VHDL Issue Number:      1004
Classification:         Language Definition Problem
Language Version:       VHDL-93
Summary:                Are deferred constants still deferred after their full
                        declaration?
Related Issues:         0008, 0020, 0059
Relevant LRM Sections:  2.6, 4.3.1.1
Key Words and Phrases:  Deferred constants,
                        full declaration of deferred constants
Current Status:         Analyzed
1076-1993 Disposition:  N/A
Disposition Rationale:  N/A
Superseded By:          N/A
-----------------------
Date Submitted:         1989/02/23
Author of Submission:   Paul Menchini
Author's Affiliation:   Menchini Consultancy Inc.
Author's Post Address:  2 Davis Drive, PO Box 13036
                        Research Triangle Park, NC  27709-3036
Author's Phone Number:  (919) 990-9506
Author's Fax Number:    (919) 990-8561
Author's Net Address:   mench@mercury.interpath.com
-----------------------
Date Analyzed:          1994/07/25
Author of Analysis:     John Willis (willis@vhdl.org)
Revision Number:        $Revision: 1.3 $
Date Last Revised:      $Date: 1995/05/15 20:07:17 $


Description of Problem
----------------------
The LRM is unclear on the semantics deferred constants after their full
declaration in a package body.

To illustrate, consider the following example:

    package P is
      constant C: Integer;
    end P;

    package body P is
      constant C: Integer := 0;

      -- "C" is clearly a globally static primary here, but
      -- is "C" a locally static primary here?

    end P;

Except for the fact that the declaration of C in the package body is the full
declaration of the deferred constant in the package interface, the name "C" in
the package body meets all the requirements of a locally static primary.

Note that if the deferred constant declaration of C in the package interface
was not present, then a reference to C in the package body (after the
declaration of C) would clearly be a locally static expression.


Proposed Resolution
-------------------
Explicitly state in Section 4.3.1.1 that the name of a full declaration of a
constant is to be treated no differently that a "normal" constant declaration
in the subsequent text of the design unit containing the full declaration.


VASG-ISAC Analysis & Rationale
------------------------------
The proposed resolution is a language extension.  It seems to be useful, safe,
and upward compatible.


VASG-ISAC Recommendation for IEEE Std 1076-1993
-----------------------------------------------
No change in language.

VASG-ISAC Recommendation for Future Revisions
---------------------------------------------
Insert a paragraph or sentence in Section 4.3.1.1 stating "In the text 
between a full constant declaration and the end of the design unit containing 
the full constant declaration, the name of the full constant declaration is
considered to be an explicitly declared constant, even if the full constant
declaration were preceded by a deferred constant declaration."