Re: Forward declarations ... the straw that broke the camel's back

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.c
Subject	Re: Forward declarations ... the straw that broke the camel's back
Date	2016-06-30 16:56 +0100
Organization	A noiseless patient Spider
Message-ID	<nl3ff1$dg6$1@dont-email.me> (permalink)
References	(3 earlier) <dtjk6hFrf0bU1@mid.individual.net> <nl2sgm$7ia$1@dont-email.me> <dtkdq8Fdt6U1@mid.individual.net> <nl36pt$cmm$1@dont-email.me> <849a6b03-ea90-4bed-b9f5-4b96ec3d4d18@googlegroups.com>

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On 30/06/2016 16:24, supercat@casperkitty.com wrote:
> On Thursday, June 30, 2016 at 8:28:38 AM UTC-5, Bart wrote:
>> How do you share declarations then across modules?
>
> One approach which can work well is to have the compilation process
> produce, either as two separate files or combined into one, a
> collection of information similar to what a .h file would contain,
> along with a bunch of object code.  The compiler can produce the first
> blob of information from a source file without needing to resolve any
> external dependencies, so the compiler can start by running every
> source file through the initial scan process.  Since that process
> doesn't rely upon any dependencies, the files can be processed in any
> order.

Are you talking about compiling a language like C as it is now?

In that case that runs into difficulties because A may depend on imports 
from B, and B depends on imports from A. (Imagine one large module split 
into two mutually dependent ones.)

You might not compile, or even partially compile A, because it depends 
on stuff from B. And vice versa.

That's solved now by creating a common header H where such problematic 
declarations are written manually, before either A or B is compiled. 
That works well, but you have to deal with the forward and duplication 
declarations that have been complained about.

(Outside of C, I've tried several schemes where duplicated declarations 
are largely eliminated, and most declarations within a file or functions 
can be out of order.

However, that requires a strict hierarchical module structure, and can 
need a full re-compile in strict order. But from time to time it is 
necessary to access names across the hierarchy, and then it is necessary 
to resort to manually written declarations, breaking the one-definition 
rule. But that's a tiny fraction of all declarations.

Another scheme I've played with does a non-compiling 'pre-pass' of 
source files as needed, generating an exports file (like the information 
file in your proposal). That introduces some restrictions in what can be 
shared across modules, but it will cope with circular imports.

(With the extra convenience that with modules M1 to M10, each can simply 
import all the other modules; even itself so that the set of imports is 
the same in each file.)

What I'm looking at now is to simply recompile everything in a project, 
but again with a strict module hierarchy. But that requires a very fast 
compiler (so that a typical project can be re-built from scratch in a 
fraction of a second).

The trouble is none of these schemes is as simple as the way that C 
compilers work now, primitive thought it might be.)

