Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!amdahl!pyramid!prls!philabs!phri!bc-cis!john
From: john@bc-cis.UUCP (John L. Wynstra)
Newsgroups: comp.lang.c
Subject: sizeof( _variable_ )
Message-ID: <1264@bc-cis.UUCP>
Date: 20 Jul 88 11:59:21 GMT
Reply-To: john@bc-cis.UUCP (John L. Wynstra)
Distribution: na
Organization: Brooklyn College of CUNY, Brooklyn, NY
Lines: 30


	I recently ran up against this one, and, would like to toss it out to
NetLand.  I had coded (on a 3b2 running System V.3) the following,

typedef struct {
	char	x[10];
	char	y;
	char	xx[10];
	char	yy;
} Stuff;

Stuff z;

Later on in the same code I had a reference to sizeof(z) expecting to get 22
(which is btw what I just now got on the bsd 4.2 vax), but what I got was 24!

	"Aha!" said I, "either character data is being aligned to even byte
boundaries [which, with an octal dump, I later proved to myself it wasn't] or
I've discovered a compiler bug".  A colleague at work pointed out that, perhaps,
what I'm seeing is that storage is being allocated in units of 4 bytes, but
somehow that just doesn't seem right:  I should think that sizeof( _variable_ )
should be the length of the _variable_ not the length of the memory allocated
to it.  Ah, well...

	So, can anyone out there enlighten me as to what is going on?

--john

PS: As luck would have it I was posting while our news feeder was recieving,
and, try as I might, I have no way of knowing if I was quick enough in my
attempt to cancel the first posting.  Sorry if this got out twice.