Re: Macro Expansion

From	BartC <bc@freeuk.com>
Newsgroups	comp.lang.c
Subject	Re: Macro Expansion
Date	2017-01-08 17:17 +0000
Organization	A noiseless patient Spider
Message-ID	<o4ts55$mgl$1@dont-email.me> (permalink)
References	<o4rcbl$4cp$1@dont-email.me> <878tqlykwg.fsf@news.bourguet.org> <o4tdl4$1k5$1@dont-email.me> <87r34dwqo9.fsf@news.bourguet.org>

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On 08/01/2017 14:51, Jean-Marc Bourguet wrote:
> BartC <bc@freeuk.com> writes:
>
>> But 'a(10)' can also be part of normal code, not inside a macro
>> definition. Then the 'b' that is generated is in a different 'token-space'
>> from the "(10)" in the rest of the file (and likely to still exist as
>> characters not tokens). Rescanning an entirely source file is hopelessly
>> inefficient just for the off-chance someone might be using such macros.
>
> You don't rescan the whole file. The rescan of the expansion is made once
> more than you though and in its context.
>
> You don't know the steps people are ready to avoid using an external tool
> while still using compact code. The technique is used in practice.  Look
> for chaos pp and the boost preprocessor library for such kind of techniques
> (the goal of those libraries is to encapsulate them in an more convenient
> interface).

I looked at chaos-pp. I didn't know the purpose of your comment and 
thought it was another pre-processor implementation to look at.

I just saw hundred and hundreds of files in dozens of folders: headers, 
xml, xsl and html. But I realised after a while that there were no .c 
files. Just 471 header files.

Presumably then (as the README was help, and the html, after I 
downloaded it all, had no obvious entry point), this is just an example 
of a massive library built solely with the C preprocessor.

And very daunting it looks. Even if I wasn't handicapped by having no 
idea what it's supposed to do, how does one even start testing their own 
pre-processor with something like this[1]? If it was normal C code 
(declarations, functions, all the familiar stuff), it would be very 
straightforward. But with this preprocessor language...

How did a no-nonsense language such as C end up with a dependency on a 
macro language so arcane that apparently few can fully understand it?

-------------------

([1] A testing method I'd envisioned was to write the preprocessed 
output as a flat text file, and do the same with something like gcc -E. 
Then compare the two visually, or compile them. Or feed my output 
through gcc -E and see if the result exactly matches the other.)

-- 
Bartc

Thread

Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 18:35 +0000
  Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-01-07 11:23 -0800
    Re: Macro Expansion Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-07 21:28 +0000
  Re: Macro Expansion Siri Cruise <chine.bleu@yahoo.com> - 2017-01-07 11:45 -0800
    Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 20:16 +0000
      Re: Macro Expansion Siri Cruise <chine.bleu@yahoo.com> - 2017-01-07 12:23 -0800
        Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 20:31 +0000
          Re: Macro Expansion Siri Cruise <chine.bleu@yahoo.com> - 2017-01-07 12:42 -0800
          Re: Macro Expansion Ian Collins <ian-news@hotmail.com> - 2017-01-08 14:42 +1300
            Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 13:18 +0000
  Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 20:15 +0000
    Re: Macro Expansion Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-07 20:42 +0000
      Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 22:50 +0000
        Re: Macro Expansion Ian Collins <ian-news@hotmail.com> - 2017-01-08 11:59 +1300
          Re: Macro Expansion Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-01-07 15:10 -0800
        Re: Macro Expansion supercat@casperkitty.com - 2017-01-07 17:24 -0800
          Re: Macro Expansion Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-15 21:55 -0800
            Re: Macro Expansion supercat@casperkitty.com - 2017-01-16 09:06 -0800
              Re: Macro Expansion Tim Rentsch <txr@alumni.caltech.edu> - 2017-01-31 08:51 -0800
                Re: Macro Expansion supercat@casperkitty.com - 2017-01-31 13:06 -0800
                Re: Macro Expansion Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-03 07:49 -0800
                Re: Macro Expansion supercat@casperkitty.com - 2017-02-03 12:03 -0800
                Re: Macro Expansion Tim Rentsch <txr@alumni.caltech.edu> - 2017-02-09 09:00 -0800
        Re: Macro Expansion Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-08 01:37 +0000
          Re: Macro Expansion Jean-Marc Bourguet <jm@bourguet.org> - 2017-01-08 10:22 +0100
  Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-01-07 12:18 -0800
    Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 20:28 +0000
      Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-01-07 12:36 -0800
        Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-07 22:59 +0000
  Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-01-08 00:20 -0800
    Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 13:30 +0000
      Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-10 14:00 +0000
        Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-01-10 07:43 -0800
          Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-10 17:47 +0000
            Re: Macro Expansion Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-01-10 22:49 +0000
              Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-10 23:28 +0000
              Re: Macro Expansion "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-10 18:51 -0500
                Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-11 00:06 +0000
          Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-10 20:30 +0000
            Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-04-26 10:04 -0700
              Re: Macro Expansion Keith Thompson <kst-u@mib.org> - 2017-04-26 12:00 -0700
                Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-04-26 12:24 -0700
              Re: Macro Expansion bartc <bc@freeuk.com> - 2017-04-26 20:12 +0100
                Re: Macro Expansion Thiago Adams <thiago.adams@gmail.com> - 2017-04-26 12:34 -0700
                Re: Macro Expansion jameskuyper@verizon.net - 2017-04-26 13:46 -0700
  Re: Macro Expansion Jean-Marc Bourguet <jm@bourguet.org> - 2017-01-08 10:13 +0100
    Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 13:10 +0000
      Re: Macro Expansion Jean-Marc Bourguet <jm@bourguet.org> - 2017-01-08 15:51 +0100
        Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 17:17 +0000
          Re: Macro Expansion supercat@casperkitty.com - 2017-01-08 11:04 -0800
            Re: Macro Expansion Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-01-08 11:10 -0800
              Re: Macro Expansion supercat@casperkitty.com - 2017-01-08 14:08 -0800
            Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 19:49 +0000
              Re: Macro Expansion supercat@casperkitty.com - 2017-01-08 14:17 -0800
          Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 19:19 +0000
          Re: Macro Expansion Jean-Marc Bourguet <jm@bourguet.org> - 2017-01-08 21:43 +0100
      Re: Macro Expansion supercat@casperkitty.com - 2017-01-08 10:43 -0800
      Re: Macro Expansion Keith Thompson <kst-u@mib.org> - 2017-01-08 12:39 -0800
  Re: Macro Expansion antispam@math.uni.wroc.pl - 2017-01-08 22:54 +0000
    Re: Macro Expansion "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-08 18:36 -0500
      Re: Macro Expansion antispam@math.uni.wroc.pl - 2017-01-09 01:15 +0000
        Re: Macro Expansion "James R. Kuyper" <jameskuyper@verizon.net> - 2017-01-08 20:49 -0500
    Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-08 23:53 +0000
      Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-09 01:11 +0000
      Re: Macro Expansion antispam@math.uni.wroc.pl - 2017-01-09 01:31 +0000
        Re: Macro Expansion BartC <bc@freeuk.com> - 2017-01-10 11:28 +0000

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