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From: diamond@tkou02.enet.dec.com (diamond@tkovoa)
Newsgroups: comp.lang.c
Subject: Re: SIMPLE malloc & pointer question
Message-ID: <1898@tkou02.enet.dec.com>
Date: 7 Aug 90 07:55:48 GMT
References: <7206@helios.TAMU.EDU>
Reply-To: diamond@tkou02.enet.dec.com (diamond@tkovoa)
Organization: Digital Equipment Corporation Japan , Tokyo
Lines: 24

In article <7206@helios.TAMU.EDU> jdm5548@diamond.tamu.edu (James Darrell McCauley) writes:

 >main() {
 >  int *a,*b;
Initially, a and b are NULL pointers (do not point to anything usable).
 >  b=(int *)malloc( (unsigned) 4*sizeof(int));
Now b points to some storage that the program can use, and a is still null.
 >  inita(a,b);
Now b still points to some storage that the program can use, and a is still
null.  The null pointer in a was copied to inita's first argument.  The
useful pointer in b was copied to initb's second argument.  Nothing was
copied back.  C function calls are call-by-value, not call-by-value-return,
not call-by-reference.
 >}
 >inita (a,b) int a[],b[]; {
 >  a=(int *)malloc( (unsigned) 4*sizeof(int));
This changes one of inita's variables from null to a useful pointer.
Unfortunately, no one gives the useful pointer back to main.
 >}

(Note to the FAQ list maintainer:  Does the FAQ list mention call-by-value?)
-- 
Norman Diamond, Nihon DEC     diamond@tkou02.enet.dec.com
This is me speaking.  If you want to hear the company speak, you need DECtalk.