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Re: curiosity about compiler phases

Subject Re: curiosity about compiler phases
Newsgroups comp.lang.c
References <9585199f-546a-46f8-ac2a-de27cc08a3f5@googlegroups.com> <FcZBF.211$rX6.122@fx22.am4> <PXZBF.74624$hh5.43882@fx07.iad>
From Bart <bc@freeuk.com>
Message-ID <dK_BF.12$LP4.8@fx40.am4> (permalink)
Organization virginmedia.com
Date 2019-11-23 00:06 +0000

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On 22/11/2019 23:12, Scott Lurndal wrote:
> Bart <bc@freeuk.com> writes:
>> On 07/11/2019 13:28, Thiago Adams wrote:
>>> I am doing some review in my lexer and I found the following
>>> curiosity when I was experimenting compiler explorer online.
>>>
>>> When I print the preprocessor output -E of this code:
>>>
>>> in\
>>> t i =09;
>>>
>>> using x86-64 gcc 4.4.7, it prints:
>>> int i =09;
>>>
>>> using x86-64 gcc 4.6.4, it prints:
>>> int
>>>     i =09;
>>
>> Every so often you come across crazy things that C allows in its
>> preprocessor; this is one of them. Not just being able to split up lines
>> between tokens, but even in the middle of tokens!
> 
> Not all crazy.  Simply unix standard line continuation.
> 

That figures. C and Unix share a few crazy things.

Where a language has line continuation to split source across multiple 
lines, then it is highly unusual to allow that split in the middle of a 
token.

What is the purpose other than it was just a side effect of the way the 
first C preprocessor happened to be thrown together? I've never come 
across any programs that rely on it.

The 3 syntax highlighting editors I've just tried don't support it either.

It would also be a very poor program that relies on code such as the 
following:

prin\
t

prin\
t

     prin\
t

(One of these has an extra space between 'n' and 't'.)

Line continuation is hardly needed in C anyway, because lines naturally 
continue (only needed inside macro defs). So it is really token 
continuation for keywords, identifiers and numeric constants too long to 
comfortable fit on one line.

In other words, it's a 'feature' that deserves to be taken out and shot.

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Thread

curiosity about compiler phases Thiago Adams <thiago.adams@gmail.com> - 2019-11-07 05:28 -0800
  Re: curiosity about compiler phases Nick Bowler <nbowler@draconx.ca> - 2019-11-22 19:25 +0000
  Re: curiosity about compiler phases "A. K." <minforth@arcor.de> - 2019-11-22 12:19 -0800
  Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-22 22:22 +0000
    Typo? (Was: curiosity about compiler phases) gazelle@shell.xmission.com (Kenny McCormack) - 2019-11-22 22:34 +0000
      Re: Typo? (Was: curiosity about compiler phases) Bart <bc@freeuk.com> - 2019-11-22 23:49 +0000
        Re: Typo? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-11-22 19:26 -0700
    Re: curiosity about compiler phases scott@slp53.sl.home (Scott Lurndal) - 2019-11-22 23:12 +0000
      Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-23 00:06 +0000
        Re: curiosity about compiler phases Richard Damon <Richard@Damon-Family.org> - 2019-11-22 20:34 -0500
        Re: curiosity about compiler phases Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-23 01:47 +0000
          Re: curiosity about compiler phases Richard Damon <Richard@Damon-Family.org> - 2019-11-22 21:21 -0500
            Re: curiosity about compiler phases Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-24 03:26 +0000
              Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-24 11:29 +0000
                Re: curiosity about compiler phases Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-24 16:49 +0000
          Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-23 12:21 +0000
            Re: curiosity about compiler phases Richard Damon <Richard@Damon-Family.org> - 2019-11-23 10:08 -0500
            Re: curiosity about compiler phases scott@slp53.sl.home (Scott Lurndal) - 2019-11-23 15:49 +0000
              Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-23 16:21 +0000
                Re: curiosity about compiler phases Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-11-24 03:37 +0000
                Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-24 11:25 +0000
                Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-25 14:06 +0000
    Re: curiosity about compiler phases Keith Thompson <kst-u@mib.org> - 2019-11-22 21:25 -0800
      Beyond our pay grade (Was: curiosity about compiler phases) gazelle@shell.xmission.com (Kenny McCormack) - 2019-11-23 07:43 +0000
    Re: curiosity about compiler phases Thiago Adams <thiago.adams@gmail.com> - 2019-11-23 06:28 -0800
      Re: curiosity about compiler phases Thiago Adams <thiago.adams@gmail.com> - 2019-11-23 06:39 -0800
      Re: curiosity about compiler phases Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2019-11-23 09:46 -0500
        Re: curiosity about compiler phases Richard Damon <Richard@Damon-Family.org> - 2019-11-23 10:16 -0500
      Re: curiosity about compiler phases Bart <bc@freeuk.com> - 2019-11-23 16:13 +0000
        Re: curiosity about compiler phases Thiago Adams <thiago.adams@gmail.com> - 2019-11-25 03:24 -0800
  Re: curiosity about compiler phases Bonita Montero <Bonita.Montero@gmail.com> - 2019-11-23 08:43 +0100

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