Subject: RE: [sv-bc] import p::*
From: Francoise Martinolle (fm@cadence.com)
Date: Fri Jan 30 2004 - 06:52:20 PST
David,
The original intent is clear to me; it is even better now that Stu will
change the wording.
If the following statement:
Hierarchical references to imported identifiers are allowed as if they
were defined in the importing scope.
means that if I have imported the declaration c from package p in the
module top, I can refer to "c"as top.c and it would be the same as p::c??
I really don't think we want to allow this.
I think that hierarchical references to declarations imported from packages
should be using
the package name. p::c is a hierarchical reference.
Francoise
'
At 02:29 PM 1/29/2004 -0800, David W. Smith wrote:
>The intent in all of our discussions on the final proposal was that for
>all intents and purposes the name did not exist unless it was used.
>Therefore it could not be referenced. The variable only is declared if it
>is actually imported from the package. It is only imported from the
>package if it is visible and if it is used. If it is not used there is no
>declaration in the scope. The question of import is defined in:
>
>
>
>Hierarchical references to imported identifiers are allowed as if they
>were defined in the importing scope.
>
>
>
>There is no way to make a hierarchical reference to an identifier in a
>package. At least I do not remember this ever being suggested. Since
>modules and packages are in different name spaces I really hope that no
>one tries to create such a thing or we will have a conflict.
>
>
>
>Regards
>
>David
>
>
>
>
>
>-----Original Message-----
>From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
>Francoise Martinolle
>Sent: Thursday, January 29, 2004 2:19 PM
>To: Arturo Salz; sv-bc@eda.org
>Subject: Re: [sv-bc] import p::*
>
>
>
>In fact I think that someone could tell the difference of behaviour of the
>wildcard import in the following cases:
> 1) If we can refer to the imported items by hierarchical names relative
> to the importing module (I don't know if you can, clarification is
> expected in SV LRM, I think that the pakcages imported items can only
> have hierarchical package scoped names)
>
>Then suppose one of the sub-instances of the importing module has a
>hierarchical name reference to a declared item in package p,
>if the effect of the wildcard import is that only referenced items are
>imported, then the hierarchical reference top.c is undefined; if the
>effect of the wildcard import is that all items are imported regardless of
>their use, then top.c is defined.
>ex:
>package p
>reg c = 0;
>endpackage
>
>import p::*;
>module top
> bot u1();
>endmodule
>
>module bot;
>reg r = top.c; // where c is being imported through package p and is now a
>declaration inside module top
>endmodule
>
>2) a $dumpvars is supposed to dump all the variables in the module, I
>assume that this would also apply to imported items.
>import p::*
>module top
>initial
>$dumpvars(top);
>endmodule
>
>3) there is a non standard VXL rule for function look up which NC
>supports; the behaviour of the wildcard import would have some implication
>on the resolution of the function declaration.
>VXL allows to have simple reference to function in lower instances when
>the function is declared in a higher level module containing this instance.
>Depending on the behaviour of import p::*, you would either get p::f
>function or top.f function
>in the following example.
>
>
>package p
>function f (input i);
>begin
> $display("package p");
> f =1;
>end
>endfunction
>endpackage
>
>
>module top
>function f(input i)
>begin
> $display ("top.f");
> f = 0;
>end
>endfunction
>
> mid m1 ();
>endmodule
>
>import p::*;
>module mid;
> bot b1();
>endmodule
>
>module bot
>reg r;
>initial
> r = f(); // which f is referenced?
>endmodule
>
>
>At 11:28 AM 1/29/2004 -0800, Arturo Salz wrote:
>
>Francoise,
>
>The interpretation of the person in your group is not semantically
>incorrect. This is kind of Heisenberg's uncertainty principle. If
>everything in the package is imported (except for those identifiers
>explicitly imported or declared) then a simple reference to any identifier
>from the package will work (i.e., the identifier is imported). If,
>however, an identifier is not referenced in the importing scope then it is
>irrelevant whether the identifier is actually imported or not. Basically,
>the effect of an identifier not being imported is not visible.
>I do agree with you that the original intent may be better captured by the
>following change:
>
>A wildcard import makes each identifier within the package a candidate for
>import. Each such identifier is imported only when it is referenced in the
>importing scope and it is neither declared nor explicitly imported into
>the scope. Similarly, a wildcard import of an identifier is overridden by
>a subsequent declaration of the same identifier in the same scope.
> Arturo
>
>----- Original Message -----
>From: <mailto:fm@cadence.com>Francoise Martinolle
>To: <mailto:sv-bc@eda.org>sv-bc@eda.org
>Sent: Thursday, January 29, 2004 9:27 AM
>Subject: [sv-bc] import p::*
>
>The LRM is not clear on the semantics of the p::*.
>Somebody from my group read the LRM and from his reading he implied that
>the p::*
>will import everything in the package except if there is already a
>explicit declaration
>of the same name.
>The LRM extract is:
>Copyright 2003 Accellera. All rights reserved.269
>A wildcard import makes each identifier within the package a candidate for
>import. Each such identifier is imported only when it is neither declared
>nor explicitly imported into the scope. Similarly, a wildcard import of an
>identifier is overridden by a subsequent declaration of the same
>identifier in the same scope.
>
>
>I though that the interpretation (also suggested by the example below the
>table where it is said that it "forces the import") was that the package
>declaration items are candidate for import,
>and are only imported if there is a simple reference to that declaration
>item. This was my understanding of what was intended.
>
>for example:
>import p::*;
>module top;
>// nothing from package p is imported
>endmodule
>
>import p::*
>module top;
>reg r = p::c; // nothing from package p is imported, p::c is a
>hierarchical reference
>endmodule
>
>import p::*;
>module top
>reg r = c; // c and only c from package p is imported.
>endmodule
>
>can you please let me know which interpretation is correct and fix the
>wording if necessary.
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