>From: "Rich, Dave" <Dave_Rich@mentor.com> > >As far as "correctness" is concerned, the current LRM has no >restrictions on what the handle on the RHS of the constructor could be >pointing to, other than in must be assignment compatible to the handle >on the LHS. Null certainly fits within these rules, and the LRM mentions >no need to generate an error. Making a copy requires accessing the non-static members via the handle. Accessing non-static members via a null handle is illegal. So the LRM says that this is illegal. If you wanted it to be legal, the LRM would have to say that this special case is *not* illegal. As an aside, the LRM does not say that accessing via a null handle produces an error (unless this has been changed). The result is indeterminate, and implementations can issue an error. >But I suspect people are more interested in what the *desirable* >behavior should be. If we take an analogy from C, malloc(0) returns a >null pointer and is not an exception case. I don't believe that this >will be a problem for debug as most people want to do a deep copy, and >the shallow copy will be at the root of that deep copy, if at all. If the user wanted the original (possibly null) object, they would use the original object. They are asking for a new object, initialized to the value of the original object. They expect to get an object. The user may have wanted some fields of the new object to start out the same as the original object as a default, but to overwrite some fields with different values. If the new returns a null, those overwrites will be illegal. You can make a definition that this special case returns null, but I think Arturo is right that this is probably a user error, and they would like to know about it sooner rather than later. Steven Sharp sharp@cadence.com -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.Received on Fri Jan 19 12:00:34 2007
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