Major JIT Optimizer BUG

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Boaz Sedan - 14 Nov 2005 16:01 GMT

Try running the following code (tested on .Net1.1 SP1) in both debug and
release builds. Notice the different results:

In the release build, Method B (which modifies an instance field) is never
called!!!

------------------------------------------------------
using System;

namespace MajorBUG
{
class Class1
{
static void Main(string[] args)
{
A a = new A();
Console.WriteLine(a.data);
a.C("XYZ");
Console.WriteLine(a.data);
}
}

class A
{
public string data = "ABC";

public void C(string value)
{
if (B(value))
return;
}

public bool B(string value)
{
data = value;
return true;
}
}
}

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Mattias Sjögren - 14 Nov 2005 18:42 GMT

>Try running the following code (tested on .Net1.1 SP1) in both debug and
>release builds. Notice the different results:

I can't repro it, here it prints the expected result in both builds.

Mattias

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Jon Skeet [C# MVP] - 14 Nov 2005 22:19 GMT

> >Try running the following code (tested on .Net1.1 SP1) in both debug and
> >release builds. Notice the different results:
>
> I can't repro it, here it prints the expected result in both builds.

Have you tried compiling it from the command line? Here are my results:

c:\test>csc /debug+ Test.cs
Microsoft (R) Visual C# .NET Compiler version 7.10.6001.4
for Microsoft (R) .NET Framework version 1.1.4322
Copyright (C) Microsoft Corporation 2001-2002. All rights reserved.

c:\test>test
ABC
XYZ

c:\test>csc /debug- /o+ Test.cs
Microsoft (R) Visual C# .NET Compiler version 7.10.6001.4
for Microsoft (R) .NET Framework version 1.1.4322
Copyright (C) Microsoft Corporation 2001-2002. All rights reserved.

c:\test>test
ABC
ABC

It seems to be okay with .NET 2.0 though.
I must say, I'm very surprised by this - I haven't seen anything
similar before.

I'll raise this with MS personally...

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Mattias Sjögren - 15 Nov 2005 17:39 GMT

>Have you tried compiling it from the command line?

Yup that's what I did, but I may have forgotten /o or ran the wrong
executable or some other stupid mistake. My bad.

Mattias

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Metallikanz! - 27 Nov 2005 07:06 GMT

The problem is not reproducible from VS (2003, 1.1 SP1) even in the retail build with the optimization thingie on.

But when we use csc it sure does come, the inconsistency baffles me!!

Metallikanz!

Mattias Sjögren <mattias.dont.want.spam@mvps.org> wrote:

> >Try running the following code (tested on .Net1.1 SP1) in both debug and
> >release builds. Notice the different results:
>
> I can't repro it, here it prints the expected result in both builds.

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Mattias Sjögren - 28 Nov 2005 22:37 GMT

>The problem is not reproducible from VS (2003, 1.1 SP1) even in the retail build with the optimization thingie on.

If you launch from VS make sure you use "Start without debugging".
Otherwise the app will start with the debugger attached which changes
the JIT behavior.

Mattias

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Major JIT Optimizer BUG

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