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Strange about Dump() function.


Ola Theander -- olathean@kajen.com
Monday, January 20, 1997

Environment: MSVC 4.2b Windows NT 4.0 

Hello all!

I experimented a bit with overriding the Dump() function. I never botherd
to use this possibility before, but now i find it rather nice. Although i
have a little problem. When i get the ordinary object dump after a memory
leak, my override of the Dump() wasn't called. Here is what i've done.

I created a ordinary MFC MDI project, with the default options. Then i
added a bit of code to test the Dump() override.

1)
Made the app class a friend of the view class (so i could create an
instance of the view in the app class).

class CTestView : public CView
{
	friend class CTestApp;
........
.......
.........
};

2)
Then i added this code to the Dump override of the View class.

void CTestView::Dump(CDumpContext& dc) const
{
	CView::Dump(dc);

	dc << "Testing, testing!!!";
}

3)

I created an instance of the CTestView class in the InitInstance function
of the app class, which i skip to delete on purporse. Like this.

BOOL CTestApp::InitInstance()
{
	// Standard initialization
	// If you are not using these features and wish to reduce the size
	//  of your final executable, you should remove from the following
	//  the specific initialization routines you do not need.

#ifdef _AFXDLL
	Enable3dControls();			// Call this when using MFC in a shared DLL
........
........
........
.......
	//***This is my test.********************************************

	CTestView *p_TestView;
	p_TestView =new CTestView;

	//*****************************************************************

	return TRUE;
}

4)

Then i compiled the project and run it. When it started, i just quited it
right off. Then i automaticly recived a object dump in the developer studio
output window. It looked like this.

Detected memory leaks!
Dumping objects ->
C:\Kjellkod\Vc32\Test\Test.cpp(97) : {116} client block at 0x00412ED0,
subtype 0, 68 bytes long.
a CTestView object at $00412ED0, 68 bytes long
Object dump complete.
The program 'C:\Kjellkod\Vc32\Test\Debug\Test.exe' has exited with code 0
(0x0).

No sign of the output text "Testing, testing!!!" here. This is what i think
is very strange. Here, if any, is the place where you is interested in the
dump output.
I hope this explains what i'm after.

Kind regards, Ola Theander


Bing Hou -- hou@tfn.com
Wednesday, January 22, 1997

Ola,

The 'Detected memory leaks! Dumping objects->' block is outputed by the 
AFX_EXITDUMP class's dtor, it has nothing to do with dumping your CView 
derived class. In order for your overriden Dump function to be called, you 
need to insert the code:
        #ifdef _DEBUG
           afxDump<<(CObject*)p_TestView;
        #endif
right after the object is created and before the app exits.

Bing Hou
hou@tfn.com
=========================
  Jambalaya Baby!!!
=========================


______________________________ Reply Separator 
_________________________________
Subject: Strange about Dump() function.
Author:  "Ola Theander"  at Internet
Date:    1/20/97 8:13 PM


Environment: MSVC 4.2b Windows NT 4.0 

Hello all!

I experimented a bit with overriding the Dump() function. I never botherd 
to use this possibility before, but now i find it rather nice. Although i 
have a little problem. When i get the ordinary object dump after a memory 
leak, my override of the Dump() wasn't called. Here is what i've done.
     
I created a ordinary MFC MDI project, with the default options. Then i 
added a bit of code to test the Dump() override.
     
1)
Made the app class a friend of the view class (so i could create an 
instance of the view in the app class).
     
class CTestView : public CView
{
        friend class CTestApp;
........
.......
.........
};
     
2)
Then i added this code to the Dump override of the View class.
     
void CTestView::Dump(CDumpContext& dc) const 
{
        CView::Dump(dc);
     
        dc << "Testing, testing!!!";
}
     
3)
     
I created an instance of the CTestView class in the InitInstance function 
of the app class, which i skip to delete on purporse. Like this.
     
BOOL CTestApp::InitInstance()
{
        // Standard initialization
        // If you are not using these features and wish to reduce the size 
        //  of your final executable, you should remove from the following 
        //  the specific initialization routines you do not need.
     
#ifdef _AFXDLL
        Enable3dControls();                     // Call this when using MFC in a
shared DLL
........
........
........
.......
        //***This is my test.********************************************
     
        CTestView *p_TestView;
        p_TestView =new CTestView;
     
        //*****************************************************************
     
        return TRUE;
}
     
4)
     
Then i compiled the project and run it. When it started, i just quited it 
right off. Then i automaticly recived a object dump in the developer studio 
output window. It looked like this.
     
Detected memory leaks!
Dumping objects ->
C:\Kjellkod\Vc32\Test\Test.cpp(97) : {116} client block at 0x00412ED0, 
subtype 0, 68 bytes long.
a CTestView object at $00412ED0, 68 bytes long 
Object dump complete.
The program 'C:\Kjellkod\Vc32\Test\Debug\Test.exe' has exited with code 0 
(0x0).
     
No sign of the output text "Testing, testing!!!" here. This is what i think 
is very strange. Here, if any, is the place where you is interested in the 
dump output.
I hope this explains what i'm after.
     
Kind regards, Ola Theander

Mike Blaszczak -- mikeblas@nwlink.com
Friday, January 24, 1997

[Mini-digest: 3 responses]

At 20:13 1/20/97 +0100, Ola Theander wrote:
>Environment: MSVC 4.2b Windows NT 4.0 

>Then i compiled the project and run it. When it started, i just quited it
>right off. Then i automaticly recived a object dump in the developer studio
>output window. It looked like this.

