CLR Debugging

1. CLR Process

• Source code -> Compiler -> .NET Assembly -> CLR JIT
• Application domains (System, Shared, Default)
• Assemblies (Private, Shared) (logical constructs)
• Modules (physical constructs)
• Types (Fundamental unit of programmability) (Value types, Reference types)
• Method Tables (Also known as a type handle, Contains information that describes the type)
• Method Descriptors
  • Additional information that completes the descriptive nature of types
  • Type handle contains basic information about method on the type
  • Method descriptor augments that information (JIT status, Address of JIT’ed code)

Ref : http://msdn.microsoft.com/en-us/magazine/cc163791.aspx

2. Debugger Extensions

• SOS (Son of Strike)
• SOSEX (3rd party extension, http://www.stevestechspot.com/)
• PSSCOR2/PSSCOR4

3. Debugger Command Categories

• Object inspection
  • !DumpObject : Dumps a single reference object
  • !DumpArray: Dumps an array object
  • !GCRoot: Dumps the reference chain of an object
  • !mdv : Displays local variables
  • !strings: Dump out all the strings
  • !threads: shows the last exception thrown on any given thread
  • !PrintException : shows the exception information of the specified exception
• Code and Threads
  • !U : Disassembles the code at the specific address
  • !IP2MD: Returns the method descriptor for the given code address
  • !threads : Displays all managed threads in the process
  • !ClrStack : Displays the managed call stack of the current thread
  • ~*e!ClrStack: Displays all managed threads and their callstack
• Diagnostics
  • !VerifyHeap : Validates managed heap integrity
  • !GCHandles : Shows all handles in the process
  • !GCHandleLeaks: Attempts to find leaked handles
  • !VMStat: Virtual memory statistics
• CLR data structures
  • !DumpDomain: Dumps out the application domains
  • !ThreadPool : Dumps out information on the CLR thread pool
  • !DumpIL : Dumps the IL for the specified address

 4. Managed Debug Assistants

• Similar to Application Verifier
• Enabled via the registry and config files (HKLM\Software\Microsoft\.NETFramework\MDA=“1”, <appname>.exe.dma.config)

SOS Cheat Sheet: http://blogs.msdn.com/b/alejacma/archive/2009/06/30/sos-cheat-sheet-net-2-0-3-0-3-5.aspx