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\Microsoft.NET\Framework64\v4.0.20506\culture.dll
(ff8.17a8): Break instruction exception - code 80000003 (first chance)
*** ERROR: Symbol file could not be found.  Defaulted to export symbols for C:\Windows\SYSTEM32\ntdll.dll -
ntdll!DbgBreakPoint:
00000000`77b7d7b0 cc              int     3

Continue debugging:

0:004> g

Exceptions - lots of them:

(ff8.16dc): CLR exception - code e0434352 (first chance)
(ff8.16dc): CLR exception - code e0434352 (first chance)
(ff8.16dc): CLR exception - code e0434352 (first chance)
(ff8.16dc): CLR exception - code e0434352 (first chance)
(ff8.16dc): CLR exception - code e0434352 (first chance)
(ff8.16dc): CLR exception - code e0434352 (first chance)
(ff8.1860): Break instruction exception - code 80000003 (first chance)

Break on CLR exceptions:

0:004> sxe clr
0:004> g

(ff8.16dc): CLR exception - code e0434352 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
*** ERROR: Symbol file could not be found.  Defaulted to export symbols for C:\Windows\system32\KERNELBASE.dll -
KERNELBASE!RaiseException+0x3d:
000007fe`fdb8bb5d 4881c4c8000000  add     rsp,0C8h

Load sos ( in .Net 2/3 use use !loadby sos mscorwks):

0:000> !loadby sos clr

View Stack:

0:000> !CLRStack
PDB symbol for clr.dll not loaded
OS Thread Id: 0x16dc (0)
Child SP         IP               Call Site
000000000096e6a8 000007fefdb8bb5d [HelperMethodFrame: 000000000096e6a8]
000000000096e7c0 000007ff00170360 ConsoleApplication3.Program.ThrowAndCatchException()
000000000096e810 000007ff001701fb ConsoleApplication3.Program.Main(System.String[])
000000000096ec90 000007feef474ca4 [GCFrame: 000000000096ec90]

View Exception:

0:000> !PrintException
Exception object: 0000000002c88c18
Exception type:   System.NotImplementedException
Message:          The method or operation is not implemented.
InnerException:   <none>
StackTrace (generated):
<none>
StackTraceString: <none>
HResult: 80004001
0:000>

Pretty neat - eh?

Posted in: cdb windbg