C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Private operator delete in base class          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Sergey P. Derevyago Guest Posted: Thu Aug 03, 2006 8:54 pm    Post subject: Private operator delete in base class Is the following program well-formed? -----------------------------------8<----------------------------------- #include <stddef.h> // size_t struct B { virtual ~B() {} private: void* operator new(size_t size); void operator delete(void* ptr, size_t size); }; struct D : B { }; int main() { D d; } -----------------------------------8<----------------------------------- The point is that B::operator delete() is (intentionally) never called but compilers issue the following error message: main.cpp: In destructor `virtual D::~D()': main.cpp:8: `static void B::operator delete(void*, unsigned int)' is private main.cpp:15: within this context -- With all respect, Sergey. http://ders.angen.net/ mailto : ders at skeptik.net --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top keyvan Guest Posted: Sat Aug 05, 2006 7:44 am    Post subject: Re: Private operator delete in base class hi You can not Create Object from D or B becouse you defiine B cnstructor private & GC can not remove Object d in end of main Becouse B destructor is private. you can use this code. int main() { D *d; } Amir Arayeshi ArayeshiAmir (AT) yahoo (DOT) com "Sergey P. Derevyago" wrote: Quote: Is the following program well-formed? -----------------------------------8<----------------------------------- #include <stddef.h> // size_t struct B { virtual ~B() {} private: void* operator new(size_t size); void operator delete(void* ptr, size_t size); }; struct D : B { }; int main() { D d; } -----------------------------------8<----------------------------------- The point is that B::operator delete() is (intentionally) never called but compilers issue the following error message: main.cpp: In destructor `virtual D::~D()': main.cpp:8: `static void B::operator delete(void*, unsigned int)' is private main.cpp:15: within this context -- With all respect, Sergey. http://ders.angen.net/ mailto : ders at skeptik.net --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Greg Herlihy Guest Posted: Mon Aug 07, 2006 6:18 pm    Post subject: Re: Private operator delete in base class "Sergey P. Derevyago" wrote: Quote: Is the following program well-formed? -----------------------------------8<----------------------------------- #include <stddef.h> // size_t struct B { virtual ~B() {} private: void* operator new(size_t size); void operator delete(void* ptr, size_t size); }; struct D : B { }; int main() { D d; } -----------------------------------8<----------------------------------- The point is that B::operator delete() is (intentionally) never called but compilers issue the following error message: main.cpp: In destructor `virtual D::~D()': main.cpp:8: `static void B::operator delete(void*, unsigned int)' is private main.cpp:15: within this context This program is ill-formed according to §12.4/11: "At the point of definition of a virtual destructor (including an implicit definition (12.), the non-array deallocation function is looked up in the scope of the destructor's class (10.2), and, if no declaration is found, the function is looked up in the global scope. If the result of this lookup is ambiguous or inaccessible, or if the lookup selects a placement deallocation function, the program is ill-formed." The explanation is simply: "[ Note: this assures that a deallocation function corresponding to the dynamic type of an object is available for the delete-expression (12.5). - end note ]" In other words, because the compiler cannot guarantee that an object whose dynamic type is D will never be deleted, it must require that D has an accessible deallocation function from its destructor. Greg --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Nikolaos D. Bougalis Guest Posted: Tue Aug 08, 2006 7:54 am    Post subject: Re: Private operator delete in base class keyvan wrote: Quote: You can not Create Object from D or B becouse you defiine B cnstructor private & GC can not remove Object d in end of main Becouse B destructor is private. What are you talking about? We're dealing with struct not class, which has a default access specifier of 'public' so the declared destructor is public. Also no constructor is provided by the OP, so the compiler will generate a default public one in his case. -n --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top coliveira@gmail.com Guest Posted: Tue Aug 08, 2006 1:04 pm    Post subject: Re: Private operator delete in base class B::delete is never called directly, but as D derives from B, its delete operator exists and is private too. -Carlos "Sergey P. Derevyago" wrote: Quote: Is the following program well-formed? -----------------------------------8<----------------------------------- #include <stddef.h> // size_t struct B { virtual ~B() {} private: void* operator new(size_t size); void operator delete(void* ptr, size_t size); }; struct D : B { }; int main() { D d; } -----------------------------------8<----------------------------------- The point is that B::operator delete() is (intentionally) never called but compilers issue the following error message: main.cpp: In destructor `virtual D::~D()': main.cpp:8: `static void B::operator delete(void*, unsigned int)' is private main.cpp:15: within this context -- With all respect, Sergey. http://ders.angen.net/ mailto : ders at skeptik.net --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Alberto Ganesh Barbati Guest Posted: Tue Aug 08, 2006 1:05 pm    Post subject: Re: Private operator delete in base class "Sergey P. Derevyago" ha scritto: Quote: Is the following program well-formed? According to me, yes, it is. Comeau online and VC7.1 both agree with me and compile it withouth errors. Quote: main.cpp: In destructor `virtual D::~D()': main.cpp:8: `static void B::operator delete(void*, unsigned int)' is private main.cpp:15: within this context You fail to mention which compiler you are using. It looks like a compiler bug to me. Ganesh --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Alberto Ganesh Barbati Guest Posted: Tue Aug 08, 2006 1:05 pm    Post subject: Re: Private operator delete in base class keyvan ha scritto: Quote: You can not Create Object from D or B becouse you defiine B cnstructor private & GC can not remove Object d in end of main Becouse B destructor is private. Hmm... you seems to be totally off-track to me. First, B is not being defined a private constructor, in fact it is not being defined any constructor at all, that means it is getting an implicit default constructor which ought to be public (in case you want to object: no, the presence of a private operator new does *not* make the constructor private). Second, B is not being defined a private destructor: as it's a struct and not a class, the destructor is definitely defined as public (in case you want to object: no, the presence of a private operator delete does *not* make the destructor private). Third, what has GC to do with C++??? Aren't you making confusion with C++/CLI or (gulp!) C#? Ganesh --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Sergey P. Derevyago Guest Posted: Tue Aug 08, 2006 9:33 pm    Post subject: Re: Private operator delete in base class Alberto Ganesh Barbati wrote: Quote: You fail to mention which compiler you are using. It looks like a compiler bug to me. 1. g++.exe (GCC) 3.2.3 (mingw special 20030504-1) a.cpp: In destructor `virtual D::~D()': a.cpp:8: `static void B::operator delete(void*, unsigned int)' is private a.cpp:15: within this context 2. Borland C++ 5.6 for Win32 Copyright (c) 1993, 2002 Borland Error: Unresolved external 'B::operator delete(void *, unsigned int)' referenced from D:\SRC\TMP2\A.OBJ 3. Digital Mars Compiler Version 8.42n a.cpp(11) : Error: member 'B::operator del' of class 'D' is not accessible -- With all respect, Sergey. http://ders.angen.net/ mailto : ders at skeptik.net --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Nikolaos D. Bougalis Guest Posted: Wed Aug 09, 2006 9:10 am    Post subject: Re: Private operator delete in base class Alberto Ganesh Barbati wrote: Quote: Second, B is not being defined a private destructor: as it's a struct and not a class, the destructor is definitely defined as public (in case you want to object: no, the presence of a private operator delete does *not* make the destructor private). While that is true, the program is still ill-formed and the compiler is correct to complain. For details, see the post by Greg Herlihy in this thread. -n --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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