Re: How to safely release the memory when I dynamic create the the dialog ? [modified] - C / C++ / MFC Discussion Boards

Re: Help needed in Solving LNK2001

Richard MacCutchan18-Aug-10 22:19

Richard MacCutchan

18-Aug-10 22:19

bleedingfingers wrote:
Doesn't it tell why this error is issued and isn't that good enough to fix it?

Possibly, but rather than ask if he has it installed you could have posted a link to the page with the solution so the OP understands what you meam.

It's time for a new signature.

Re: Help needed in Solving LNK2001

bleedingfingers18-Aug-10 22:25

bleedingfingers

18-Aug-10 22:25

Yeah, must have. I figured he could get what I meant but he didn't seem to Wink | ;)

...byte till it megahertz...

Re: Help needed in Solving LNK2001

Cedric Moonen18-Aug-10 21:50

Cedric Moonen

18-Aug-10 21:50

This typically looks like you forgot to provide a body for the constructor and destructor of your Method class.

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Re: Help needed in Solving LNK2001

Richard MacCutchan18-Aug-10 21:54

Richard MacCutchan

18-Aug-10 21:54

You have a call to a Method() constructor and destructor in your module Program, but you have not included the body of the class in your project. Alternativel you need a extern "C" declaration around your class.

It's time for a new signature.

How to safely release the memory when I dynamic create the the dialog ?

wangningyu18-Aug-10 20:50

wangningyu

18-Aug-10 20:50

I try this way ,but feel it doesn't safety.

#include "TestDlg.h"

class CMainDlg : CDialog
{
public:
    CTestDlg    *m_pTestDlg;
    void ShowDlg();
    void FreeDlg();
}

void CMainDlg::ShowDlg()
{
    m_pTestDlg = new CTestDlg();
    m_pTestDlg->Create(IDD_TEST_DLG,this);
    m_pTestDlg->CenterWindow();
    m_pTestDlg->ShowWindow(SW_SHOWNORMAL);
    m_pTestDlg->UpdateWindow();
}

void CMainDlg::FreeDlg()
{
    if( m_pTestDlg != NULL )
    {
        delete m_pTestDlg;
    }
}

Is this right ?

How to safty free the memory ?

Thanks for your reply !
Best Regards !

Re: How to safely release the memory when I dynamic create the the dialog ?

Eugen Podsypalnikov18-Aug-10 21:08

Eugen Podsypalnikov

18-Aug-10 21:08

You could try the following Smile | :)

void CMainDlg::FreeDlg()
{
  if (m_pTestDlg) {
    if (m_pTestDlg->GetSafeHwnd()) {
      m_pTestDialog->EndDialog(IDCANCEL);
    }
    delete m_pTestDlg;
    m_pTestDlg = NULL; // the same line should be placed in the main dialog constructor
  }
}

void CMainDlg::OnDestroy()
{
  FreeDlg(); // an extra check :)
}

virtual void BeHappy() = 0;

Re: How to safely release the memory when I dynamic create the the dialog ?

Niklas L18-Aug-10 22:37

Niklas L

18-Aug-10 22:37

Another point is that there is no point in having a pointer for your dialog if you at any point are worried about memory. You could just use CTestDlg m_testDlg;

Using a pointer as you have has only one advantage. You can use a forward declaration of CTestDlg in your header file to avoid compile time dependencies. This will reduce compilation time if you later make changes to CTestDlg. In practice, this applies to large project only.

Also, the UpdateWindow() call is superfluous.

home

Re: How to safely release the memory when I dynamic create the the dialog ? [modified]

Aescleal18-Aug-10 22:44

Aescleal

18-Aug-10 22:44

Normally I'd agree about using a member rather than a dynamically created object. However in the case of a modeless dialogue box you can have the problem of resetting the members of the dialogue (if the dialogue box is closed and reopened) which can lead to some funky fiddling with manually calling destructors and placement new. As soon as you start thinking about that you might as well just say sod it and recreate the object as you need to use it.

Cheers,

Ash

Edited as I said completely the wrong thing and confused Niklas. Sorry!

modified on Thursday, August 19, 2010 7:26 AM

Re: How to safely release the memory when I dynamic create the the dialog ?

Niklas L18-Aug-10 23:24

Niklas L

18-Aug-10 23:24

When having a modal dialog I have never found the use of dynamically allocate the object. I just create it as automatic on the stack in whatever function I need it.

home

Re: How to safely release the memory when I dynamic create the the dialog ?

