Issue 1544:  Marshalling of union type codes (interop)
Source:  (, )
Nature:  Revision
Severity: 
Summary: Summary: On page 13-14, the spec says for marshaling of type codes:
 
 	"Note that the tuples identifying struct, exception, and enum
 	 members must be in the order defined in the OMG IDL definition
 	 text."
 
 This is right and proper, otherwise I wouldn"t know in what order things are
 encoded or what their ordinal values are. However, the text does *not*
 mention unions, so the order in which a type code describes the union
 members is left to the implementation.
 
 Suggestion: Require union members to also appear in the order in which
 they are defined in the IDL.
 

Resolution: 
Revised Text: 
Actions taken:
June 24, 1998: received issue
June 24, 1998: moved from orb_revision to interop
February 17, 1999: closed issue
Discussion: 

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Date: Wed, 24 Jun 1998 14:15:37 +1000 (EST)
From: Michi Henning <michi@dstc.edu.au>
To: issues@omg.org, orb_revision@omg.org
Subject: Marshaling of union type codes

On page 13-14, the spec says for marshaling of type codes:

	"Note that the tuples identifying struct, exception, and enum
	 members must be in the order defined in the OMG IDL
definition
	 text."

This is right and proper, otherwise I wouldn't know in what order
things are
encoded or what their ordinal values are. However, the text does *not*
mention unions, so the order in which a type code describes the union
members is left to the implementation.

Suggestion: Require union members to also appear in the order in which
they are defined in the IDL.

Rationale: The Notification Service uses positional notation for
filtering
on any values with type codes that do not contain member names. This
works
fine for structures. For example, $.1 denotes the second member of a
structure.

Unfortunately, the same notation could *not* be used to denote union
members, because union members are not marshaled in any guaranteed
order.
The Notification Service therefore had to come up with a different
notation
for unions.

If union members are marshaled into type codes in the same order as
they
appear in the IDL, this problem goes away. I expect that every ORB on
the planet marshals union type codes this way already, so this
change shouldn't cause any pain, but would tighten up the spec.

							Cheers,

								Michi.

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