Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!rutgers!cbmvax!vu-vlsi!colin
From: colin@vu-vlsi.UUCP
Newsgroups: comp.lang.c
Subject: Re: Auto variable with sizeof == 0
Message-ID: <626@vu-vlsi.UUCP>
Date: Fri, 13-Feb-87 11:24:07 EST
Article-I.D.: vu-vlsi.626
Posted: Fri Feb 13 11:24:07 1987
Date-Received: Sat, 14-Feb-87 02:14:20 EST
References: <4114@brl-adm.ARPA> <4053@utcsri.UUCP> <159@batcomputer.tn.cornell.edu>
Reply-To: colin@vu-vlsi.UUCP (Colin Kelley)
Organization: Villanova Univ. EE Dept.
Lines: 33
Summary: Another solution to the malloc() case

In article <159@batcomputer.tn.cornell.edu> braner@batcomputer.UUCP (braner) writes:
>
>In the famous "microEMACS" by David Conroy, which has been widely
>utilized and modified, the basic text-line structure looks like this:
>
>typedef struct LINE {
>	struct LINE *nextline;
>	struct LINE *prevline;
>	short       size;		/* s.b. int! */
>	short       used;
>	char        text[];		/* !!!!!!!!! */
>}	LINE;
>
>The idea is to allocate memory for lines as follows:
>
>	lineptr = malloc(sizeof(LINE)+length);

Some other people suggested declaring the text field to be char *text, but
I'm surprised no one suggested this:

Declare the text field to be char text[1], then use

	lineptr = malloc(sizeof(LINE)-1+length);

Almost all compilers will optimize sizeof(LINE)-1 into a single constant, so
the code generated is likely to be exactly the same as that generated for
the uEmacs example above...[Of course you can cast the argument to (unsigned)
to keep lint happy.]

Gnuplot (which we posted a couple weeks ago) uses this technique because it
seemed to be the most portable...

	-Colin Kelley  ..{cbmvax,pyrnj,bpa}!vu-vlsi!colin