Path: utzoo!mnetor!uunet!husc6!bloom-beacon!gatech!mcnc!rti!xyzzy!kulik
From: kulik@xyzzy.UUCP (Al Kulik)
Newsgroups: comp.lang.c
Subject: Re: macros with parameters in MSC 5.0
Message-ID: <666@xyzzy.UUCP>
Date: 4 Mar 88 20:31:08 GMT
References: <11879@brl-adm.ARPA> <2631@haddock.ISC.COM> <898@PT.CS.CMU.EDU> <290@alice.marlow.reuters.co.uk>
Reply-To: kulik@xyzzy.UUCP ()
Organization: Data General Corporation, Research Triangle, NC
Lines: 37

In article <290@alice.marlow.reuters.co.uk> fox@alice.marlow.reuters.co.uk (Paul Fox) writes:
>ANSI gets around this [macro argument substitution in string literals] via the
>'#' and '##' operators -- available within the preprocessor phase only. As I 
>read it 
>
># define	CTRL(x)		#x & 037
>		CTRL(A);
>
>gives:		"A" & 037
>
># define	CTRL(x)		'##x##' & 037
>		CTRL(A);        ^^^^^^^
>
>gives:		'A' & 037
>

I don't know about this. It seems to me that this would result in
'##x##' & 037. '##x##' is a character constant which is a preprocessor
token; the preprocessor will not recognize the ##s within the token, they're
just part of the constant.

In the first case above, "A" & 037 results in the address of the literal
"A" being ANDed bitwise with the constant 037, which may not be what you want.

To obtain something like the second case:

#define CTRL(x)	#x[0] & 037.








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