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Re: container_of macro...

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On 2021-03-10, William Ahern <william@25thandClement.com> wrote:
> Chris M. Thomasson <chris.m.thomasson.1@gmail.com> wrote:
>> Its been a while since I used the container_of macro, however, it can 
>> come in handy wrt creating linked data-structures. Here is an example I 
>> coded up, just to see if I could do it from scratch, after all these years:
>
> The biggest problem with container_of is that it's not typesafe. I never
> understood why the GNU and Linux ecosystem adopted that approach instead of
> the classic BSD macros:
>
>   https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/src/sys/sys/queue.h

There is virtually no difference; that approach is exactly the
container_of approach.

Like container_of, there are macros which are given the name of a
structure member and calcluate offsets.

For instance:

     SLIST_FOREACH(TYPE *var, SLIST_HEAD *head, SLIST_ENTRY NAME);

looks to me exactly like doing:

     for_each_node(N, HEAD)  {
        TYPE *var = container_of(TYPE, N, NAME);

     }

we walk over a list, and then map each node back to a containing
object by assuming it is embedded as a member called NAME.


-- 
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal

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container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-08 17:24 -0800
  Re: container_of macro... Öö Tiib <ootiib@hot.ee> - 2021-03-09 02:06 -0800
    Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:02 -0800
  Re: container_of macro... Kaz Kylheku <563-365-8930@kylheku.com> - 2021-03-09 15:59 +0000
    Re: container_of macro... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-03-09 17:35 +0000
      Re: container_of macro... Kaz Kylheku <563-365-8930@kylheku.com> - 2021-03-09 17:51 +0000
        Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:13 -0800
    Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:05 -0800
  Re: container_of macro... William Ahern <william@25thandClement.com> - 2021-03-09 18:56 -0800
    Re: container_of macro... Kaz Kylheku <563-365-8930@kylheku.com> - 2021-03-10 03:47 +0000
      Re: container_of macro... William Ahern <william@25thandClement.com> - 2021-03-12 17:01 -0800
        Re: container_of macro... Jim <jim.cromie@gmail.com> - 2021-03-16 22:14 -0700
    Re: container_of macro... "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-03-10 17:07 -0800

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