C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  placement new and exception          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message wijhierbeneden Guest Posted: Sat Oct 30, 2004 1:24 pm    Post subject: placement new and exception On http://www.parashift.com/c++-faq-lite/freestore-mgmt.html in [16.9] In p = new Fred(), does the Fred memory "leak" if the Fred constructor throws an exception? there is this code: // Original code: Fred* p = new Fred(); Fred* p = (Fred*) operator new(sizeof(Fred)); try { new(p) Fred(); // Placement new } catch (...) { operator delete(p); // Deallocate the memory throw; // Re-throw the exception } What exception can placement new throw??? Back to top Pavel Vozenilek Guest Posted: Sat Oct 30, 2004 1:58 pm    Post subject: Re: placement new and exception "wijhierbeneden" wrote: Quote: What exception can placement new throw??? Those thrown by constructor. /Pavel Back to top JKop Guest Posted: Sat Oct 30, 2004 4:25 pm    Post subject: Re: placement new and exception Quote: Fred* p = (Fred*) operator new(sizeof(Fred)); I don't recognize the syntax above. How about: Fred* p = reinterpret_cast<Fred* const &>( new char[sizeof(Fred)] ); Back to top David Lindauer Guest Posted: Sat Oct 30, 2004 8:24 pm    Post subject: Re: placement new and exception JKop wrote: Quote: Fred* p = (Fred*) operator new(sizeof(Fred)); I don't recognize the syntax above. How about: Fred* p = reinterpret_cast<Fred* const &>( new char[sizeof(Fred)] ); it is valid to take an overloaded operator function, and access it directly. For example: myclass &operator +(myclass &a, myclass &b) { } .... .... myclass yy,zz ,ss; ss = operator +(yy,zz) ; is the same as: ss = yy + zz ; in rare circumstances this is useful... David Back to top Old Wolf Guest Posted: Sun Oct 31, 2004 7:49 pm    Post subject: Re: placement new and exception JKop <NULL (AT) NULL (DOT) NULL> wrote: wiejherbeneden wrote: Quote: Fred* p = (Fred*) operator new(sizeof(Fred)); I don't recognize the syntax above. How about: Fred* p = reinterpret_cast<Fred* const &>( new char[sizeof(Fred)] ); JKop wrote on 27 Oct 2004 (4 days ago) in the thread titled "Your C++ Homework": If we throw the Standard Library out of the window for the moment, then I would be comfortable saying here that I'm an expert C++ programmer - I pretty much understand and know how to use all of the features of C++. Back to top JKop Guest Posted: Tue Nov 02, 2004 9:06 am    Post subject: Re: placement new and exception Old Wolf posted: Quote: JKop <NULL (AT) NULL (DOT) NULL> wrote: wiejherbeneden wrote: Fred* p = (Fred*) operator new(sizeof(Fred)); I don't recognize the syntax above. How about: Fred* p = reinterpret_cast<Fred* const &>( new char[sizeof(Fred)] ); JKop wrote on 27 Oct 2004 (4 days ago) in the thread titled "Your C++ Homework": If we throw the Standard Library out of the window for the moment, then I would be comfortable saying here that I'm an expert C++ programmer - I pretty much understand and know how to use all of the features of C++. Am I the only one that finds this pathetic? Is it a lack of self-esteem that motivates you to ridicule others? -JKop Back to top Bob Hairgrove Guest Posted: Tue Nov 02, 2004 10:17 pm    Post subject: Re: placement new and exception On Tue, 02 Nov 2004 09:06:31 GMT, JKop <NULL (AT) NULL (DOT) NULL> wrote: Quote: Old Wolf posted: JKop wrote on 27 Oct 2004 (4 days ago) in the thread titled "Your C++ Homework": If we throw the Standard Library out of the window for the moment, then I would be comfortable saying here that I'm an expert C++ programmer - I pretty much understand and know how to use all of the features of C++. Am I the only one that finds this pathetic? Probably. -- Bob Hairgrove [email]NoSpamPlease (AT) Home (DOT) com[/email] Back to top wijhierbeneden Guest Posted: Wed Nov 03, 2004 8:46 am    Post subject: Re: placement new and exception "Pavel Vozenilek" <pavel_vozenilek (AT) yahoo (DOT) co.uk> wrote Quote: "wijhierbeneden" wrote: What exception can placement new throw??? Those thrown by constructor. /Pavel And which ones?? bad_alloc can't be thrown because there must not been allocated any memory. Can you give an example about an exception??? Back to top Richard Herring Guest Posted: Wed Nov 03, 2004 10:44 am    Post subject: Re: placement new and exception In message <236f4e4.0411030046.709936eb (AT) posting (DOT) google.com>, wijhierbeneden <wijhierbeneden (AT) hotmail (DOT) com> writes Quote: "Pavel Vozenilek" <pavel_vozenilek (AT) yahoo (DOT) co.uk> wrote in message news:<2uhl0lF22nddtU1 (AT) uni-berlin (DOT) de>... "wijhierbeneden" wrote: What exception can placement new throw??? Those thrown by constructor. /Pavel And which ones?? bad_alloc can't be thrown because there must not been allocated any memory. Not necessarily. Placement new only suppresses the normal allocation for the object itself. If the object has pointer members, its constructor may attempt a normal allocation for whatever they point to, and that allocation may throw. Quote: Can you give an example about an exception??? -- Richard Herring Back to top Ron Natalie Guest Posted: Wed Nov 03, 2004 2:45 pm    Post subject: Re: placement new and exception Richard Herring wrote: Quote: Not necessarily. Placement new only suppresses the normal allocation for the object itself. If the object has pointer members, its constructor may attempt a normal allocation for whatever they point to, and that allocation may throw. ....or the constructors class members. Back to top Richard Herring Guest Posted: Wed Nov 03, 2004 3:18 pm    Post subject: Re: placement new and exception In message <4188ecd8$0$31343$9a6e19ea (AT) news (DOT) newshosting.com>, Ron Natalie <ron (AT) sensor (DOT) com> writes Quote: Richard Herring wrote: Not necessarily. Placement new only suppresses the normal allocation for the object itself. If the object has pointer members, its constructor may attempt a normal allocation for whatever they point to, and that allocation may throw. ...or the constructors class members. Indeed, recursively, ad infinitum. I just picked the simplest case. -- 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.