剖析C++模板會不會使代碼膨脹

2020-02-24 14:35:32

字體：大中小

來源：轉載

供稿：網友

有人說C++模板會使代碼膨脹，可又人說不會，他的依據是如果模板會使代碼膨脹, 那么ATL和WTL里為什么還要大量使用模板? 同樣功能，ATL和WTL編譯出的可執行文件可比MFC編譯的要小的多。我當時一愣，事實確實如同事所說，難道模板會使代碼膨脹的觀點是錯誤的嗎?接下來一起剖析C++模板會不會使代碼膨脹。

MFC因為本身代碼量和復雜性在那里，所以它生成比較大的exe無可厚非。我們這里重點關注為什么ATL/WTL使用模板，但是卻不會使生成的exe變大。

我們知道使用模板時，同一模板生成不同的模板實類后會是多份代碼，比如 vector， vector, vector, 這里總共會生成3份不同的vector代碼，這就是我們平時所說的代碼膨脹。

那么為什么ATL/WTL就沒有代碼膨脹的問題呢?
我這里以 ATL里的窗口代碼為例來分析這個問題，因為我對WinDbg比較熟悉，下面我會以WinDbg為工具來分析我以前的寫得那個俄羅斯方塊程序。

首先我們看一下ATL的窗口代碼:

template
class ATL_NO_VTABLE CWindowImpl : public CWindowImplBaseT
{
public:
??? DECLARE_WND_CLASS(NULL)

??? static LPCTSTR GetWndCaption()
??? {
??????? return NULL;
??? }

??? HWND Create(HWND hWndParent, _U_RECT rect = NULL, LPCTSTR szWindowName = NULL,
??????????? DWORD dwStyle = 0, DWORD dwExStyle = 0,
??????????? _U_MENUorID MenuOrID = 0U, LPVOID lpCreateParam = NULL)
??? {
??????? if (T::GetWndClassInfo().m_lpszOrigName == NULL)
??????????? T::GetWndClassInfo().m_lpszOrigName = GetWndClassName();
??????? ATOM atom = T::GetWndClassInfo().Register(&m_pfnSuperWindowProc);

??????? dwStyle = T::GetWndStyle(dwStyle);
??????? dwExStyle = T::GetWndExStyle(dwExStyle);

??????? // set caption
??????? if (szWindowName == NULL)
??????????? szWindowName = T::GetWndCaption();

??????? return CWindowImplBaseT::Create(hWndParent, rect, szWindowName,
??????????? dwStyle, dwExStyle, MenuOrID, atom, lpCreateParam);
??? }
};

