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Path: utzoo!mnetor!seismo!vrdxhq!bms-at!stuart
From: stuart@bms-at.UUCP (Stuart D. Gathman)
Newsgroups: comp.lang.c
Subject: pointers to arrays
Message-ID: <273@bms-at.UUCP>
Date: Tue, 18-Nov-86 15:07:40 EST
Article-I.D.: bms-at.273
Posted: Tue Nov 18 15:07:40 1986
Date-Received: Tue, 18-Nov-86 22:05:49 EST
Organization: Business Management Systems, Inc., Fairfax, VA
Lines: 47
Keywords: What? Why? How?

I am still confused about several things concerning pointers to arrays.

There does seem to be such a type, even in K & R.

1) How does one get such an animal?  The only methods I can figure are

	a) a cast: ( type (*)[] ) array_of_type
	b) a function returning such a type (but the return must use a cast!)

2) The SysV semop(2) is defined as:

	int semop(int,struct sembuf **,int)

   but in the lint library as:

	int semop(int,struct sembuf (*)[],int)

   The semop(2) definition is definitely wrong.  The lint definition
   is possibly correct.  I have ended up pretending it is:

	int semop(int,struct sembuf *,int)

   Am I really supposed to write the code like this:?

	struct sembuf s[5];
	. . .
	rc = semop(sid,(struct sembuf (*)[])s,5)

3) It seems to me that any distinction between a pointer to an array
   and a pointer to its first element is purely semantic.  (And given
   the semantic difficult of obtaining a pointer to an array, why use
   them?)  There is no pointer conversion that I can imagine involved.

4) Given:

	TYPE **foo, (*bar)[];

   both **foo and **bar refer to an object of type TYPE.  Perhaps
   this is the source of the error in the SysV documentation.

* * *

When are pointers to arrays appropriate?  

Is there an easier (and more natural) way to use them in an expression?
-- 
Stuart D. Gathman	<..!seismo!{vrdxhq|dgis}!bms-at!stuart>