Denomo: GDI handle leak check for Delphi

Last week I had to find an anoying GDI handle leak in one of the touch panel apps of my current customer. After some time it ran out of resources.

I started ProcesExplorer, double clicked on the touch panel process (so I could watch the number of GDI handles) and clicked through some screens of the application. I saw a growing GDI counter...

Next I placed some breakpoints and stepped through the code to find out where it came from. It took me quite some time, but I finally found it (of course: in a place I did not expect :-) a TBitmap was created for a button everytime but never released).

Next day, I got the same bug issue in another application. So I started thinking how to speed up finding these kind of leaks. I knew there was an application that could do it for me, but I could not find it back on internet. But after some googling I found a Delphi project: Denomo. It detours a number of Windows API's, like CreateBitmap, CreateBrush, etc and generates a list of unreleased handles and a stack trace per handle (where it was created) when you close your applicaiton.

However, it was not (unicode) compatible with Delphi 2010, and it needed a dll to run and a remote control app for the logging.

I made some small changes to make it compatible with Delphi 2010 (unicode, at least for the parts I needed) and made it standalone (no dll + remote control needed):

http://code.google.com/p/asmprofiler/source/browse/trunk/EXT/Denomo/

I also made a small demo/test project:

http://code.google.com/p/asmprofiler/source/browse/trunk/EXT/Denomo/gdileaktest/Project7.dpr

Now I can find GDI handle leaks very easy!