From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <ee9e417a0610201318o469eeec9lacd7c7ed2924fcc1@mail.gmail.com>
Date: Fri, 20 Oct 2006 16:18:52 -0400
From: "Russ Cox" <rsc@swtch.com>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu>
Subject: Re: [9fans] Include guards and multiple includes
In-Reply-To: <7871fcf50610201227s17987c4at9bafba8729f8a6b9@mail.gmail.com>
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References: <219D85AA-959D-464C-90C2-0F132809F0B9@telus.net>
	<7871fcf50610201227s17987c4at9bafba8729f8a6b9@mail.gmail.com>
Topicbox-Message-UUID: cf64fee8-ead1-11e9-9d60-3106f5b1d025

There was a time when there was an efficiency argument
to be made (don't have to read and parse the files over and over),
but gcc did an end run around it by recognizing files with
the traditional #ifndef #define #endif sequence and
then not even re-opening the file the next time it gets
included.

Arguably gcc didn't even have to do this, though: the rest
of the compiler is so slow that parsing the headers multiple
times is hardly the performance bottleneck.

Russ