Path: utzoo!attcan!uunet!steinmetz!davidsen
From: davidsen@steinmetz.ge.com (William E. Davidsen Jr)
Newsgroups: comp.arch
Subject: Re: Shifting question
Message-ID: <11651@steinmetz.ge.com>
Date: 26 Jul 88 13:15:45 GMT
References: <705@bnr-rsc.UUCP> <11556@steinmetz.ge.com> <11606@steinmetz.ge.com> <12638@mimsy.UUCP>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Organization: General Electric CRD, Schenectady, NY
Lines: 68

In article <12638@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
| In article <11606@steinmetz.ge.com> davidsen@steinmetz.ge.com
| (William E. Davidsen Jr) writes:
| >reading the [draft proposed X3J11 C] standard certainly seems to
| >say [that sizeof is allowed in preprocessor expressions] at this time.
| >... If sizeof is NOT legal in preprocessor directives, then the standard
| >should be clarified, ...
| 
| It is explicitly disallowed in one tiny clause in the second most recent
| draft.  (I have not yet had time to look at the most recent draft.)

  Actually I believe that the clause you mention was deleted. Here is a
message and my reply:
================================================================
From: dmr@research.att.com
Date: Tue, 26 Jul 88 01:15:16 EDT
To: wedu@ge-crd.arpa
Subject: #if sizeof

p. 87, line 24-25 of the Jan draft (the constraint in 3.8.1) say
"Additional restrictions apply.... The expression ... shall not
contain a sizeof operator...."

	Dennis Ritchie
====
Subject: Re: #if sizeof
Date: 26 Jul 88 08:36:16 EDT (Tue)
From: davidsen@crdos1.UUCP (Wm E. Davidsen)


Thanks for the reference from the January draft. The v3 draft in 3.8.1
constraints says:


  The expression that controls conditional inclusion shall be an
integral constant expression except that: it shall not contain a cast;
identifiers (including those lexically identical to keywords) are
interpreted as described below{74}; and it may contain unary operator
expressions of the form:

        defined identifier
or
        defined ( identifier )

which evaluate to 1 if the identifier is currently defined as a macro
name (that is, if it is predefined or if it has been the subject of a
#define preprocessing directive without an intervening #undef directive
with the same subject identifier), 0 if not.

  Each preprocessing token which remains after all macro replacements
have occured shall be in the lexical form of a token.

----------------------------------------------------------------
74  Because the controlling constant expression is evaluated during
    translation phase 4, all identifiers either are or are not macro
    names - there simply are no keywords, enumeration constants, and
    so on.


Whatever was in the January draft seems to be removed.
================================================================

  I can believe that this is a typo, although I would rather believe
that sizeof is now allowed.
-- 
	bill davidsen		(wedu@ge-crd.arpa)
  {uunet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me