RE: [sv-ec] Ballot issue #182, Mantis 2514: Out of block constraints

Why not add both keywords:
 pure constraints
and 
 extern constraints

Same as it was finnaly cleared for methods

DANiel

-----Original Message-----
From: owner-sv-ec@server.eda.org [mailto:owner-sv-ec@server.eda.org] On
Behalf Of jonathan.bromley@doulos.com
Sent: 21 kwietnia 2009 14:01
To: sv-ec@eda.org
Cc: Bresticker, Shalom; Rich, Dave
Subject: RE: [sv-ec] Ballot issue #182, Mantis 2514: Out of block
constraints

[Dave Rich, concerning a constraint
prototype that lacks an implementation]

> This is either a compile/elaboration error, or it is not an error.

Right.  It seems that implementations have converged on the permissive
approach - I'm guessing there has been some user pressure there - and the
meaning is fairly clear; an unimplemented constraint is presumably the same
as
  constraint foo {1;}
and has no effect.  This all seems quite sensible to me, but I agree with
the existing implementations: it likely represents a user oversight, and
should evince a warning.

However, it's also evident that different tools regard the constraint
prototype in different lights.  One simulator clearly thinks of the
constraint prototype as being, in effect, a "pure virtual" that is OK in an
abstract class but should be overridden in any concrete derived class.
Other simulators give the warning for an unimplemented constraint prototype
even when it appears in an abstract class.  I'm inclined to support the
"pure virtual" position, but it may have repercussions I haven't thought of.
In particular, it tangles the syntax of derived-class constraints with that
of out-of-block constraints.

Advice please?
--
Jonathan Bromley
Consultant

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