Re: Alternative C compilers on x86_64 Linux?

From	George Neuner <gneuner2@comcast.net>
Newsgroups	comp.compilers
Subject	Re: Alternative C compilers on x86_64 Linux?
Date	2016-09-29 22:57 -0400
Organization	A noiseless patient Spider
Message-ID	<16-09-043@comp.compilers> (permalink)
References	(1 earlier) <16-09-033@comp.compilers> <16-09-034@comp.compilers> <16-09-035@comp.compilers> <16-09-037@comp.compilers> <16-09-042@comp.compilers>

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On Thu, 29 Sep 2016 14:03:55 +0100, BartC <bc@freeuk.com> wrote:

>Most C compilers seem to support multiple C source files as input. This
>is similar to my scheme of compiling multiple sources one after the
>other. So if the input to a compiler looks like this:
>
>    gcc -c A.c B.c C.c
>
>where each of A, B and C include the same header file H.h, then once H.h
>has been processed for A.c, the results of that (symbol tables and so
>on) could be re-used for B and C without needing to process either H.h
>or H.pch again.

But it isn't done that way: the compilation of each .c file is treated
independently.  A common header file will be (re)processed for each
code file that includes it.

Also recall that the standard headers form a nesting hierarchy: some
of the more common headers indirectly pull in many others.  Nesting
also is common in wizard generated code, and in C++ template
libraries, etc.

A pre-compiled header contains already digested data that can be
plugged (more or less) directly into the compiler's internal data
structures.  Loading a .pch file very often is much faster than
(re)compiling its constituent source files, and the time savings grow
with the number of files involved.

It works best when you have many code files all of which include a
common *set* of headers.  You extract the common includes from the
code files into a single common header file.  In each code file you
then include that one common header.  Then precompile it.

For a project with just a handful of files it really doesn't matter
... but with complex projects with hundreds of source files I've
gotten ~80% reductions in build time by using precompiled headers.  I
have seen 45 minute clean builds turn into <10 minutes.

George

Thread

Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-02 03:01 +0000
  Re: Alternative C compilers on x86_64 Linux? jacobnavia <jacob@jacob.remcomp.fr> - 2016-09-05 00:20 +0200
    Re: Alternative C compilers on x86_64 Linux? alexfrunews@gmail.com - 2016-09-05 17:26 -0700
      Re: diagnosing C errors, was Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-09 12:31 +0100
        Re: diagnosing C errors, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-09 16:06 +0000
        Re: diagnosing C errors, was Alternative C compilers on x86_64 Linux? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2016-09-10 00:38 +0200
  Re: Alternative C compilers on x86_64 Linux? Nemo <nemo@invalid.invalid> - 2016-09-04 18:32 -0400
  Re: Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-04 23:48 +0000
  Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-05 13:19 +0100
    Re: Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-06 02:15 +0000
      Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-06 21:35 +0100
        Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-08 11:58 -0400
          Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-08 22:54 +0000
            Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-09 00:51 -0400
              Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-09 06:05 +0000
                Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-09 14:02 -0400
                Re: dead code or otherwise, was Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-09 19:57 +0000
      Re: duplicate cases, was Alternative C compilers on x86_64 Linux? Andy Walker <anw@cuboid.co.uk> - 2016-09-07 17:01 +0100
  Re: Alternative C compilers on x86_64 Linux? Florian Weimer <fw@deneb.enyo.de> - 2016-09-05 20:06 +0200
  Re: Alternative C compilers on x86_64 Linux? alexfrunews@gmail.com - 2016-09-05 17:22 -0700
    Re: Alternative C compilers on x86_64 Linux? Kaz Kylheku <221-501-9011@kylheku.com> - 2016-09-06 02:18 +0000
  Re: Alternative C compilers on x86_64 Linux? rockbrentwood@gmail.com - 2016-09-07 17:00 -0700
  Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-12 18:42 +0000
    Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-12 22:37 +0100
      Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-13 17:35 +0000
        Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-14 18:14 +0000
  Re: Alternative C compilers on x86_64 Linux? rugxulo@gmail.com - 2016-09-26 15:29 -0700
    Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-27 05:40 +0000
      Re: Alternative C compilers on x86_64 Linux? rugxulo@gmail.com - 2016-09-27 16:36 -0700
        Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-28 18:16 +0100
          Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-29 14:03 +0100
            Re: Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-29 22:57 -0400
            Re: Alternative C compilers on x86_64 Linux? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2016-09-30 05:03 +0200
              Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-30 12:00 +0100
                Re: Alternative C compilers on x86_64 Linux? Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2016-09-30 20:15 +0200
                Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-10-01 22:17 +0100
            Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-09-30 12:28 +0100
              Re: Alternative C compilers on x86_64 Linux? BartC <bc@freeuk.com> - 2016-10-17 22:49 +0100
        Re: Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-28 21:24 -0400
      Re: Alternative C compilers on x86_64 Linux? George Neuner <gneuner2@comcast.net> - 2016-09-28 01:01 -0400
        Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-29 02:55 +0000
      Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com - 2016-09-29 05:30 -0600
        Re: Alternative C compilers on x86_64 Linux? arnold@skeeve.com (Aharon Robbins) - 2016-09-30 10:13 +0000

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