CView::OnFilePrint crashing MFC application - visual-c++

Question

We have an MFC application that has been used and maintained for many years. Recently we made some administrative changes to some computers that are running the application. Now the software occasionally crashes when printing from the application.
We are using pretty standard MFC code to initiate the printing. We added try/catch blocks around what we felt like are the pertinent areas of the code with no luck. Whatever is failing does not seem to throw.
We get the typical dialog stating that "____ MFC Application has stopped working". Closing the program is the only option.
The windows event logger shows that our application is the Faulting application.
The exception code is 0xc0000005, which appears to be an Access Denied error.
The application is in the CView::OnFilePrint() code when the crash occurs.
We have added some logging, and we know that we get through DoPreparePrinting, and OnBeginPrinting.
We believe that CDC::StartDoc would be the next thing called, then CView::OnPrepareDC. We don't get to OnPrepareDC when we fail.
We don't seem to find the source code for CView::OnFilePrint, so we are not sure what it looks like. From research online, we think that things happen in this order in OnFilePrint:
// what we think is in OnFilePrint:
CView::OnFilePrint()
{
OnPreparePrinting(); <- we get through our override of this
OnBeginPrinting(); <- we get through our override of this
// loop back to here on multiple docs
CDC::StartDoc();
CView::OnPrepareDC(); <- we do not reach our override of this
CView::OnPaint();
CDC::EndPage();
// loop back on multiple docs
...
// finish if last doc...
}
I would like to have the source for it so we could attempt to rewrite it and try to gracefully fail instead of failing by crashing.
I'm looking for:
1) any suggestions as to how to figure out why the process of printing causes our application to crash.
2) A location for where the CView::OnFilePrint code is located, if available.
(the only idea I have left to narrow down the problem is to call our own version of this so that we can step through it and add logging and/or see if we can at least fail gracefully when it the problem occurs.)
The printer is Xerox Phaser 3610, for what its worth.

Answer 1

source code for CView::OnFilePrint should be in C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\atlmfc\src\mfc\viewprnt.cpp, depending on VS version. There could also be a problem with printer initialization/access.
If there is any error it is most likely due to printer initialization. You can override OnFilePrint and add CPrintInfo printInfo for testing. Example:
//ON_COMMAND(ID_FILE_PRINT, &CView::OnFilePrint)
//ON_COMMAND(ID_FILE_PRINT_DIRECT, &CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT, OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_DIRECT, OnFilePrint)
void CMyView::OnFilePrint()
{
try
{
CPrintInfo printInfo;
}
catch(...)
{
//log error
AfxMessageBox(L"error");
}
CView::OnFilePrint();
}
As noted in comments, another possibility is that there is a bug somewhere else in the code, which may not necessarily be related to printing.

