C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  typeid of a pointer and reference          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Ulrich Eckhardt Guest Posted: Sat Jan 24, 2004 1:24 pm    Post subject: typeid of a pointer and reference Greetings! I stumbled arcoss some code that puzzled me. The first snippet uses pointers like this: Base* p1 = new Base; Base* p2 = new Derived; assert( typeid(p1) == typeid(p2) ); I assume this assertion will never fire. Base& r1 = aBase; Base& r2 = aDerived; assert( typeid(r1) == typeid(r2) ); I assume that this assertion will fire, but I wonder if it always will or only when class Base has virtual parts, so it can determine the dynamic type from the reference. thanks Uli [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Jonathan Turkanis Guest Posted: Mon Jan 26, 2004 10:37 am    Post subject: Re: typeid of a pointer and reference "Ulrich Eckhardt" <doomster (AT) knuut (DOT) de> wrote Quote: Greetings! I stumbled arcoss some code that puzzled me. The first snippet uses pointers like this: Base* p1 = new Base; Base* p2 = new Derived; assert( typeid(p1) == typeid(p2) ); I assume this assertion will never fire. Correct, since pointers are not polymorphic types. Quote: Base& r1 = aBase; Base& r2 = aDerived; assert( typeid(r1) == typeid(r2) ); I assume that this assertion will fire, but I wonder if it always will or only when class Base has virtual parts, so it can determine the dynamic type from the reference. If Base is a polymorphic type, i.e., if it is a class type defining one or more virtual functions, the assertion will fire (in debug mode ). Otherwise, both typeid expressions refer to type_info objects representing the type Base. The relevant section of the standard is 5.2.8, paragraphs 2 and 3. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ Language (Moderated) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.