Is it possible to implement a GC.GetAliveInstancesOf<T>() (for use in debugging)?

Question

Hi,

I know this was answered before, but I'd like to pose a somewhat different question.

Is there any conceivable way to implement GC.GetAliveInstancesOf(), that can be evaluated in Visual Studio Debug Watch window? Sasha Goldstein shows one solution in this article, but it requires every class you want to query inherit from a specific base class.

I'll emphasize that I only want to use this method during debugging, so I don't care that the GC may change an object's address in memory during runtime.

One idea might be to somehow harness the !dumpheap –type command of SOS, and do some magic trick to create a temporary variable and have it point out to the memory address printed by SOS.

Does anyone have a solution that works?

Answer 1

There is just about nothing that could drag down the garbage collector more than it having to second-guess that some kind of user code could be interested in finding roots that it doesn't own. Keeping it as snappy as possible is crucial. For that matter, the only way you could ever see what is being referenced with some kind of confidence is to freeze all threads that might be allocating memory from the garbage collected heap.

Well, that's possible, debuggers do that. You already know the way Windbg does it. It however wasn't designed to be a tool that was optimized to track managed objects. There are other tools that were: memory profilers. Plenty to choose from, don't try to build your own. From the freeware (and time-wasting) CLR Profiler, to the 3rd party offerings like Ants and dotTrace and many others. A couple of hundred bucks to solve your problem, there is no way you can do better by yourself for less.