Re: Meta-C question about header order

From	Kaz Kylheku <kaz@kylheku.com>
Newsgroups	comp.lang.c
Subject	Re: Meta-C question about header order
Date	2014-04-14 16:25 +0000
Organization	Aioe.org NNTP Server
Message-ID	<20140414090455.107@kylheku.com> (permalink)
References	(1 earlier) <include-sort-20140412221141@ram.dialup.fu-berlin.de> <bqvap4Fhg97U1@mid.individual.net> <lie4jc$2r1$1@dont-email.me> <bqvl3kFhg97U8@mid.individual.net> <lifi4h$3fe$1@dont-email.me>

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On 2014-04-14, Martin Shobe <martin.shobe@yahoo.com> wrote:
>> Why in the heads? If you forget one, the compiler tells you
>> "foo_t undeclared" and you include the header with typedef foo_t
>> above it. Repeat if necessary. This Turing machine can be proven to halt. :-)
>
> Yes, and the developers need to remember where foo_t is declared. 
> They'll have to know this even when they don't care about foo_t because 
> it's only an implementation detail five levels deep on the dependency 
> graph. By requiring each header to include all the information it needs, 
> the developer doesn't even have to know foo_t exists, let alone where to 
> find it. (Or, even worse, which one to use.)

The theme we are seeing from the naysayers is developers shouldn't have to know
this, or shouldn't care about that, and in general should be able to focus on a
small part of the program through a narrow peep-hole in order to make an
intended change while learning as little as possible about the program.

That may be very well and fine in most of the industry, but in certain programs
that are developed to be polished gems of engineerng by people who take pride,
this idea of "know as little as possible" is poor ideological fit.

> As for removing include directives from header files, I do it whenever I 
> modify a header file in such a way that the include directive is no 
> longer needed. Furthermore, it's not a question of who might need that 
> header file up the food chain, it's only a question of is that header 
> needed to provide what this header is supposed to provide. If something 
> downstream no longer compiles, then I fix that there. It's also how most 
> of the people I've worked with do it.

"Something downstream" could be every single source file. Suppose "b.h" does
not actually need "a.h" itself, but everything implicitly depends on "a.h"
bringing in "b.h". For instance, everything has printf in it, and "b.h" is what
brings in <stdio.h>, though b.h doesn't actually use it. (Or just something
like size_t, which could have been obtained minimally from <stddef.h>).

These kinds of problems in the nested include system tend not to get fixed:
nobody wants to.

