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From: nathan@orstcs.UUCP (nathan)
Newsgroups: net.lang.c++
Subject: Initializing static members
Message-ID: <34200012@orstcs.UUCP>
Date: Fri, 28-Mar-86 21:00:00 EST
Article-I.D.: orstcs.34200012
Posted: Fri Mar 28 21:00:00 1986
Date-Received: Wed, 2-Apr-86 01:39:26 EST
Organization: Oregon State University - Corvallis, OR
Lines: 43
Nf-ID: #N:orstcs:34200012:000:1457
Nf-From: orstcs!nathan    Mar 28 18:00:00 1986

Initialization of static members:

I recently discussed C++ with a fine fellow at Mentor Graphics
(who may wish to remain anonymous; I neglected to ask), and
the question came up of how to initialize a static class member.  

With the restriction that no initializer may be provided for the field
(apparently a syntactic hurdle), and that (!) no constructor may
be provided for the class containing it (!), the problem begins to look
interesting.

Question: can a constructor be provided for a derivation of a class
containing a static?  If so, we could do this:

	// in bleah.h
	class bleah {
		static int here;
	public:
		int Here() { return 100; }
	}

	...
	// in bleah.c
	class bleah_hack : bleah {
		bleah_hack() { here = Here(); }
	} b;

Some notes about the example are in order:
	The member function Here() is pretending to be a
	constant field, but it's not even a constant *expression*
	for initializer purposes.  One hopes the optimizer can
	make it as efficient as a true constant.  By the way, 'b'
	above defaults to static, not extern; see r8.1.

If constructors for the derived class are illegal, a friend class
may be needed, kluge-ier yet.

This whole problem, of consts and statics in class declarations,
seems pretty fundamental -- as if the restriction on constructors,
if circumvented this way and not rejected by the compiler, might result
in bad code.  Who understands this issue?

Nathan C. Myers		orstcs!nathan		nathan@oregon-state