-- 
Bartc

Thread

Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-29 10:36 -0700
  Re: Forward declarations ... the straw that broke the camel's back supercat@casperkitty.com - 2016-06-29 16:04 -0700
    Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-29 16:30 -0700
      Re: Forward declarations ... the straw that broke the camel's back Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-29 19:52 -0700
        Re: Forward declarations ... the straw that broke the camel's back Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-30 13:00 +0100
          Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 05:42 -0700
            Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 18:11 +0100
              Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 10:30 -0700
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 19:54 +0100
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 12:31 -0700
                Re: Forward declarations ... the straw that broke the camel's back Ian Collins <ian-news@hotmail.com> - 2016-07-01 07:59 +1200
                Re: Forward declarations ... the straw that broke the camel's back Gareth Owen <gwowen@gmail.com> - 2016-06-30 21:31 +0100
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 14:19 -0700
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 14:31 -0700
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 21:18 +0100
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 14:26 -0700
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 22:44 +0100
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 17:23 -0700
                Re: Forward declarations ... the straw that broke the camel's back David Brown <david.brown@hesbynett.no> - 2016-07-05 21:38 +0200
                Re: Forward declarations ... the straw that broke the camel's back Richard Heathfield <rjh@cpax.org.uk> - 2016-07-05 21:05 +0100
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-05 13:32 -0700
                Re: Forward declarations ... the straw that broke the camel's back David Brown <david.brown@hesbynett.no> - 2016-07-05 23:20 +0200
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-05 14:25 -0700
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-05 16:14 -0700
                Re: Forward declarations ... the straw that broke the camel's back David Brown <david.brown@hesbynett.no> - 2016-07-06 11:18 +0200
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-06 03:36 -0700
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-05 16:23 -0700
                Re: Forward declarations ... the straw that broke the camel's back David Brown <david.brown@hesbynett.no> - 2016-07-06 11:29 +0200
                Re: Forward declarations ... the straw that broke the camel's back Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-07-06 02:49 -0700
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-06 05:18 -0700
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-07-06 13:57 +0100
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-06 06:24 -0700
                Re: Forward declarations ... the straw that broke the camel's back David Brown <david.brown@hesbynett.no> - 2016-07-06 15:22 +0200
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-06 07:12 -0700
                Re: Forward declarations ... the straw that broke the camel's back Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-07-06 08:08 -0700
                Re: Forward declarations ... the straw that broke the camel's back supercat@casperkitty.com - 2016-07-06 09:00 -0700
                Re: Forward declarations ... the straw that broke the camel's back Ian Collins <ian-news@hotmail.com> - 2016-07-07 08:01 +1200
                Re: Forward declarations ... the straw that broke the camel's back supercat@casperkitty.com - 2016-07-06 13:30 -0700
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-07-06 17:30 +0100
    Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 00:39 +0100
      Re: Forward declarations ... the straw that broke the camel's back jacobnavia <jacob@jacob.remcomp.fr> - 2016-06-30 22:08 +0200
  Re: Forward declarations ... the straw that broke the camel's back gordonb.h5sc5@burditt.org (Gordon Burditt) - 2016-06-29 20:52 -0500
    Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-29 19:00 -0700
      Re: Forward declarations ... the straw that broke the camel's back Ian Collins <ian-news@hotmail.com> - 2016-06-30 16:06 +1200
        Re: Forward declarations ... the straw that broke the camel's back Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-30 02:48 -0700
          Re: Forward declarations ... the straw that broke the camel's back Ian Collins <ian-news@hotmail.com> - 2016-06-30 23:25 +1200
            Re: Forward declarations ... the straw that broke the camel's back Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-06-30 04:39 -0700
              Re: Forward declarations ... the straw that broke the camel's back jacobnavia <jacob@jacob.remcomp.fr> - 2016-06-30 21:50 +0200
            Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-06-30 06:49 -0700
              Re: Forward declarations ... the straw that broke the camel's back jacobnavia <jacob@jacob.remcomp.fr> - 2016-06-30 22:23 +0200
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-04 10:43 -0700
                Vaporware (Was: Forward declarations ... the straw that broke ...) gazelle@shell.xmission.com (Kenny McCormack) - 2016-07-04 17:59 +0000
                Re: Forward declarations ... the straw that broke the camel's back Randy Howard <rhoward.mx@EverybodyUsesIt.com> - 2016-07-06 12:38 -0500
                Re: Forward declarations ... the straw that broke the camel's back "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2016-07-06 11:38 -0700
          Re: Forward declarations ... the straw that broke the camel's back Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-06-30 19:51 +0100
            Re: Forward declarations ... the straw that broke the camel's back jacobnavia <jacob@jacob.remcomp.fr> - 2016-06-30 21:59 +0200
              Re: Forward declarations ... the straw that broke the camel's back Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-07-01 01:05 -0700
        Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 11:32 +0100
          Re: Forward declarations ... the straw that broke the camel's back Ian Collins <ian-news@hotmail.com> - 2016-06-30 23:23 +1200
            Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 14:28 +0100
              Re: Forward declarations ... the straw that broke the camel's back supercat@casperkitty.com - 2016-06-30 08:24 -0700
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 16:56 +0100
              Re: Forward declarations ... the straw that broke the camel's back jacobnavia <jacob@jacob.remcomp.fr> - 2016-06-30 22:17 +0200
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-06-30 22:22 +0100
                Re: Forward declarations ... the straw that broke the camel's back jacobnavia <jacob@jacob.remcomp.fr> - 2016-07-01 08:25 +0200
                Re: Forward declarations ... the straw that broke the camel's back BartC <bc@freeuk.com> - 2016-07-01 12:09 +0100

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