[Mono-list] Named parameters for Attributes

Greg Whelan greg@gregwhelan.com
Thu, 09 May 2002 16:48:15 -0700

I'm trying to utilize an attribute which has named parameters.

ie. the first line in this code frag:

public class Zippy {

Where the attribute is defined like so:

using System;

public sealed class BarAttribute : System.Attribute
  public BarAttribute() {}
  public int foo;
  public int Foo {
    get { return foo; }
    set { foo = value; }

When I attempt to compile Zippy.cs I get:

[gregw@dhcp csharp]$ mcs -r Bar.dll --target library Zippy.cs

** (process:11532): WARNING **: unhandled exception 
System.NullReferenceException: "A null value was found where an object 
instance was required"
in Mono.CSharp.Attribute:Resolve ()
in Mono.CSharp.Attribute:ApplyAttributes ()
in Mono.CSharp.TypeContainer:Emit ()
in Mono.CSharp.RootContext:EmitCode ()
in Mono.CSharp.Driver:MainDriver ()
in Mono.CSharp.Driver:Main ()

As a wild-a**-guess to the source of the problem I notice that in the 
attribute_arguments rule in cs-parser.jay that a null value is 
mysteriously added to the args list

        | named_argument_list
        ArrayList args = new ArrayList ();
        args.Add (null);                // <----- huh?
        args.Add ($1);
        $$ = args;

Developing on Linux on an otherwise "working as expected" (aka 
kicking-a** as expected) mono-0.11_baselabs-20020508.i386.rpm.