Date: Sun, 15 Jan 2017 12:43:07 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Ian Lepore <ian@freebsd.org> Cc: "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r312236 - head/sys/net80211 Message-ID: <CAJ-VmomFOgi=subpa0A=adBUJfGJLKfnBWuSYcx6b3x%2BKTtXNA@mail.gmail.com> In-Reply-To: <1484510213.86335.110.camel@freebsd.org> References: <201701151949.v0FJnl2h027169@repo.freebsd.org> <1484510213.86335.110.camel@freebsd.org>
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On 15 January 2017 at 11:56, Ian Lepore <ian@freebsd.org> wrote:
>
> What is the point of the !! in these macros? The expressions already
> have boolean type (even in C++ where it matters) due to the ==.
> Removing the !! would also make one level of parens redundant.
It's just a habit i picked up from linux-land. That way it really is
only 1 or 0, so things like debugging output and such make easier
sense.
It's also fixed a handful of bugs in the past (but I can't think of
exact cases right now) - primarily where other code expected 1 or 0
(for things like shifts into protocol fields) and the macro returns 0
or ${LARGEVAL}.
-adrian
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