Thread

Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-12 19:37 +0000
  Re: Meta-C question about header order Keith Thompson <kst-u@mib.org> - 2014-04-12 13:51 -0700
    Re: Meta-C question about header order glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-13 00:11 +0000
    Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 11:40 +0000
      Re: Meta-C question about header order "BartC" <bc@freeuk.com> - 2014-04-13 13:10 +0100
      Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-13 06:29 -0700
      Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-13 14:41 +0000
    Re: Meta-C question about header order Ken Brody <kenbrody@spamcop.net> - 2014-04-15 10:36 -0400
  Re: Meta-C question about header order Richard Damon <Richard@Damon-Family.org> - 2014-04-12 16:58 -0400
    Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-13 03:40 +0000
      Re: Meta-C question about header order Ian Collins <ian-news@hotmail.com> - 2014-04-13 16:26 +1200
        Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-13 05:02 +0000
          Re: Meta-C question about header order Ian Collins <ian-news@hotmail.com> - 2014-04-13 17:21 +1200
            Re: Meta-C question about header order Ken Brody <kenbrody@spamcop.net> - 2014-04-15 10:59 -0400
            Re: Meta-C question about header order Ken Brody <kenbrody@spamcop.net> - 2014-04-15 11:02 -0400
          Re: Meta-C question about header order Ken Brody <kenbrody@spamcop.net> - 2014-04-15 10:59 -0400
            Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-15 08:26 -0700
            Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-15 15:56 +0000
      Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 11:34 +0000
      Re: Meta-C question about header order Richard Damon <Richard@Damon-Family.org> - 2014-04-13 15:04 -0400
      Re: Meta-C question about header order Ken Brody <kenbrody@spamcop.net> - 2014-04-15 10:52 -0400
  Re: Meta-C question about header order Ian Collins <ian-news@hotmail.com> - 2014-04-13 11:09 +1200
    Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 11:47 +0000
      Re: Meta-C question about header order Ian Collins <ian-news@hotmail.com> - 2014-04-14 08:54 +1200
        Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-13 21:37 +0000
          Re: Meta-C question about header order Ian Collins <ian-news@hotmail.com> - 2014-04-14 09:49 +1200
        Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-14 19:17 +0000
          Re: Meta-C question about header order Ian Collins <ian-news@hotmail.com> - 2014-04-15 10:24 +1200
            Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-16 19:58 +0000
          Re: Meta-C question about header order Richard Damon <Richard@Damon-Family.org> - 2014-04-14 21:45 -0400
  Re: Meta-C question about header order luser- -droog <luser.droog@gmail.com> - 2014-04-12 16:48 -0700
    Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 11:52 +0000
  Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-13 01:04 +0000
  Re: Meta-C question about header order "BartC" <bc@freeuk.com> - 2014-04-13 10:15 +0100
    Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-13 04:06 -0700
    Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 12:01 +0000
      Re: Meta-C question about header order "BartC" <bc@freeuk.com> - 2014-04-13 13:46 +0100
        Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 13:58 +0000
  Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 11:29 +0000
    Re: Meta-C question about header order Martin Shobe <martin.shobe@yahoo.com> - 2014-04-13 08:48 -0500
      Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-13 14:25 +0000
        Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-13 15:02 +0000
        Re: Meta-C question about header order Martin Shobe <martin.shobe@yahoo.com> - 2014-04-13 21:45 -0500
          Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-14 01:16 -0700
            Re: Meta-C question about header order "BartC" <bc@freeuk.com> - 2014-04-14 10:16 +0100
            Re: Meta-C question about header order Richard Damon <Richard@Damon-Family.org> - 2014-04-14 21:33 -0400
          Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-14 16:25 +0000
            Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-14 09:47 -0700
            Re: Meta-C question about header order Martin Shobe <martin.shobe@yahoo.com> - 2014-04-14 13:29 -0500
              Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-14 19:31 +0000
                Re: Meta-C question about header order Les Cargill <lcargill99@comcast.com> - 2014-04-14 20:03 -0500
                Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-15 01:04 +0000
              Re: Meta-C question about header order Keith Thompson <kst-u@mib.org> - 2014-04-14 15:15 -0700
            Re: Meta-C question about header order Richard Damon <Richard@Damon-Family.org> - 2014-04-14 22:01 -0400
            Re: Meta-C question about header order "BartC" <bc@freeuk.com> - 2014-04-15 09:51 +0100
              Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-15 06:01 -0700
                Re: Meta-C question about header order "BartC" <bc@freeuk.com> - 2014-04-15 14:29 +0100
                Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-15 10:38 -0700
                Re: Meta-C question about header order Kaz Kylheku <kaz@kylheku.com> - 2014-04-15 18:27 +0000
                Re: Meta-C question about header order Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-04-15 12:45 -0700
                Re: Meta-C question about header order ralph <nt_consulting@yahoo.com> - 2014-04-15 22:02 -0500
          Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-14 17:44 +0000
  Re: Meta-C question about header order Tim Rentsch <txr@alumni.caltech.edu> - 2014-04-19 01:25 -0700
    Re: Meta-C question about header order Richard Damon <Richard@Damon-Family.org> - 2014-04-19 10:30 -0400
      Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-23 19:47 +0000
        Re: Meta-C question about header order James Kuyper <jameskuyper@verizon.net> - 2014-04-23 15:53 -0400
      Re: Meta-C question about header order Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-10 09:25 -0700
    Re: Meta-C question about header order Jens Schweikhardt <usenet@schweikhardt.net> - 2014-04-23 19:27 +0000
      Re: Meta-C question about header order Tim Rentsch <txr@alumni.caltech.edu> - 2014-06-10 09:40 -0700

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