MFC的来龙去脉-----消息循环，找处理场所

一、MFC应用程序如何启动，并进入消息循环?

-启动的核心：

　　建立主线程，进入程序的main函数，然后进入消息循环。

-路径：

　　定义全局theApp对象->调用类默认构造函数->调用MFC库自动link的winmain初始化，及入口->调用AfxWinMain函数->启动消息循环

　　以下文章介绍了在theApp对象构造后，如何执行到afxwinmain的：

     http://www.cnblogs.com/qinfengxiaoyue/archive/2013/02/25/2932141.html

　　以下是afxwinmain代码：

 1 int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
 2     _In_ LPTSTR lpCmdLine, int nCmdShow)
 3 {
 4     ASSERT(hPrevInstance == NULL);
 5 
 6     int nReturnCode = -1;
 7     CWinThread* pThread = AfxGetThread();
 8     CWinApp* pApp = AfxGetApp();
 9 
10     // AFX internal initialization
11     if (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))
12         goto InitFailure;
13 
14     // App global initializations (rare)
15     if (pApp != NULL && !pApp->InitApplication())
16         goto InitFailure;
17 
18     // Perform specific initializations
19     if (!pThread->InitInstance())
20     {
21         if (pThread->m_pMainWnd != NULL)
22         {
23             TRACE(traceAppMsg, 0, "Warning: Destroying non-NULL m_pMainWnd\n");
24             pThread->m_pMainWnd->DestroyWindow();
25         }
26         nReturnCode = pThread->ExitInstance();
27         goto InitFailure;
28     }
29     nReturnCode = pThread->Run();
30