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

From: <jonathan.bromley_at_.....>
Date: Tue Apr 21 2009 - 05:00:57 PDT
[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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Received on Tue Apr 21 05:09:46 2009

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