Deleting from TreeWidget... Memoryleak

[VireX]

It's not a slot or a signal though. It has nothing to do with either. It's not connected to anything.

Let me show you a more detailed code for that, this is updated with logs so we can see better, there must be a bug in Qt or something because this makes no sense:

inline static void SafeDeleteItem( QTreeWidgetItem *pItem )
{
	QTreeWidgetItem *pParent = (QTreeWidgetItem*)pItem->parent();
	LOG("SafeDelete Text: %s (%x)", Q2A( pItem->text( 0 ) ), pItem );
	assert( pParent );
	int idx = pParent->indexOfChild( pItem );
	LOG("index=%d; ParentText: %s",idx, Q2A( pParent->text(0) ));
	LOG("Can We access pItem? %s    %s", Q2A( pItem->text(0) ), Q2A(pItem->parent()->text(0)));
	pParent->takeChild( idx );
  LOG("Can We access Parent? %s", Q2A( pParent->text(0) ));
  LOG("Can We access pItem? %s    %s", Q2A( pItem->text(0) ), Q2A(pItem->parent()->text(0)));
 
	ASSERT( !pItem->parent() );
	ASSERT( pParent->indexOfChild ( pItem ) == -1 );
	ASSERT( !pItem->treeWidget() );
	LOG("parent=%d",pParent->treeWidget() );
	ASSERT( pParent->treeWidget() );
 
	delete pItem; // mem leak
 
	LOG("SafeDeleteOut" );
 
}

inline static void SafeDeleteItem( QTreeWidgetItem *pItem )
{
	QTreeWidgetItem *pParent = (QTreeWidgetItem*)pItem->parent();
	LOG("SafeDelete Text: %s (%x)", Q2A( pItem->text( 0 ) ), pItem );
	assert( pParent );
	int idx = pParent->indexOfChild( pItem );
	LOG("index=%d; ParentText: %s",idx, Q2A( pParent->text(0) ));
	LOG("Can We access pItem? %s    %s", Q2A( pItem->text(0) ), Q2A(pItem->parent()->text(0)));
	pParent->takeChild( idx );
  LOG("Can We access Parent? %s", Q2A( pParent->text(0) ));
  LOG("Can We access pItem? %s    %s", Q2A( pItem->text(0) ), Q2A(pItem->parent()->text(0)));

	ASSERT( !pItem->parent() );
	ASSERT( pParent->indexOfChild ( pItem ) == -1 );
	ASSERT( !pItem->treeWidget() );
	LOG("parent=%d",pParent->treeWidget() );
	ASSERT( pParent->treeWidget() );

	delete pItem; // mem leak

	LOG("SafeDeleteOut" );

}

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OUTPUT in log:

22:55:23 SafeDelete Text: bob (2e25d20)
22:55:23 index=1; ParentText: CorrectParentText
22:55:23 Can We access pItem? bob CorrectParentText
22:55:23 Can We access Parent? CorrectParentText
22:55:23 Can We access pItem? bob CorrectParentText
22:55:23 Debug assert failed on line 239 of testone.h.

How can I access pItem->parent()->text(0), but then, the next line assert fails ON:
ASSERT(!pItem->parent())

I don't understand this.

EDIT:
If I remove the asserts, it goes by this function OUT... and then it comes back to this function again in the next item in the list... and crashes on the SECOND
LOG("Can We access pItem? %s %s", Q2A( pItem->text(0) ), Q2A(pItem->parent()->text(0)));

Like as if takeChild destroys the parent or something.

[wysota]

What calls that "DeleteUser" method? How does the structure of the tree look like? Do those items really have parent items?

[VireX]

As you can see by the log data:

22:55:23 SafeDelete Text: bob (2e25d20)
22:55:23 index=1; ParentText: CorrectParentText
22:55:23 Can We access pItem? bob CorrectParentText
22:55:23 Can We access Parent? CorrectParentText
22:55:23 Can We access pItem? bob CorrectParentText
22:55:23 Debug assert failed on line 239 of testone.h.

This means, that bob has a parent named CorrectParentText, and so I don't understand how an assert can fail, when it calls the parent() even though we just did it the line before, unless its some sort of weird bug in takeChild causing memory corruption or something.

what the last two lines mean is this:
pItem->parent()->text( 0 ); <--- no crash.
pItem->parent() <--- crash.

[wysota]

Correct me if I'm wrong but it seems to me the behaviour is perfectly fine with what your code looks like. The thing you do is more or less like the following:
1. find index of pItem which is child of pParent
2. pParent->takeItem(pItem)
3. access pItem->parent()
4. app asserts

The thing is that in (2) you remove the item from its parent, thus it doesn't have a parent anymore, therefore accessing the parent before (2) is fine, but after (2) causes the assert to fire because the parent is not valid anymore (it's null).