Visual Studio 2010 + sos.dll: finding memory leaks

During development phase of my current project I try to figure out if my application has memory leaks. The client where I am working prevent me from installing software on my development computer. I don’t have installed Microsoft Windows SDK, so I cannot use WinDBG. This article is a quick post to introduce Visual Studio 2010 and sos.dll

Project configuration

Before starting your application, on the project properties> Debug tab, make sure that “Enable unmanaged code debugging” is enabled.

Starting analyzing

Start your debugging your application, execute the scenario where you found that there is a memory leak, break at the end of this execution (Break All or CTRL+ALT+DEL).

In Visual Studio, Open the immediate windows and load sos.dll.

For .net 4.0 application:

.load C:\windows\Microsoft.NET\Framework\v4.0.30319\sos.dll

or

.load sos

For .net 2.0, 3.0 or 3.5 application:

.load C:\windows\Microsoft.NET\Framework\v2.0.50727\sos.dll

Enter the following command line to get the summary of object types that are still in memory:

!dumpheap –stat

If one of the type should not be in memory, you can filter for a specific type:

!dump –type MyNamespace.MyType

This lists all objects of this specific type in the heap. Once you have the address of one specific object you can get a dump of a specific object:

!gcroot 02369d30

This dump lists all the objects that references, and that forces the object to be kept in the heap. After you should investigate deeper

Main commands to use

Command	Comment
!dumpheap –stat	Summary of classes
MyNamespace.MyType	Lists all objects in the heap of this specific type
!gcroot 02369d30	Returns the ump of a specific object

Interesting links

MSDN reference : https://msdn.microsoft.com/fr-fr/library/bb190764.aspx

Tess Ferrandez blog: https://blogs.msdn.com/b/tess/ (very interesting blog). She wrote several good post but also one dedicated on “Debugging Silverlight applications with windbg and sos.dll”