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From: rankin@eql.caltech.edu
Newsgroups: comp.lang.c
Subject: Re: Preprocessor macro to quote its argument
Summary: no need to malign VAX C
Message-ID: <1990Aug19.204802.1@eql.caltech.edu>
Date: 20 Aug 90 04:48:02 GMT
References: <1112@mti.mti.com> <1114@mti.mti.com>
Sender: news@laguna.ccsf.caltech.edu
Reply-To: rankin@eql.caltech.edu
Organization: Environmental Quality Laboratory, Caltech
Lines: 28

[ He wants to turn a macro argument into a quoted string, which is done
significantly differently in ANSI C than in 'traditional' C. ]

In article <1114@mti.mti.com>, adrian@mti.mti.com (Adrian McCarthy) writes:
>[text deleted]
> For ANSI preprocessors, use:
> 	#define Q1(x)	#x
> For pre-ANSI preprocessors, the original solution *may* work.  Reportedly,
> 	#define Q1(x)	" x "
> may even work with many pre-ANSI preprocessors, though not VAX C.

     The second method works fine in VAX C (which is not [yet?] ANSI
compliant).  The preprocessor is just an internal phase of the integrated
compiler, but that doesn't make any difference in a case like this.

$  type t.c   			!t.c is a trivial test file
#define Q1(x) " x "
char *string = Q1(xyzzy);
$  cc/preprocess_only t		!read t.c, write t.i
$  type t.i			!display the result
# 1 "USER:[RANKIN]T.C;1"

char *string = " xyzzy ";

     Older versions of the compiler didn't support an explicit preprocess-
only option, but they still did the macro substitution this way.

		Pat Rankin, rankin@eql.caltech.edu