From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,55f6e230b02eff2f X-Google-Attributes: gid103376,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!postnews.google.com!y42g2000hsy.googlegroups.com!not-for-mail From: Matthew Heaney Newsgroups: comp.lang.ada Subject: Re: Containers - nontrivial element access Date: Tue, 02 Oct 2007 09:40:57 -0700 Organization: http://groups.google.com Message-ID: <1191343257.343180.80480@y42g2000hsy.googlegroups.com> References: <1191275759.184463.238350@n39g2000hsh.googlegroups.com> <5mdfipFcv1dsU1@mid.individual.net> NNTP-Posting-Host: 66.162.65.129 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" X-Trace: posting.google.com 1191343257 8244 127.0.0.1 (2 Oct 2007 16:40:57 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Tue, 2 Oct 2007 16:40:57 +0000 (UTC) In-Reply-To: <5mdfipFcv1dsU1@mid.individual.net> User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.7) Gecko/20070914 Firefox/2.0.0.7,gzip(gfe),gzip(gfe) Complaints-To: groups-abuse@google.com Injection-Info: y42g2000hsy.googlegroups.com; posting-host=66.162.65.129; posting-account=ps2QrAMAAAA6_jCuRt2JEIpn5Otqf_w0 Xref: g2news2.google.com comp.lang.ada:2248 Date: 2007-10-02T09:40:57-07:00 List-Id: On Oct 1, 7:52 pm, "Alex R. Mosteo" wrote: > > I don't think that's reproducible as-is with the standard containers. It > must be more verbose. There's no way to get a reference to the element in > the Ada containers (unless you want to go the 'Unrestricted_Access way > inside Update_Element, but that would require anyway extending the standard > containers), so you can have dangling cursors but no dangling pointers. If this is a vector, you can use index values. > There was a recent thread (started by myself) on the amount of copying > involved in the use of the containers. Someone said that returning accesses > was deemed too unsafe and thus dropped, IIRC. I have not a strong position > on if dangling cursors is a great improvement over dangling accesses, given > what we gain/lose; in my experience a dangling cursor has been always as > bad as a dangling pointer, in the sense that the program was erroneous > beyond recovery; admittedly I have never got a memory violation using the > containers so post-hoc diagnostics are quicker. If you're using GNAT, then compile the container instantiations with - gnata, and the container will detect dangling cursors. Try it!