>Detected memory leaks!
>Dumping objects ->
>C:\Kjellkod\Vc32\Test\Test.cpp(97) : {116} client block at 0x00412ED0,
>subtype 0, 68 bytes long.
>a CTestView object at $00412ED0, 68 bytes long
>Object dump complete.
>The program 'C:\Kjellkod\Vc32\Test\Debug\Test.exe' has exited with code 0
>(0x0).

>No sign of the output text "Testing, testing!!!" here. This is what i think
>is very strange. Here, if any, is the place where you is interested in the
>dump output.
>I hope this explains what i'm after.

MFC won't dump objects after a memory leak unless you ask it to.  You need
to alter the dump context object that MFC's managing for you.  If you,
early in your CWinApp::InitInstance(), add this line of code:

	afxDump.SetDepth(1);

you'll have MFC dump both memory leaks _and_ call the Dump() members of 
objects which have leaked.

By default, the depth is zero.  That's just because it's pedantically more
conservative.

.B ekiM
http://www.nwlink.com/~mikeblas/
Why does the "new" Corvette look like a 1993 RX-7?
These words are my own. I do not speak on behalf of Microsoft.

-----From: "Ola Theander" 

----------
> Fr=E5n: Bing Hou 
> Till: Mfc -mailinglist ; Ola Theander

> =C4mne: Re: Strange about Dump() function.
> Datum: den 22 januari 1997 16:01
>=20
> Ola,
>=20
> The 'Detected memory leaks! Dumping objects->' block is outputed by the=
=20
> AFX_EXITDUMP class's dtor, it has nothing to do with dumping your CView=
=20
> derived class. In order for your overriden Dump function to be called,
you=20
> need to insert the code:
>         #ifdef _DEBUG
>            afxDump<<(CObject*)p_TestView;
>         #endif
> right after the object is created and before the app exits.
>=20
> Bing Hou
> hou@tfn.com
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D
>   Jambalaya Baby!!!
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D
>=20

Greetings Bing!

Thanks for your answer.
Ok, but isn't this a bit strange? Say you have an array of object pointer=
s.
In this list you add and remove objects along with the execution of the
program. When you exit the application you recive the information that yo=
u
have a memory leak. At this point the pointer to the object may be lost
since a long time. In this case you don't have any use of the Dump()
function. This illustrates my point. If you still have the pointer to the
object and is aware that you haven't deleted it, i don't consider the
object leaked since you know that you didn't delete it.

Kind regards, Ola Theander

-----From: Yeung Chi Kong 

Ola,

The 'Detected memory leaks! Dumping objects->' block is outputed by the 
AFX_EXITDUMP class's dtor, it has nothing to do with dumping your CView 
derived class. In order for your overriden Dump function to be called, you 
need to insert the code:
        #ifdef _DEBUG
           afxDump<<(CObject*)p_TestView;
        #endif
right after the object is created and before the app exits.

Bing Hou
hou@tfn.com
=========================
  Jambalaya Baby!!!
=========================

______________________________ Reply Separator 
_________________________________
Subject: Strange about Dump() function.
Author:  "Ola Theander"  at Internet
Date:    1/20/97 8:13 PM

Environment: MSVC 4.2b Windows NT 4.0 

Hello all!

I experimented a bit with overriding the Dump() function. I never botherd 
to use this possibility before, but now i find it rather nice. Although i 
have a little problem. When i get the ordinary object dump after a memory 
leak, my override of the Dump() wasn't called. Here is what i've done.

I created a ordinary MFC MDI project, with the default options. Then i 
added a bit of code to test the Dump() override.

1)
Made the app class a friend of the view class (so i could create an 
instance of the view in the app class).

class CTestView : public CView
{
        friend class CTestApp;
........
.......
.........
};

2)
Then i added this code to the Dump override of the View class.

void CTestView::Dump(CDumpContext& dc) const 
{
        CView::Dump(dc);

        dc << "Testing, testing!!!";
}

3)

I created an instance of the CTestView class in the InitInstance function 
of the app class, which i skip to delete on purporse. Like this.

BOOL CTestApp::InitInstance()
{
        // Standard initialization
        // If you are not using these features and wish to reduce the size 
        //  of your final executable, you should remove from the following 
        //  the specific initialization routines you do not need.

#ifdef _AFXDLL
        Enable3dControls();                     // Call this when using MFC in a
shared DLL
........
........
........
.......
        //***This is my test.********************************************

        CTestView *p_TestView;
        p_TestView =new CTestView;

        //*****************************************************************

        return TRUE;
}

4)

Then i compiled the project and run it. When it started, i just quited it 
right off. Then i automaticly recived a object dump in the developer studio 
output window. It looked like this.

Detected memory leaks!
Dumping objects ->
C:\Kjellkod\Vc32\Test\Test.cpp(97) : {116} client block at 0x00412ED0, 
subtype 0, 68 bytes long.
a CTestView object at $00412ED0, 68 bytes long 
Object dump complete.
The program 'C:\Kjellkod\Vc32\Test\Debug\Test.exe' has exited with code 0 
(0x0).

No sign of the output text "Testing, testing!!!" here. This is what i think 
is very strange. Here, if any, is the place where you is interested in the 
dump output.
I hope this explains what i'm after.

Kind regards, Ola Theander

||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
||                                                          ||
||   My Home Page address                                   ||
||	===> http://www.speednet.net/~cytusso/yeung/22.htm  ||
||       						    ||
||   E-mail address 					    ||
||	=====> Yeung Chi Kong	    ||
||                                                          ||
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||

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