From -9215852091343789311 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,96a8c01f7043c2d9 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2002-09-27 08:31:12 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!kibo.news.demon.net!mutlu.news.demon.net!demon!mail2news.demon.co.uk!devnull From: pierrebai@hotmail.com (Pierre Baillargeon) Newsgroups: comp.std.c++ Subject: Re: Proposal: exception stack unwinding resumption Date: Fri, 27 Sep 2002 15:31:11 +0000 (UTC) Organization: http://groups.google.com/ Lines: 63 Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <6df0c6a8.0209261854.4b087f03@posting.google.com> References: <6df0c6a8.0208260746.633710cb@posting.google.com> <6df0c6a8.0209170602.2cb54634@posting.google.com> <6df0c6a8.0209201925.6faa9e57@posting.google.com> <6df0c6a8.0209230602.2aba3ca8@posting.google.com> <6df0c6a8.0209240716.6fb5ec00@posting.google.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: mail2news.demon.co.uk 1033140671 5503 10.0.0.1 (27 Sep 2002 15:31:11 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Fri, 27 Sep 2002 15:31:11 +0000 (UTC) X-Received: from mulga.cs.mu.oz.au ([128.250.1.22]) by news.demon.co.uk with esmtp (Exim 4.05) id 17ux5B-0001Qc-00 for mail2news@news.news.demon.net; Fri, 27 Sep 2002 15:31:10 +0000 X-Received: by mulga.cs.mu.OZ.AU id BAA11989; Sat, 28 Sep 2002 01:30:36 +1000 (EST) X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Path: comp-std-cpp-robomod!not-for-mail X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Delivered-To: std-c++@ncar.ucar.edu X-Newsgroups: comp.std.c++ X-NNTP-Posting-Date: 27 Sep 2002 02:54:45 GMT Xref: archiver1.google.com comp.std.c++:14262 belvis@pacbell.net (Bob Bell) wrote in message news:... > pierrebai@hotmail.com (Pierre Baillargeon) wrote in message news:<6df0c6a8.0209240716.6fb5ec00@posting.google.com>... > > Your proposal doesn't make it safe to throw from a destructor. It just > prevents the program from calling std::terminate when a destructor > throws, which is somewhat different. I guess that's the capsule > summary of what I don't like about this proposal. [...] > I can't speak for Francis, but I would interpret his remark as > "destructors should behave as if they were declared with a throw() > exception specification." In other words, any exception escaping a > destructor would lead to a call to std::unexpected. That's the > behavior I would like. [...] > If an exception is thrown from some function that is _not_ a > constructor, then only stack objects are destroyed. Therefore, if > A::~A above throws, since the B part is not a stack object, B::~B will > not be called. > > I'd be interested in anybody else's opinion on this as well. I just > ran a quick test in CodeWarrior 7, and it seems to agree with my > interpretation. [...] > > I agree, it's the weak point of my proposal. Would it be more > > acceptable if the proposed behavior would always be enabled? That > > would not change the meaning of existing code, since it has really > > been properly tested and reviewed right? ;-). Seriously folks, would > > the proposal be more acceptable like that? I didn't say acceptable > > (yet), just more... > > Actually, it would be a step in the right direction. But getting back > to the capsule summary line at the beginning of this post, it still > would not make exceptions exiting from destructors safe. Now I think I understand the fundamental misunderstanding we had: I assumed that throwing from a destructor destroyed the data members and base classes, while you didn't. I rechecked the standard (after reading Francis Glassborow's reply): it does mention partially destructed objects, so I was right and CodeWarrior 7 is wrong. So the capsule summary of my proposal is rather: if a destructor throws an exception, and if terminate() would be called, it is as if a try block catched the exception. I still find it amazing that people have objections to this. I understand that people could refuse to design destructors that can throw, but I find it strange that they would actively resists having the C++ language support those that would like to write such code. --- [ 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.jamesd.demon.co.uk/csc/faq.html ]