From -7582120789561802102 X-Google-Language: ENGLISH,ASCII X-Google-Thread: f78e5,ccbfcafab96cf493 X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 2001-11-25 18:00:05 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!news.ems.psu.edu!news.cis.ohio-state.edu!news.maxwell.syr.edu!dispose.news.demon.net!news.demon.co.uk!demon!mail2news.demon.co.uk!not-for-mail From: Edward Diener Newsgroups: comp.std.c++ Subject: Re: Proposol to increase robustness of programs Date: Mon, 26 Nov 2001 01:59:06 GMT Organization: EarthLink Inc. -- http://www.EarthLink.net Approved: Fergus Henderson , moderator of comp.std.c++ Message-ID: <3C006716.4070201@earthlink.net> References: <3BFE97B3.91430FB1@wanadoo.fr> Reply-To: eldiener@earthlink.net X-Trace: mail2news.demon.co.uk 1006739952 mail2news:29404 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) User-Agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:0.9.4) Gecko/20011019 Netscape6/6.2 X-Accept-Language: en-us MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed NNTP-Posting-Date: Sat, 24 Nov 2001 19:31:09 PST Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by mulga.cs.mu.OZ.AU id MAA26069 Lines: 81 Xref: archiver1.google.com comp.std.c++:8294 Lo=EFc Joly wrote: > Hello everybody, > This is my first post on this group, so I hope I am on-topic... >=20 > 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. >=20 > Motivation : > struct A > { > virtual void f(char *s); > }; >=20 > struct B : A > { > virtual void f(char *s); > }; >=20 > int main () > { > A* a =3D new B; > a->f(); > } >=20 > 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. >=20 >=20 > 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 : >=20 > struct B : A > { > override virtual void f(char *s); > }; >=20 > 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). >=20 > struct B : A > { > virtual void f(char *s) =3D 1; > } >=20 > 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 =3D0 syntax ;). >=20 >=20 >=20 >=20 > I would like to know what do you think of this proposal; and if there i= s > something I can do to make it accepted in the next standard, I would > like to have some advise about it. I do not like your proposal for the reason that you are attempting to=20 add a feature to the language merely to prevent a programming error,=20 rather than justifying some new functionality in C++ or making the=20 syntax clearer in a much needed way. Additions to C++ merely to prevent=20 programming errors is, to me, not in the spirit of the language. --- [ 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 ]