From -2389379351109589159 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,7c21e57f4a25e5f3 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-05-27 12:06:01 PST Path: archiver1.google.com!newsfeed.google.com!newsfeed.stanford.edu!skynet.be!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: kavdeiv@mail.ru (Kiril Avdeiv) Newsgroups: comp.std.c++ Subject: Re: deleted pointers in a container Date: Sun, 27 May 2001 19:05:54 GMT Organization: http://groups.google.com/ Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <873f7ae8.0105271040.32362b99@posting.google.com> References: <3AF0BE2C.F07A2FB7@acm.org> <3AF69057.1778277E@acm.org> <873f7ae8.0105250552.71767b39@posting.google.com> <3B0EE5D3.7C7D90B6@acm.org> X-Trace: mail2news.demon.co.uk 990990359 mail2news:21673 mail2news mail2news.demon.co.uk X-Complaints-To: abuse@demon.net X-Mail2News-Path: news.demon.net!mulga.cs.mu.oz.au X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit NNTP-Posting-Date: 27 May 2001 18:40:19 GMT Lines: 68 Xref: archiver1.google.com comp.std.c++:5347 James Dennett wrote in message news:<3B0EE5D3.7C7D90B6@acm.org>... > Kiril Avdeiv wrote: > > > > James Dennett wrote in message news:<3AF69057.1778277E@acm.org>... > > > Assaf Lavie wrote: > > > > > > > > >IIRC that's not specified by the Standard. Maybe it should > > > > >be, or maybe it is and I've just missed it. > > > > > > > > Why do you make the assertion that copying deallocated pointers (not > > > > de-referencing them) yields undefined behavior if it is not specified by the > > > > standard? > > > > > > The fact that copying deallocated pointers yields undefined > > > behaviour *is* clearly stated by the Standard. > > > > James, I am very grateful if you show where it is stated. > > 5.3.5/4 contains "Note: the value of a pointer that refers to > deallocated storage is indeterminate." but I don't think that's > the piece I want. > > Ah... 3.7.3.2/4 is the one: "If the argument given to a > deallocation function in the standard library is a pointer that > is not the null pointer value (4.10), the deallocation function > shall deallocate the store referenced by the pointer, rendering > invalid all pointers referring to any part of the deallocated > storage. The effect of using an invalid pointer value > (including passint it to a deallocation function) is undefined." > > There's a footnote (33) which points out that "On some > implementations, it causes a system-generated runtime fault." > > If you agree that copying a pointer is a "use" of the pointer, > this clearly states that > > int *p(new int); > delete p; // invalidates p > int *q(p); // use of invalid pointer > > invokes undefined behaviour. Thank you for the answer. However, the standard says "an object or a non-overloaded function is used if it appears in a potentially evaluated expression". Given that, if we take the cuttings from the standard that you quoted, we have that there's no way to assign to an unitialized pointer: int i, * pi; pi = &i; // pi - an invalid pointer value - is used. Undefined behavior? I think the findings are enough for a defect report, because the sentence "The effect of using an invalid pointer value (including passint it to a deallocation function) is undefined" is incorrect. Thank you Kiril --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.research.att.com/~austern/csc/faq.html ]