C / C++ / MFC Discussion Boards

james_bond10-Jul-09 8:00

10-Jul-09 8:00

Problem: "Debug Assert Error" in VC++.NET

1) I have a Clistctrl object placed in a dialog.
2) An mfc worker thread calls a display function to update the Clistctrl.
3) The display function uses methods such as Clistctrl::setitemtext etc to update the Clistctrl display.

The application works fine.
--------------

However ONLY when I close the application

1) i get a "debug assert error".
2) I've noticed that the mfc worker thread crashes.
--------------

This "debug assert error" happens (I believe) because:

1) When the application closes, the Clistctrl object is destroyed.
2) But the display function that is called by the worker thread continues
accessing the destroyed Clistctrl object by calling the Clistctrl::setitemtext function.
3) Thus the thread crashes leading to the debug assert error.

-------------
Question:
1) Am i correct in assuming the cause of the "debug assert error" ? If not, correct me please.
2) How do i fix the above problem ?

Any help will be greatly appreciated

Re: "Debug Assert Error" in VC++.NET

josda100010-Jul-09 8:33

josda1000

10-Jul-09 8:33

It sounds like you're right, though I don't know all of the intricacies of your code. But assuming you're right, I suggest that when you tell the program to exit (via CAppDlg), I'd call that separate thread and tell it to stop working. I would not in this case send a message to it, but instead call a function directly. Once that function exits, your app can continue to shut down safely.

Try that, and see what happens.

Re: "Debug Assert Error" in VC++.NET

james_bond10-Jul-09 10:56

james_bond

10-Jul-09 10:56

Hi,

How do i set an event handler for when the user clicks on the close 'x' button of the application window?

Also, please note that I'm a novice in VC++.NET.

Any help will be greatly appreciated.

Re: "Debug Assert Error" in VC++.NET

josda100010-Jul-09 11:07

josda1000

10-Jul-09 11:07

do a search on WM_CLOSE in bing or goolge or another search engine. that should help.

Re: "Debug Assert Error" in VC++.NET

james_bond10-Jul-09 14:05

james_bond

10-Jul-09 14:05

Hi,

I've tried to exit the thread on the "close" event. Unfortunately, the worker
thread seems to crash somewhere in between the following 2 instants.
a) when the user clicks on the close button 'x' of the
application window AND
b) when the "close" event handler is called.

Thus the "Debug Assert failure "problem persists.

Should i try the suggestion posted by Stuart Dootson ?

Any help will be greatly appreciated.

Re: "Debug Assert Error" in VC++.NET

josda100010-Jul-09 16:02

josda1000

10-Jul-09 16:02

A) Is the CDialog::OnClose() method called before or after you try to shut down the thread? This could have been a quick hack to fix the problem, though not a solid solution.

B) Seriously, Stuart is right. Threads should post messages to the main application, and not to dialogs directly, that way pointers and objects that are not valid are thrown away easily by the operating system, and you don't have to worry about this sort of thing consistently. I would rework the code as suggested by Stuart. But it shouldn't be that difficult.

Re: "Debug Assert Error" in VC++.NET

Stuart Dootson10-Jul-09 8:35

Stuart Dootson

10-Jul-09 8:35

You don't want to manipulate UI from a worker thread. You can post windows messages safely enough, but calling control methods will, at best, send a message rather than posting it, which isn't a good idea, believe me.

Try posting an app-specific message to the UI threads queue using PostThreadMessage. Respond to that message in the UI by redrawing the UI.

Also, you probably want to tell the worker to stop before terminating and wait for it to do so.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Release Mode issue

dipuks10-Jul-09 7:30

dipuks

10-Jul-09 7:30

Hello,

I am trying to run my Win32 application in Release mode. The application breaks and it pops up a message box with title "Microsoft Visual C++ Debug Library" and the first line in message box is "Debug Error!"

Below that, there is some "Buffer overrun ........." message.

And it has 3 buttons, ABORT, RETRY, CANCEL.

Just confused why in Release mode it popos up a message box with Debug Error.

Is it a problem with Release Configuration setting?

