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Stack overflow from .NET code in IIS, but not in Winforms

Answer 1

+1 A:

You need some decent symbols for the CLR. Set _NT_SYMBOL_PATH (in WinDBG, use File/Symbol File Path) so that it includes:

SRV*C:\WebSymbols*http://msdl.microsoft.com/download/symbols

That tells the debugger symbol engine that it can download symbols from Microsoft's online symbol server to C:\WebSymbols. Pick another folder if you prefer them to be cached elsewhere.

It looks like Question, QuestionList, Answer, etc are structs - that is, value types - so they're allocated on the stack rather than on the heap. You may need to create your own class that wraps these types so they're on the heap instead.

Mike Dimmick 2008-09-18 15:02:01

Answer 2

A:

According to stack object dump "ASI.ParadigmPlus.GrilleApp.GA1000" is 96872 bytes. You might want to figure out what that object is all about. That's a pretty big chunk of your stack space right there.

Jeffrey L Whitledge 2008-09-18 15:04:41

Answer 3

A:

Thanks for the replies. I have loaded the symbols as instructed by Mike, and I am getting more info now, but nothing that has led me to an explanation yet.

I looked into the code for the GA1000 class, but I have no idea what could be causing it to take up 97k on the stack. As I understand things, shouldn't it just take 4 bytes? I thought reference types (all classes should be) just got a pointer to the heap put on the stack. If I do a !clrstack -l on the thread that's about to crash, I see that there are quite a few (315) locals on the stack inside the function QuestionChangeLogic, but as I understand it these should only take 4 bytes each for reference types, and a fixed (small) number for value types (4 for int, 8 for double, etc.) which certainly doesn't compute to the lareg ammount of stack that seems to be missing.

Is there a way for me to examine a managed stack frame to see it's size and where the memory is going ?

David Hay 2008-09-18 18:01:52

Answer 4

A:

Analyzing the callstack I clearly see that the method that is causing this exception is:

ASI.ParadigmPlus.LoadedWindows.WID904.QuestionChangeLogic

How come you have 315 variables in this method? Isn't that too much?

"!clrstack -a" (after running "!dso") should give you much more information of each managed frame.

Sacha 2008-09-20 09:02:14

Answer 5

+5 A:

Hi all, I thought I'd post back here with the resolution to this in case someone else runs into it. The replies above were all helpful, and pointed out why i might be overflowing the stack -- but the thing that I still couldn't come to grips with was why the exact same code ran fine in our winforms app.

What I eventually discovered was that at some point microsoft changed the stack size of IIS threads from 1MB (like in the general .NET context) to 256k. This explained everything, including the especially frustrating fact that even the ASPX version ran fine under the visual studio dev server. I resolved the problem by working with this particular customer to drastically cut the ammount of code in the QuestionChangeLogic function mentioned above (when I looked up the source, the function had > 15,000 lines!).

Thanks for the help guys.

David Hay 2008-10-06 16:25:26

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Stack overflow from .NET code in IIS, but not in Winforms

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