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Date: Thu, 05 Dec 2013 16:07:45 +0100
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
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To: freebsd-hackers@freebsd.org
Subject: Re: Global variables in system programs
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Cc: Eitan Adler <lists@eitanadler.com>
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Hello,

a small status update since some of my ROUTE(8) patches have been committed to 
FreeBSD HEAD recently.

A library interface to the core network commands and utilities is useful, but 
it turned out that the ROUTE(8) program was just the most simple one to 
convert.  I tried to do this also with IFCONFIG(8), but gave up (it uses some 
sort of module registry via linker sets, etc.).  I use now a different 
approach.  I initialize/destroy all global variables in a custom 
set-up/tear-down routine and protect the commands with a global mutex.  Calls 
to the error and exit functions are wrapped to use a long jump.  This works 
well so far with ROUTE(8), IFCONFIG(8), NETSTAT(1), PING(8) and PING6(8).

What really helps is adding static and const qualifiers whenever possible. 
Function static variables are a problem since they cannot be initialized with a 
single set-up/tear-down routine for a module.  Signals are also a problem in a 
multi-threaded environment (used by PING6(8)).

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber@embedded-brains.de
PGP     : Public key available on request.

Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.