Newsgroups: comp.std.c
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Another sizeof question
Message-ID: <1990Nov1.164935.4398@zoo.toronto.edu>
Organization: U of Toronto Zoology
References: <13171@crdgw1.crd.ge.com> <1990Oct28.223702.27918@zoo.toronto.edu> <13294@crdgw1.crd.ge.com>
Date: Thu, 1 Nov 90 16:49:35 GMT

In article <13294@crdgw1.crd.ge.com> volpe@camelback.crd.ge.com (Christopher R Volpe) writes:
>But, could you or someone else point me to a reference in the Standard
>that says that a constant expression in a preprocessor context cannot
>contain sizeof? I'm sure it's in there but I can't find it. 

Note, in 3.1, that the definition of preprocessing-token does not include
`keyword' as a possibility.  Until pp-tokens get converted to tokens in
phase 7 (see 2.1.1.2), `sizeof' is an identifier, not a keyword.  And in
3.8.1, we see that in #if, after macro substitution and etc, "all remaining
identifiers are replaced with the pp-number 0, and then each preprocessing
token is converted into a token".  So `sizeof' can appear in #if, but it
is an ordinary identifier, not the keyword that denotes the operator
described in 3.3.3.4.  No facility of C expressions that is invoked via
a keyword can be used in #if expressions.
-- 
"I don't *want* to be normal!"         | Henry Spencer at U of Toronto Zoology
"Not to worry."                        |  henry@zoo.toronto.edu   utzoo!henry