30 October 2008

Wild World of Visual Studio -- Unfriendly Package

While developing "The Most Intelligent Add-In To Visual Studio" we often face issues that originates from the outside of our code. Being that Visual Studio itself, other packages and add-ins installed, OS components or other things added to the mix - it is always extremely hard to reproduce, debug and understand. Usually we have to perform post-mortem debugging, when all we have is mini-dump from the user experiencing the crash. And we are very happy when we have mini-dump! Often we have to resort to psychic debugging, speculating about what could have happened, trying this and that until we find the cause and issue the fix.

I though I could share some stories of pure insanity we happened to participate in recently. May be another add-in developer is scratching his head in an attempt to understand the source of strange sounds from beneath the ground, and these stories will help. Or it may be just interesting reading for you. Or not :)

The first one is the most recent one and is pretty simple.

Story 1 -- Unfriendly Package

Our customers were complaining about Visual Studio crashing on start with ReSharper installed when running non-admin. Disabling ReSharper allows Visual Studio to load normally. When you see such behavior, you are absolutely sure ReSharper is guilty, aren't you?

We've learned to be cautious in such cases. So I asked user (thanks Jon!) to capture mini-dump and send it to me for investigation. While downloading it, I was preparing myself to long hours of WinDbg magic, but !ClrStack revealed it in a second. SnippetDesigner was not able to access its files, since it placed it in privileged folder. It did so in the background thread and didn't catch exceptions. The result is CLR termination, which get Visual Studio to nowhere with itself.

But wait! Why disabling ReSharper helped to avoid crash? Well, actually crash happens during SnippetDesigner package loading. Normally, it occurs when its window is opened (and it indeed crashes VS at this point without ReSharper). However, ReSharper uses Visual Studio API to get some configuration information, which can be extended with packages. So, by calling this API ReSharper caused those packages to load, essentially triggering the bug in SnippetDesigner on startup.

Case closed, opened another one.

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