_tWinMain 与wWinMain 区别

MFC封装了WIN API.大家都知道.但是MFC应用程序的真正流程又有多少人知道呢?
下面就是我对MFC启动代码的一些剖析.

在TCHAR.H里,有这么2小段define.通过我的简化,我们可以看到:



//TCHAR.H
#ifdef _UNICODE
#define _tWinMain wWinMain
#else
#define _tWinMain WinMain
#endif


　　 由于为了支持UNICODE,C运行库对WinMain其实区分了UNICODE版和ANSI版.对UNICODE版的程序,C运行库将调用wWinMain,而对于ANSI版的应用,则调用WinMain.这是第一点.

　　 然后,其实MFC的代码设计时是自动支持UNICODE的,所以,MFC的WinMain在APPMODUL.CPP被定义为
_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
　　 这样以一来,无论用户#define _UNICODE与否,MFC的WinMain都会被调用.接下来,_tWinMain的实际运作如下:


extern "C" int WINAPI
_tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPTSTR lpCmdLine, int nCmdShow)
{
// call shared/exported WinMain
return AfxWinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);
}


　　 这样,AfxWinMain就和MFC挂上了钩.甚至在PETER NORTON的书中,都仅讲到了AfxWinMain乃是MFC的WinMain,但是,NORTON同志看来没有讲述清楚这点.因为,WinMain仍然是WinMain,C运行库并没有因为MFC的存在而重新设计AfxWinMain的入口.
在MS的AfxWinMain(WINMAIN.CPP)里我们可以看到如下代码:
int AFXAPI AfxWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPTSTR lpCmdLine, int nCmdShow)
{
ASSERT(hPrevInstance == NULL);
int nReturnCode = -1;
CWinThread* pThread = AfxGetThread();
CWinApp* pApp = AfxGetApp();

// AFX internal initialization
if (!AfxWinInit(hInstance, hPrevInstance, lpCmdLine, nCmdShow))
goto InitFailure;

// App global initializations (rare)
if (pApp != NULL && !pApp->InitApplication())
goto InitFailure;

// Perform specific initializations
if (!pThread->InitInstance())
{
if (pThread->m_pMainWnd != NULL)
{
TRACE0("Warning: Destroying non-NULL m_pMainWnd/n");
pThread->m_pMainWnd->DestroyWindow();
}
nReturnCode = pThread->ExitInstance();
goto InitFailure;
}
nReturnCode = pThread->Run();

InitFailure:
#ifdef _DEBUG
// Check for missing AfxLockTempMap calls
if (AfxGetModuleThreadState()->m_nTempMapLock != 0)
{
TRACE1("Warning: Temp map lock count non-zero (%ld)./n",
AfxGetModuleThreadState()->m_nTempMapLock);
}
AfxLockTempMaps();
AfxUnlockTempMaps(-1);
#endif

AfxWinTerm();
return nReturnCode;
}