finalization handle remains in the memory. how to remove this reference?

Question

I need to optimize my application in memory usage. so I used .net performance profiler... but some references in my application are still alive and are never collected by GC even if I force it to collect.

The reference that is alive is a "finalization handle" type. I don't know what to do to remove this kind of reference.... please help.

Answer 1

This is not a memory leak, just sloppy coding on the part of the author(s) of AMProLibrary.

As you observed, the profiler is telling you that the referenced object is of type "Finalization Handle". What that means is that it is coming from the finalizer queue. The finalizer queue is what the .NET garbage collector uses to hold all objects that implement a finalizer method. The finalizer is the mechanism used to ensure that unmanaged resources are properly released during garbage collection. An object that contains unmanaged resources implements the IDisposable pattern, including the Finalize method, which is where the unmanaged resources are released. When the garbage collector processes "finalizable" objects (as indicated by the value of a bit in the object's header), it moves them into the finalizer queue. During collection, the GC iterates through the finalizer queue and calls the Finalize method on each of those objects.

What the author of the library evidently failed to do is to call GC.SuppressFinalize() from within the Dispose method. This normally removes the object from the finalizer queue by clearing the "finalizable" bit in the object's header, and indicates that the Finalize method does not need to be called.

For testing purposes, you can force the finalizers to run by calling the GC.WaitForPendingFinalizers function. For example:

System.GC.Collect();
System.GC.WaitForPendingFinalizers();
System.GC.Collect();

However, you should not actually use code like this in a production application. Forcing a collection rarely makes sense. This will just prove the validity of the hypothesis stated above.

In general, you should not rely on the finalizer to release unmanaged resources. All objects that implement IDisposable should be explicitly disposed of by your code, either by manually calling the Dispose method or, preferably, by wrapping their creation in a using block that will automatically call Dispose when the block's scope is exited.