Aescleal19-Aug-10 1:26

Aescleal

19-Aug-10 1:26

If I had a brain I'd be dangerous. I should really proof read what I write more. There was a finger faux-pas in my response, I should have said "modeless."

For a modal dialogue I wholeheartedly agree - you'd be cracked to not stick it on the stack.

Cheers,

Ash

Re: How to safely release the memory when I dynamic create the the dialog ?

Aescleal18-Aug-10 22:39

Aescleal

18-Aug-10 22:39

A quick point...

IF you're creating a modeless dialogue box (created with Create) then make sure you kill it off using DestroyWindow, not EndDialog.

IF you do and you're sure that CTestDlg is only going to be created dynamically then overide PostNCDestroy to clean up the C++ object. It's a bit disgusting but there are so many MFC classes that do it you might as well join in the fun! The advantage is that all you have to do is destroy the window and it'll clean up after itself:

void CTestDialog::PostNCDestroy()
{
    delete this;
}

Cheers,

Ash

Re: How to safely release the memory when I dynamic create the the dialog ?

Rick York19-Aug-10 15:34

Rick York

19-Aug-10 15:34

The statement "delete this" is amusing. I always add the comment "// hari kari".

Anyway, common practice is to keep a pointer to the modeless dialog in the object that creates it so you can just bring it forward if it is reinvoked ie., the pointer is not null. What I do in this case is I pass the address of that pointer to the dialog object so it can null it when it is closed - usually preceding the "delete this" statement. The PostNCDestroy method then looks like this :

void CTestDialog::PostNCDestroy()
{
    if( m_pSelf )
        *m_pSelf = NULL;    // null parent's pointer to us
    delete this;
}

That is the best and easiest way I have come up with to deal with the issue so far.

Re: How to safely release the memory when I dynamic create the the dialog ?

Cool_Dev18-Aug-10 23:43

Cool_Dev

18-Aug-10 23:43

in addition to what Aescleal told, over-riding PostNcDestroy is useful when you are dealing with a number of pop up child windows and letting the user to close them dynamically.

How to get the total files numbers of a whole computer?

Aric Wang18-Aug-10 16:32

Aric Wang

18-Aug-10 16:32

Does it have some functions? to get the file nubmers of the whole computer? How does the vir killer software to do that,how could they control the progress of the whole files of the computer? Rose | [Rose]

I am not a genius, but shed more sweat!

Re: How to get the total files numbers of a whole computer?

Niklas L18-Aug-10 19:59

Niklas L

18-Aug-10 19:59

You can traverse all files in a file system by using the FindFirstFile[^], FindNextFile[^] and FindClose[^] API. That will take a while. You could then check for changes using FindFirstChangeNotification[^] et al functions.

Anti virus programs use different techniques, like hooks[^] for file access functions, and maybe even rootkits.

Just a few ideas.

home

Deadlocked UI need a little help

Spawn@Melmac18-Aug-10 11:33

Spawn@Melmac

18-Aug-10 11:33

I have what seems to be a random deadlock in my application which I am hoping someone can shed some light on.

The occurance of the deadlock is random but the call stack is far from it... below is the stack I am getting.

