MANAGED DEBUGGING with WINDBG. Thread Stacks. Part 2

Hi all,

This post is a continuation of MANAGED DEBUGGING with WINDBG. Thread Stacks. Part 1.

THREAD STACKS. Part 2

· We can inspect the objects with unmanaged commands:

The reference to an object points to the method table (which is a pointer to the table with the method descriptors) followed by the data of the object. There are 4 other bytes before the pointer to the method table which are the syncblk.

The graph below will show the following info, fields and methods in a different way which will help us understand how an object looks in memory:

0:000> !do 0x01aef338

Name: WindowsApplication1.Form1

MethodTable: 001c6ecc

EEClass: 002d0a30

Size: 352(0x160) bytes

(C:\__WORKSHOP\Demos\BuggyNETApp\bin\Debug\WindowsApplication1.exe)

Fields:

MT Field Offset Type VT Attr Value Name

...

7ae75b24 40011e0 80 ...Drawing.Rectangle 1 instance 01aef3b8 displayRect

...

7b47f3dc 4000011 154 ...dows.Forms.Button 0 instance 01af0398 _Button6

...

0:000> !DumpVC 7ae75b24 01aef3b8

Name: System.Drawing.Rectangle

MethodTable 7ae75b24

EEClass: 7ae75aac

Size: 24(0x18) bytes

(C:\Windows\assembly\GAC_MSIL\System.Drawing\2.0.0.0__b03f5f7f11d50a3a\System.Drawing.dll)

Fields:

MT Field Offset Type VT Attr Value Name

79102290 4000462 0 System.Int32 0 instance 0 x

79102290 4000463 4 System.Int32 0 instance 0 y

79102290 4000464 8 System.Int32 0 instance 384 width

79102290 4000465 c System.Int32 0 instance 352 height

...

0:000> !DumpMT -md 0x001c6ecc

EEClass: 002d0a30

Module: 001c2c3c

Name: WindowsApplication1.Form1

mdToken: 02000008 (C:\__WORKSHOP\Demos\BuggyNETApp\bin\Debug\WindowsApplication1.exe)

BaseSize: 0x160

ComponentSize: 0x0

Number of IFaces in IFaceMap: 15

Slots in VTable: 399

--------------------------------------

MethodDesc Table

Entry MethodDesc JIT Name

7b05e348 7b4a4668 PreJIT System.Windows.Forms.Form.ToString()

...

002c1828 001c6d80 JIT WindowsApplication1.Form1.get_Button1()

...

001cc221 001c6e08 NONE WindowsApplication1.Form1.Run()

...

Note: Click on the image to enlarge.

Next post: MANAGED DEBUGGING with WINDBG. Managed Heap. Part 1.

Index: MANAGED DEBUGGING with WINDBG. Introduction and Index.

Regards,

Alex (Alejandro Campos Magencio)