RE: [sv-ec] A question about copy constructors

Do you have a good reason for wanting this behaviour?

If you have a system that is passing class handles throughout a system,
and null is a valid state for a handle, you want to be able to propagate
that null handle throughout that system.

Since you have to dynamically check the handle for a subclass anyways,
you should be able to deal with a null handle.

Dave


> -----Original Message-----
> From: Arturo Salz [mailto:Arturo.Salz@synopsys.com]
> Sent: Thursday, January 18, 2007 10:50 AM
> To: Rich, Dave; William Paulsen; Arturo Salz; sv-ec@eda-stds.org
> Subject: RE: [sv-ec] A question about copy constructors
> 
> I don't agree. Attempting to copy a null object should result in an
> error. Likewise, the idiom "p3 = new null;" ought to be a compiler
> error.
> 
> 	Arturo
> 
> -----Original Message-----
> From: Rich, Dave [mailto:Dave_Rich@mentor.com]
> Sent: Thursday, January 18, 2007 9:14 AM
> To: William Paulsen; Arturo Salz; sv-ec@eda-stds.org
> Subject: RE: [sv-ec] A question about copy constructors
> 
> I believe a copy of null is null, especially since we have established
> the dynamic nature of the object being copied.
> 
> If the BNF allows a shallow copy of an explicit null handle, then let
it
> be.
> 
> Dave
> 
> 
> > -----Original Message-----
> > From: William Paulsen [mailto:paulsen@cadence.com]
> > Sent: Thursday, January 18, 2007 6:29 AM
> > To: Arturo Salz; Rich, Dave; sv-ec@eda-stds.org
> > Subject: RE: [sv-ec] A question about copy constructors
> >
> > Thanks Dave, Arturo & Francoise for the comments,
> >
> > And here's another related question: What should happen if the
source
> > object in the copy ctor is null?
> >
> > module m;
> > 	class c;
> > 	endclass
> >
> > 	c p1 = null;
> > 	c p2 = new p1;   // What happens: error, p2 == null, something
> > else?
> > 	c p3 = new null; // Is this legal syntax?  What does it do?
> > endmodule
> >
> >
> > Thanks,
> > Bill
> >
> >
> >
> > -----Original Message-----
> > From: Arturo Salz [mailto:Arturo.Salz@synopsys.com]
> > Sent: Wednesday, January 17, 2007 7:06 PM
> > To: Rich, Dave; William Paulsen; Arturo Salz; sv-ec@eda-stds.org
> > Subject: RE: [sv-ec] A question about copy constructors
> >
> > Dave,
> >
> > I believe that the language of 1382 does indeed designate the
dynamic
> > type. This is because it refers to the type of the *object* being
> > copied, not the type of the *handle* that refers the object being
> > copied. This could be clarified with a minor friendly enhancement to
> > 1382, possibly as a separate mantis item.
> >
> > 	Arturo
> >
> > -----Original Message-----
> > From: Rich, Dave [mailto:Dave_Rich@mentor.com]
> > Sent: Wednesday, January 17, 2007 3:42 PM
> > To: William Paulsen; Arturo Salz; sv-ec@eda-stds.org
> > Subject: RE: [sv-ec] A question about copy constructors
> >
> > Bill,
> >
> > I can only speak for the people here at Mentor; yes we agree that
the
> > dynamic class type is what is best.
> >
> > Since 1382 has already passed in the WG and is being edited into the
> > upcoming draft, the most efficient thing to do is to open up a new
> > mantis item.
> >
> > Dave
> >
> >
> > > -----Original Message-----
> > > From: William Paulsen [mailto:paulsen@cadence.com]
> > > Sent: Wednesday, January 17, 2007 3:22 PM
> > > To: Arturo Salz; Rich, Dave; sv-ec@eda-stds.org
> > > Subject: RE: [sv-ec] A question about copy constructors
> > >
> > > Dave Rich:
> > >
> > > Do people agree with Arturo about the type of "p1" in the example
> > below?
> > > (This is different from the first email comments I received.)
> > >
> > >
> > > And can 1382 be reopened, so that the errata can be modified?
Item
> 1
> > in
> > > the new paragraph would now be:
> > >
> > > "1. An object of the >>> dynamic <<< class type being copied is
> > > allocated. This allocation shall not call the object's constructor
> or
> > > execute any variable declaration initialization assignments.
> > >
> > >
> > > Thanks,
> > > Bill
> > >
> > >
> > > -----Original Message-----
> > > From: Arturo Salz [mailto:Arturo.Salz@synopsys.com]
> > > Sent: Tuesday, January 16, 2007 8:10 PM
> > > To: William Paulsen; Rich, Dave; sv-ec@eda-stds.org
