C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How to initialize a pointer in c++,          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message 海风 Guest Posted: Wed Jun 07, 2006 9:10 am    Post subject: How to initialize a pointer in c++, How to initialize a pointer in c++, Mostly, I use null, for example, char * szName = null; However, if i compile it without including afxdisp.h , .net compiler tell me that the identifier is not declared. but if i base on lunix operate system, is it correct also. I think i shoud use 0, for example, char * szName =0; is it more general? thank in advanced Back to top Jonathan Mcdougall Guest Posted: Wed Jun 07, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, Ian Collins wrote: Quote: 海风 wrote: How to initialize a pointer in c++, Mostly, I use null, for example, char * szName = null; However, if i compile it without including afxdisp.h , .net compiler tell me that the identifier is not declared. Not a standard header. Use NULL. Or just 0. Jonathan Back to top Ian Collins Guest Posted: Wed Jun 07, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, 海风 wrote: Quote: How to initialize a pointer in c++, Mostly, I use null, for example, char * szName = null; However, if i compile it without including afxdisp.h , .net compiler tell me that the identifier is not declared. Not a standard header. Use NULL. -- Ian Collins. Back to top Gernot Frisch Guest Posted: Wed Jun 07, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, "Ian Collins" <ian-news (AT) hotmail (DOT) com> schrieb im Newsbeitrag news:4enhpqF1fles1U6 (AT) individual (DOT) net... Quote: benben wrote: Ian Collins wrote: 海风 wrote: How to initialize a pointer in c++, Mostly, I use null, for example, char * szName = null; However, if i compile it without including afxdisp.h , .net compiler tell me that the identifier is not declared. Not a standard header. Use NULL. NULL is not defined by default. What is? NULL is part of standard C++, null isn't. There's nothing wrong with using 0, it's all a matter of style. #define NULL 0L NULL indicates that the variable is a pointer. An NULL is a pointer to invalid memory. Back to top Ian Collins Guest Posted: Wed Jun 07, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, benben wrote: Quote: Ian Collins wrote: 海风 wrote: How to initialize a pointer in c++, Mostly, I use null, for example, char * szName = null; However, if i compile it without including afxdisp.h , .net compiler tell me that the identifier is not declared. Not a standard header. Use NULL. NULL is not defined by default. What is? NULL is part of standard C++, null isn't. There's nothing wrong with using 0, it's all a matter of style. -- Ian Collins. Back to top benben Guest Posted: Wed Jun 07, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, Ian Collins wrote: Quote: 海风 wrote: How to initialize a pointer in c++, Mostly, I use null, for example, char * szName = null; However, if i compile it without including afxdisp.h , .net compiler tell me that the identifier is not declared. Not a standard header. Use NULL. NULL is not defined by default. Ben Back to top red floyd Guest Posted: Fri Jun 09, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, marius lazer wrote: Quote: Noah Roberts wrote: It can't be both, which is it? Does the standard not define NULL or is it against the standard to define NULL as (void*)0? The C++ standard does not define NULL, but most compiler or system header files do (leftover from K&R C). If your NULL is defined as (void*)0 or 0L or whatever other than plain 0 do not use it! The standard states to use unadorned 0 so that's what I've been doing since '93. Actually, footnote 180 to 18.1/4 says that 0L is legit. However (void*)0 is specifically banned. Back to top Richard Herring Guest Posted: Mon Jun 12, 2006 9:10 am    Post subject: Re: How to initialize a pointer in c++, In message <EJxig.22086$VE1.13261 (AT) newssvr14 (DOT) news.prodigy.com>, Phlip <phlipcpp (AT) yahoo (DOT) com> writes Quote: marius lazer wrote: Yes, but these are the "old" C header files wrapped in the std namespace. C++ has no need for NULL. All code should clearly state its intent to the reader. if(p) may be fun and cute, but if(NULL == p) clearly states its intent. But, depending on what your p actually represents, the ownership model, etc. etc., one of the following if (is_a_valid_pointer(p)) if (!has_expired(p)) if (is_allocated(p)) would be clearer still, and also avoids the problem that caused you to write your comparison the unnatural way round. Where do you draw the line? Personally I'd consider if (p) to be a natural idiom of the language, and therefore perfectly clear and, moreover, concise. -- Richard Herring 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 (comp.lang.c++) 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.