[vhdl-200x] Feedback sought for change to package std_logic_textio

From: Chuck Swart - MTI <cswart_at_.....>
Date: Tue Jun 24 2008 - 18:39:13 PDT
the ISAC is serving in the role of LRM review committee for the current 
LRM balloting effort.
In the review process for version D4.2 of the LRM the following issue
was discovered. It is identified as Bugzilla number 234 and you can read 
it (no login required for reading)
at https://bugzilla.mentor.com.
Below is the issue and proposed solution as described in that Bugzilla 
report. It seems like a good solution, but requires
changes to package std_logic_texio  (aliases must be added). Note that a 
similar problem involving
moving functions rising_edge and falling_edge from one package to 
another was solved the same way.
Please let us know ASAP if you have any issues with this proposed solution.

Chuck Swart

At the ISAC telecon on 19 June, it was pointed out that the way the
std_logic_textio package is defined introduces an incompatibility with the prior
version defined by the donor. The procedures defined in the prior version are
now defined in std_logic_1164, and std_logic_textio is empty. The premise is
that users will have a use class that uses all of both packages, viz

use ieee.std_logic_1164.all, ieee.std_logic_textio.all;

Under this scenario, the placement of the declarations does not matter, as they
will become directly visible regardless.

However, if a users writes selected names for the procedures that were in
std_logic_textio, the difference in placement is exposed. The models will no
longer work.

A remedy was suggested, taking advantage of the revised semantics of aliases and
homographs. The procedure declarations in the prior version of std_logic_textio
can be replaced by aliases designating the corresponding declarations in the new
version of std_logic_1164. That way, selected names for std_logic_textio
procedures will still work. In the more usual scenario of a use clause referring
to all of both packages, each alias and its designated declaration both become
directly visible, but there is no ambiguity as they both denote the same named

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Received on Tue Jun 24 18:40:26 2008

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