、delete()来动态的分配、释放存储空间。C++中的new()与C中的malloc（）相比，有以下两个优点：

<1>new（）自动返回正确的指针类型，不需要对返回指针进行类型转换。

int  \* p  =  new int \[ 20 \];

<2> new（）可以将创建的对象初始化。

int  \* p  =  new int(20);

释放内存时，无论是由malloc（）还是由new一次性分配的内存空间，必须一次性释放。该内存块可以是n个连续的自定义struct空间或n个连续基本类型空间。

<3>函数中分配内存

如果非得要用指针参数去申请内存，那么应该改用“指向指针的指针”，如下所示

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      void GetMemory2(char **p, int num) 
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    <div style="MARGIN-LEFT: 21.25pt">
      { 
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    <div style="MARGIN-LEFT: 21.25pt">
      &nbsp;&nbsp;&nbsp; *p = 
     <span style="FONT-SIZE: 11pt; COLOR: black">new </span>char[sizeof(char) * num]; 
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      } 
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      void Test2(void) 
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      { 
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      &nbsp;&nbsp;&nbsp; char *str = NULL; 
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      &nbsp;&nbsp;&nbsp; GetMemory2(&amp;str, 100);&nbsp;// 注意参数是 &amp;str，而不是str 
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      &nbsp;&nbsp;&nbsp; strcpy(str, "hello");&nbsp;&nbsp; 
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      &nbsp;&nbsp;&nbsp; cout&lt;&lt; str &lt;&lt; endl; 
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      &nbsp;&nbsp;&nbsp; free(str);&nbsp; 
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      } 
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使用 new创建对象数组时，不能对各个对象进行初始化。对对象数组中的每一个对象进行初始化有以下两个方法：

<1>定义专门函数来完成初始化（如下表右）；

<2>在类中增加不带参数的构造函数来初始化（如下表左）。

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    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">class</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> { </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">public</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">:</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">ox</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">oy</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt; TEXT-INDENT: 22pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">();</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">};</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point::point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">ox</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">oy</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">){ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">ox</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">oy</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; }</span> 
    </div> 
    <div style="TEXT-INDENT: 22pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point::point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(){ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> =</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">10</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> =</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">10</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">main</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">()</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">); </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//</span>声明对象指针，创建对象并调用带参数的构造函数，初始化对象 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">5</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">]; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//</span>声明对象数组指针，创建对象并调用不带参数的构造函数，初始化对象 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> p1;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> []</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> </td> 
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    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">Class</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> { </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">Public</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">:</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="TEXT-INDENT: 22pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">setPoint</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> ox, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> oy);</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">};</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">::</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">setPoint</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> ox, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> oy){ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; x = ox;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; y = oy;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; }</span> 
    </div> 
    <div>
      &nbsp; 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">main</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">()</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">point</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">5</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">]; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//</span>声明对象数组指针，创建对象 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">for</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">=</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&lt;</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">5</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">++)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; p2[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">].setPoint(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">10</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">10</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//调用</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">setPoint函数对成员变量促使化</span> 
    </div> 
    <div style="TEXT-INDENT: 22pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> []</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div>
      &nbsp; 
    </div> 
    <div>
      &nbsp; 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

类的每个指针成员要么指向有效的内存，要么就指向空，在析构函数里可简单地 delete，而不用担心该指针是不是被new过。

使用 new（）创建多维数组时，必须提供各维的大小。如：

int  (\* l )\[ 2 \];

l =  new int \[ 2 \]\[2\]; //ok

l =  new int \[ 2 \]\[\]; //error

l =  new int \[\]\[ 2 \]; //error

创建两维数组，举例

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    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> **</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">*[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">];</span> 
     <span style="FONT-SIZE: 11pt; COLOR: fuchsia">//首先分配指针数组中各个指针(p[0],p[1],p[2])的空间(int*型空间，非int型空间)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">for</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> &lt; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">++)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; { </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">I</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">] = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> [</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">];</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">I</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">][</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">] = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">I</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">][</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">] = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">I</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">][</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">] = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; }</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">for</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">( </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> &lt; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">++)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; { </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> []</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">];</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">I</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">] = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">NULL</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; }</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> []</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">=</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">NULL</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> </td> 
   <td style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 243pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 32pt"> 
    <div style="TEXT-INDENT: 22pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> (*</span> 
     <span style="FONT-SIZE: 11pt; COLOR: red">l</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">]; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//指向一维数组的指针</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: red">l</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">= </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">][</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">]; </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">for</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> &lt;</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">++)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">for</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">j</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">0</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">j</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> &lt;</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">2</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">j</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">++)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: red">l</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">][</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">j</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">] = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">+</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">j</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> []</span> 
     <span style="FONT-SIZE: 11pt; COLOR: red">l</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