Any help is welcome.

Thanks in advance!

Re: Release Mode issue

Stuart Dootson10-Jul-09 8:31

Stuart Dootson

10-Jul-09 8:31

No, it sounds more like a problem with your code - the "Buffer overrun" gives it away.

Although...why does it say "Microsoft Visual C++ Debug Library" - are you linking with a release variant of the run-time (in project properties, check C/C++->Code Generation->Runtime Library)?

Anyway - if you've got the correct runtime variant, turn on debug information (you can, even in a Release mode app) and run your app under the debugger. See where in your code the exception is raised.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Release Mode issue

Cyrilix10-Jul-09 11:29

Cyrilix

10-Jul-09 11:29

Check to see if you're not initializing any pointers to 0. Debug mode will do this for you, but in release mode, a pointer may start off with a garbage value, and consequently, if you try to use it, any one of a number of weird things can happen.

CD Drive functions

dipuks10-Jul-09 7:27

dipuks

10-Jul-09 7:27

Hello,

I am working on a Win32 application in C/C++ using Visual Studio 2003.

There is a feature to write application data to a CD. This feature works fine. The issue is with, when the User enters a CD to the drive the application should be able to auto detect that and prompt the User.

Is there a Windows function to do that?

Is there a function which will retrieve whether a CD has been inserted to the CD Drive?

Thanks in advance!

Re: CD Drive functions

David Crow10-Jul-09 8:00

David Crow

10-Jul-09 8:00

Handle the WM_DEVICECHANGE message. The event will be DBT_DEVICEARRIVAL.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

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default parameters - functions

john john mackey10-Jul-09 6:41

john john mackey

10-Jul-09 6:41

if I define a function like

int MakeBigger(int nVal1, int nVal2, int nMultiplier /*=2*/)
{
   int nRetValue;
   nRetValue = (nVal1+nVal2) * nMultiplier;
   return (nRetValue);
}

is it necessary that the default parameter (nMultiplier) be the last parameter in the list?

For example, could the following be valid:

int MakeBigger(int nVal1, int nMultiplier/*=2*/, int nVal2)
{
}

or also

int MakeBigger(int nMultiplier/*=2*/, int nVal1, int nVal2)
{
}

ALSO
Is it valid to have more than one default parameter? AND what is the correct syntax:

int MyFn(int nDefaultParam/*=2*/)

int MyFn(int nDefaultParam=2)

Thanks,
Johnny

Re: default parameters - functions

krmed10-Jul-09 7:01

krmed

10-Jul-09 7:01

Default parameters must be last in your function definitions.

You can have more than one default parameter:

int MyFn(int nParam1, bool bRequired = true, float fMultiplier = 2.26);

Hope that helps.

Karl - WK5M
PP-ASEL-IA (N43CS)
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Re: default parameters - functions

john john mackey10-Jul-09 7:34

john john mackey

10-Jul-09 7:34

Thanks!

I have seen two types of syntax regarding the definition of the default values:

void MyFn(int nDefault/*=2*/)

and

void MyFn(int nDefault=2)

Which is "proper"?

Re: default parameters - functions

David Crow10-Jul-09 8:02

David Crow

10-Jul-09 8:02

john john mackey wrote:
Which is "proper"?

Only the latter since the former is just a comment.

Re: default parameters - functions

josda100010-Jul-09 8:05

josda1000

10-Jul-09 8:05

void MyFn(int nDefault=2) is necessary somewhere in the code. If you declare this function in a class, then put this code in the class. If you are declaring it before the function call and definition, you can declare it like this as well. Then, you can use void MyFn(int nDefault/*=2*/) when you define the function.

Otherwise, when you define the function, you must write void MyFn(int nDefault=2) as the function header.

Re: default parameters - functions

John R. Shaw10-Jul-09 8:09

John R. Shaw

10-Jul-09 8:09

The second one would be the prototype and the first one would be the actual function.

void MyFn(int nDefault=2); // prototype
void MyFn(int nDefault/*=2*/)   // function
{ ... }

The only reason for applying the second one to the functions is so that it reflects the prototype (a.k.a. documents prototype parameter).

