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Date:      Wed, 12 Mar 2003 22:58:42 -0600
From:      Dan Nelson <dnelson@allantgroup.com>
To:        Sean Hamilton <sh@bel.bc.ca>
Cc:        hackers@FreeBSD.ORG
Subject:   Re: first parameter to select
Message-ID:  <20030313045842.GG2336@dan.emsphone.com>
In-Reply-To: <000501c2e911$96ea79a0$d1d7e8d8@slugabed.org>
References:  <000501c2e911$96ea79a0$d1d7e8d8@slugabed.org>

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In the last episode (Mar 12), Sean Hamilton said:
> What is the first parameter to select(2) for? Microsoft's select
> ignores it, and it does not appear to have any valid use since it
> only allows constraints on values which are assigned by the system.

I'd hate to have the kernel scan a 6000-element (or whatever maxfiles
is on your system) array every time I called select with nfds=10.

If MS ignores the nfds parameter, it risks accessing uninitialized
memory or selecting on fds that the user no longer wants to look at. 
I'd call it a bug.
 
> Purely historic?

Performance.

-- 
	Dan Nelson
	dnelson@allantgroup.com

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