Automated way of checking if all instances of a type have been properly disposed of [modified]

Vikram A Punathambekar

No, this isn't a programming question, so please read properly before lynch-voting :) And if you decide to lynch vote this after all, an explanation would be appreciated. I discovered today that a core component of my app has a lot of instances of a custom type, HDElement*, that are not disposed of. This is causing a HUGE memory leak and it has fallen on my shoulders to remove this leak. Does anybody know of a way to see if all instances have Dispose() called on them? The thought of creating a custom FxCop rule did occur to me, but I've never done that before, and don't know if this is even possible. At the moment, I am going through every source file and adding try...finally blocks that call Dispose() on all HDElement instances :(( I was wondering if there's a better way of doing this? I am using VS 2008 but am targeting .NET 2.0. * HDElement is part of a library provided by another team in another continent in the same company, and holds lots of unmanaged resources that the GC cannot take care of.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

modified on Monday, January 19, 2009 11:55 AM to include framework version.

leppie · modified on Monday, January 19, 2009 11:55 AM to include framework version.

Ask them to use SafeHandle (or whatever it is called). The question is: Are you allocating memory for those objects? If not, the burden is NOT on you to clean up resources. If so, use SafeHandle.

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Vikram A Punathambekar

My app is creating all these instances, so my app should be disposing of them. I will take a look at SafeHandle tomorrow, thanks.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

leppie

Vikram A Punathambekar wrote:

My app is creating all these instances

That's good, at least you can keep track. Use a list to store them.

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Vikram A Punathambekar

leppie wrote:

Use a list to store them.

You are joking, right? Dozens of .CS files; instances are local variables, static members, instance members, you name it. The best thing to do, IMO, is go over them manually, make the changes, and have somebody else review them.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

Rob Philpott · modified on Monday, January 19, 2009 11:55 AM to include framework version.

No, I can't see it. How is this anything other than a programming question?

Regards, Rob Philpott.

leppie

It's borderline. I gave him the benefit of the doubt, that he was looking for some sort of plugin library :)

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Rama Krishna Vavilala · modified on Monday, January 19, 2009 11:55 AM to include framework version.

Is there a finalizer in the HDElement class and that is the Dispose pattern is properly implemented. If yes then where are you experiencing memory leaks? and why is that such a major issue are the users experiencing some issues? Now it may be that GC may not be reclaiming HDElement at a time when you expect if the bulk of the memory used by HDElement is in the unmanaged resources. If you can modify the source code of HDElement, I think you should consider AddMemoryPressure method.

Gary Wheeler · modified on Monday, January 19, 2009 11:55 AM to include framework version.

Vikram, there's a "using" statement in C# that does the try...finally thing in a nice syntax that guarantees that Dispose() gets called. I'd have a link to the MSDN, but my access to MSDN seems to be oddly broken at the moment.

Software Zen: delete this;

R Giskard Reventlov

You do need to implement IDisposable and ensure that the Dispose method actually does something! I think there may be a couple of articles here that give a good overview (you can find them). If not I can send you some code if you like.

me, me, me

Gary Wheeler

It sounds like Vikram already has a Dispose() method in place. I was merely trying to offer him a more succinct way of making sure it was called.

Software Zen: delete this;

R Giskard Reventlov

And a darned good way as well.

me, me, me

Member 96 · modified on Monday, January 19, 2009 11:55 AM to include framework version.

If I wasn't boycotting the voting process I'd lynch vote you a 1 for asking what is clearly a programming question in the lounge.

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Chris Maunder · modified on Monday, January 19, 2009 11:55 AM to include framework version.

Mate, I reckon this falls smakc-bang in the middle of the big circle marked 'Programming questions' :D

cheers, Chris Maunder

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Ennis Ray Lynch Jr · modified on Monday, January 19, 2009 11:55 AM to include framework version.

I almost never 1 vote people.

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Vikram A Punathambekar

To be honest, I wasn't asking, "How can I avoid this memory leak?" I expected an answer like "Tool X can do this for you", or "You're buggered, you'll have to review the whole code and do it by hand". If this still qualifies as a programming question, my unqualified apologies.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

Vikram A Punathambekar

Thanks for the reply, Gary, but I wasn't looking for coding tips to handle the memory leak. I know perfectly well what needs to be done, I was wondering if there is a tool that can do this for me or I had to review the entire code.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

Vikram A Punathambekar

Thanks for the tip, and thanks for not flaming :) HDElement holds unmanaged resources, so the GC won't do. Modifying its source is out of question, so I will have to review all of my app's code and call Dispose manually.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

Vikram A Punathambekar

Thanks for the comment, Rob, but I didn't know asking for automated tools qualified as a programming question. Still, I have created a separate apology thread.

Cheers, Vıkram.

I don't suffer from insanity, I enjoy every moment of it.

S Senthil Kumar · modified on Monday, January 19, 2009 11:55 AM to include framework version.

I ran into a similar problem a while back, but we owned the code for the type (you could always disassemble/assemble). My solution was to store the stack trace of the constructor of every instance of that type as a member in that type, and then in the finalizer, log the stack trace. I also ran a timer in the background that periodically called GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect();. That way, the finalizer would run for all instances that did not get disposed, and I would be able to see where those instances got created. I would then run the application and try to exercise all paths in the code that deal with that type. I would then go through the log and fix code that was not disposing instances. The trick is to make sure that all code paths that involve that type are exercised, and that's what makes this non-deterministic. A tool like NCover would probably help track code coverage. You just gave me an idea - it would be nice to have a tool automate the first part (track instances and report where they are created in code). Now I know what I'll be doing over the Republic Day weekend :) Hope this helps.

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