Possible Bug in Print Preview

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   Using 10.4.2 I've discovered that my application and the sample Print Preview program crash when trying to display a CEditView in print preview.  (I didn't notice whether 10.4.0 crashes.)

MFC asserts in debug mode in the MFC module dcprev.cpp at CPreviewDC::ComputeDeltas(...) .

Other types of view display properly in print preview.

I've also disovered that the standard MFC implementation CPreviewView also crashes the same way, so it is possible this is a bug with Microsoft.

Does anyone know whether this is a known bug, or any workaround?

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JonN Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 January 2004 Location: United Kingdom Status: Offline Points: 8	Post Options Post Reply Quote JonN Report Post Thanks(0) Quote Reply Topic: Possible Bug in Print Preview Posted: 30 January 2007 at 12:37pm
	Using 10.4.2 I've discovered that my application and the sample Print Preview program crash when trying to display a CEditView in print preview. (I didn't notice whether 10.4.0 crashes.) MFC asserts in debug mode in the MFC module dcprev.cpp at CPreviewDC::ComputeDeltas(...) . Other types of view display properly in print preview. I've also disovered that the standard MFC implementation CPreviewView also crashes the same way, so it is possible this is a bug with Microsoft. Does anyone know whether this is a known bug, or any workaround?

Oleg Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 21 May 2003 Location: United States Status: Offline Points: 11234	Post Options Post Reply Quote Oleg Report Post Thanks(0) Quote Reply Posted: 31 January 2007 at 1:19am
	Hi, What vc version do you have? What line of code in MFC sources have problem?
	Oleg, Support Team CODEJOCK SOFTWARE SOLUTIONS

JonN Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 January 2004 Location: United Kingdom Status: Offline Points: 8	Post Options Post Reply Quote JonN Report Post Thanks(0) Quote Reply Posted: 31 January 2007 at 4:05am
	Hi Oleg I'm running VC 2005 with SP1 installed. The crash occurs in line 604 of dcprev.cpp, in the line *pnCurDelta = tmAttrib.tmAveCharWidth; It appears that the pointer pnCurDelta is NULL, which cannot be correct!

JonN Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 January 2004 Location: United Kingdom Status: Offline Points: 8	Post Options Post Reply Quote JonN Report Post Thanks(0) Quote Reply Posted: 31 January 2007 at 6:26am
	A bit more research and it looks like this is a Microsoft bug introduced into VC2005 by SP1. The Superpad MFC example also fails with the same error. As yet no fix has been posted. . For more info see: https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=254738 Jon Neades www.mathtech.co.uk

JonN Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 11 January 2004 Location: United Kingdom Status: Offline Points: 8	Post Options Post Reply Quote JonN Report Post Thanks(0) Quote Reply Posted: 31 January 2007 at 9:16am
	This problem lies in a change to the code in the calling function CPreviewDC::TabbedTextOut(..) Starting at line 722 in dcprev.cpp we now have in SP1 int* pDeltas = NULL; LPTSTR pOutputString = NULL; int nRightFixup; ::ATL::CAutoVectorPtr<int> spDeltas; ::ATL::CAutoVectorPtr<TCHAR> spOutputString; if(!spDeltas.Allocate(nCount) \|\| !spOutputString.Allocate(nCount)) { return 0; } UINT uCount = nCount; CSize sizeFinalExtent = ComputeDeltas(x, lpszString, uCount, TRUE, nTabPositions, lpnTabStopPositions, nTabOrigin, pOutputString, pDeltas, nRightFixup); Note that the ComputeDeltas call supplies the uninitialized pOutputString, pDeltas as parameters rather than the new spOutputString, spDeltas which are correctly defined and initialized using the ATL::CAutoVectorPt calls. Earlier versions used the standard new and delete to allocate and delete the pOutputString, pDeltas variables. Still not sure of the easiest workaround though. Rebuilding the MFC libraries is not very appealing! Jon Neades www.mathtech.co.uk