C / C++ / MFC

Re: Problem with pointers memory allocation on the same memory area

24-May-20 21:29

Stephane Capo wrote:
What is ar ?

It is an instance of CArchive Class | Microsoft Docs[^]

Richard MacCutchan24-May-20 21:25

Re: Problem with pointers memory allocation on the same memory area

24-May-20 21:25

You appear to be confusing serialization and deserialization. The first line above ar >> m_pFont; is deserializing from the archive into the m_pFont object. So where is the deserialize code that loads the object from the archive, and what type is m_pFont?

Member 959508024-May-20 21:52

Re: Problem with pointers memory allocation on the same memory area

24-May-20 21:52

You are right. I've just modified and corrected my previous post ...

Member 959508024-May-20 22:40

Re: Problem with pointers memory allocation on the same memory area

24-May-20 22:40

Well, in fact, I've two cases :

if I serialize with the following way, I've got some CLibStyle::m_pFont on the same memory during the serialization :

C++

CLibStyle Style;
for (int nNumRow = 0; nNumRow ++; nNumRow <nNbRow)
	for (int nNumCol = 0; nNumCol ++; nNumCol <nNbCol)
	{
		Style.Free();
		m_pGrid->GetStyleRowCol( nRow, nCol, Style);
		Style.Serialize(ar);
	}

if I serialize with this second way, I've got problem during deserialization in the ar >> m_pFont line : CArchive::ReadObject can't find the corresponding runtime class ...

C++

CLibStyle *pStyle;
for (int nNumRow = 0; nNumRow ++; nNumRow <nNbRow)
	for (int nNumCol = 0; nNumCol ++; nNumCol <nNbCol)
	{
		pStyle = new CLibStyle();
		m_pGrid->GetStyleRowCol( nRow, nCol, *pStyle);
		pStyle->Serialize(ar);
	}

Richard MacCutchan24-May-20 22:54

Re: Problem with pointers memory allocation on the same memory area

24-May-20 22:54

Well your code remains unclear. However, if m_pFont is a pointer, then you are going to have problems unless you also serialize the object that it is pointing at. Deserializing a pointer without the underlying object means that it will be pointing to some random portion of memory.

Member 959508024-May-20 23:03

Re: Problem with pointers memory allocation on the same memory area

24-May-20 23:03

This point is treated by the MFC CArchive::ReadObject and CArchive::WriteObject methods which are automatically called by the >> or << operator. They are able to detecte or serialize the associated RuntimeClass.

Richard MacCutchan24-May-20 23:19

Re: Problem with pointers memory allocation on the same memory area

24-May-20 23:19

Well if that is working then you need to use your debugger to find out what is going wrong. Also it is still not clear exactly what is wrong when you have deserialized from the archive.

The comments at Storing and Loading CObjects via an Archive | Microsoft Docs[^] seem to imply that you may need to use the Serialize function rather than the insertion/extraction operators.

Member 95950801-Jun-20 20:36

Re: Problem with pointers memory allocation on the same memory area

1-Jun-20 20:36

Thanks for this interesting link.

This one is also interesting : TN002: Persistent Object Data Format | Microsoft Docs

phil.o25-May-20 0:21

phil.o

25-May-20 0:21

The most obvious flaw I can see is that your are interverting loop test and variable increment in your for loops.
The syntax is

C++

for (init; condition; increment)

, and you are using

C++

for (init; increment; condition)

instead.

"Five fruits and vegetables a day? What a joke!
Personally, after the third watermelon, I'm full."

Re: Problem with pointers memory allocation on the same memory area

Richard MacCutchan25-May-20 0:31

Re: Problem with pointers memory allocation on the same memory area

25-May-20 0:31

Well spotted, but I would expect his app to crash if that is in the actual running system.

Member 959508025-May-20 1:25

Re: Problem with pointers memory allocation on the same memory area

25-May-20 1:25

Yes, very well spotted ... I wrote the sample code too quickly Wink | ;)

phil.o25-May-20 1:36

phil.o

25-May-20 1:36

I also wonder why these loops are needed, since you do not even use nNumRow and nNumCol in the loops. What is the relation of the loop variables nNumRow and nNumCol to the ar variable?

"Five fruits and vegetables a day? What a joke!
Personally, after the third watermelon, I'm full."

Re: Problem with pointers memory allocation on the same memory area

Richard MacCutchan25-May-20 1:46

Re: Problem with pointers memory allocation on the same memory area

25-May-20 1:46

It is no wonder we are getting confused if you are not even showing the actual code that has the problem.

Member 95950801-Jun-20 20:42

Printing With Crystal Report

1-Jun-20 20:42

Thank you all for your help.

The example code is very close to the actual code and the problem is that sometimes, depending on the computer, because of the operator >> to deserialize the style m_pFont, several m_pFont pointed to the same memory area.

I studied the problem with a minimal grid ... and finally realized that in my application I was not using this m_pFont. I modified my code so that I would no longer use it at all, destroy it and set it to NULL which definitively resolved my problem.

If I don't fully explain the phenomenon, I think it comes from the fact that these m_pFont contained the same data and that the operators << consider the pointer had already been serialized as explained in the TN002: Persistent Object Data Format | Microsoft Docs ... Maybe ...

Regards

a_alise21-May-20 11:09

a_alise

21-May-20 11:09

Any Thing To Send Data To Crystal Report By VC++ 6.0
,We Can Say , PrintOut Method
Object : Change No Copies Dynamic Through Code

Re: Printing With Crystal Report

_Flaviu22-May-20 0:12

_Flaviu

22-May-20 0:12

Other application can print out without problem ? Have tried to print to another printer ? Or, have you tried to run that command on another machine ? You can find more if you do some debugging on your code ...

modified 24-May-20 2:43am.

Dynamic Created CEdit using CreateEx

Beginner_mfc20-May-20 3:48

Beginner_mfc

20-May-20 3:48

I used the below code for creating CEdit dynamically, code compiled but editbox is not visible on screen

[CODE]

CEdit *tedit = new CEdit:
tedit->CreateEx(WS_EX_CLIENTEDGE , L"Edit", L" ", ES_AUTOHSCROLL | ES_LEFT | WS_BORDER | WS_VISIBLE | WS_CHILD ,this,IDC_EDIT);

[/CODE]

Re: Dynamic Created CEdit using CreateEx

Richard MacCutchan20-May-20 5:06

Re: Dynamic Created CEdit using CreateEx

20-May-20 5:06

You need to provide more details of your code. That line should work according to the documentation. There must be something else that needs to be done.

Victor Nijegorodov20-May-20 6:42

Victor Nijegorodov

20-May-20 6:42

Does it compile? It looks like the parameter CRect is missing.
Other info you could find here: How to do flat style of CEdit (EDITTEXT) and CComboBox in CDialog

C++

Member 1461181419-May-20 5:46

Member 14611814

19-May-20 5:46

<l>I am trying to learn c++ programming language and am still an amateur at it. I have a problem with "passing arrays in a function" and all am asking is what would be the easiest way to handle this problem?

Robust Services Core | Software Techniques for Lemmings | Articles

Greg Utas19-May-20 6:08

Greg Utas

19-May-20 6:08

Here is a thread[^] that should answer your question, and then some.

Richard MacCutchan19-May-20 6:13

19-May-20 6:13

Greg Utas wrote:
and then some

Should that be "and then lots"? Wink | ;)

CPallini19-May-20 20:50

CPallini

19-May-20 20:50

Be aware that the standard C++ library gently offers many alternative containers[^] to arrays.