0:001> ~0s;kbn
eax=002f0f60 ebx=00000000 ecx=00000f60 edx=00000f60 esi=0079cc10 edi=0015ec54
eip=61088bc4 esp=0015ea90 ebp=0015ebd0 iopl=0         nv up ei pl nz na pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000206
mfc90ud!CWnd::OnWndMsg+0x224:
61088bc4 335508          xor     edx,dword ptr [ebp+8] ss:002b:0015ebd8=00000087
 # ChildEBP RetAddr  Args to Child              
00 0015ebd0 61088962 00000087 00000000 00000000 mfc90ud!CWnd::OnWndMsg+0x224 
01 0015ebf0 61085d80 00000087 00000000 00000000 mfc90ud!CWnd::WindowProc+0x32
02 0015ec6c 61086346 0015f884 000b1068 00000087 mfc90ud!AfxCallWndProc+0xf0 
03 0015ec8c 61081a3b 000b1068 00000087 00000000 mfc90ud!AfxWndProc+0xa6 
04 0015ecc8 750c6238 000b1068 00000087 00000000 mfc90ud!AfxWndProcBase+0x5b 
05 0015ecf4 750c68ea 610819e0 000b1068 00000087 USER32!InternalCallWinProc+0x23
06 0015ed6c 750ccd1a 00000000 610819e0 000b1068 USER32!UserCallWinProcCheckWow+0x109
07 0015edb0 750ccd81 00c8ba70 00000000 610819e0 USER32!SendMessageWorker+0x581
08 0015edd4 750e0fb1 000b1068 00000087 00000000 USER32!SendMessageW+0x7f
09 0015ee00 750e29a2 00cadd90 00000000 00c87810 USER32!xxxRemoveDefaultButton+0x5f
0a 0015ee30 750dc0cd 00cadd90 00000000 00290b46 USER32!xxxCheckDefPushButton+0x12d
0b 0015ee68 610eebb3 001e0ada 00000000 f53163fb USER32!IsDialogMessageW+0x156
0c 0015ee80 6108f76e 0079cbc8 0058cff8 0015eea8 mfc90ud!CWnd::IsDialogMessageW+0x73 
0d 0015ee90 610c730f 0079cbc8 0058cff8 0058cff8 mfc90ud!CWnd::PreTranslateInput+0x6e 
0e 0015eea8 6108afbd 0079cbc8 0058cff8 00190712 mfc90ud!CDialog::PreTranslateMessage+0xef 
0f 0015eebc 611174df 001e0ada 0079cbc8 0015eedc mfc90ud!CWnd::WalkPreTranslateTree+0x8d 
10 0015eed8 61118595 0079cbc8 002f9940 0015eef8 mfc90ud!AfxInternalPreTranslateMessage+0x4f 
11 0015eee8 61117555 0079cbc8 002f9940 0015ef18 mfc90ud!CWinThread::PreTranslateMessage+0x25 
12 0015eef8 61117391 0079cbc8 0015ef14 61081be9 mfc90ud!AfxPreTranslateMessage+0x25 
13 0015ef18 611188ee 002f9940 0015ef30 611173e1 mfc90ud!AfxInternalPumpMessage+0xe1 
0:000> .frame c
0c 0015ee80 6108f76e mfc90ud!CWnd::IsDialogMessageW+0x73 
0:000> dv
           this = 0x0058cff8
          lpMsg = 0x0079cbc8
0:000> dt lpMsg -r
Local var @ 0x15ee88 Type tagMSG*
0x0079cbc8 
   +0x000 hwnd             : 0x000a0bb6 HWND__
      +0x000 unused           : ??
   +0x004 message          : 0x201
   +0x008 wParam           : 1
   +0x00c lParam           : 917536
   +0x010 time             : 0x32b9eaf
   +0x014 pt               : tagPOINT
      +0x000 x                : 2742
      +0x004 y                : 915

Now the stack from USER32!SendMessageW+0x7f is pretty consistent and it always seems to be message 0x201 (WM_LBUTTONDOWN). Once in this state control is never returned to my code so I am sure I am missing something but I do not know what.

I don't have any code that is looking for WM_LBUTTONDOWN and I have not set anything relating to it, as far as I can tell, and I know when the problem occurs I have not been anywhere near the LBUTTON on my mouse!?!?

In searching around I came across a site in German that says the problem is caused by missing WS_GROUP from the RC. So I added some and I am still having the same problem.

If anyone has had this before and/or can give me some ideas as to what I am missing I would appreciate it.

Many thanks

Alan

Re: Deadlocked UI need a little help

Spawn@Melmac19-Aug-10 10:52

Spawn@Melmac

19-Aug-10 10:52

After a little more digging I have discovered that I am getting stuck in a loop inside CWnd with a WM_GETDLGCODE being passed to all of the controls in my application?|?|? The main dialog consists of

BEGIN
    CONTROL         "",IDC_MNG_TAB,"SysTabControl32",0x0,17,25,248,300
    PUSHBUTTON      "Edit",IDC_MNG_EDIT,31,345,51,14,WS_GROUP
    PUSHBUTTON      "Apply",IDC_MNG_APPLY,112,345,50,14,WS_DISABLED | WS_GROUP
    DEFPUSHBUTTON   "Cancel",IDC_MNG_CANCEL,194,345,50,14,WS_GROUP
    CONTROL         "",IDC_MAIN_TREE,"SysTreeView32",WS_BORDER | WS_HSCROLL | WS_GROUP | WS_TABSTOP,299,75,209,250
    CONTROL         "",IDC_RPT_TAB,"SysTabControl32",0x0,544,25,248,300
    PUSHBUTTON      "Execute",IDC_RPT_EXECUTE,561,345,50,14,WS_GROUP
    PUSHBUTTON      "Cancel",IDC_RPT_CANCEL,724,345,50,14,WS_GROUP
    CONTROL         284,IDC_LOGO,"Static",SS_BITMAP,299,329,209,39
    GROUPBOX        "Manage",IDC_MNG,7,7,268,369
    GROUPBOX        "Monitor",IDC_MONITOR,285,7,237,369
    GROUPBOX        "Report",IDC_RPT,532,7,268,369
    GROUPBOX        "Status",IDC_ST_STATUS,299,21,209,44
    CONTROL         0,IDC_STATUS,"Static",SS_BITMAP,324,31,159,28
END

The group boxes and tab controls are owner drawn.

