C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  delete [ ] fp qn          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message mescaline Guest Posted: Mon Dec 29, 2003 2:44 pm    Post subject: delete [ ] fp qn Hi, suppose I do: class One{}; int main(){ One * A = new One[100]; // an array of objects on the heap ... delete A; // instead of delete []A; return 0; } .... I read in Eckel, that "this releases the proper amount of storage" -- How? Also, then there is no memory leak, right? What are the disadvantages of doing the above then instead of "delete []A;"? thanks m Back to top Jeff Schwab Guest Posted: Mon Dec 29, 2003 2:45 pm    Post subject: Re: delete [ ] fp qn mescaline wrote: Quote: Hi, suppose I do: class One{}; int main(){ One * A = new One[100]; // an array of objects on the heap ... delete A; // instead of delete []A; return 0; } ... I read in Eckel, that "this releases the proper amount of storage" -- How? Also, then there is no memory leak, right? What are the disadvantages of doing the above then instead of "delete []A;"? thanks m Use delete[]. I don't know why Eckel would say differently. Back to top Ron Natalie Guest Posted: Mon Dec 29, 2003 2:52 pm    Post subject: Re: delete [ ] fp qn Quote: ... I read in Eckel, that "this releases the proper amount of storage" -- How? Also, then there is no memory leak, right? What are the disadvantages of doing the above then instead of "delete []A;"? The disadvantage is that it is undefined behavior. If Eckel said that, he's wrong. There's no guarantee that anything specific happens. It's quite possible you'll hose the allocators. Back to top Martijn Lievaart Guest Posted: Mon Dec 29, 2003 3:41 pm    Post subject: Re: delete [ ] fp qn On Mon, 29 Dec 2003 06:44:36 -0800, mescaline wrote: Quote: Hi, suppose I do: class One{}; int main(){ One * A = new One[100]; // an array of objects on the heap ... delete A; // instead of delete []A; return 0; } ... I read in Eckel, that "this releases the proper amount of storage" -- How? I haven't read Eckel, but given how highly regarded he is, I doubt he wrote that, or not in this context. Quote: Also, then there is no memory leak, right? What are the disadvantages of doing the above then instead of "delete []A;"? It invokes undefined behaviour. Anything may happen. Anything may even include works, seems to work but it might also blow up. HTH, M4 Back to top Unforgiven Guest Posted: Mon Dec 29, 2003 4:12 pm    Post subject: Re: delete [ ] fp qn mescaline wrote: Quote: Hi, suppose I do: class One{}; int main(){ One * A = new One[100]; // an array of objects on the heap ... delete A; // instead of delete []A; return 0; } ... I read in Eckel, that "this releases the proper amount of storage" -- How? Also, then there is no memory leak, right? What are the disadvantages of doing the above then instead of "delete []A;"? If you say: One *B = new One; Memory is allocated and the constructor is called. If you say: One *A = new One[100]; Memory is allocated and 100 constructors are called. Similarly if you say: delete[] A; All 100 destructors are called and memory is deallocated But if you say: delete A; Only 1 destructor is called and memory is deallocated. While at the very least all compilers I know (I'm not sure if the standard has anything to say about this) will deallocate all memory, only the first of the in this case 100 objects is properly destructed. If the other 99 objects manage any resources (like memory) that rely on the destructor to be released, those will leak if you don't use delete[]. -- Unforgiven "Most people make generalisations" Freek de Jonge Back to top Ron Natalie Guest Posted: Mon Dec 29, 2003 4:16 pm    Post subject: Re: delete [ ] fp qn "Unforgiven" <jaapd3000 (AT) hotmail (DOT) com> wrote Quote: But if you say: delete A; Only 1 destructor is called and memory is deallocated. Nope, it's undefined behavior. It's quite possible that the memory doesn't get deallocated properly either. It's worse than a leak. 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.