> > > Subject: RE: [sv-ec] A question about copy constructors
> > >
> > > Bill,
> > >
> > > I agree that the LRM needs to clarify this point.
> > >
> > > The only type that I think makes sense is the dynamic type (c3 in
> your
> >
> > > example).
> > >
> > > 	Arturo
> > >
> > > -----Original Message-----
> > > From: William Paulsen [mailto:paulsen@cadence.com]
> > > Sent: Tuesday, January 16, 2007 2:51 PM
> > > To: Arturo Salz; Rich, Dave; sv-ec@eda-stds.org
> > > Subject: RE: [sv-ec] A question about copy constructors
> > >
> > >
> > > But the errata for mantis 1382 seems ambiguous.  The first
sentence
> of
> >
> > > item 1 of the new paragraph says for shallow copy:
> > >
> > > "An object of the class type being copied is allocated."
> > >
> > >
> > > Is this the static type?   Or the dynamic type?
> > >
> > > In my example below, the static type of p2 is "class c2", but the
> > > dynamic type is "class c3":
> > >
> > >      c1 p1 = new p2;  // what is the type of the object: c1, c2,
or
> > c3?
> > >
> > >
> > > I think the errata should be explicit about the type (static or
> > > dynamic).
> > >
> > >
> > > Thanks,
> > > Bill
> > >
> > >
> > > Here's the mantis 1832 errata:
> > >
> > > http://www.eda.org/svdb/file_download.php?file_id=1500&type=bug
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Arturo Salz [mailto:Arturo.Salz@synopsys.com]
> > > Sent: Tuesday, January 16, 2007 3:38 PM
> > > To: Rich, Dave; William Paulsen; sv-ec@eda-stds.org
> > > Subject: RE: [sv-ec] A question about copy constructors
> > >
> > > Oops. I take that back. I just went and re-read the proposal.
> > >
> > > Dave is right. The constructor new p2 creates an object of type c2
> and
> >
> > > the handle to the new object is assigned to p1.
> > >
> > > Sorry for the confusion.
> > >
> > > 	Arturo
> > >
> > > -----Original Message-----
> > > From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf
Of
> > > Arturo Salz
> > > Sent: Tuesday, January 16, 2007 12:28 PM
> > > To: Rich, Dave; William Paulsen; sv-ec@eda-stds.org
> > > Subject: RE: [sv-ec] A question about copy constructors
> > >
> > > That is not what mantis 1382 was about.
> > >
> > > In the example p1 is of type c1 (the base class). I believe the
> > question
> > > is whether the shallow copy performs an auto-cast from p2 to p1 in
> > this
> > > case. I believe the answer is yes.
> > >
> > > 	Arturo
> > >
> > > -----Original Message-----
> > > From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf
Of
> > > Rich, Dave
> > > Sent: Tuesday, January 16, 2007 11:44 AM
> > > To: William Paulsen; sv-ec@eda-stds.org
> > > Subject: RE: [sv-ec] A question about copy constructors
> > >
> > > This was mantis 0001382 which was approved in September.
> > >
> > > p1 will be point to an object of type c2.
> > >
> > > Dave
> > >
> > >
> > > > -----Original Message-----
> > > > From: owner-sv-ec@server.eda.org
> [mailto:owner-sv-ec@server.eda.org]
> > > On
> > > > Behalf Of William Paulsen
> > > > Sent: Tuesday, January 16, 2007 11:31 AM
> > > > To: sv-ec@server.eda-stds.org
> > > > Subject: [sv-ec] A question about copy constructors
> > > >
> > > > Hi,
> > > >
> > > > The LRM does not seem to be clear about the last statement in
the
> > > > example below.  Can someone clarify this?
> > > >
> > > > Thanks,
> > > > Bill Paulsen
> > > >
> > > >
> > > >
> > > > module m;
> > > >     class c1
> > > >     endclass
> > > >
> > > >     class c2 extends c1;
> > > >     endclass
> > > >
> > > >     class c3 extends c2;
> > > >     endclass
> > > >
> > > >     c3 p3 = new;
> > > >     c2 p2 = p3;
> > > >     c1 p1 = new p2;  // what is the type of the object: c1, c2,
or
> > c3?
> > > > endmodule
> > > >
> > > >
> > > > --
> > > > This message has been scanned for viruses and dangerous content
by
> > > > MailScanner, and is believed to be clean.
> > > >
> > >
> > >
> > > --
> > > This message has been scanned for viruses and dangerous content by
> > > MailScanner, and is believed to be clean.
> > >
> > >
> > >
> > > --
> > > This message has been scanned for viruses and dangerous content by
> > > MailScanner, and is believed to be clean.
> > >


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.