DllMain的执行线程

DllMain的执行线程

DllMain()有4个通知：

DLL_PROCESS_ATTACH

DLL_THREAD_ATTACH

DLL_THREAD_DETACH

DLL_PROCESS_DETACH

其中：DLL_PROCESS_ATTACH/DLL_PROCESS_DETACH由主线程执行

DLL_THREAD_ATTACH由新建线程执行，DLL_PROCESS_DETACH由消亡线程执行

  

对于隐式加载的DLL来说，应用程序会在执行main函数前加载DLL，执行main函数后卸载DLL。其过程如下：

1）应用程序主线程执行DllMain()，通知DLL_PROCESS_ATTACH

2）应用程序主线程执行main()

3）程序中新建线程，为已加载的DLL执行DllMain()，通知DLL_THREAD_ATTACH

4）线程执行线程函数

5）线程退出线程函数

6）线程为已加载的DLL执行DllMain()，通知DLL_THREAD_DETACH

7）应用程序主线程退出main()

8）应用程序主线程执行DllMain()，通知DLL_PROCESS_DETACH

  

测试代码：

一个DLL工程，导出一个函数void Foo(); 

 
    // 
     dllmain.cpp : 定义DLL 应用程序的入口点。 
    
#include  
    " 
    stdafx.h 
    " 
    
 #include <tchar.h> 
    
 #include <stdio.h> 
    
 
    
 BOOL APIENTRY DllMain( HMODULE hModule, 
    
                        DWORD  ul_reason_for_call, 
    
                        LPVOID lpReserved 
    
                      ) 
    
 { 
    
      
    const  
    int kBuffLen =  
    256; 
    
     TCHAR szLog[kBuffLen]; 
    
     DWORD dwThreadId = ::GetCurrentThreadId(); 
    
      
    switch (ul_reason_for_call) 
    
     { 
    
      
    case DLL_PROCESS_ATTACH: 
    
         { 
    
             _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [DLL] Thread(%d) execute DLL_PROCESS_ATTACHn 
    "), dwThreadId); 
    
             OutputDebugString(szLog); 
    
         } 
    
          
    break; 
    
      
    case DLL_THREAD_ATTACH: 
    
         { 
    
             _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [DLL] Thread(%d) execute DLL_THREAD_ATTACHn 
    "), dwThreadId); 
    
             OutputDebugString(szLog); 
    
         } 
    
          
    break; 
    
      
    case DLL_THREAD_DETACH: 
    
         { 
    
             _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [DLL] Thread(%d) execute DLL_THREAD_DETACHn 
    "), dwThreadId); 
    
             OutputDebugString(szLog); 
    
         } 
    
          
    break; 
    
      
    case DLL_PROCESS_DETACH: 
    
         { 
    
             _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [DLL] Thread(%d) execute DLL_PROCESS_DETACHn 
    "), dwThreadId); 
    
             OutputDebugString(szLog); 
    
         } 
    
          
    break; 
    
     } 
    
      
    return TRUE; 
    
 } 
   

   

应用程序工程，包含DLL的lib库，引用Foo() 

 
    /* 
    
     验证一下DllMain()的执行线程
     验证结果：
         DLL_PROCESS_ATTACH/DLL_PROCESS_DETACH由主线程执行
         DLL_THREAD_ATTACH/DLL_THREAD_DETACH由创建和消亡的线程执行   
   
    */ 
    
 #include <Windows.h> 
    
 #include <tchar.h> 
    
 
    
 
    #pragma comment(lib, "../Debug/DLLMainDLL.lib") 
    
 
    
 
    void Foo(); 
    
 
    void Bar() 
    
 { 
    
      
    // 
     调用一下DLL的函数，使DLL链接进EXE的import table 
    
    Foo(); 
    
 } 
    
 
    
 
    
 DWORD WINAPI ThreadFunc(LPVOID lpParam) 
    
