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Date: Sun, 11 Apr 2010 20:13:40 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Roman Divacky <rdivacky@freebsd.org>
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
	src-committers@freebsd.org, Bruce Evans <brde@optusnet.com.au>
Subject: Re: svn commit: r206424 - head/usr.bin/xlint/lint1
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On Sun, 11 Apr 2010, Roman Divacky wrote:

> On Sun, Apr 11, 2010 at 07:16:12PM +1000, Bruce Evans wrote:
>> ....  However2, the system ALIGN() on
>> amd64 doesn't know the correct alignment either (both essentially had
>> 64 bits hard-coded).  Now xlint uses a different hard-coded alignment
>> (128 bits).
>
> so you suggest fixing the ALIGN on amd64? ie. to make it 128bit?

It's an ABI change, thus needs careful release engineering.  _ALIGN
(= ALIGN) is used in the CMSG ABI in <sys/socket.h> so I think would
affect public ABIs.

amd64 has a strict ABI which I think involves 128-byte alignment for
long doubles (not sure if it specifies anything for non-C things like
copies of SSE registers).  The system should have a macro to support
the maximal alignment and it is easiest to use ALIGN() for this
(otherwise you would need a new macro for this and keep ALIGN() for
pointers and longs...).

Bruce