How Do I Use the User-Mode Dump Heap (UMDH) to Debug Magic xpi? (Magic xpi 4.1)

Memory leaks can be hard to trace. Microsoft has provided developers with a useful utility that works with the operating system to analyze Windows heap allocations for a specific process.

This utility, called UMDH (User-Mode Dump Heap) is part of the Debugging Tools for Windows. The general usage would be to take a snapshot of the memory state in a "quiet mode", reproduce the memory leak and take another snapshot, and then compare the two shots.

To use the User-Mode Dump Heap (UMDH) to debug Magic xpi, follow these steps:

1. Download a copy of the Debugging Tools for Windows from:
   
   http://archive.msdn.microsoft.com/debugtoolswindows/Release/ProjectReleases.aspx?ReleaseId=4912
   
   You should download a file called dbg_x86_6.12.2.633.msi.

2. Open a command prompt and open the Debugging Tools for Windows installation directory, usually %ProgramFiles%\Debugging Tools for Windows\ (in a 64bit OS you need to add the "(*86)").

3. Define an environment variable _NT_SYMBOL_PATH to point to the directory of the pdb files.

4. Enable the user stack trace: gflags -i +ust
   
   Note: You can also do this via the global flags UI.

5. Start the runtime engine. Then run the Magic xpi application/server.

6. Reach a starting point. After running the executable, go through tasks that you plan to use again.

7. Make a snapshot, calling the file begin.txt:
   
   umdh -p: -f:
   
   For example: umdh -p:1234 -f:d:\temp\begin.txt

8. Run the same programs a few more times to create a memory leak, and then reach the same open windows state that existed when you ran the first snapshot.
   
   Again, create a snapshot, this time called end.txt:
   
   umdh -p:1234 -f:d:\temp\end.txt (This is a different file this time.)
   
   Now run a comparison between the files:
   
   umdh -d d:\temp\begin.txt d:\temp\end.txt -f:d:\temp\diff.txt

9. Send the diff.txt.

10. Disable the user stack trace: gflags -i -ust