CWnd-AssertVaild

Errror description

MFC dll中的界面在Debug时调用UpdateData()函数,会判断窗口的运行环境是否跨线程,如果创建窗口的线程与调用该函数的线程不是同一个,就会触发CWnd的AssertVaild()函数中断.提示:

it is likely that you have passed a C++ object from one thread to another and have used that object in a way that was not intended.把一个C++对象从一个线程传到另一个线程,使用对象的方式不正确(与代码的原本设计相悖)

void CWnd::AssertValid() const
{
	if (m_hWnd == NULL)
		return;     // null (unattached) windows are valid

	// check for special wnd??? values
	ASSERT(HWND_TOP == NULL);       // same as desktop
	if (m_hWnd == HWND_BOTTOM)
		ASSERT(this == &CWnd::wndBottom);
	else if (m_hWnd == HWND_TOPMOST)
		ASSERT(this == &CWnd::wndTopMost);
	else if (m_hWnd == HWND_NOTOPMOST)
		ASSERT(this == &CWnd::wndNoTopMost);
	else
	{
		// should be a normal window
		ASSERT(::IsWindow(m_hWnd));

		// should also be in the permanent or temporary handle map
		CHandleMap* pMap = afxMapHWND();
		ASSERT(pMap != NULL);

		CObject* p=NULL;
		if(pMap)
		{
			ASSERT( (p = pMap->LookupPermanent(m_hWnd)) != NULL ||
					(p = pMap->LookupTemporary(m_hWnd)) != NULL);
		}
		ASSERT((CWnd*)p == this);   // must be us

		// Note: if either of the above asserts fire and you are
		// writing a multithreaded application, it is likely that
		// you have passed a C++ object from one thread to another
		// and have used that object in a way that was not intended.
		// (only simple inline wrapper functions should be used)
		//
		// In general, CWnd objects should be passed by HWND from
		// one thread to another.  The receiving thread can wrap
		// the HWND with a CWnd object by using CWnd::FromHandle.
		//
		// It is dangerous to pass C++ objects from one thread to
		// another, unless the objects are designed to be used in
		// such a manner.
	}
}

Solution

1.在窗口或者控件类重载 CWnd::AssertValid() 函数,写个空函数屏蔽原函数,不推荐使用.
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class CExampleDialog: public CDialog{
public:
#ifdef _DEBUG
virtual void AssertValid() const {};
#endif
}
只需要在Debug时重载,在release时不会出错,因为在CWnd中这个函数也是在Debug才生效
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#ifdef _DEBUG
void CWnd::AssertValid() const
{
//....
}
void CWnd::Dump(CDumpContext& dc) const
{
//....
}
#endif
2.这个错误主要是跨线程使用窗口的一些资源导致,在UpdateData()或其他资源使用前调用

AFX_MANAGE_STATE(AfxGetStaticModuleState());

将状态切换.例如有如下函数需要在模块外调用且需要使用窗口/控件资源,

bool ExampleFunc()
{
	bool bRtn=true;
	AFX_MANAGE_STATE(AfxGetStaticModuleState());//切换线程状态  
	UpdateData(TRUE);
	//....
	return bRtn;
}