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From: gwyn@brl-smoke.UUCP
Newsgroups: comp.lang.c,news.software.b
Subject: Re: passing NULL to functions
Message-ID: <5804@brl-smoke.ARPA>
Date: Mon, 27-Apr-87 17:53:13 EDT
Article-I.D.: brl-smok.5804
Posted: Mon Apr 27 17:53:13 1987
Date-Received: Wed, 29-Apr-87 01:14:05 EDT
References: <150@sds.UUCP> <1129@ius2.cs.cmu.edu>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 19
Xref: utgpu comp.lang.c:1867 news.software.b:538

In article <1129@ius2.cs.cmu.edu> edw@ius2.cs.cmu.edu (Eddie Wyatt) writes:
>  Are you saying that you are not guarenteed sizeof(char *) == sizeof(int *)
>sizeof(long *) == sizeof(whatever *)?

Yup.  Consider a word-addressed machine (no byte addressing), for example
a 16-bit one to make it likely that there simply aren't any spare address bits.
To select a byte within a word you'll have to use more than 16 bits, so a
(char *) would probably be 32 bits while an (int *) would probably be 16.

Although I made up this example, there in fact are C implementations using
different sizes for different pointer types.  I think Prime or DGC do..

>#define alloc(type)		((type *) malloc(sizeof(type)))

Yup, although you might want one more set of () around the first `type'.

>#define mfree(x)		free(x)

More convenient is		free((char *)(x))	/* (void *) if supported */