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VHDL Issue Number:        

Language_Version          VHDL-2002
Classification            Language Definition Problem
Summary                   Unconstrained array formals should not get subtype 
                          from actuals
Relevant_LRM_Sections     2.1.1.1 Constant and variable parameters
                          2.1.1.2 Signal parameter
                          3.2.1.1 Index constraints and discrete ranges
Related_Issues            
Key_Words_and_Phrases     
Authors_Name              James Unterburger
Authors_Phone_Number      503-685-0860
Authors_Fax_Number        
Authors_Email_Address     jamesu@model.com
Authors_Affiliation       Model Technology Inc.
Authors_Address1          8005 SW Boeckman Rd.
Authors_Address2          Wilsonville, OR 97070
Authors_Address3          

Current Status:           Forwarded

Superseded By:

------------------------
Date Submitted:           22 February 2005
Date Analyzed:            04 March 2005
Author of Analysis:       Chuck Swart
Revision Number:          1
Date Last Revised:        04 March 2005

Description of Problem
----------------------

Clauses 2.1.1.1 and 2.1.1.2 state that, for a formal whose interface
declaration has a subtype indication that denotes an unconstrained
array type, "the subtype of the formal in any call to the subprogram
is taken from the actual associated with that formal in the call to
the subprogram".  Yet in 3.2.1.1, in the places where it mentions
formals of unconstrained array types, only the derivations of the
"index ranges" are specified, because no subtype is in fact being
created or implied.

Proposed Resolution
-------------------

I think the intent is to have the index range(s) obtained from the
actual, and the use of the word "subtype" in 2.1.1.1 and 2.1.1.2 is
incorrect.  Perhaps they should be reworded to avoid using the term
"subtype".

VASG-ISAC Analysis & Rationale
------------------------------

The inconsistency should be resolved. However, it is anticipated that
clauses 2.1.1.1 and 2.1.1.2 will be extensively rewritten as part of
Fast Track item FT-14 Records of unconstrained type.  The most
reasonable solution is to fold this change in with the FT-14
changes. If FT-14 is not approved, then the ISAC will need to
reexamine this issue.

VASG-ISAC Recommendation for IEEE Std 1076-2002
-----------------------------------------------

No changes.

VASG-ISAC Recommendation for Future Revisions
---------------------------------------------

Forward this issue to VHDL200x as part of FT-14.



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