Answer 2

Inside of CView::OnFilePrint, this occurs:
CWnd * hwndTemp = AfxGetMainWnd();
It turns out that if you don't call OnFilePrint from the main thread, this returns NULL.
Due to slight timing changes when the computers were logged onto a domain, OnFilePrint was being called from another thread. This causes the above call to return null, then when this line gets executed:
hwndTemp->EnableWindow(FALSE);
The application crashes.
There are several ways to fix this. One is to use this:
CWnd * hwndTemp = AfxGetApp()->GetMainWnd();
In place of this:
CWnd * hwndTemp = AfxGetMainWnd();
Another way is to assure that OnFilePrint is only called from the main thread.
A cut to the chase version of the code in CView::OnFilePrint is here:
// disable main window while printing & init printing status dialog
// Store the Handle of the Window in a temp so that it can be enabled
// once the printing is finished
CWnd * hwndTemp = AfxGetMainWnd(); // <--- CAN RETURN NULL HERE
hwndTemp->EnableWindow(FALSE); // <--- CRASH WILL OCCUR HERE
CPrintingDialog dlgPrintStatus(this);
Full version of CView::OnFilePrint is below.
The OnFilePrint code, with the problem area noted:
void CView::OnFilePrint()
{
// get default print info
CPrintInfo printInfo;
ASSERT(printInfo.m_pPD != NULL); // must be set
if (LOWORD(GetCurrentMessage()->wParam) == ID_FILE_PRINT_DIRECT)
{
CCommandLineInfo* pCmdInfo = AfxGetApp()->m_pCmdInfo;
if (pCmdInfo != NULL)
{
if (pCmdInfo->m_nShellCommand == CCommandLineInfo::FilePrintTo)
{
printInfo.m_pPD->m_pd.hDC = ::CreateDC(pCmdInfo->m_strDriverName,
pCmdInfo->m_strPrinterName, pCmdInfo->m_strPortName, NULL);
if (printInfo.m_pPD->m_pd.hDC == NULL)
{
AfxMessageBox(AFX_IDP_FAILED_TO_START_PRINT);
return;
}
}
}
printInfo.m_bDirect = TRUE;
}
if (OnPreparePrinting(&printInfo))
{
// hDC must be set (did you remember to call DoPreparePrinting?)
ASSERT(printInfo.m_pPD->m_pd.hDC != NULL);
// gather file to print to if print-to-file selected
CString strOutput;
if (printInfo.m_pPD->m_pd.Flags & PD_PRINTTOFILE && !printInfo.m_bDocObject)
{
// construct CFileDialog for browsing
CString strDef(MAKEINTRESOURCE(AFX_IDS_PRINTDEFAULTEXT));
CString strPrintDef(MAKEINTRESOURCE(AFX_IDS_PRINTDEFAULT));
CString strFilter(MAKEINTRESOURCE(AFX_IDS_PRINTFILTER));
CString strCaption(MAKEINTRESOURCE(AFX_IDS_PRINTCAPTION));
CFileDialog dlg(FALSE, strDef, strPrintDef,
OFN_HIDEREADONLY|OFN_OVERWRITEPROMPT, strFilter, NULL, 0);
dlg.m_ofn.lpstrTitle = strCaption;
if (dlg.DoModal() != IDOK)
return;
// set output device to resulting path name
strOutput = dlg.GetPathName();
}
// set up document info and start the document printing process
CString strTitle;
CDocument* pDoc = GetDocument();
if (pDoc != NULL)
strTitle = pDoc->GetTitle();
else
EnsureParentFrame()->GetWindowText(strTitle);
DOCINFO docInfo;
memset(&docInfo, 0, sizeof(DOCINFO));
docInfo.cbSize = sizeof(DOCINFO);
docInfo.lpszDocName = strTitle;
CString strPortName;
if (strOutput.IsEmpty())
{
docInfo.lpszOutput = NULL;
strPortName = printInfo.m_pPD->GetPortName();
}
else
{
docInfo.lpszOutput = strOutput;
AfxGetFileTitle(strOutput,
strPortName.GetBuffer(_MAX_PATH), _MAX_PATH);
}
// setup the printing DC
CDC dcPrint;
if (!printInfo.m_bDocObject)
{
dcPrint.Attach(printInfo.m_pPD->m_pd.hDC); // attach printer dc
dcPrint.m_bPrinting = TRUE;
}
OnBeginPrinting(&dcPrint, &printInfo);
if (!printInfo.m_bDocObject)
dcPrint.SetAbortProc(_AfxAbortProc);
/**********************************************************************
Problem area.
If the calling thread is not the main thread, the call to AfxGetMainWnd
can return NULL. In this case, hwndTemp->EnableWindow(FALSE) will crash
the application.
**********************************************************************/
// disable main window while printing & init printing status dialog
// Store the Handle of the Window in a temp so that it can be enabled
// once the printing is finished
CWnd * hwndTemp = AfxGetMainWnd(); // <--- CAN RETURN NULL HERE
hwndTemp->EnableWindow(FALSE); // <--- CRASH WILL OCCUR HERE
CPrintingDialog dlgPrintStatus(this);
CString strTemp;
dlgPrintStatus.SetDlgItemText(AFX_IDC_PRINT_DOCNAME, strTitle);
