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Message-ID: <19990208223512.36113@murlibobo.cs.mu.OZ.AU>
Date: Mon, 8 Feb 1999 22:35:12 +1100
From: Fergus Henderson <fjh AT cs DOT mu DOT OZ DOT AU>
To: OSKAR BERRETEAGA <oskarb AT fagorautomation DOT es>
Cc: "'cygwin AT sourceware DOT cygnus DOT com'" <cygwin AT sourceware DOT cygnus DOT com>
Subject: Re: Double alignment trouble
References: <c=ES%a=_%p=FAGOR?AUTOMATION%l=NTCORREO-990208092125Z-1442 AT ntcorreo DOT fagorautomation DOT es>
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In-Reply-To: <c=ES%a=_%p=FAGOR?AUTOMATION%l=NTCORREO-990208092125Z-1442@ntcorreo.fagorautomation.es>; from OSKAR BERRETEAGA on Mon, Feb 08, 1999 at 10:21:25AM +0100

On 08-Feb-1999, OSKAR BERRETEAGA <oskarb AT fagorautomation DOT es> wrote:
> 
> I've been trying to change the way gcc aligns double type variables but
> with no possitive result.

The newsgroup gnu.gcc.help might be a more appropriate forum for this
question.

> These are the options I've set with gcc: -malign-double (alone or with
> one of the following -march='pentium' -m386 -m486) and the full command
> line is: gcc -c test.c -malign-double -o test.o

`-malign-double' is the default.  If you want to disable it, you need
to use `-mno-align-double'.  However, this will typically have a
negative effect on performance, and may cause binary compatibility
problems, so I don't recommend using this option.

> I've even used the  __attribute__((aligned(2))) for both the struct and
> the double var but, again, it seems it has no effect on double
> alignment.

Please RTFM. The documentation of the `aligned' attribute is quite clear:

 |	This attribute specifies a minimum alignment ...
 ...	                           ^^^^^^^^
 |	The `aligned' attribute can only increase the alignment;
 |	but you can decrease it by specifying `packed' as well.

-- 
Fergus Henderson <fjh AT cs DOT mu DOT oz DOT au>  |  "Binaries may die
WWW: <http://www.cs.mu.oz.au/~fjh>  |   but source code lives forever"
PGP: finger fjh AT 128 DOT 250 DOT 37 DOT 3        |     -- leaked Microsoft memo.

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