Any help would be appreciated.

Alan

Logging Semaphore names

keloth8718-Aug-10 10:18

keloth87

18-Aug-10 10:18

H,
I want to read semaphore object names from each active processes. Is there any windows API available? Any method or idea to implement this?

Re: Logging Semaphore names

Cool_Dev18-Aug-10 20:40

Cool_Dev

18-Aug-10 20:40

here is an Handle Enumeration example from sysinternals using NtQuerySystemInformation API

http://forum.sysinternals.com/topic14546.html

Unfortunately, NtQuerySystemInformation Function is not recommended to use

Alternatively i could find another sample using DbgEng API, though its not meant for this purpose.

http://www.debuginfo.com/examples/handledump.html

vector of template class

forwardsim18-Aug-10 9:23

forwardsim

18-Aug-10 9:23

Hi,

I want to fill a vector that memorize multiple instances of a template class (those instances potentially use different template type).

Here my question in code :

// a basic template class
template< class T >
class CTest
{
 // something
}

// ...

// then some instances
CTest< int > a;
CTest< int > b;
CTest< double > c;

// Then we can fill a vector like this
vector< CTest< int > * > myints;
myints.push_back( &a );
myints.push_back( &b );

// But, is it possible to do something like that

vector< CTest * > all; // this line compiles

// but not those...
all.push_back( &a ); // fill template class instance using int type 
all.push_back( &c ); // fill template class instance using double type

In short, I don't find the correct way to fill my vector 'all'...
All my tries give a "cannot convert parameter from something to another thing" error.

Anyone know if it is possible and how ?

Thanks in advance for all your answers,

SV

Re: vector of template class

Richard MacCutchan18-Aug-10 9:44

Richard MacCutchan

18-Aug-10 9:44

forwardsim wrote:
All my tries give a "cannot convert parameter from something to another thing" error.

Why post an interpretation of the message you see rather than the real message, which would actually help people to figure out what is wrong.

It's time for a new signature.

Re: vector of template class

forwardsim18-Aug-10 10:08

forwardsim

18-Aug-10 10:08

Thanks for your interest.

I didn't write the real message for three reasons. First, I try a lot of things and I got a lot of different messages, but all construct from this general sentence. Second, when I copied an example of error, a lot of characters didn't copied correctly. Finally, I was expecting anyway that interesting people will try it.

If you try the example code in my post, the error shown is :

error C2664: 'std::vector<_Ty>::push_back' : cannot convert parameter 1 from 'CTest<t> *__w64 ' to 'CTest *const &'

Hope that helps you figure out what to do...

Thanks again,

SV.

Re: vector of template class

Aescleal18-Aug-10 10:10

Aescleal

18-Aug-10 10:10

Quick C++ quiz for you...

If I define a template class:

template<typename T>
class test
{
};

What's the type of a and b in the following declarations?

test<A> a;
test<B> b;

Quick hint - they're not the same.

Now as std::vectors can only hold objects of a single type it's impossible to mix objects of different instantiations of a template class.

Incidentally are you sure you wrote:

std::vector< test * > all;

or something similar? To the best of my knowledge that shouldn't compile and on a bunch of compilers I tried it on they all complained mightily about the fact that test was a template.

Cheers,

Ash

Re: vector of template class

forwardsim18-Aug-10 10:34

forwardsim

18-Aug-10 10:34

Thanks.

I understand your point since it's my feeling.

The fact that :

std::vector< test * > all;

passes without complains from my compiler gives me some hopes. Unfortunately, I don't have any other compilator around to try it.

I'm using Microsoft Visual C++ 2005.

SV.

Re: vector of template class

Aescleal18-Aug-10 11:11

Aescleal

18-Aug-10 11:11

Ouch, looks like a nasty compiler bug - it should reject the declaration of the vector.

Just had a quick prod with VC++ 2005 - it allows the declaration/definition of the object but you can't do a lot with it, thankfully.

Cheers,

Ash

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