When is "volatile" used instead of "lock" ?

[Ben Voigt [C++ MVP]]

I think we may be talking at cross-purposes. I'm talking about a
situation which is theoretically possible in the CLI model, but not in
the .NET 2.0 model:

public class Foo
{
public int Bar; // Yeah, but with a property etc

public Foo(int b)
{
Bar = b;
}
}


Thread 1: Thread 2:
sharedVar = new Foo(10);
Console.WriteLine(sharedVar.Bar);


In theory (with the ECMA model), sharedVar's new value can be visible
to thread 2 before the write to sharedVar.Bar - meaning that thread 2
could end up printing "0".

That has been tightened up in the .NET 2.0 memory model.

That's related to the result of the new expression, though, not visibility
of the new reference. What if the Foo constructor had "sharedVar = this;"?

 

[Jon Skeet [C# MVP]]

That's related to the result of the new expression, though, not visibility
of the new reference.

Well, it's the result of the new reference becoming visible before all
the writes in the constructor are necessarily visible.

What if the Foo constructor had "sharedVar = this;"?

Then you could have an equally nasty situation.