From -4498538768688562358 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,8366734ec6aad121 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1994-06-18 15:30:13 PST Newsgroups: comp.std.c++ Path: nntp.gmd.de!Germany.EU.net!EU.net!howland.reston.ans.net!europa.eng.gtefsd.com!MathWorks.Com!solaris.cc.vt.edu!uunet!majipoor.cygnus.com!news!jason From: jason@cygnus.com (Jason Merrill) Subject: Re: new foo[0] In-Reply-To: fjh@munta.cs.mu.OZ.AU's message of Sat, 18 Jun 1994 19:06:33 GMT Content-Type: text/plain; charset=US-ASCII Message-ID: Sender: news@cygnus.com Nntp-Posting-Host: deneb.cygnus.com Organization: Cygnus Support, Mountain View, CA References: <9415818.9649@mulga.cs.mu.OZ.AU> <9417005.12163@mulga.cs.mu.OZ.AU> Mime-Version: 1.0 Date: Sat, 18 Jun 1994 22:08:33 GMT Lines: 27 >>>>> Fergus Henderson writes: > Ah - now that you mention it - no, not in all contexts. > I do think that it's use as the operand of `unary &' should be allowed. > I don't know what the ARM or the latest working paper has to say > about that. (But most likely this is one of the areas where the > working paper is "incorect, incomplet, and inConSisTeNT".) I think that this falls into the provisions of [expr.add], since this expression is equivalent to &(*(myfoo0+0)). This section says basically that evaluating a pointer arithmetic expression which points one past the end of an array is allowed, but using that expression as the operand of the unary * operator yields undefined behavior. A strict reading would indicate that the behavior of &myfoo[0] is thus undefined, but I suspect that [expr.add] only meant to deal with actual dereferences. > [On a related note, I don't think it should be allowed as the > initializer for a reference, as in for example > foo& r = myfoo0[0]; Certainly such usage would yield undefined behavior, if 'r' were ever actually used for anything, and consequently an implementation can give a diagnostic for such code. I think that explicitly prohibiting this particular initialization would, however, be excessive special-casing. Jason