From: Ian Lance Taylor <ian@airs.com>
To: Chris Lattner <sabre@nondot.org>
Cc: gcc-help@gcc.gnu.org
Subject: Re: attribute aligned(4) ignored
Date: Tue, 26 Jul 2005 03:22:00 -0000 [thread overview]
Message-ID: <m3u0iife3a.fsf@gossamer.airs.com> (raw)
In-Reply-To: <Pine.LNX.4.61.0507252003000.10523@nondot.org>
Chris Lattner <sabre@nondot.org> writes:
> Hi All, I'm trying to reduce the alignment of the double in this
> structure to 4 bytes (from 8) on Darwin. The goal of doing this is to
> reduce the structure to 12 bytes in size. Here is my testcase:
>
> struct Test {
> double D __attribute__((aligned(4))); // only 4 bytes, not 8!
> int X;
> };
>
> int X() {
> return sizeof(struct Test); // Should return 12, not 16.
> }
>
> Despite my attempt above, the structure is still 16 bytes in size, due
> to the tail padding required to pad the structure to ensure 8-byte
> alignment.
>
> Does anyone know how to reduce the alignment of the double,
> eliminating the tail padding?
How about
double D __attribute__((aligned(4), packed));
Ian
next prev parent reply other threads:[~2005-07-26 3:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-26 1:04 Chris Lattner
2005-07-26 3:22 ` Ian Lance Taylor [this message]
2005-07-26 4:58 ` Chris Lattner
2005-07-26 5:02 ` corey taylor
2005-07-26 5:04 ` Chris Lattner
2005-07-26 5:25 ` Ian Lance Taylor
2005-07-26 5:57 ` Chris Lattner
2005-07-26 6:27 ` Ian Lance Taylor
2005-07-26 6:44 ` Chris Lattner
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