Issue 1385:  Discriminated Union value issue (java-rtf)
Source:  (, )
Nature:  Revision
Severity: 
Summary: Summary: An IDL Discriminated Union has a discriminator of some type. The
 discriminator is permitted to take any value allowed by its type -
 nothing in the CORBA spec constrains the discriminator"s value to be
 those of the branch labels present in the union or just one catch-all
 default. For this reason, CORBA 2.2, section 3.8.2 defines a Discriminated
 Union"s value as follows:  <example>So, if I were to create a foo and set the discriminator to 74, someone
 receiving this instance from me should be able to discern that the
 discriminator"s value was set to 74.
 
 As it stands, the IDL->Java mapping provides for discovering the value
 of the discriminator, so if some other ORB sent me a foo with the
 discriminator set to 74 I could discern this, but as far as I can tell
 from reading the current IDL->Java mapping (CORBA 2.2 - no relevant
 changes appear to be present on orbos/98-03-10) there is no way that I
 could set the discriminator"s value to 74.
 
 

Resolution: closed issue
Revised Text: 
Actions taken:
May 19, 1998: received issue
July 30, 1998: closed issue
Discussion: 

End of Annotations:=====
Return-Path: <jmischki@wheel.dcn.davis.ca.us>
From: Jeffrey Mischkinsky <jmischki@wheel.dcn.davis.ca.us>
Subject: new java rtf issue
To: issues@omg.org, juergen@omg.org
Date: Mon, 18 May 1998 20:48:24 -0700 (PDT)

Hi Juergen,
  Please open a new Java-rtf issue.
    thx,
      jeff

An IDL Discriminated Union has a discriminator of some type. The
discriminator is permitted to take any value allowed by its type -
nothing in the CORBA spec constrains the discriminator's value to be
those of the branch labels present in the union or just one catch-all
default. For this reason, CORBA 2.2, section 3.8.2 defines a
Discriminated
Union's value as follows:

   "It is not required that all possible values of the union
   discriminator be listed in the <switch_body>. The value
   of a union is the value of the discriminator together with
   one of the following:
     o If the discriminator value was explicitly listed in a case
       statement, the value of the element associated with that
       case statement;
     o If a default case label was specified, the value of the
       element associated with the default case label;
     o No additional value.
     Access to the discriminator and the related element is
     language-mapping dependent."


The implication is that the following

union foo switch (int)
	{
	case 1: string bar;
	};

declares a union type foo whose value consists either of:
- the integer value 1 together with a string value for bar
OR
- some integer value other than 1.

So, if I were to create a foo and set the discriminator to 74, someone
receiving this instance from me should be able to discern that the
discriminator's value was set to 74.

As it stands, the IDL->Java mapping provides for discovering the value
of the discriminator, so if some other ORB sent me a foo with the
discriminator set to 74 I could discern this, but as far as I can tell
from reading the current IDL->Java mapping (CORBA 2.2 - no relevant
changes appear to be present on orbos/98-03-10) there is no way that I
could set the discriminator's value to 74.

-- 
Jeff Mischkinsky                
jmischki@dcn.davis.ca.us        +1 530-758-9850
jeffm@inprise.com		+1 650-312-5158
jeffm@visigenic.com             +1 650-312-5158