subject_24072.htm

一些关于vc的问答

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序号：24072 发表者：编程吧 发表日期：2002-12-09 13:54:43
<br>主题：关于深入浅出MFC中的一个问题
<br>内容：在第13章中那个Text范例程序中<BR>在InitInstance中除了缺省的那个CMultiDocTemplate* pDocTemplate;<BR>又创建了一个CMultiDocTemplate* m_pTemplateHex（不过是作为CTextApp的一个成员变量定义的）<BR>如下：<BR>&nbsp;&nbsp;&nbsp;&nbsp;m_pTemplateHex = new CMultiDocTemplate(<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;IDR_TEXTTYPE,<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RUNTIME_CLASS(CTextDoc),<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RUNTIME_CLASS(CChildFrame), // custom MDI child frame<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;RUNTIME_CLASS(CHexView));<BR>&nbsp;&nbsp;&nbsp;&nbsp;AddDocTemplate(m_pTemplateHex);<BR><BR>然后在ExitInstance中，如下：<BR>int CTextApp::ExitInstance() <BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;delete m_pTemplateHex;<BR>&nbsp;&nbsp;&nbsp;&nbsp;// 如果加上这一句，关闭程序时会出错，去掉这一句就没事<BR>&nbsp;&nbsp;&nbsp;&nbsp;// 但如果去掉这一句，m_pTemplateHex到底释放了没有呢？<BR><BR>&nbsp;&nbsp;&nbsp;&nbsp;return CWinApp::ExitInstance();<BR>}<BR><BR>我跟踪了一下，错误是在CWinApp::SaveStdProfileSettings()中抛出的<BR>int CWinApp::ExitInstance()<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;// if we remember that we're unregistering,<BR>&nbsp;&nbsp;&nbsp;&nbsp;// don't save our profile settings<BR><BR>&nbsp;&nbsp;&nbsp;&nbsp;if (m_pCmdInfo == NULL ||<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;m_pCmdInfo-&gt;m_nShellCommand != CCommandLineInfo::AppUnregister)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (!afxContextIsDLL)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;SaveStdProfileSettings();<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;~~~~~~~~~~~~~~~~~~~~~~~~<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...<BR>}<BR><BR>void CWinApp::SaveStdProfileSettings()<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;ASSERT_VALID(this);<BR>&nbsp;&nbsp;&nbsp;&nbsp;// 就是这里出错，不明白？<BR>&nbsp;&nbsp;&nbsp;&nbsp;...<BR>}<BR><BR><BR>看了一下MFC源代码，觉得m_pTemplateHex应该是在下面的时候释放的。<BR>感觉即使不delete m_pTemplateHex，好像也因该会释放，但不明白上面为什么会出错？<BR>CDocManager::~CDocManager()<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;// for cleanup - delete all document templates<BR>&nbsp;&nbsp;&nbsp;&nbsp;POSITION pos = m_templateList.GetHeadPosition();<BR>&nbsp;&nbsp;&nbsp;&nbsp;while (pos != NULL)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;POSITION posTemplate = pos;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;CDocTemplate* pTemplate = (CDocTemplate*)m_templateList.GetNext(pos);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (pTemplate-&gt;m_bAutoDelete)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;m_templateList.RemoveAt(posTemplate);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;delete (CDocTemplate*)pTemplate;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR>}
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回复者：tjhe 回复日期：2002-12-09 20:16:14
<br>内容：文档模板是CDocManager自动删除。如果在应用类中删除，应用类的CDocManager将会有无效的(已被删除的)文档模板。<BR>
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回复者：编程吧 回复日期：2002-12-09 21:08:26
<br>内容：但是程序是在还没运行到CDocManager的析构函数~CDocManager（）是出错的<BR>不知为什么<BR>（出错的位置在上面标明了)<BR>
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<font color=red>答案被接受</font><br>回复者：tjhe 回复日期：2002-12-10 10:19:09
<br>内容：应该是<BR>void CWinApp::SaveStdProfileSettings()<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;ASSERT_VALID(this);<BR>&nbsp;&nbsp;&nbsp;&nbsp;...<BR>}<BR>中的ASSERT_VALID(this);要判断应用类的所有文档模板的合法性（通过CDocManager）<BR>2002-12-10 10:20:01