RE: [Plib-devel] [PATCH] puListBox.cxx: don't crash with empty li st + setTopItem(0)

[Fay J. F Dr C. U. AFSEO/SK <joh...@eg...>]

Melchior,

	That is a good find, but I'm a little concerned about the fix.  I
would prefer the following code:

puListBox.cxx:74
  void puListBox::setTopItem( int item_index )
  {
    top = item_index ;
+   if ( top > num-1 )
+     top = num-1;
    if ( top < 0 )
      top = 0 ;
-   else if ( top > num-1 )
-     top = num-1;

    puPostRefresh () ;
  }

That will handle your case and will also handle a case in which "item_index"
is greater than the number of entries.  You might wind up crashing anyway,
though.

	I appear to be CVS-challenged again.  Would somebody else please put
this in for us?

John F. Fay
Technical Fellow, Jacobs/Sverdrup TEAS Group
850-729-6330
joh...@eg...
 
-----Original Message-----
From: pli...@li...
[mailto:pli...@li...] On Behalf Of Melchior FRANZ
Sent: Tuesday, April 18, 2006 10:19 AM
To: pli...@li...
Subject: [Plib-devel] [PATCH] puListBox.cxx: don't crash with empty list +
setTopItem(0)

The attached patch makes sure that plib doesn't crash if a puListBox was
created with an empty list and the top item is set to 0 (which happens on
"up" arrow in puList, for example). In this case

    else if ( top > num-1 )

evaluates to (0 > -1) -> true, which sets 

       top = num-1;   -> -1

which accesses invalid memory with list[-1] in puListBox.cxx:135.

m.