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In this question @Jon skeet referenced this old blog post by the authority Chris Brumme.

I was wondering, do I need to follow all calls to GC.SuppressFinalize(this) with a GC.KeepAlive(this) to avoid weird race conditions where a finalizer can be invoked during the time a disposer is running in heavily multithreaded applications?

If so, can you come up with a sample program that exposes this bug?

Community
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Sam Saffron
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  • I think whatever issue used to be here no longer, even if I try really hard to make it fail it does not ... http://gist.github.com/106190 – Sam Saffron May 03 '09 at 23:13

3 Answers3

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No. GC.KeepAlive doesn't actually do anything; its purpose is to 'fool' the runtime into preventing a specific object from being garbage collected between the start of the method and the call to GC.KeepAlive.

Any method call will keep an object alive in this way: you could pass it to Console.WriteLine, call ToString, or even... GC.SuppressFinalize.

(Or as MSDN puts it:

The KeepAlive method performs no operation and produces no side effects other than extending the lifetime of the object passed in as a parameter.)

Tim Robinson
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I was asked this recently by a colleague, and posted the answer on my blog, along with example code:

https://blog.stephencleary.com/2009/08/q-if-dispose-calls-suppressfinalize-is.html

You may also be interested in other Disposable blog posts of mine, one of which explores when SuppressFinalize or KeepAlive() is required.

Jason Sparc
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Stephen Cleary
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Just curious, in what scenario would this give a problem? Say the Dispose() method is past the point where it references any members of the object. What could go wrong with the finalizer freeing the object?

Andomar
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  • nothing if the dispose method is coded correctly, im just curious about the way the CLR fuctions, also adding that extra line in your disposer isnt such a big deal ... – Sam Saffron May 03 '09 at 11:38