C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  replacing operator new          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Mark P Guest Posted: Thu Apr 20, 2006 10:06 pm    Post subject: replacing operator new Consider a class in which I redefine operator new(std::size_t): struct A { void* operator new(std::size_t size) {/* my implementation */} }; This has the consequence of hiding the placement version of operator new: void* operator new(std::size_t size, void* location); I can deal with this by defining placement new within A to call the global placement new: void* operator new(std::size_t size, void* location) { return ::operator new(size,loc); } Is this the recommended way to handle this situation? Is it possible to achieve the same effect by some sort of using declaration? Thanks, Mark Back to top mlimber Guest Posted: Fri Apr 21, 2006 1:06 pm    Post subject: Re: replacing operator new Mark P wrote: Quote: Consider a class in which I redefine operator new(std::size_t): struct A { void* operator new(std::size_t size) {/* my implementation */} }; This has the consequence of hiding the placement version of operator new: void* operator new(std::size_t size, void* location); I can deal with this by defining placement new within A to call the global placement new: void* operator new(std::size_t size, void* location) { return ::operator new(size,loc); } Is this the recommended way to handle this situation? Is it possible to achieve the same effect by some sort of using declaration? Thanks, Mark _C++ Coding Standards_ by Sutter and Alexandrescu recommends in Item 46 that if you provide any class-specific new, provide all of the standard forms (plain, placement, and nothrow). Otherwise, any form you don't provide will be hidden from users of your class (e.g., the STL, which uses placement new extensively). If you have a base class that defines new operators, you can hoist them into your derived class with "using", but you can't pull in names from the global namespace (e.g. ::operator new) that way, so you'll have to write forwarding functions to the global operators (as you did above). Also, don't forget to supply a matching delete operator for each non-placement new operator that you provide. Failing to do so is bad (see _C++ Coding Standards_, Item 45). Cheers! --M Back to top Mark P Guest Posted: Fri Apr 21, 2006 6:07 pm    Post subject: Re: replacing operator new mlimber wrote: Quote: Mark P wrote: Consider a class in which I redefine operator new(std::size_t): struct A { void* operator new(std::size_t size) {/* my implementation */} }; This has the consequence of hiding the placement version of operator new: void* operator new(std::size_t size, void* location); I can deal with this by defining placement new within A to call the global placement new: void* operator new(std::size_t size, void* location) { return ::operator new(size,loc); } Is this the recommended way to handle this situation? Is it possible to achieve the same effect by some sort of using declaration? Thanks, Mark _C++ Coding Standards_ by Sutter and Alexandrescu recommends in Item 46 that if you provide any class-specific new, provide all of the standard forms (plain, placement, and nothrow). Otherwise, any form you don't provide will be hidden from users of your class (e.g., the STL, which uses placement new extensively). If you have a base class that defines new operators, you can hoist them into your derived class with "using", but you can't pull in names from the global namespace (e.g. ::operator new) that way, so you'll have to write forwarding functions to the global operators (as you did above). Also, don't forget to supply a matching delete operator for each non-placement new operator that you provide. Failing to do so is bad (see _C++ Coding Standards_, Item 45). Cheers! --M Thanks for the clarifications. Mark Back to top        C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1 Powered by phpBB © 2001, 2006 phpBB Group