From: Joe Buck <Joe.Buck@synopsys.COM>
To: Nathan Sidwell <nathan@codesourcery.com>
Cc: Chris Lattner <sabre@nondot.org>,
Tiago Stein <tiago@lisha.ufsc.br>,
gcc@gcc.gnu.org
Subject: Re: Double abstract class Inheritance concern.
Date: Mon, 29 Mar 2004 18:49:00 -0000 [thread overview]
Message-ID: <20040329084751.A32489@synopsys.com> (raw)
In-Reply-To: <4067D6DD.1060607@codesourcery.com>; from nathan@codesourcery.com on Mon, Mar 29, 2004 at 08:57:17AM +0100
Chris Lattner wrote:
> > I believe the reason is that the ABI does not permit multiple different
> > instances of A to be located at the same address, even if they have zero
> > size. If the size of the structure was 8, all of "A", "B", and "A" would
> > have offset zero.
> >
> > I'm not sure WHY this is required, but this is the reason it happens at
> > least. A declaration of "A X[100];" allocates 100 bytes as
> > a result of the same rule.
On Mon, Mar 29, 2004 at 08:57:17AM +0100, Nathan Sidwell wrote:
> It is a C++ language requirement that no two logically distinct objects
> of the same type have the same address.
However, g++ still finds plenty of opportunities to allocate zero bytes
for a struct/class object, when it is not adjacent to any other objects of the
same type (e.g. an empty base class, or an empty data member of a struct
or class).
next prev parent reply other threads:[~2004-03-29 16:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-29 14:03 Chris Lattner
2004-03-29 17:16 ` Nathan Sidwell
2004-03-29 18:49 ` Joe Buck [this message]
-- strict thread matches above, loose matches on Subject: below --
2004-03-29 13:57 Tiago Stein
2004-03-29 15:15 ` Alexandre Oliva
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