上面是一個模板類，它應該會生成多份模板實例代碼：我們可以用WinDbg的符號搜索命令來做驗證:
輸入 x HYTeris!ATL::CWindowImpl

0:000> x HYTeris!ATL::CWindowImpl004592f0 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
004343a0 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
00437c90 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
00430440 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
0041c990 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
0044cf50 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
004539a0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00435800 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00434640 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::~CWindowImpl,ATL::CWinTraits > (void)
00437440 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
00436020 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00453f70 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
00424e30 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
004338a0 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
0041c4f0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00441b50 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::CWindowImpl,ATL::CWinTraits > (void)
004365f0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00455120 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::CWindowImpl,ATL::CWinTraits > (void)
0040ea20 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00453fa0 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
0041abc0 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00459c20 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
0045f640 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
004608a0 HYTeris!ATL::CWindowImpl >::GetWndClassInfo (void)
0045fed0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00433a70 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00437c60 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
0044fb70 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
0041acf0 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
00459510 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::GetWndCaption (void)
00437a90 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
00430490 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
00424de0 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00433ac0 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
00433850 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00433b60 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00452050 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
0044f8e0 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
0044cec0 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
004340e0 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
00433ef0 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::~CWindowImpl,ATL::CWinTraits > (void)
004348c0 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::~CWindowImpl,ATL::CWinTraitsOR > > (void)
004535b0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
00454170 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
00459c70 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
00451ed0 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00451f20 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
0045c4b0 HYTeris!ATL::CWindowImpl >::CWindowImpl > (void)
00436320 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
004536a0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
004604a0 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::GetWndCaption (void)
0040eca0 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
0045ff90 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
00437cc0 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
004366e0 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
0045e620 HYTeris!ATL::CWindowImpl >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
004608d0 HYTeris!ATL::CWindowImpl >::GetWndCaption (void)
004520a0 HYTeris!ATL::CWindowImpl >::~CWindowImpl > (void)
0045d210 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::CWindowImpl,ATL::CWinTraitsOR > > (void)
004d84a8 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d84b8 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d7970 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d7960 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d914c HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8dd0 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8b04 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d8b14 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d8ae8 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e31b8 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004e2980 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d88c4 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8330 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d88f0 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::`RTTI Base Class Array' = 
004d88e0 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::`RTTI Class Hierarchy Descriptor' = 
004d8a40 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e30f0 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d8a5c HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d8a6c HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004e21d0 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d8c70 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e2e78 HYTeris!ATL::CWindowImpl,ATL::CWinTraits > `RTTI Type Descriptor' = 
004e1f00 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d9208 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d9218 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004e1ad8 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d834c HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d835c HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d8c9c HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d8c8c HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d856c HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d855c HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004e2bb8 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d7fa0 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d7fb0 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d91ec HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e2048 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d8174 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d8184 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d8dfc HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004d8dec HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004e2728 HYTeris!ATL::CWindowImpl,ATL::CWinTraits > `RTTI Type Descriptor' = 
004e28c8 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d8fac HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::`RTTI Base Class Array' = 
004d8f9c HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::`RTTI Class Hierarchy Descriptor' = 
004d848c HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8f80 HYTeris!ATL::CWindowImpl,ATL::CWinTraits >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8158 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8540 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d7944 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d7f84 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e2aa0 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d9168 HYTeris!ATL::CWindowImpl >::`RTTI Class Hierarchy Descriptor' = 
004d9178 HYTeris!ATL::CWindowImpl >::`RTTI Base Class Array' = 
004e1628 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004e2148 HYTeris!ATL::CWindowImpl > `RTTI Type Descriptor' = 
004d95c4 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::`RTTI Base Class Array' = 
004d95b4 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::`RTTI Class Hierarchy Descriptor' = 
004e3400 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > > `RTTI Type Descriptor' = 
004d9598 HYTeris!ATL::CWindowImpl,ATL::CWinTraitsOR > >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 

上面的符號可以驗證我們多份實例的猜想。
可以看到 CWindowImpl和我們的窗口繼承類（T），窗口基類(TBase), 窗口風格（TWinTraits）相關，所以數量很多。? 那么為什么這么多的符號，也就是這么多的函數代碼，exe大小沒有被撐大？
那時因為CWindowImpl類函數本身很小，我們從函數的代碼量上就可以看出來。

用同樣的方法，我們可以繼續分析 CWindowImplBaseT

template
class ATL_NO_VTABLE CWindowImplBaseT : public CWindowImplRoot
{
public:
??? WNDPROC m_pfnSuperWindowProc;

??? CWindowImplBaseT() : m_pfnSuperWindowProc(::DefWindowProc)
??? {}

??? static DWORD GetWndStyle(DWORD dwStyle)
??? {
??????? return TWinTraits::GetWndStyle(dwStyle);
??? }
??? static DWORD GetWndExStyle(DWORD dwExStyle)
??? {
??????? return TWinTraits::GetWndExStyle(dwExStyle);
??? }

