From owner-svn-src-projects@FreeBSD.ORG  Tue Mar  5 11:41:53 2013
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Date: Tue, 5 Mar 2013 22:21:09 +1100 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Gleb Smirnoff <glebius@FreeBSD.org>
Subject: Re: svn commit: r247710 - projects/calloutng/sys/kern
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Cc: Davide Italiano <davide@FreeBSD.org>, src-committers@FreeBSD.org,
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On Tue, 5 Mar 2013, Gleb Smirnoff wrote:

> On Tue, Mar 05, 2013 at 08:43:33PM +1100, Bruce Evans wrote:
> B> > I think for new code we should prefer C99's bool to boolean_t.
> B>
> B> Why?  There is no existing practice for this in the kernel.  There is some
> B> in the Linux kernel :-).
>
> Why? Because it is standard. What for? To make it more easy for newcomers
> to start hacking on FreeBSD kernel.

I think you mean "harder".  Now the newcomers need to know:
- the old method, which is used in most places
- the new method
- style rules for old, new and mixed methods
- arcane C99 points like whether bool can be used in bit-fields (I had to
   look this up to check it.  It can).

I now see technical reasons to never use bool in kernel or other low-level
code.  It will cause minor pessimizations converting nonzero to true (1)
at runtime, and for converting bool to register_t when passing parameters
(bool is 1 byte on x86).  To use bool in structs (when not packing it into
bit-fields), we need to know too much about its size to pack it properly...

Bruce