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Date: Wed, 11 Dec 2019 09:26:17 +0000
From: Alexey Dokuchaev <danfe@freebsd.org>
To: Hans Petter Selasky <hps@selasky.org>
Cc: John Baldwin <jhb@freebsd.org>, src-committers@freebsd.org,
 svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject: Re: svn commit: r355600 - in head: share/man/man9 sys/kern sys/sys
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References: <201912102158.xBALwUF9075354@repo.freebsd.org>
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On Tue, Dec 10, 2019 at 11:09:41PM +0100, Hans Petter Selasky wrote:
> On 2019-12-10 22:58, John Baldwin wrote:
> >   While here, add <sys/callout.h> to the manpage.
> 
> FYI:
> 
> Linux guys eliminated the "void *c_arg" in their timer implementation by
> using container_of() to get callback argument. We could possibly do the
> same!

#define container_of(ptr, type, member) ({                              \
        void *__mptr = (void *)(ptr);                                   \
        BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) &&   \
                         !__same_type(*(ptr), void),                    \
                         "pointer type mismatch in container_of()");    \
        ((type *)(__mptr - offsetof(type, member))); })

That's one of those things that make Linux so unpleasant to work with.
Frankly, I don't think we want that for FreeBSD.

./danfe