Re: __vfptr is null

From:

"Ben Voigt" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.mfc,microsoft.public.vc.language,microsoft.public.win32.programmer.ui

Date:

Thu, 31 Aug 2006 14:04:08 -0500

Message-ID:

<evgZ#ATzGHA.480@TK2MSFTNGP06.phx.gbl>

<amitdedhia@yahoo.com> wrote in message
news:1156885478.430222.174060@h48g2000cwc.googlegroups.com...

Hello

I am working on an MDI application. The application's main toolbar
has 4 buttons on it (Lets say A, B, C and D). There is a tab control on
the MainFrame. It has many tabs on it. However, depending on which of
the 4 buttons above has been pressed, only 2 tabs are visible at a
time.

After the application starts, if I click on button C, then I see two
visible tabs. When I click on the right most tab, a window (of type
CMDIChildWnd-derived class) is created. This window has a splitter on
it. It has a data member of type CSplitterWnd.

Everything works fine until I did not click button D.

Once I click button D and do some specific operations and then if I
click on button C - I again see two visible tabs. However, clicking
on rightmost tab thereafter results in an assert. The assert comes
because the __vfPtr member of CSplitterWnd data member is null.

Any idea why this would be happening?

Most likely a buffer overflow, or else using an object pointer as if it were
a plain-old-data pointer. For example, you can't memset(obj, 0, sizeof
*obj) safely on an object that has virtual member functions.

Thanks and regards
Amit Dedhia