Article View: comp.std.c
Article #1916Re: Another sizeof question
From: Stephen Clamage
Date: Thu, 01 Nov 1990 17:17
Date: Thu, 01 Nov 1990 17:17
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1463 bytes
Chris Volpe writes: >I understand now what the rule is regarding sizeof, and why it is. >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. To the preprocessor, sizeof is just an identifier, not a keyword. You will note that the Standard section 3.8 describes what the preprocessor recognizes, and sizeof is not mentioned. Neither are "for", "while", "switch", or other C keywords. Consider this: int x; #if goto(x) == 2 or this: int x; extern int foo(int); #if foo(x) == 2 Writing int x; #if sizeof(x) == 2 has precisely the same effect. "Goto", "foo", and "sizeof" are treated by the preprocessor as ordinary identifiers: if they are not #defined to the proprocessor, they are treated as constant integers with value 0. -- Steve Clamage, TauMetric Corp, steve@taumet.com
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!watserv1!watmath!att!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!sun-barr!lll-winken!uunet!taumet!steve From: steve@taumet.com (Stephen Clamage) Newsgroups: comp.std.c Subject: Re: Another sizeof question Message-ID: <497@taumet.com> Date: 1 Nov 90 17:17:29 GMT References: <13171@crdgw1.crd.ge.com> <1990Oct28.223702.27918@zoo.toronto.edu> <13294@crdgw1.crd.ge.com> Organization: Taumetric Corporation, San Diego Lines: 26