Leaking GDI objects can be seen from the task manager or from Process Explorer. (Well you don't see the leaks, but you can see if object uasage count continually goes up.)
There are also tools that allow to view GDI objects by type, such as GDIView[a], DeLeaker, DPUS or the GDIDebug (sourecode).
[a] Note that I consider GDIView a great tool to get the job done of identifying and confirming the existance GDI leaks, but it doesn't really help you to find the leaking code in large applications. (I will also note here that the tool works very nicely and seems well behaved, although its homepage is a littlebit weird (-: )
There is also a WinDBG plugin called leaktrap that uses MSs Detours Library.
I also know (and have used) AQTime's Resource Profiler that allows to detect GDI (and other) resource leaks in an application including stack traces for the leaking calls.
Now, my actual question however is: Is it possible to detect leaking GDI objects from within the VC++ debugger? So that one doesn't need a separate tool and GDI leaks can be caught during normal debugging and not have to be checked separately.
