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Re: Optimizing the code: way to reduce if, else if-s within the loop?

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BartC <bc@freeuk.com> writes:

> On 22/01/2017 10:54, Ben Bacarisse wrote:
>> Alla _ <modelling.data@gmail.com> writes:
>>
>>> On Saturday, January 21, 2017 at 9:28:19 PM UTC+3, Barry Schwarz wrote:
>>>> On Sat, 21 Jan 2017 08:52:25 -0800 (PST), Alla _
>>>> <modelling.data@gmail.com> wrote:
>>> <snip>
>>>> Method 2:  If your system supports the offsetof macro and if you
>>
>> A C implementation without offsetof is not conforming.  It's a part of
>> the language you can rely on being there.
>
> This seems a common way of implementing it:
>
> #define offsetof(s,m) (int)&(((s *)0)->m)

That would be wrong so I'm sorry to hear it's a common way.

> or:
>
> #define offsetof(t,i)   ((size_t)((char *)&((t *)0)->i - (char *)0))
>
> So I don't think anyone would be stuck for such a macro.

You should not be stuck for such a macro because it's part of standard
C!  It's just a distraction to suggest there might be some problem with
it.  It's been in C for more than 27 years.

> (gcc of course has to be a little different, with offsetof being a
> synonym for __builtin_offsetof.)

The implementations you show are not portable and gcc is not limited to
working on one architecture.

-- 
Ben.

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Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-21 08:52 -0800
  Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-21 09:35 -0800
  Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-21 10:28 -0800
    Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-21 23:49 -0800
    Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 00:29 -0800
      Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-22 10:54 +0000
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 03:28 -0800
          Re: Optimizing the code: way to reduce if, else if-s within the loop? Keith Thompson <kst-u@mib.org> - 2017-01-22 07:44 -0800
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 08:24 -0800
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-22 10:43 -0800
              Re: Optimizing the code: way to reduce if, else if-s within the loop? Keith Thompson <kst-u@mib.org> - 2017-01-22 12:22 -0800
        Re: Optimizing the code: way to reduce if, else if-s within the loop? BartC <bc@freeuk.com> - 2017-01-22 11:33 +0000
          Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-22 13:23 +0000
            Re: Optimizing the code: way to reduce if, else if-s within the loop? BartC <bc@freeuk.com> - 2017-01-22 13:28 +0000
              Re: Optimizing the code: way to reduce if, else if-s within the loop? Keith Thompson <kst-u@mib.org> - 2017-01-22 07:47 -0800
                Re: Optimizing the code: way to reduce if, else if-s within the loop? BartC <bc@freeuk.com> - 2017-01-22 16:00 +0000
                Re: Optimizing the code: way to reduce if, else if-s within the loop? David Brown <david.brown@hesbynett.no> - 2017-01-22 18:23 +0100
                Re: Optimizing the code: way to reduce if, else if-s within the loop? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-22 13:47 -0500
                Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-22 10:43 -0800
                Re: Optimizing the code: way to reduce if, else if-s within the loop? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-22 13:53 -0500
                Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-22 18:57 +0000
                Re: Optimizing the code: way to reduce if, else if-s within the loop? BartC <bc@freeuk.com> - 2017-01-22 19:18 +0000
                Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-22 21:54 +0000
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-23 02:41 -0800
          Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-23 11:20 +0000
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-23 03:53 -0800
              Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-23 12:12 +0000
    Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 03:24 -0800
      Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-22 13:16 +0000
      Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-22 07:47 -0800
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 08:16 -0800
          Re: Optimizing the code: way to reduce if, else if-s within the loop? "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-22 11:54 -0500
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 11:23 -0800
          Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-22 11:08 -0800
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 22:19 -0800
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 22:41 -0800
              Re: Optimizing the code: way to reduce if, else if-s within the loop? Robert Wessel <robertwessel2@yahoo.com> - 2017-01-23 02:17 -0600
              Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-23 02:16 -0800
                Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-23 03:59 -0800
              Re: Optimizing the code: way to reduce if, else if-s within the loop? Keith Thompson <kst-u@mib.org> - 2017-01-23 08:44 -0800
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 08:23 -0800
      Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-22 07:52 -0800
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-22 08:17 -0800
    Re: Optimizing the code: way to reduce if, else if-s within the loop? Richard Heathfield <rjh@cpax.org.uk> - 2017-01-23 17:11 +0000
      Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-23 10:35 -0800
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-23 10:38 -0800
        Re: Optimizing the code: way to reduce if, else if-s within the loop? BartC <bc@freeuk.com> - 2017-01-23 19:06 +0000
        Re: Optimizing the code: way to reduce if, else if-s within the loop? Barry Schwarz <schwarzb@dqel.com> - 2017-01-23 14:31 -0800
          Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-23 21:31 -0800
          Re: Optimizing the code: way to reduce if, else if-s within the loop? Alla _ <modelling.data@gmail.com> - 2017-01-24 01:56 -0800
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Manfred <noname@invalid.add> - 2017-01-24 14:38 +0100
            Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-24 13:57 +0000
  Re: Optimizing the code: way to reduce if, else if-s within the loop? BartC <bc@freeuk.com> - 2017-01-23 12:38 +0000
    Re: Optimizing the code: way to reduce if, else if-s within the loop? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-23 15:08 +0000
  Re: Optimizing the code: way to reduce if, else if-s within the loop? m.labanowicz@gmail.com - 2017-01-23 07:08 -0800

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