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From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: "array" vs. "&array" ?
Message-ID: <15638@haddock.ima.isc.com>
Date: 12 Jan 90 19:46:07 GMT
References: <24521@gryphon.COM> <CHUCKP.90Jan10103228@halley.ncr-fc.FtCollins.NCR.com> <21764@mimsy.umd.edu> <5248@buengc.BU.EDU>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 26

In article <5248@buengc.BU.EDU> bph@buengc.bu.edu (Blair P. Houghton) writes:
>Usually when you ask for the pointer to an array you get a
>pointer to the first element of the array.

No, you get a pointer to the entire array (in ANSI C) or an error (in K&R C),
except in those pre-ANSI compilers that chose, as an extension, to make the
misinterpretation you describe (usually accompanied by a warning).

>E.g.:
>	type_t *aptr, a[MAXINDEX+1];
>	aptr = &a;

I don't know of any compiler that will accept that line without a diagnostic.

To reiterate the ANSI convention (the only one worth mentioning, since the
other behavior is really just correcting a "probably typo" for &a[0]):
	type_t (*aptr)[SIZE], a[SIZE];
	aptr = &a;
	if ( *aptr == a )
	    puts( "Will always print this." );

Note that "*aptr" and "a" are both array objects, and hence in the rvalue
context of the compare *each* will be converted to a pointer:
	if ( &(*aptr)[0] == &a[0] )

Karl W. Z. Heuer (karl@haddock.isc.com or ima!haddock!karl), The Walking Lint