??? virtual WNDPROC GetWindowProc()
??? {
??????? return WindowProc;
??? }
??? static LRESULT CALLBACK StartWindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
??? static LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
??? HWND Create(HWND hWndParent, _U_RECT rect, LPCTSTR szWindowName,
??????????? DWORD dwStyle, DWORD dwExStyle, _U_MENUorID MenuOrID, ATOM atom, LPVOID lpCreateParam = NULL);
??? BOOL DestroyWindow()
??? {
??????? ATLASSERT(::IsWindow(m_hWnd));
??????? return ::DestroyWindow(m_hWnd);
??? }
??? BOOL SubclassWindow(HWND hWnd);
??? HWND UnsubclassWindow(BOOL bForce = FALSE);

??? LRESULT DefWindowProc()
??? {
??????? const _ATL_MSG* pMsg = m_pCurrentMsg;
??????? LRESULT lRes = 0;
??????? if (pMsg != NULL)
??????????? lRes = DefWindowProc(pMsg->message, pMsg->wParam, pMsg->lParam);
??????? return lRes;
??? }

??? LRESULT DefWindowProc(UINT uMsg, WPARAM wParam, LPARAM lParam)
??? {
#ifdef STRICT
??????? return ::CallWindowProc(m_pfnSuperWindowProc, m_hWnd, uMsg, wParam, lParam);
#else
??????? return ::CallWindowProc((FARPROC)m_pfnSuperWindowProc, m_hWnd, uMsg, wParam, lParam);
#endif
??? }

??? virtual void OnFinalMessage(HWND /*hWnd*/)
??? {
??????? // override to do something, if needed
??? }
};

