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MFC - CList RemoveAt() function

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Join Date: Dec 2004

Posts: 489

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Acidburn

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MFC - CList RemoveAt() function

May 4th, 2006

Hello guys i keep getting a

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Unhandled exception at 0x7c177ac0 (mfc71d.dll) in LSMUtility.exe: 0xC0000005: Access violation reading location 0xcdcdcdbd.

However according to MSDN the code is right:

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void CTemp::OnDelete()
{
	// TODO: Add your control notification handler code here
	CLSMUtilityDlg *main_dlg = (CLSMUtilityDlg *) GetParent();
 
	if(pos != main_dlg->BTList.GetTailPosition())
	{
		main_dlg->BTList.RemoveAt(pos);
		MessageBox("deleted");
	}
}
void CTemp::OnDelete()
{
	// TODO: Add your control notification handler code here
	CLSMUtilityDlg *main_dlg = (CLSMUtilityDlg *) GetParent();
	
	if(pos != main_dlg->BTList.GetTailPosition())
	{
		main_dlg->BTList.RemoveAt(pos);
		MessageBox("deleted");
	}
}

the above code works and the error only occurs if itterate through the list by using Next and Back buttons and functions:

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void  CTemp::OnNext()
{
	// TODO: Add your control notification handler code here
		CLSMUtilityDlg *main_dlg = (CLSMUtilityDlg *) GetParent();
		if(pos != main_dlg->BTList.GetTailPosition())
	{
		 main_dlg->BTList.GetNext(pos);
		Display();
	}
	else
		MessageBox("end");
}
 
//and Pervious
 
void CTemp::OnPervious()
{
	// TODO: Add your control notification handler code here
	CLSMUtilityDlg *main_dlg = (CLSMUtilityDlg *) GetParent();
	if(pos != main_dlg->BTList.GetHeadPosition())
	{
		 main_dlg->BTList.GetPrev(pos);
		Display();
	}
	else
 
		MessageBox("At beginning");
}
void  CTemp::OnNext()
{
	// TODO: Add your control notification handler code here
		CLSMUtilityDlg *main_dlg = (CLSMUtilityDlg *) GetParent();
		if(pos != main_dlg->BTList.GetTailPosition())
	{
		 main_dlg->BTList.GetNext(pos);
		Display();
	}
	else
		MessageBox("end");
}

//and Pervious

void CTemp::OnPervious()
{
	// TODO: Add your control notification handler code here
	CLSMUtilityDlg *main_dlg = (CLSMUtilityDlg *) GetParent();
	if(pos != main_dlg->BTList.GetHeadPosition())
	{
		 main_dlg->BTList.GetPrev(pos);
		Display();
	}
	else

		MessageBox("At beginning");
}

Can anyone suggest where i've gone wrong please?

Thanks

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Join Date: Apr 2004

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Dave Sinkula Dave Sinkula is offline

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Re: MFC - CList RemoveAt() function

May 4th, 2006

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Access violation reading location 0xcdcdcdbd.

Isn't that how uninitialized memory is filled in debug mode?

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Join Date: Dec 2004

Posts: 489

Reputation: Acidburn is an unknown quantity at this point

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Acidburn

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Re: MFC - CList RemoveAt() function

May 4th, 2006

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Originally Posted by Dave Sinkula

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Access violation reading location 0xcdcdcdbd.
Access violation reading location 0xcdcdcdbd.
Isn't that how uninitialized memory is filled in debug mode?

I think so, but I'm not sure how to fix it, it would appear that when i delete an object from the list, it gets deleted, but if i click pervious that works but then if i delete that and click 'next' i get that error.