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 14:28 +0100
Organization	A noiseless patient Spider
Message-ID	<nl36pt$cmm$1@dont-email.me> (permalink)
References	(1 earlier) <XPSdnejVuPfp5unKnZ2dnUU7-KnNnZ2d@posted.internetamerica> <cf02fb20-4290-4b65-968e-f1a2e3f3c7b4@googlegroups.com> <dtjk6hFrf0bU1@mid.individual.net> <nl2sgm$7ia$1@dont-email.me> <dtkdq8Fdt6U1@mid.individual.net>

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On 30/06/2016 12:23, Ian Collins wrote:
> On 06/30/16 10:32 PM, BartC wrote:
>> On 30/06/2016 05:06, Ian Collins wrote:

>>> Wouldn't your scheme require the compiler to check every source file to
>>> see if a function signature has changed and retain a cache of all the
>>> callers of all function in order to detect errors?
>>
>> How does it work now?
>>
>> You have, for example, 50 .c files and one .h file containing all shared
>> function declarations that is included by all the .c files.
>>
>> If an exported function changes in any .c file, the .h file must be
>> manually updated, and that will trigger a recompile of all 50 .c files.
>
> So you don't put everything in one header.

How do you share declarations then across modules?

If there is a global function F used by all 50 modules M1 to M50, you 
either declare F in a single header H included in all M modules, or you 
have to duplicate the declaration for F in M1 to M50, possibly by 
creating headers H1 to H50.

The latter will solve your problems with parallel compilation (at a 
massive maintenance cost and a quadratic explosion in the number of 
header files), but if F changes, I don't see how you can avoid 
recompiling everything.

Now if you have some sort of supervisory system in place which keeps 
track of the definition of F and where it is referenced in all modules, 
then it can take care of all such details, including even generating the 
headers needed, and can invoke the minimal amount of re-compilations.

(Anyway, my current experiments with fast compilation suggests that a 
build system could simply do a pre-scan of all relevant modules to 
extract these dependencies, and it could do so /very/ much more quickly 
than a full compile. There are many possibilities.

Although if applied to current C, it would be dragged down by the 
complications introduced by its macro system, by conditional 
compilation, and the fact that subsequent compilation of the same header 
- with no source changes - might give a different result. (To say 
nothing about many C projects also depending heavily on external tools 
where the source might not even exist until just before compilation.)

In the absence of radically changing the language, strict guidelines and 
assumptions would need to be used when writing C projects, if such new 
approaches are to be useful.)

-- 
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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