0:000> x HYTeris!ATL::CWindowImplBaseT0040f170 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, unsigned short, void *)
0040ec20 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::GetWndStyle (unsigned long)
00435970 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::OnFinalMessage (struct HWND__ *)
004604d0 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::GetWndStyle (unsigned long)
00434a10 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::~CWindowImplBaseT<:ceditt>,ATL::CWinTraits > (void)
0040ec60 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::GetWndExStyle (unsigned long)
00461740 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::WindowProc (struct HWND__ *, unsigned int, unsigned int, long)
0044c040 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::WindowProc (struct HWND__ *, unsigned int, unsigned int, long)
004346e0 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::~CWindowImplBaseT<:cbuttont>,ATL::CWinTraits > (void)
0041c440 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::CWindowImplBaseT<:cwindow> > (void)
00435940 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::GetWindowProc (void)
00459580 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::GetWndExStyle (unsigned long)
00461950 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, unsigned short, void *)
004395b0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::StartWindowProc (struct HWND__ *, unsigned int, unsigned int, long)
00439ea0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::DefWindowProcW (unsigned int, unsigned int, long)
00461620 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::StartWindowProc (struct HWND__ *, unsigned int, unsigned int, long)
004596e0 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, unsigned short, void *)
0041ced0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::WindowProc (struct HWND__ *, unsigned int, unsigned int, long)
0044c370 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::UnsubclassWindow (int)
00460510 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::GetWndExStyle (unsigned long)
00457f70 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::WindowProc (struct HWND__ *, unsigned int, unsigned int, long)
0045f830 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::GetWindowProc (void)
00457820 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits > (void)
004374b0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::GetWndExStyle (unsigned long)
00434ad0 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::~CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > > (void)
004595c0 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::StartWindowProc (struct HWND__ *, unsigned int, unsigned int, long)
004358f0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::CWindowImplBaseT<:cwindow> > (void)
00445920 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::OnFinalMessage (struct HWND__ *)
00461ad0 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::DefWindowProcW (unsigned int, unsigned int, long)
0041c4c0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::OnFinalMessage (struct HWND__ *)
00437470 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::GetWndStyle (unsigned long)
004398e0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::Create (struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, unsigned short, void *)
0040ed50 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::StartWindowProc (struct HWND__ *, unsigned int, unsigned int, long)
004458a0 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::CWindowImplBaseT<:ceditt>,ATL::CWinTraits > (void)
0045f7e0 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > > (void)
0041ad30 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::~CWindowImplBaseT<:cwindow> > (void)
00430550 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::~CWindowImplBaseT<:cwindow> > (void)
0045f860 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::OnFinalMessage (struct HWND__ *)
004582a0 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::UnsubclassWindow (int)
0041c490 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::GetWindowProc (void)
0044cb50 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::DefWindowProcW (unsigned int, unsigned int, long)
0044c250 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::SubclassWindow (struct HWND__ *)
004458f0 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::GetWindowProc (void)
00459540 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::GetWndStyle (unsigned long)
00458180 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::SubclassWindow (struct HWND__ *)
00457870 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::GetWindowProc (void)
00457910 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::OnFinalMessage (struct HWND__ *)
0040e990 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::DestroyWindow (void)
004396d0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::WindowProc (struct HWND__ *, unsigned int, unsigned int, long)
0041d1c0 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::DefWindowProcW (unsigned int, unsigned int, long)
004578a0 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::DefWindowProcW (unsigned int, unsigned int, long)
004d8fc8 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8ff4 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::`RTTI Base Class Array' = 
004d8fe4 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits >::`RTTI Class Hierarchy Descriptor' = 
004d79b4 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::`RTTI Base Class Array' = 
004d79a4 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::`RTTI Class Hierarchy Descriptor' = 
004e2798 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits > `RTTI Type Descriptor' = 
004d819c HYTeris!ATL::CWindowImplBaseT<:cwindow> >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d8938 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::`RTTI Base Class Array' = 
004d8928 HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::`RTTI Class Hierarchy Descriptor' = 
004d960c HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::`RTTI Base Class Array' = 
004d95fc HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::`RTTI Class Hierarchy Descriptor' = 
004e2ee8 HYTeris!ATL::CWindowImplBaseT<:cbuttont>,ATL::CWinTraits > `RTTI Type Descriptor' = 
004d81c8 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::`RTTI Base Class Array' = 
004d81b8 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::`RTTI Class Hierarchy Descriptor' = 
004e34a0 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > > `RTTI Type Descriptor' = 
004d95e0 HYTeris!ATL::CWindowImplBaseT<:clistviewctrlt>,ATL::CWinTraitsOR > >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e1f68 HYTeris!ATL::CWindowImplBaseT<:cwindow> > `RTTI Type Descriptor' = 
004e1688 HYTeris!ATL::CWindowImplBaseT<:cwindow> > `RTTI Type Descriptor' = 
004d7988 HYTeris!ATL::CWindowImplBaseT<:cwindow> >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d890c HYTeris!ATL::CWindowImplBaseT<:ceditt>,ATL::CWinTraits >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 

可以看到 CWindowImplBaseT只與窗口基類和窗口風格相關，數量已經減小很多，CWindowImplBaseT模板類本身函數數量不多，函數代碼量大小也不大。

然后再看CWindowImplRoot,

template
class ATL_NO_VTABLE CWindowImplRoot : public TBase, public CMessageMap
{
public:
??? CWndProcThunk m_thunk;
??? const _ATL_MSG* m_pCurrentMsg;
??? DWORD m_dwState;

??? enum { WINSTATE_DESTROYED = 0x00000001 };

// Constructor/destructor
??? CWindowImplRoot() : m_pCurrentMsg(NULL), m_dwState(0)
??? { }

??? virtual ~CWindowImplRoot()
??? {
#ifdef _DEBUG
??????? if(m_hWnd != NULL)??? // should be cleared in WindowProc
??????? {
??????????? ATLTRACE(atlTraceWindowing, 0, _T("ERROR - Object deleted before window was destroyed/n"));
??????????? ATLASSERT(FALSE);
??????? }
#endif //_DEBUG
??? }

// Current message
??? const _ATL_MSG* GetCurrentMessage() const
??? {
??????? return m_pCurrentMsg;
??? }

