[Mono-bugs] [Bug 437338] New: HasValue is true on a nullable field which gets null assigned

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=437338


           Summary: HasValue is true on a nullable field which gets null
                    assigned
           Product: Mono: Runtime
           Version: 2.0
          Platform: x86-64
        OS/Version: Linux
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: JIT
        AssignedTo: lupus at novell.com
        ReportedBy: singer at conemis.com
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---


Created an attachment (id=246886)
 --> (https://bugzilla.novell.com/attachment.cgi?id=246886)
the same code i posted in the description

The following code does some constructor chaining. In one of the chained
constructors the value null is passed to a nullable which is stored in a public
field of the created instance. If you call the HasValue property of this
nullable it should return false. But it returns true on x86_64 if you create
more than one instance of this type.
(g)mcs emits the same IL code on 32 and 64 bit, so i guess the problem is in
the jit.

Here is the code (sorry i did not get it smaller):
  using System;
  public struct ValTyp
  {
    public static readonly ValTyp Empty = new ValTyp(Guid.Empty, 0, 0);
    public Guid g;
    public int i1;
    public int i2;
    public ValTyp(Guid g, int i1, int i2)
    {
      this.g = g;
      this.i1 = i1;
      this.i2 = i2;
    }
  }
  public abstract class Foo
  {
    public ValTyp? nvt;
    protected Foo(ValTyp vt, ValTyp? nvt)
    {
      this.nvt = nvt;
      Console.WriteLine("in Foo's ctor: nvt.HasValue==" +
        nvt.HasValue.ToString());
    }
  }
  public class Moo : Foo
  {
    public Moo(ValTyp vt, int i) :
      base(vt, null) { } // <-- nvt is set to null here
    public Moo(ValTyp vt) : this(vt, 0) { }
  }
  public static class Bar
  {
    public static void Main()
    {
      Moo moo = new Moo(ValTyp.Empty);
      Console.WriteLine("in Main(1): moo.nvt.HasValue==" +
        moo.nvt.HasValue.ToString());
      moo = new Moo(ValTyp.Empty);
      Console.WriteLine("in Main(2): moo.nvt.HasValue==" +
        moo.nvt.HasValue.ToString());
      if(moo.nvt.HasValue)
        Console.WriteLine("HURRAY! It's Magic!");
    }
  }

On x86_64 this code outputs:
  in Foo's ctor: nvt.HasValue==False
  in Main(1): moo.nvt.HasValue==False
  in Foo's ctor: nvt.HasValue==True
  in Main(2): moo.nvt.HasValue==True
  HURRAY! It's Magic!
And on x86, sparc and arm (all three are 32 bit) it outputs (as expected):
  in Foo's ctor: nvt.HasValue==False
  in Main(1): moo.nvt.HasValue==False
  in Foo's ctor: nvt.HasValue==False
  in Main(2): moo.nvt.HasValue==False

I tested it on Mono 1.9, 1.9.1 and 2.0. All three the same on x86_64.
Unfortunately i do not have another 64 bit architecture to test it.


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