C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Prototype for operator new required?          C++Talk.NET Forum Index -> C++ Language (Moderated) View previous topic :: View next topic   Author Message Matthias Hofmann Guest Posted: Tue Oct 28, 2003 6:38 pm    Post subject: Prototype for operator new required? Hello! I have learned from the standard that the function prototype for operator new is declared in a header file of the standard library. However, I can use the new operator in my programmes without including any of the standard headers. Is there no declaration of operator new required because it is *implicitly* declared? And if so, why is its prototype declared in the standard library's header? Best regards, Matthias Hofmann [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Christoph Schulz Guest Posted: Wed Oct 29, 2003 4:50 pm    Post subject: Re: Prototype for operator new required? Hello! Matthias Hofmann <hofmann (AT) anvil-soft (DOT) com> wrote: Quote: Hello! I have learned from the standard that the function prototype for operator new is declared in a header file of the standard library. However, I can use the new operator in my programmes without including any of the standard headers. Is there no declaration of operator new required because it is *implicitly* declared? And if so, why is its prototype declared in the standard library's header? See 3.7.3/2: [...] The following allocation and deallocation functions (18.4) are implicitly declared in global scope in each translation unit of a program void* operator new(std::size_t) throw(std::bad_alloc); void* operator new[](std::size_t) throw(std::bad_alloc); void operator delete(void*) throw(); void operator delete[](void*) throw(); These implicit declarations introduce only the function names operator new, operator new[], operator delete, operator delete[]. [Note: the implicit declarations do not introduce the names std, std::bad_alloc, and std::size_t, or any other names that the library uses to declare these names. Thus, a new-expression, delete-expression or function call that refers to one of these functions without including the header <new> is wellformed. However, referring to std, std::bad_alloc, and std::size_t is illformed unless the name has been declared by including the appropriate header. ] [...] Regards, Christoph [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ron Natalie Guest Posted: Wed Oct 29, 2003 6:17 pm    Post subject: Re: Prototype for operator new required? "Matthias Hofmann" <hofmann (AT) anvil-soft (DOT) com> wrote Quote: Hello! I have learned from the standard that the function prototype for operator new is declared in a header file of the standard library. However, I can use the new operator in my programmes without including any of the standard headers. Is there no declaration of operator new required because it is *implicitly* declared? And if so, why is its prototype declared in the standard library's header? The simple (no placement) new has an implicit declaration. If you want to use the implementation provided placement new, you can get it declared by #including <new>. Of course any ones you specifically provide need their own declaration. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ben Hutchings Guest Posted: Wed Oct 29, 2003 11:16 pm    Post subject: Re: Prototype for operator new required? In article <bnk6h2$sc7$2 (AT) news1 (DOT) nefonline.de>, Matthias Hofmann wrote: Quote: Hello! I have learned from the standard that the function prototype for operator new is declared in a header file of the standard library. However, I can use the new operator in my programmes without including any of the standard headers. Confusingly, "operator new" is not the same thing as the "new" operator. The "new" operator 1) allocates memory (may fail, but I'm ignoring that for now) 2) construct an object in that memory 2.1) if that throws an exception, frees the memory then rethrows Quote: Is there no declaration of operator new required because it is *implicitly* declared? And if so, why is its prototype declared in the standard library's header? The standard (non-placement, throwing) operator new, new[], delete and delete[] functions are implicitly declared (standard section 3.7.3 paragraph 2). The placement operator new/delete functions must be explicitly declared, which is the purpose of <new>. I don't know why the standard functions are supposed to be declared there as well. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Micah Cowan Guest Posted: Thu Oct 30, 2003 4:12 pm    Post subject: Re: Prototype for operator new required? Ben Hutchings <do-not-spam-benh (AT) bwsint (DOT) com> writes: Quote: In article <bnk6h2$sc7$2 (AT) news1 (DOT) nefonline.de>, Matthias Hofmann wrote: Hello! I have learned from the standard that the function prototype for operator new is declared in a header file of the standard library. However, I can use the new operator in my programmes without including any of the standard headers. Confusingly, "operator new" is not the same thing as the "new" operator. The "new" operator 1) allocates memory (may fail, but I'm ignoring that for now) 2) construct an object in that memory 2.1) if that throws an exception, frees the memory then rethrows I'm pretty sure OP was aware of the distinction, which is also pretty much irrelevant to his question: the "new" operator (as defined by the Standard) would fail to work at all were there no definitions for "operator new" for it to find (with declarations for them in scope). -- Micah J. Cowan [email]micah (AT) cowan (DOT) name[/email] [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Dhruv Guest Posted: Thu Oct 30, 2003 7:08 pm    Post subject: Re: Prototype for operator new required? On Tue, 28 Oct 2003 13:38:27 -0500, Matthias Hofmann wrote: Quote: Hello! I have learned from the standard that the function prototype for operator new is declared in a header file of the standard library. However, I can use the new operator in my programmes without including any of the standard headers. Is there no declaration of operator new required because it is *implicitly* declared? And if so, why is its prototype declared in the standard library's header? Yes, it is implicitly included by the compiler whenever you use new or operator new. It is howevere defined in the standard header <new>. operator new (std::size_t); will be responsible for memory allocation, and placement new defined as: operator new (std::size_t, void*); will just return the void* pointer passed (typically) , because the new operator will construct the object at that location. Unless the library defines other stuff like alignment to be borne by this placement new. Regards, -Dhruv. [ See http://www.gotw.ca/resources/clcm.htm for info about ] [ comp.lang.c++.moderated. First time posters: Do this! ] Back to top Ben Hutchings Guest Posted: Fri Oct 31, 2003 10:05 am    Post subject: Re: Prototype for operator new required? Micah Cowan wrote: <snip> Quote: I'm pretty sure OP was aware of the distinction, which is also pretty much irrelevant to his question: the "new" operator (as defined by the Standard) would fail to work at all were there no definitions for "operator new" for it to find (with declarations for them in scope). I don't see why. It works without declarations of std::size_t and std::bad_alloc, which an explicit declaration of operator new depends on. [ 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.