📄 win32环境下dll编程原理.htm
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<p class=MsoNormal style='word-break:break-all'><span lang=EN-US
style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'> </span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> </span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>比较大应用程序都由很多模块组成，这些模块分别完成相对独立的功能，它们彼此协作来完成整个软件系统的工作。其中可能存在一些模块的功能较为通用，在构造其它软件系统时仍会被使用。在构造软件系统时，如果将所有模块的源代码都静态编译到整个应用程序</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>EXE</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件中，会产生一些问题：一个缺点是增加了应用程序的大小，它会占用更多的磁盘空间，程序运行时也会消耗较大的内存空间，造成系统资源的浪费；另一个缺点是，在编写大的</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>EXE</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>程序时，在每次修改重建时都必须调整编译所有源代码，增加了编译过程的复杂性，也不利于阶段性的单元测试。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
<br>
Windows</span><span style='mso-bidi-font-size:10.5pt;font-family:
宋体;mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>系统平台上提供了一种完全不同的较有效的编程和运行环境，你可以将独立的程序模块创建为较小的</span><span lang=EN-US
style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL(Dynamic Linkable Library)</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件，并可对它们单独编译和测试。在运行时，只有当</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>EXE</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>程序确实要调用这些</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块的情况下，系统才会将它们装载到内存空间中。这种方式不仅减少了</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>EXE</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件的大小和对内存空间的需求，而且使这些</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块可以同时被多个应用程序使用。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>Microsoft Windows</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>自己就将一些主要的系统功能以</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块的形式实现。例如</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>IE</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>中的一些基本功能就是由</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件实现的，它可以被其它应用程序调用和集成。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
<br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;
mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>一般来说，</span><span lang=EN-US style='mso-bidi-font-size:10.5pt;
font-family:Tahoma'>DLL</span><span style='mso-bidi-font-size:10.5pt;
font-family:宋体;mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;
mso-bidi-font-family:Tahoma'>是一种磁盘文件（通常带有</span><span lang=EN-US
style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>扩展名），它由全局数据、服务函数和资源组成，在运行时被系统加载到进程的虚拟空间中，成为调用进程的一部分。如果与其它</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>之间没有冲突，该文件通常映射到进程虚拟空间的同一地址上。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块中包含各种导出函数，用于向外界提供服务。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>Windows</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>在加载</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块时将进程函数调用与</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件的导出函数相匹配。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;
mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>在</span><span lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:
Tahoma'>Win32</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;
mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>环境中，每个进程都复制了自己的读</span><span lang=EN-US style='mso-bidi-font-size:
10.5pt;font-family:Tahoma'>/</span><span style='mso-bidi-font-size:10.5pt;
font-family:宋体;mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;
mso-bidi-font-family:Tahoma'>写全局变量。如果想要与其它进程共享内存，必须使用内存映射文件或者声明一个共享数据段。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块需要的堆栈内存都是从运行进程的堆栈中分配出来的。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
DLL</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>现在越来越容易编写。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>Win32</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>已经大大简化了其编程模式，并有许多来自</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>AppWizard</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>和</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>MFC</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>类库的支持。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
<br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>一、导出和导入函数的匹配</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
<br>
DLL</span><span style='mso-bidi-font-size:10.5pt;font-family:
宋体;mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>文件中包含一个导出函数表。这些导出函数由它们的符号名和称为标识号的整数与外界联系起来。函数表中还包含了</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>中函数的地址。当应用程序加载</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块时时，它并不知道调用函数的实际地址，但它知道函数的符号名和标识号。动态链接过程在加载的</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>模块时动态建立一个函数调用与函数地址的对应表。如果重新编译和重建</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件，并不需要修改应用程序，除非你改变了导出函数的符号名和参数序列。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>简单的</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件只为应用程序提供导出函数，比较复杂的</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件除了提供导出函数以外，还调用其它</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件中的函数。这样，一个特殊的</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>可以既有导入函数，又有导入函数。这并不是一个问题，因为动态链接过程可以处理交叉相关的情况。</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;
mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>在</span><span lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:
Tahoma'>DLL</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;
mso-ascii-font-family:Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:
Tahoma'>代码中，必须像下面这样明确声明导出函数：</span><span lang=EN-US style='mso-bidi-font-size:
10.5pt;font-family:Tahoma'> <br>
__declspec(dllexport) int MyFunction(int n); <br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>但也可以在模块定义</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>(DEF)</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件中列出导出函数，不过这样做常常引起更多的麻烦。在应用程序方面，要求像下面这样明确声明相应的输入函数：</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'> <br>
__declspec(dllimport) int MyFuncition(int n); <br>
</span><span style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:
Tahoma;mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>仅有导入和导出声明并不能使应用程序内部的函数调用链接到相应的</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>DLL</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件上。应用程序的项目必须为链接程序指定所需的输入库（</span><span
lang=EN-US style='mso-bidi-font-size:10.5pt;font-family:Tahoma'>LIB</span><span
style='mso-bidi-font-size:10.5pt;font-family:宋体;mso-ascii-font-family:Tahoma;
mso-hansi-font-family:Tahoma;mso-bidi-font-family:Tahoma'>文件）。而且应用程序事实上必须至少包含一个对</span><span
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