Program analyses debugger information file (PDB, so Microsoft Visual C++ only) and presents info about user defined structures (size, padding, etc).
Original blog post: http://msinilo.pl/blog/?p=425
Note that you will need msdia90.dll classes to be registered. Download VC++ 2008 redistributable (64 bit), install it, and also manually register the DLL (from admin command prompt: regsvr32 msdia90.dll).