INTP
"Program testing can be used to show the presence of bugs, but never to show their absence."Edsger Dijkstra

Re: default parameters - functions

rew´RaZiel17-Jul-09 21:40

rew´RaZiel

17-Jul-09 21:40

Which is a bad practice. Since modification of default value would need to change two places in code...

Create 16 bit process under 32bit using CreateProcess

RoryODonnell10-Jul-09 4:41

RoryODonnell

10-Jul-09 4:41

Does anybody know how the NTVDM.EXE, launched CREATE_SEPARATE_WOW_VDM via CreateProcess, shuts itself down.

I have a 16bit app and a 16bit DLL. Lets assume that the 16 bit DLL allocates some resources and then frees them in the WEP function.
The 16 bit app is created via 32bit call CreateProcess with CREATE_SEPARATE_WOW_VDM. However, upon 16 bit app termination, the 16 bit DLL WEP function is not automatically called.
The 16bit DLL WEP code IS called when CREATE_SHARED_WOW_VDM flags settings is used. Does anyone know why or have they seen this behavior before?

I am starting to get alot of insufficient resources error messages and was wondering is it related. Now, it is completely feasible that there are other memory/resource leaks in the 16bit app/dll. I'm just trying to rule this out first.

Error message =
The Win 16 Subsystem has insufficent resources to continue running. Click on OK, close your applications, and restart your machine.

crashed ( i CSimpleStringT ) when new control are added to dialog

Bilge Kaan10-Jul-09 4:02

Bilge Kaan

10-Jul-09 4:02

Hello,
After I have added some new controls to dialog and add variables related with these new controls
,application crashes.( no crash after controls are added but related variable are not defined) When I break application and try to debug it , I saw that it is crashing
within void Reallocate( _In_ int nLength ) function of CSimpleStringT class.Any comments ...

Re: crashed ( i CSimpleStringT ) when new control are added to dialog

David Crow10-Jul-09 4:33

David Crow

10-Jul-09 4:33

Can you remove all of the related variables and then add them back in one at a time until the problem appears?

Re: crashed ( i CSimpleStringT ) when new control are added to dialog

Bilge Kaan10-Jul-09 5:04

Bilge Kaan

10-Jul-09 5:04

I have already remove all latest added control, and try to put one bye one and change their IDs also. I got the some result.As soon as first variable defined after first control is put onto dialog , it crashes.

Re: crashed ( i CSimpleStringT ) when new control are added to dialog

David Crow10-Jul-09 5:28

David Crow

10-Jul-09 5:28

Bilge Kaan wrote:
...it crashes.

Exception, assertion, or some other anomaly?

Linking error LNK2019 while building DLL

Member 154408710-Jul-09 2:37

Member 1544087

10-Jul-09 2:37

Hi,

I am working on one C++ DLL. That dll is internally using some statically build common.lib. When I am building the DLL, I am getting following linking errors:

Creating library Release Standard Heap/paecustomactions.lib and object Release Standard Heap/paecustomactions.exp
common.lib(properocommon.obj) : error LNK2019: unresolved external symbol __imp__mymalloc referenced in function _MIDL_user_allocate@4
common.lib(properocommon.obj) : error LNK2019: unresolved external symbol __imp__myrealloc referenced in function "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl PROPERO::FormatStringA(char const *,...)" (?FormatStringA@PROPERO@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@PBDZZ)
common.lib(hcheapfix.obj) : error LNK2019: unresolved external symbol __imp__myfree_cond referenced in function _myfree
common.lib(sysconfig.obj) : error LNK2019: unresolved external symbol __imp__mycalloc referenced in function "public: __thiscall PROPERO::Runnable::Runnable(int,int,unsigned short const *)" (??0Runnable@PROPERO@@QAE@HHPBG@Z)
common.lib(stackTrace32.obj) : error LNK2001: unresolved external symbol __imp__mycalloc
../bin/i386/release/paecustomactions.dll : fatal error LNK1120: 4 unresolved externals

Can you please guide me to solve this issue?

Thanks in advance

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