??? // "handled" management for cracked handlers
??? BOOL IsMsgHandled() const
??? {
??????? const _ATL_MSG* pMsg = GetCurrentMessage();
??????? ATLASSERT(pMsg != NULL);
??????? ATLASSERT(pMsg->cbSize >= sizeof(_ATL_MSG));
??????? return pMsg->bHandled;
??? }
??? void SetMsgHandled(BOOL bHandled)
??? {
??????? _ATL_MSG* pMsg = (_ATL_MSG*)GetCurrentMessage();??? // override const
??????? ATLASSERT(pMsg != NULL);
??????? ATLASSERT(pMsg->cbSize >= sizeof(_ATL_MSG));
??????? pMsg->bHandled = bHandled;
??? }

// Message forwarding and reflection support
??? LRESULT ForwardNotifications(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled);
??? LRESULT ReflectNotifications(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled);
??? static BOOL DefaultReflectionHandler(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, LRESULT& lResult);
};

0:000> x HYTeris!ATL::CWindowImplRoot*
004364d0 HYTeris!ATL::CWindowImplRoot<:clistviewctrlt> >::~CWindowImplRoot<:clistviewctrlt> > (void)
004367d0 HYTeris!ATL::CWindowImplRoot<:ceditt> >::~CWindowImplRoot<:ceditt> > (void)
00457c30 HYTeris!ATL::CWindowImplRoot<:cbuttont> >::CWindowImplRoot<:cbuttont> > (void)
00460550 HYTeris!ATL::CWindowImplRoot<:clistviewctrlt> >::CWindowImplRoot<:clistviewctrlt> > (void)
004479d0 HYTeris!ATL::CWindowImplRoot<:ceditt> >::CWindowImplRoot<:ceditt> > (void)
0041c360 HYTeris!ATL::CWindowImplRoot<:cwindow>::~CWindowImplRoot<:cwindow> (void)
00435f40 HYTeris!ATL::CWindowImplRoot<:cbuttont> >::~CWindowImplRoot<:cbuttont> > (void)
004613f0 HYTeris!ATL::CWindowImplRoot<:cwindow>::ForwardNotifications (unsigned int, unsigned int, long, int *)
00438f50 HYTeris!ATL::CWindowImplRoot<:cwindow>::ReflectNotifications (unsigned int, unsigned int, long, int *)
0041c8e0 HYTeris!ATL::CWindowImplRoot<:cwindow>::CWindowImplRoot<:cwindow> (void)
004e2800 HYTeris!ATL::CWindowImplRoot<:ceditt> > `RTTI Type Descriptor' = 
004d897c HYTeris!ATL::CWindowImplRoot<:ceditt> >::`RTTI Base Class Array' = 
004d896c HYTeris!ATL::CWindowImplRoot<:ceditt> >::`RTTI Class Hierarchy Descriptor' = 
004d9640 HYTeris!ATL::CWindowImplRoot<:clistviewctrlt> >::`RTTI Class Hierarchy Descriptor' = 
004d9650 HYTeris!ATL::CWindowImplRoot<:clistviewctrlt> >::`RTTI Base Class Array' = 
004d8950 HYTeris!ATL::CWindowImplRoot<:ceditt> >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d9028 HYTeris!ATL::CWindowImplRoot<:cbuttont> >::`RTTI Class Hierarchy Descriptor' = 
004d9038 HYTeris!ATL::CWindowImplRoot<:cbuttont> >::`RTTI Base Class Array' = 
004e16dc HYTeris!ATL::CWindowImplRoot<:cwindow> `RTTI Type Descriptor' = 
004e3530 HYTeris!ATL::CWindowImplRoot<:clistviewctrlt> > `RTTI Type Descriptor' = 
004d9624 HYTeris!ATL::CWindowImplRoot<:clistviewctrlt> >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d79c8 HYTeris!ATL::CWindowImplRoot<:cwindow>::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004e2f58 HYTeris!ATL::CWindowImplRoot<:cbuttont> > `RTTI Type Descriptor' = 
004d79f4 HYTeris!ATL::CWindowImplRoot<:cwindow>::`RTTI Base Class Array' = 
004d79e4 HYTeris!ATL::CWindowImplRoot<:cwindow>::`RTTI Class Hierarchy Descriptor' = 
004d900c HYTeris!ATL::CWindowImplRoot<:cbuttont> >::`RTTI Base Class Descriptor at (0,-1,0,64)' = 

