第一次深入MFC 调试一个小小的错误
作者：CrazyAzreal 来源：ccw 添加时间：2006-5-26 10:34:07 以前常认为自己mfc学得不错,因为有CSDN+MSDN+GOOGLE,可是今天收到一个网友(女的哦!)的消息,说他有个程序有点问题,她把程序发到我的邮箱里去了,我down了下来.研究了一吓,这个程序给我补了一些基础知识,并认识到其实自己还很菜.然后就写了这篇文章了.
那个程序(网友给我发的那个程序)是一个SDI程序,错误是在点击文件(自动生成的那个)->保存(打开\另存为)时会出错,是一个断言的错误提示形式,这时我就去看了看她的CXXXDoc里,OnSaveDocument()是怎样写的,去看了看,发现并没有重载这个函数,这时就郁闷啦?那到底错在哪里呢?我马上想到不如debug一吓吧,在debug下,我再点文件->保存,可是并没有断下来?它直接就弹出个错误框.不知道是为什么,苦思了一会,在没办法的情况下,又试了一吓,,看能不能断下来,可是还是断不下来,又在没办法+失望的情况下,我点了重试(ASSERT的提示框不是有三个按钮的吗,分别是终止\重试\忽略),这下就可以断下来了?哈,我看看是断到哪里,噢,断到了CDocument::DoSave(...)里去了,我看了看,这个函数被CDocument::DoFileSave()所调用,看看CDocument::DoFileSave()的实现:
BOOL CDocument::DoFileSave()
{
DWORD dwAttrib = GetFileAttributes(m_strPathName);
if (dwAttrib & FILE_ATTRIBUTE_READONLY)
{
// we do not have read-write access or the file does not (now) exist
if (!DoSave(NULL))
{
TRACE0("Warning: File save with new name failed.\n");
return FALSE;
}
}
else
{
if (!DoSave(m_strPathName))
{
TRACE0("Warning: File save failed.\n");
return FALSE;
}
}
return TRUE;
} |
明显,第一个if是另存为时调用的,下面的则为保存时的.
然后我又看了看CDocument::DoSave(LPCTSTR lpszPathName, BOOL bReplace)
BOOL CDocument::DoSave(LPCTSTR lpszPathName, BOOL bReplace)
// Save the document data to a file
// lpszPathName = path name where to save document file
// if lpszPathName is NULL then the user will be prompted (SaveAs)
// note: lpszPathName can be different than 'm_strPathName'
// if 'bReplace' is TRUE will change file name if successful (SaveAs)
// if 'bReplace' is FALSE will not change path name (SaveCopyAs)
{
CString newName = lpszPathName;
if (newName.IsEmpty())
{
CDocTemplate* pTemplate = GetDocTemplate();
ASSERT(pTemplate != NULL);
newName = m_strPathName;
if (bReplace && newName.IsEmpty())
{
newName = m_strTitle;
// check for dubious filename
int iBad = newName.FindOneOf(_T(" #%;/\\"));
if (iBad != -1)
newName.ReleaseBuffer(iBad);
// append the default suffix if there is one
CString strExt;
if (pTemplate->GetDocString(strExt, CDocTemplate::filterExt) &&
!strExt.IsEmpty())
{
ASSERT(strExt[0] == '.');
newName += strExt;
}
}
if (!AfxGetApp()->DoPromptFileName(newName,
bReplace ? AFX_IDS_SAVEFILE : AFX_IDS_SAVEFILECOPY,
OFN_HIDEREADONLY | OFN_PATHMUSTEXIST, FALSE, pTemplate))
return FALSE; // don't even attempt to save
}
CWaitCursor wait;
if (!OnSaveDocument(newName))
{
if (lpszPathName == NULL)
{
// be sure to delete the file
TRY
{
CFile::Remove(newName);
}
CATCH_ALL(e)
{
TRACE0("Warning: failed to delete file after failed SaveAs.\n");
DELETE_EXCEPTION(e);
}
END_CATCH_ALL
}
return FALSE;
}
// reset the title and change the document name
if (bReplace)
SetPathName(newName);
return TRUE; // success
} |