From 1773733450852839384 X-Google-Language: ENGLISH,ASCII X-Google-Thread: f78e5,ccbfcafab96cf493 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-11-26 11:37:02 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news-spur1.maxwell.syr.edu!news.maxwell.syr.edu!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: "axter" Newsgroups: comp.std.c++ Subject: Re: Proposol to increase robustness of programs Date: Mon, 26 Nov 2001 19:36:41 GMT Organization: Excite@Home - The Leader in Broadband http://home.com/faster Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: References: <3BFE97B3.91430FB1@wanadoo.fr> X-Trace: mail2news.demon.co.uk 1006803406 mail2news:9243 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) X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 NNTP-Posting-Date: Sun, 25 Nov 2001 20:40:38 PST Lines: 86 Xref: archiver1.google.com comp.std.c++:8303 If you had made function f() a pure virtual function, you could avoid this problem. "Lo�c Joly" wrote in message news:3BFE97B3.91430FB1@wanadoo.fr... Hello everybody, This is my first post on this group, so I hope I am on-topic... I would like to make a proposal for an addition to the C++ standard. It pertains with virtual function that we want to be sure exist in the base class. Motivation : struct A { virtual void f(char *s); }; struct B : A { virtual void f(char *s); }; int main () { A* a = new B; a->f(); } This works just fine, but now, suppose someone in charge of maintaining the A class discovers that the declaration of f should have been : virtual void f(char const *s); He makes the change, but somehow forget to change class B. The compiler will compile silently, but the program will not do the expected thing. This is a real-world example that has already bitten me several times, and is difficult to debug. Proposal : Add something that will prevent compilation if a virtual function does not have a function to override in the base class. Some notation (with comments) may be : struct B : A { override virtual void f(char *s); }; This syntax seems rather clear to me, but requires a new keyword, and thus may break old programs (maybe we should give to 'static' yet another signification ;)). The good point is that is is very easy to compile this code on old (i.e. current) compilers (just #define away the override keyword). struct B : A { virtual void f(char *s) = 1; } This syntax is not so clear, more difficult to #define away, but does not require any new keyword. It also has the advantage of giving more consistance to the existing virtual =0 syntax ;). I would like to know what do you think of this proposal; and if there is something I can do to make it accepted in the next standard, I would like to have some advise about it. -- Lo�c --- [ 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 ] --- [ 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 ]