Dumping the method descriptor for a System.Action (delegate)

In my previous post I needed to figure out what method descriptor a System.Action points to. This is painful so I wrote a small debugger script to automate it.  To use the script, copy this code to dumpMDForAction.dbg. Many thanks to Alois Kraos for posting how to do this.

Without further ado, fire up cdb and  find a System.Action:
 
0:000> !do 0000003de7023078
Name:        System.Action
MethodTable: 000007f9d26b9a68
EEClass:     000007f9d2071c10
Size:        64(0x40) bytes
File:        C:\Windows\Microsoft.Net\assembly\GAC_64\mscorlib\v4.0_4.0.0.0__b77a5c561934e089\mscorlib.dll
Fields:
              MT    Field   Offset                 Type VT     Attr            Value Name
000007f9d26c1ac8  400002d        8        System.Object  0 instance 0000003de7023078 _target
000007f9d26c1ac8  400002e       10        System.Object  0 instance 0000003de7028800 _methodBase
000007f9d26c60d8  400002f       18        System.IntPtr  1 instance       3de52e0900 _methodPtr
000007f9d26c60d8  4000030       20        System.IntPtr  1 instance      7f97fbfc040 _methodPtrAux
000007f9d26c1ac8  4000031       28        System.Object  0 instance 0000000000000000 _invocationList
000007f9d26c60d8  4000032       30        System.IntPtr  1 instance                0 _invocationCount

Next launch the script, passing the address of the action to the script:
0:000> $$>a< dumpMDForAction.dbg 0000003de7023078
usage - $$>a< ".\dumpMDForAction.dbg" addressOfObject
<.shell waiting 10 second(s) for process>
.shell: Process exited
0:000> r $t0=7f97fbfc040
0000003de7023078
Dumping
Method Name:  PerformanceOfSmallThings.Program.
b__3()
Class:        000007f97fd022d0
MethodTable:  000007f97fbf39d0
mdToken:      0000000006000009
Module:       000007f97fbf2f90
IsJitted:     yes
CodeAddr:     000007f97fd10950
Transparency: Critical
0:000>
Happy debugging!

Comments

Post a Comment

Popular posts from this blog

Finding CLR exceptions without visual studio

(If you want to understand what exception code 0xe0434352 is, read this post ) Often exceptions are thrown and caught and you don't see them. You probably know how to debug this in Visual Studio, so let me show you how to do it in cdb. Sample Code: class Program { static void Main(string[] args) { foreach (var x in Enumerable.Range(0,2000)) { Thread.Sleep(TimeSpan.FromSeconds(1)); Console.WriteLine("Hello World"); ThrowAndCatchException(); } } private static void ThrowAndCatchException() { try { throw new NotImplementedException(); } catch(Exception) { } } } Output of the application: Hello World Hello World Hello World Nothing about an exception, but you're sure it's happening behind the covers -- fire up cdb: C:\Program Files\Debugging Tools for Windows (x64)>cdb -pn consoleapplication3.exe <SNIP> ModLoad: 000007fe`f7e90000 000007fe`f7eb4000 C:\Windows\Mi
Read more

Why do I keep getting exception code e0434352?

If you want to know how to debug CLR exceptions using cdb then read this post . Exception code e0434352 is the exception code used internally by the CLR to represent most exceptions(*). Regardless of if you throw a System.NullReferenceException or a System.ArgumentException in C#, you'll throw a SEH exception e0434352 under the covers. A fun way to validate this theory is to watch what happens to the CLR exceptions settings in cdb. Fire up cdb, and see the state of clr exceptions: 0:000> .shell -ci "sx" findstr clr clr - CLR exception - second-chance break - not handled clrn - CLR notification exception - break - handled .shell: Process exited Now, set the exception handler for exception number e0434352 and recheck the value of the clr exception handler: 0:000> sxe e0434352 0:000> .shell -ci "sx" findstr clr clr - CLR exception - break - not handled clrn - CLR notification exception - break - handled .shell: Process exited Armed with
Read more

Powershell script to enable windows to capture localhost traffic in wireshark

If you want to understand why the following scripts work read this post . Otherwise just paste the following into an elevated powershell window: Setup windows networking to allow localhost capturing in wireshark: # Find the network configuration that has the default gateway. $defaultAdapter = Get-WMIObject Win32_NetworkAdapterConfiguration | ? {$_.DefaultIPGateway} if (@($defaultAdapter).Length -ne 1) {throw "You don't have 1 default gateway, your network configuration is not supported" } # Route local IP address via the default gateway route add $defaultAdapter.IPAddress[0] $defaultAdapter.DefaultIPGateway Write-Host "Start capturing on localhost by connecting to $($defaultAdapter.IPAddress[0])" Return windows networking to normal configuration: # Find the network configuration that has the default gateway. $defaultAdapter = Get-WMIObject Win32_NetworkAdapterConfiguration | ? {$_.DefaultIPGateway} if (@($defaultAdapter).Length -ne 1) {throw "Y
Read more