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Date:      Sun, 18 Apr 1999 00:06:11 +0100 (BST)
From:      Doug Rabson <dfr@nlsystems.com>
To:        Terry Lambert <tlambert@primenet.com>
Cc:        obrien@NUXI.com, paul@originative.co.uk, gallatin@cs.duke.edu, mjacob@feral.com, mike@smith.net.au, alpha@freebsd.org
Subject:   Re: egcs ready for alpha?
Message-ID:  <Pine.BSF.4.05.9904180004310.51054-100000@herring.nlsystems.com>
In-Reply-To: <199904172252.PAA22325@usr08.primenet.com>

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On Sat, 17 Apr 1999, Terry Lambert wrote:

> > > >  > +#if 0
> > > >  >  	*(union u_spcl *)(*(nextblock)++) = *(union u_spcl *)dp;
> > 
> > It might be better to remove the cast of nextblock and dp and see what
> > warnings EGCS gives.  The ficl and vinum code had weird union casts that
> > had to be reworked for egcs.  In the above, I bet there is an alignment
> > issue wth EGCS using a different alightment rule than gcc did.
> 
> Specifically, I think it would work with a #pragma pack(4); I believe
> the default structure packing on Alpha for EGCS is 8.
> 
> In general, when you are using a structure whose data is externalized,
> and you want it to be portable, you should either serialize it (XDR
> the data into a character buffor on the way in and out), or you should
> use a #pragma pack(1).
> 
> There are a number of problems with this on the Alpha, since the Alpha
> does not like unaligned data accesses.  Unfortuantely, a recent commit
> put a fault handler in that does fixups on unaligned accesses, and the
> damn this is defaulted to "on", which does a fat lot of good for getting
> these problems *resolved* instead of *masked*.

Terry, get your facts right.  FreeBSD/alpha has always had an unaligned
fault handler (which came from NetBSD verbatim).  The recent commit was a
sysctl variable to turn the fault handler *off*.

--
Doug Rabson				Mail:  dfr@nlsystems.com
Nonlinear Systems Ltd.			Phone: +44 181 442 9037




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