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Re: Meta-C question about header order

From "BartC" <bc@freeuk.com>
Newsgroups comp.lang.c
References <bqtj0hF60hpU1@mid.individual.net>
Subject Re: Meta-C question about header order
Message-ID <fCs2v.73133$ps2.60242@fx16.am4> (permalink)
Organization virginmedia.com
Date 2014-04-13 10:15 +0100

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"Jens Schweikhardt" <usenet@schweikhardt.net> wrote in message
news:bqtj0hF60hpU1@mid.individual.net...

> consider a small project of 100 C source and 100 header files.
> The coding rules require that only C files include headers,
> headers are not allowed to include other headers

Whose rule is that? Because it seems to be broken by most standard headers.

(If I look at windows.h for example, it is a mess of conditional directives
and includes for 25 or 30 other files; I don't fancy having all that in my
own sources. Besides which, a different compiler will have a different
windows.h. You can't get away from the problem.)

 (not sure if
> this is 100% the "IWYU - Include What You Use" paradigma).
>
> The headers contain only what headers should contain:
> prototypes, typedefs, declarations, macro definitions.

The trouble, any of those could rely on 'something' which is in another
header. Yet the rest of the module does not directly use that 'something',
and shouldn't have to care about all those indirect includes (I'm not
allowed to use the word 'imports').

Should module A, needing to include library B, also have to include 29 other
include files that B uses?

And if A also needs library C, which uses some of those 29 files plus some
of its own, which order should these dozens of extra files appear in? 
Besides, a new update of B or C may have a different set of includes, but 
now you need to update all those extra includes in A.

It's best if these things are as self-contained as possible; A.c:

#include "B.h"
#include "C.h"

You don't even need to worry about whether B needs C, or C needs B, or even
if they have mutual dependencies.

> I'm not a computer scientist, but it sounds as if this requires a
> topological sort of all the '"foo.h" needs "bar.h"' relations. Now the
> interesting part is: how to automate this, i.e. how to determine "this
> header declares identifiers A, B, C and requires X, Y, Z"? I looked
> at IWYU by google, but it requires a clang source tree plus some more
> hoop jumping and that's way too elephantine, so I gave up not knowing
> whether it would provide a solution.
>
> Can you think of a lightweight way to solve this? Maybe using perl, the
> unix tool box, make, gmake, gcc, a C lexer?

I'm not sure it's even possible, because of the mutual or circular
dependencies I mentioned.

-- 
Bartc

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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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