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void outOfMem(); // decl. of func. to call if mem. alloc. // for Widget objects fails Widget::set_new_handler(outOfMem); // set outOfMem as Widget's // new-handling function Widget *pw1 = new Widget; // if memory allocation // fails, call outOfMem std::string *ps = new std::string; // if memory allocation fails, // call the global new-handling // function (if there is one) Widget::set_new_handler(0); // set the Widget-specific // new-handling function to // nothing (i.e., null) Widget *pw2 = new Widget; // if mem. alloc. fails, throw an // exception immediately. (There is // no new- handling function for // class Widget.) |
template class NewHandlerSupport{ // class-specific set_new_handler public: // support static std::new_handler set_new_handler(std::new_handler p) throw(); static void * operator new(std::size_t size) throw(std::bad_alloc); ... // other versions of op. new private: static std::new_handler currentHandler; }; template std::new_handler NewHandlerSupport { std::new_handler oldHandler = currentHandler; currentHandler = p; return oldHandler; } template void* NewHandlerSupport throw(std::bad_alloc) { NewHandlerHolder h(std::set_new_handler(currentHandler)); return ::operator new(size); } // this initializes each currentHandler to null template std::new_handler NewHandlerSupport |
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