**4.3 free和delete的使用**

用free或delete释放了内存时，如果后面要用到指针后，应立即将指针设置为NULL，防止产生“野指针”。

**4.4 重载new和delete**

重载new要和重载delete匹配。

**4.4.1 局部重载new和delete**

重载一个与类相关的new和delete函数，只需重载运算符函数成为该类的成员函数。此时重载的new和delete仅用于该特定的类，在其他数据类型上仍然使用原始版本的new和delete。即遇到new和delete时，编译程序首先检查正在使用对象所在的类是否重载了new和delete，如果重载了，则使用这个重载版本；否则，使用全局定义的new和delete。示例如下表左部：

<table style="BORDER-RIGHT: medium none; BORDER-TOP: medium none; BORDER-LEFT: medium none; BORDER-BOTTOM: medium none; BORDER-COLLAPSE: collapse"> 
 <tbody> 
  <tr> 
   <td style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 257.4pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid"> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">class</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">z</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">public</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">:</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; ~</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(){ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; }</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> * </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">operator</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> new(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">unsigned</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">size</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">operator</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> delete(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">};</span> 
    </div> 
    <div>
      &nbsp; 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">::</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">=</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">=</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> * </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">::</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">operator</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> new (</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">unsigned</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">size</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">return</span> 
     <span style="FONT-SIZE: 11pt; COLOR: purple">malloc</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">size</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//return (void *)new char[sizeof(A)];</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">::</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">operator</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> delete (</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: purple">free</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//delete p;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div>
      &nbsp; 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">main</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">a</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">a</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">10</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">); //调用类A的重载运算符new</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">a</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; //调用类A的重载运算符delete</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">100</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">); //调用系统运算符new</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; //调用系统运算符delete</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> </td> 
   <td style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 257.4pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid"> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">class</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">z</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">public</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">:</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; ~</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(){ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; }</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">};</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt">
      &nbsp; 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">::</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">, </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">=</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">x1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">=</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">y1</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> * </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">operator</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> new (</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">unsigned</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">size</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">return</span> 
     <span style="FONT-SIZE: 11pt; COLOR: purple">malloc</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">size</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//ret</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">urn (</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *)</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">char</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">[size];</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">operator</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> delete (</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{ </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: purple">free</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">p</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">);</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">//delete p;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt">
      &nbsp; 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">main</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">void</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">)</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">{&nbsp;&nbsp; </span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">a</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">;</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">a</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">A</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">3</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">,</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">10</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">); //调用重载运算符new</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">a</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; //调用重载运算符delete</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> *</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black"> = </span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">new</span> 
     <span style="FONT-SIZE: 11pt; COLOR: blue">int</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">(</span> 
     <span style="FONT-SIZE: 11pt; COLOR: green">100</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">); //调用重载运算符new</span> 
    </div> 
    <div style="MARGIN-LEFT: 21pt"> 
     <span style="FONT-SIZE: 11pt; COLOR: black">&nbsp;&nbsp;&nbsp; </span> 
     <span style="FONT-SIZE: 11pt; COLOR: maroon">delete</span> 
     <span style="FONT-SIZE: 11pt; COLOR: gray">i</span> 
     <span style="FONT-SIZE: 11pt; COLOR: black">; //调用重载运算符delete</span> 
    </div> 
    <div> 
     <span style="FONT-SIZE: 11pt; COLOR: black">}</span> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

**4.4.2 全局重载new和delete**

在任何类外重载new和delete，使它成为全局的。此时，C++中原来的new和delete被忽略，程序中使用重载的new和delete。示例如上表右部：