Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ukma!xanth!kremer
From: kremer@cs.odu.edu (Lloyd Kremer)
Newsgroups: comp.lang.c
Subject: Re: Structure padding
Message-ID: <8449@xanth.cs.odu.edu>
Date: 13 Apr 89 17:08:46 GMT
References: <440@front.se> <8392@xanth.cs.odu.edu> <124@paix.ikp.liu.se>
Organization: Old Dominion University, Norfolk, Va.
Lines: 34



In article <124@paix.ikp.liu.se> pekka@paix.ikp.liu.se (Pekka Akselin [The Mad  Midnight Hacker]) writes:
>How about this???
>
>union {
>	struct foo {
>	    char	Bar[3];
>	    char	Baz[6];
>	    char	Frotz[4];
>	} fred;
>	char	SomeString[3 + 6 + 4];
>} Strings;
>
>#define bar	Strings.Bar
>#define baz	Strings.Baz
>#define	frotz	Strings.Frotz
>
>Would there be padding between the Bar, Baz and Frotz arrays in this case?


First, the constructs Strings.Bar etc. are not valid; it would be
Strings.fred.Bar, and so on.

As to internal padding: within the array, no; within the structure, maybe.
So accessing Bar, Baz, and Frotz within Strings.SomeString may or may not be
equivalent to accessing them as Strings.fred.{member_name}.  The presence of
the array within the union has no effect on the compiler's policy regarding
internal padding within structures.


					Lloyd Kremer
					Brooks Financial Systems
					{uunet,sun....}!xanth!brooks!lloyd