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From: nmyers@mntgfx.mentor.com (Nathan Myers)
Newsgroups: comp.lang.c++
Subject: operator new() scoping
Keywords: storage management garbage collection new delete private
Message-ID: <1989Jun7.115321.22620@mntgfx.mentor.com>
Date: 7 Jun 89 18:53:20 GMT
Organization: Mentor Graphics Corporation, Beaverton Oregon
Lines: 35

Providing arguments for operators new() and delete() is a major
advance.  It offers more power than "this=" semantics, and allows
smaller, faster code.  However,

ark@alice.UUCP (Andrew Koenig) writes
> Operator new (and operator delete) obeys the same scope rules as any
> other member function: if defined inside a class, operator new hides
> any global operator new.  For example:
> 
> 	class T {
> 	/* stuff */
> 	public:
> 		void* operator new(size_t, Memory_speed);
> 	/* more stuff */
> 	};
> 
> 	T* tp = new T;		// Error!
> 
> The use of `new T' is incorrect in this example because the member
> operator new hides the global operator new, so no operator new
> can be found for T that does not require a second argument.

This seems inconsistent to me.  Other overloaded functions don't
hide their neighbors, why should operator new()?  The standard way
to hide a global is to declare a member with the same name and arguments.
Then, if I (as class T author) want to disallow ::operator new(size_t),
I can declare a private one and not define it.

A self-consistent alternative to the posted semantics is:
1. Member operator new(size_t, class Foo) doesn't hide global ::new(size_t).
2. Member operator new(size_t) may be declared private.
3. "::new T" is not valid syntax.  (It seems unnecessary, and dangerous.)

Nathan Myers
nmyers@pdx.mentor.com