From 454651875554998662 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,5cc0e5689db82f7b X-Google-Attributes: gidf78e5,public X-Google-Thread: f635e,e7776fa3664990ff X-Google-Attributes: gidf635e,public From: "Paul D. DeRocco" Subject: Re: Is type_info object static or temporary? Date: 1998/06/06 Message-ID: <3578C2EA.18AA8308@ix.netcom.com>#1/1 X-Deja-AN: 360243140 Content-Transfer-Encoding: 7bit Approved: stephen.clamage@sun.com (comp.std.c++) References: <356D82DA.36025D97@matfys.lth.se> <6kl3ar$npi$1@shell7.ba.best.com> <35727d32.0@210.134.196.10> Mime-Version: 1.0 Originator: clamage@taumet X-NNTP-Posting-Host: bst-ma5-02.ix.netcom.com X-UID: 0000000001 X-Status: $$$T Content-Type: text/plain; charset=us-ascii Organization: Vast Right-Wing Conspiracy X-NETCOM-Date: Fri Jun 05 10:18:06 PM CDT 1998 Newsgroups: comp.std.c++,comp.sys.mac.programmer.codewarrior Alexandre Oliva wrote: > > type_infos, OTOH, have a direct correspondence with > actual types Is that entirely true? Obviously, two different types will never return the same type_info, but isn't it expressly legal for the same type to return different typeinfo objects at different times, as long as they compare equal with operator==? If so, I think this is in order to accommodate dumb linkers that have no mechanism for ensuring that only a single copy of a type_info will be kept when multiple modules introduce it. It's too bad, because if the linker could be counted on to be this smart, then type_infos would become atoms, and operator== could be implemented as a simple address comparison (as could operator<). This would vastly speed up programs that use type_infos as map keys, for instance--especially if the alternative is to do a strcmp on the name strings, which is what Borland does. Incidentally, I don't really understand why Borland does that, since its linker is smart enough to ensure the uniqueness of type_info objects. -- Ciao, Paul [ 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://reality.sgi.com/austern_mti/std-c++/faq.html ]