 { 
    
      
    const  
    int kBuffLen =  
    256; 
    
     TCHAR szLog[kBuffLen]; 
    
     _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [EXE] Thread(%d) execute ThreadFunc()n 
    "), ::GetCurrentThreadId()); 
    
     OutputDebugString(szLog); 
    
 
    
     ::Sleep( 
    500); 
    
 
    
     _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [EXE] Thread(%d) exit ThreadFunc()n 
    "), ::GetCurrentThreadId()); 
    
     OutputDebugString(szLog); 
    
 
    
      
    return  
    0; 
    
 } 
    
 
    
 
    int _tmain() 
    
 { 
    
      
    const  
    int kBuffLen =  
    256; 
    
     TCHAR szLog[kBuffLen]; 
    
      
    
      
    // 
     主线程 
    
    DWORD dwMainThreadId = ::GetCurrentThreadId();    
    
     _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [EXE] MainThread(%d) execute main()n 
    "), dwMainThreadId); 
    
     OutputDebugString(szLog);     
    
 
    
      
    // 
     新建线程 
    
    HANDLE hThread = NULL; 
    
     DWORD dwThreadId =  
    0; 
    
     hThread = ::CreateThread(NULL,  
    0, ThreadFunc, NULL,  
    0, &dwThreadId); 
    
     _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [EXE] Create a new thread(%d)n 
    "), dwThreadId); 
    
     OutputDebugString(szLog); 
    
 
    
     ::WaitForSingleObject(hThread, INFINITE); 
    
     ::CloseHandle(hThread); 
    
     hThread = NULL; 
    
 
    
     _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [EXE] Thread(%d) is destroyedn 
    "), dwThreadId); 
    
     OutputDebugString(szLog); 
    
 
    
     ::Sleep( 
    500); 
    
 
    
     _stprintf_s(szLog, kBuffLen, _T( 
    " 
    [EXE] MainThread(%d) exit main()n 
    "), dwMainThreadId); 
    
     OutputDebugString(szLog); 
    
 
    
      
    return  
    0; 
    
 } 
   

 

执行结果：

在VC的控制台输出：    

    [DLL] Thread(1644) execute DLL_PROCESS_ATTACH

    [EXE] MainThread(1644) execute main()

    [EXE] Create a new thread(5816)

    [DLL] Thread(5816) execute DLL_THREAD_ATTACH

    [EXE] Thread(5816) execute ThreadFunc()

    [EXE] Thread(5816) exit ThreadFunc()

    [DLL] Thread(5816) execute DLL_THREAD_DETACH

    [EXE] Thread(5816) is destroyed

    [EXE] MainThread(1644) exit main()

    [DLL] Thread(1644) execute DLL_PROCESS_DETACH 

 

结果分析：  

1）应用程序主线程执行DllMain()，通知DLL_PROCESS_ATTACH

[DLL] Thread(1644) execute DLL_PROCESS_ATTACH

  

2）应用程序主线程执行main()

[EXE] MainThread(1644) execute main() 

 

3）程序中新建线程，为已加载的DLL执行DllMain()，通知DLL_THREAD_ATTACH

[EXE] Create a new thread(5816)

[DLL] Thread(5816) execute DLL_THREAD_ATTACH 

 

4）线程执行线程函数

[EXE] Thread(5816) execute ThreadFunc() 

 

5）线程退出线程函数

[EXE] Thread(5816) exit ThreadFunc() 

 

6）线程为已加载的DLL执行DllMain()，通知DLL_THREAD_DETACH

[DLL] Thread(5816) execute DLL_THREAD_DETACH

[EXE] Thread(5816) is destroyed

  

7）应用程序主线程退出main()

[EXE] MainThread(1644) exit main() 

 

8）应用程序主线程执行DllMain()，通知DLL_PROCESS_DETACH

[DLL] Thread(1644) execute DLL_PROCESS_DETACH