Xref: utzoo comp.arch:5689 comp.lang.c:11495 comp.std.c:207
Path: utzoo!attcan!uunet!steinmetz!davidsen
From: davidsen@steinmetz.ge.com (William E. Davidsen Jr)
Newsgroups: comp.arch,comp.lang.c,comp.std.c
Subject: Re: Shifting question
Message-ID: <11637@steinmetz.ge.com>
Date: 25 Jul 88 15:46:52 GMT
References: <705@bnr-rsc.UUCP> <11556@steinmetz.ge.com> <1988Jul19.173807.6604@utzoo.uucp> <11606@steinmetz.ge.com> <1988Jul23.231300.22872@utzoo.uucp>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Followup-To: comp.std.c
Organization: General Electric CRD, Schenectady, NY
Lines: 47

henry@utzoo.uucp (Henry Spencer) writes:

| You have an out-of-date draft, I believe.  The second-public-comment draft
| (I haven't seen the third yet) explicitly forbids sizeof in this context.

  I believe what I have is current. I got it a week ago and it's marked
as THIRD public review. The many references were all based on that
draft.

  Another note, from the sizeof (3.3.3.4) section, line 23.
    Constraints
    ===========
    
      The _sizeof_ operator shall not be applied to an expression
    function type or an incomplete type, to the parenthesized name
    of such a type, or to an lvalue that designates a bitfield
    object.


Chris Tokek said that there was a obscure phrase which
disallowed use of sizeof in the preprocessor, but 3.8.1 on the
#if says that the 2nd argument is a constant expression, and 3.4
(constant expressions) says:

    Constraints
    ===========
    
      Constant expression shall not contain assignment, increment,
    decrement, function call, or comma operators, except when they
    when they are contained within the operand of a sizeof operator.
    
  This is the only reference to constant expression in the index. If
the semantics of the #if say that the first field is a constant
expression, and the definition of constant expression specifically
includes sizeof, either sizeof is legal in the expression of #if, or
perhaps the phrase is a bit too obscure.

  I didn't think this was legal, but after some time checking the
standard I thank that the standard *seems* to say that it is.

  Since this discussion has gotten split between comp.std.c, comp.lang.c and
comp.arch, I have directed followup to comp.std.c, since the question
has changed to a standards issue.
-- 
	bill davidsen		(wedu@ge-crd.arpa)
  {uunet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me