dlgPrintStatus.SetDlgItemText(AFX_IDC_PRINT_PRINTERNAME,
printInfo.m_pPD->GetDeviceName());
dlgPrintStatus.SetDlgItemText(AFX_IDC_PRINT_PORTNAME, strPortName);
dlgPrintStatus.ShowWindow(SW_SHOW);
dlgPrintStatus.UpdateWindow();
// start document printing process
if (!printInfo.m_bDocObject)
{
printInfo.m_nJobNumber = dcPrint.StartDoc(&docInfo);
if (printInfo.m_nJobNumber == SP_ERROR)
{
// enable main window before proceeding
hwndTemp->EnableWindow(TRUE);
// cleanup and show error message
OnEndPrinting(&dcPrint, &printInfo);
dlgPrintStatus.DestroyWindow();
dcPrint.Detach(); // will be cleaned up by CPrintInfo destructor
AfxMessageBox(AFX_IDP_FAILED_TO_START_PRINT);
return;
}
}
// Guarantee values are in the valid range
UINT nEndPage = printInfo.GetToPage();
UINT nStartPage = printInfo.GetFromPage();
if (nEndPage < printInfo.GetMinPage())
nEndPage = printInfo.GetMinPage();
if (nEndPage > printInfo.GetMaxPage())
nEndPage = printInfo.GetMaxPage();
if (nStartPage < printInfo.GetMinPage())
nStartPage = printInfo.GetMinPage();
if (nStartPage > printInfo.GetMaxPage())
nStartPage = printInfo.GetMaxPage();
int nStep = (nEndPage >= nStartPage) ? 1 : -1;
nEndPage = (nEndPage == 0xffff) ? 0xffff : nEndPage + nStep;
VERIFY(strTemp.LoadString(AFX_IDS_PRINTPAGENUM));
// If it's a doc object, we don't loop page-by-page
// because doc objects don't support that kind of levity.
BOOL bError = FALSE;
if (printInfo.m_bDocObject)
{
OnPrepareDC(&dcPrint, &printInfo);
OnPrint(&dcPrint, &printInfo);
}
else
{
// begin page printing loop
for (printInfo.m_nCurPage = nStartPage;
printInfo.m_nCurPage != nEndPage; printInfo.m_nCurPage += nStep)
{
OnPrepareDC(&dcPrint, &printInfo);
// check for end of print
if (!printInfo.m_bContinuePrinting)
break;
// write current page
TCHAR szBuf[80];
ATL_CRT_ERRORCHECK_SPRINTF(_sntprintf_s(szBuf, _countof(szBuf), _countof(szBuf) - 1, strTemp, printInfo.m_nCurPage));
dlgPrintStatus.SetDlgItemText(AFX_IDC_PRINT_PAGENUM, szBuf);
// set up drawing rect to entire page (in logical coordinates)
printInfo.m_rectDraw.SetRect(0, 0,
dcPrint.GetDeviceCaps(HORZRES),
dcPrint.GetDeviceCaps(VERTRES));
dcPrint.DPtoLP(&printInfo.m_rectDraw);
// attempt to start the current page
if (dcPrint.StartPage() < 0)
{
bError = TRUE;
break;
}
// must call OnPrepareDC on newer versions of Windows because
// StartPage now resets the device attributes.
OnPrepareDC(&dcPrint, &printInfo);
ASSERT(printInfo.m_bContinuePrinting);
// page successfully started, so now render the page
OnPrint(&dcPrint, &printInfo);
if ((nStep > 0) && // pages are printed in ascending order
(nEndPage > printInfo.GetMaxPage() + nStep)) // out off pages
{
// OnPrint may have set the last page
// because the end of the document was reached.
// The loop must not continue with the next iteration.
nEndPage = printInfo.GetMaxPage() + nStep;
}
// If the user restarts the job when it's spooling, all
// subsequent calls to EndPage returns < 0. The first time
// GetLastError returns ERROR_PRINT_CANCELLED
if (dcPrint.EndPage() < 0 && (GetLastError()!= ERROR_SUCCESS))
{
HANDLE hPrinter;
if (!OpenPrinter(LPTSTR(printInfo.m_pPD->GetDeviceName().GetBuffer()), &hPrinter, NULL))
{
bError = TRUE;
break;
}
DWORD cBytesNeeded;
if(!GetJob(hPrinter,printInfo.m_nJobNumber,1,NULL,0,&cBytesNeeded))
{
if (GetLastError() != ERROR_INSUFFICIENT_BUFFER)
{
bError = TRUE;
break;
}
}
JOB_INFO_1 *pJobInfo;
if((pJobInfo = (JOB_INFO_1 *)malloc(cBytesNeeded))== NULL)
{
bError = TRUE;
break;
}
DWORD cBytesUsed;
BOOL bRet = GetJob(hPrinter,printInfo.m_nJobNumber,1,LPBYTE(pJobInfo),cBytesNeeded,&cBytesUsed);
DWORD dwJobStatus = pJobInfo->Status;
free(pJobInfo);
pJobInfo = NULL;
// if job status is restart, just continue
if(!bRet || !(dwJobStatus & JOB_STATUS_RESTART) )
{
bError = TRUE;
break;
}
}
if(!_AfxAbortProc(dcPrint.m_hDC, 0))
{
bError = TRUE;
break;
}
}
}
// cleanup document printing process
if (!printInfo.m_bDocObject)
{
if (!bError)
dcPrint.EndDoc();
else
dcPrint.AbortDoc();
}
hwndTemp->EnableWindow(); // enable main window
OnEndPrinting(&dcPrint, &printInfo); // clean up after printing
dlgPrintStatus.DestroyWindow();
dcPrint.Detach(); // will be cleaned up by CPrintInfo destructor
}
}