可以看到 CWindowImplRoot只和窗口基類(CWindow)相關，所以相關的符號就更少了。

最后我們再看一下CWindow:

0:000> x HYTeris!ATL::CWindow::*
004e1000 HYTeris!ATL::CWindow::rcDefault = struct tagRECT
00442a20 HYTeris!ATL::CWindow::DestroyWindow (void)
00425730 HYTeris!ATL::CWindow::InvalidateRect (struct tagRECT *, int)
00442340 HYTeris!ATL::CWindow::CenterWindow (struct HWND__ *)
00425850 HYTeris!ATL::CWindow::UpdateWindow (void)
0041c950 HYTeris!ATL::CWindow::CWindow (struct HWND__ *)
004391e0 HYTeris!ATL::CWindow::GetDlgItem (int)
004568a0 HYTeris!ATL::CWindow::SetWindowRgn (struct HRGN__ *, int)
00441d20 HYTeris!ATL::CWindow::GetWindowLongW (int)
00444350 HYTeris!ATL::CWindow::Create (wchar_t *, struct HWND__ *, class ATL::_U_RECT, wchar_t *, unsigned long, unsigned long, class ATL::_U_MENUorID, void *)
004391b0 HYTeris!ATL::CWindow::operator HWND__ * (void)
00459080 HYTeris!ATL::CWindow::EnableWindow (int)
00425140 HYTeris!ATL::CWindow::GetClientRect (struct tagRECT *)
00430c70 HYTeris!ATL::CWindow::SetWindowTextW (wchar_t *)
0040eb30 HYTeris!ATL::CWindow::GetWndClassName (void)
00456770 HYTeris!ATL::CWindow::MoveWindow (int, int, int, int, int)
00442ac0 HYTeris!ATL::CWindow::KillTimer (unsigned int)
00455fc0 HYTeris!ATL::CWindow::GetWindowTextW (wchar_t *, int)
0040ba20 HYTeris!ATL::CWindow::IsWindow (void)
00441db0 HYTeris!ATL::CWindow::GetParent (void)
004315b0 HYTeris!ATL::CWindow::SetWindowPos (struct HWND__ *, int, int, int, int, unsigned int)
00456810 HYTeris!ATL::CWindow::GetWindowRect (struct tagRECT *)
00431860 HYTeris!ATL::CWindow::GetStyle (void)
00455250 HYTeris!ATL::CWindow::Invalidate (int)
004318f0 HYTeris!ATL::CWindow::SetCapture (void)
00442cf0 HYTeris!ATL::CWindow::SetTimer (unsigned int, unsigned int,  *)
00431980 HYTeris!ATL::CWindow::ModifyStyle (unsigned long, unsigned long, unsigned int)
00443d10 HYTeris!ATL::CWindow::GetDlgItemTextW (int, wchar_t *, int)
0040b980 HYTeris!ATL::CWindow::SendMessageW (unsigned int, unsigned int, long)
00434be0 HYTeris!ATL::CWindow::ShowWindow (int)
004d7a38 HYTeris!ATL::CWindow::`RTTI Base Class Descriptor at (0,-1,0,64)' = 
004d7a04 HYTeris!ATL::CWindow::`RTTI Base Class Descriptor at (4,-1,0,64)' = 
004d7a20 HYTeris!ATL::CWindow::`RTTI Class Hierarchy Descriptor' = 
004d7a30 HYTeris!ATL::CWindow::`RTTI Base Class Array' = 