BUG: Incorrect / inconsistent program behaviour when the "Remove Integer Overflow Checks" option is enabled

[Ralph Purtcher-Wydenbruck]

This is a worrying bug, and indicates a potential problem in the Framework
CLR. This bug affected a project I was working on, which behaved differently
when run from the Visual Studio IDE than when run by double clicking on the
project's EXE file. The problem can be replicated easily:

Create a new project in Visual Studio 2003 and add the following code.


Module Main
Sub Main()
Dim xmlDoc As New System.Xml.XmlD ocument
xmlDoc.AppendCh ild(xmlDoc.Crea teElement("Root "))
Dim o, n As Object
Dim count As Integer
For Each o In xmlDoc.ChildNod es
For n = 0 To 9
count += 1
Next
Next
System.Windows. Forms.MessageBo x.Show("Count: " & count)
End Sub
End Module


IMPORTANT: To replicate the bug, you must

(1) Set the project compile mode to "Release"
(2) Enable the following option: Project Configuration Properties /
Optimisations / "Remove Integer Overflow Checks"

Finally, run the program from the Visual Studio IDE. The expected message,
"Count: 10", is displayed. Now run the program from it's EXE file via
Windows Explorer. A message, "Count: 1" is displayed, which is incorrect.

[Mattias Sjögren]

Re: BUG: Incorrect / inconsistent program behaviour when the "Remove Integer Overflow Checks" option is enabled

Ralph,

Interesting, that does indeed look like some kind of JIT compiler bug.

FYI, changing the loop variable n to an Integer fixes the problem. Why
did you have it declared as Object anyway?



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org

http://www.msjogren.net/dotnet/

Please reply only to the newsgroup.

[Ralph Purtcher-Wydenbruck]

Re: BUG: Incorrect / inconsistent program behaviour when the "Remove Integer Overflow Checks" option is enabled

I know it fixes it, but I wanted to show the problem. Actually, changing the
code in almost any way fixes the problem.

It's a rather worrying thought that this kind arbitrary JIT compiler problem
might affect anyone's code.

So, there was no specific reason for the Object declaration, other than the
fact that I wanted to provide a simple example that did not break the
problem. (In my shipping code I used a For / Each for the inner loop, not an
object).


"Mattias Sjögren" <mattias.dont.w ant.spam@mvps.o rg> wrote in message
news:et3CkNiqDH A.1680@TK2MSFTN GP10.phx.gbl...[color=blue]
> Ralph,
>
> Interesting, that does indeed look like some kind of JIT compiler bug.
>
> FYI, changing the loop variable n to an Integer fixes the problem. Why
> did you have it declared as Object anyway?
>
>
>
> Mattias
>
> --
> Mattias Sjögren [MVP] mattias @ mvps.org
> http://www.msjogren.net/dotnet/
> Please reply only to the newsgroup.[/color]

[Mattias Sjögren]

Re: BUG: Incorrect / inconsistent program behaviour when the &quot;Remove Integer Overflow Checks&quot; option is enabled

Ralph,
[color=blue]
>I know it fixes it, but I wanted to show the problem. Actually, changing the
>code in almost any way fixes the problem.[/color]

OK, fine. FWIW, the bug seems to be fixed in Whidbey.

[color=blue]
>It's a rather worrying thought that this kind arbitrary JIT compiler problem
>might affect anyone's code.[/color]

Well, there will always be bugs.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org

http://www.msjogren.net/dotnet/

Please reply only to the newsgroup.