From -4610582630637980138 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,8fdf6b501ff64059 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2002-01-08 07:20:03 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: "Al Grant" Newsgroups: comp.std.c++ Subject: Re: Possible DRs Date: Tue, 8 Jan 2002 15:19:36 GMT Organization: ARM Limited Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: References: <3C36019C.32739F68@sensor.com> <5lof3uk2f6t89sd4ohotn0lvmrqv8pr0s3@4ax.com> X-Trace: mail2news.demon.co.uk 1010503189 mail2news:6685 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) NNTP-Posting-Date: 8 Jan 2002 09:25:07 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Lines: 42 Xref: archiver1.google.com comp.std.c++:8872 "Stephen Clamage" wrote in message news:5lof3uk2f6t89sd4ohotn0lvmrqv8pr0s3@4ax.com... > On Fri, 4 Jan 2002 19:25:10 GMT, Ron Natalie wrote: > >> > >> 7) This one is really obscure. A union can contain two members > >> ( with subobjects ) such that these subobjects overlap. Is it legal > >> to assign one sucg object to another? > > > >This is a good one. > > Section 5.17, paragraph 8: > > If the value being stored in an object is accessed from another object > that overlaps in any way the storage of the first object, then the > overlap shall be exact and the two objects shall have the same type, > otherwise the behavior is undefined. What does "accessed from" mean? Does it mean "loaded from without an intervening sequence point"? Because surely it is acceptable to load a value from a subobject into something, take a sequence point, and then store the value into an overlapping subobject. Given the function S f(S *s) { return *s; } is it defined to pass one subobject and assign the result to an overlapping subobject? 1.9#17 says there is a sequence point between the copying of the return value (i.e. from *s, to wherever the return value is) and the evaluation of any expression outside the function. What about S f(S *s) { S x = *s; return x; } --- [ 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 ]