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From: John Baldwin <jhb@freebsd.org>
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Date: Thu, 10 Mar 2011 14:46:37 -0500
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	(bigwig.baldwin.cx); Thu, 10 Mar 2011 14:51:22 -0500 (EST)
Cc: mdf@freebsd.org
Subject: Re: style(9) rules for nested includes
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On Thursday, March 10, 2011 12:17:28 pm mdf@freebsd.org wrote:
> I recall a recent discussion/PR about nested includes in the context
> of <sys/linker_set.h> and <sys/queue.h> being a few of the only ones
> allowed.  However, I don't see anything in style(9) about this.

bde@ is probably the most authoritative.  My understanding is that the only 
nested includes allowed in sys/sys/*.h are the two listed above and any header 
that starts with an underscore (sys/_mutex.h, etc.).  The underscore variants 
were added to allow nested includes when absolutely necessary, but those 
includes are the bare minimum required to define structures, etc.

> Now we come to the reason I ask.  I'm working on a patch to change the
> static sysctl code to use the standard SYSININT/SYSUNINIT code rather
> than have special treatment in kern_linker.c, but to do this I need to
> either change quite a few places that include <sys/sysctl.h>, or
> include <sys/kernel.h> instead of <sys/linker_set.h> in sysctl.h, as
> the SI_SUB_SYSCTLS value isn't visible otherwise.

Hmm, what is the reason to use SYSINIT's instead of a dedicated linker set?
 
-- 
John Baldwin