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Re: MAXIMUM_ALIGNOF on Windows-32

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: MAXIMUM_ALIGNOF on Windows-32
Date: 2007-07-20 13:51:46
Message-ID: 4216.1184939506@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com> writes:
> The MAXIMUM_ALIGNOF value is set to 8 bytes in a Windows- 32-bit
> environment. I have very little knowledge about Windows, but at
> the face of it, this looks strange. Any idea why is this required ?

It's not entirely unreasonable.  The same thing happens on HPPA,
which is nominally a 32-bit architecture but the hardware requires
8-byte alignment of doubles (and maybe int64 too, I forget).
On newer Intel hardware it'd make sense to pad to avoid misaligned
fetches.

Anyway, we detect this directly based on the C compiler's behavior,
and you can't argue with the compiler about it.  Whatever it's
doing is right by definition.

			regards, tom lane

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Subject: Re: MAXIMUM_ALIGNOF on Windows-32
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