Re: C Translator

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.c
Subject	Re: C Translator
Date	2019-04-01 02:35 +0100
Organization	A noiseless patient Spider
Message-ID	<87v9zy7bio.fsf@bsb.me.uk> (permalink)
References	(16 earlier) <dW4oE.682614$ao.267556@fx32.am4> <q7r3rg$ua7$1@dont-email.me> <lZ8oE.867468$iV1.117974@fx25.am4> <871s2m9140.fsf@bsb.me.uk> <jfboE.1537594$Xct1.1147500@fx12.am4>

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Bart <bc@freeuk.com> writes:

> On 31/03/2019 22:37, Ben Bacarisse wrote:
>> Bart <bc@freeuk.com> writes:
>
>>> programs of my examples,
>
> I meant a complete source file such as is submitted to a C compiler.

Oh well, I took a shot and guessing what you meant by programs.

>>    static int fred(void); int main(void) {}
>
>> should compile and none requires a diagnostic.
>
> So, a source file can have any number of forward, static function
> declarations (and each can be repeated any number of times). But none
> needs to be actually defined, provided it is not referenced?

It's not a forward declaration if the thing is not referenced.  At least
that what I take forward to mean.

> Ok...

Yes.  C could have added a rule to forbid that but it seems simpler not
to bother.

>>    int fred(void); int main(void) { return fred(); }
>>
>> Undefined.  A function is used but there is no definition of it.  fred
>> has external linkage (I don't know if that is local, exported or
>> imported -- you could tell me).
>
> Really?
>
> Let me give you a hint: if I was running a business and buying goods
> from overseas, I would be importing. If I was producing goods to sell
> overseas, then I'd be exporting.
>
> The same with functions in a source file; either they're defined here
> and marked static (local), or defined here without static (exported),
> or declared here but defined elsewhere (imported).

Or they are declared here and defined nowhere (with or without static),
or defined hare /and/ elsewhere with static, or declared here and also
defined here.  That last one is very common.  I think it's simpler just
to learn what C's declarations do.

> Or it might be that I'm just being wound up because I can't believe a
> programmer cannot be aware of what 'importing' and 'exporting' a
> function might mean inside a source file.

The problem is not that I don't know what the terms usually mean, it's
that I don't find the analogy helpful.  What's more, if someone knows
some other module system they maybe confused by it.  There are just too
many things that don't carry across.

> Or, it could really be (as nothing about this language surprises me
> any more), that for C, 'external linkage' is all that is
> needed. Shared functions are just considered to be floating around
> unattached to any particular source file.

Of course.  You know that.  An import is often "from" somewhere, but an
extern declaration can be linked with a definition from anywhere (or
nowhere if the function is not used yet).

> Which means a translation from one C source file at a time into
> another language is impossible, if the target language demands that a
> shared variable must be classed as either imported or exported.

Even simple import and export mechanisms are higher-level constructs
than C's linkage, and translating "up" is almost always impossible.
Certainly it's harder than translating down.

> It seems C leaves that open, even if technically it doesn't. Since one
> of my tests had one file initialising 'abc' to 0 via 6.9.2p2, and
> another initialising it explicitly, yet all C compilers (except mine)
> compiled without comment:

I'm guessing you don't want this explained again.

-- 
Ben.

Thread

C Translator Bart <bc@freeuk.com> - 2019-03-28 16:16 +0000
  Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 00:01 +0000
    Re: C Translator Robert Wessel <robertwessel2@yahoo.com> - 2019-03-28 20:31 -0500
    Re: C Translator Keith Thompson <kst-u@mib.org> - 2019-03-28 19:02 -0700
      Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 02:34 +0000
        Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-03-29 10:58 +0100
          Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 12:47 +0000
            Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-03-29 14:57 +0100
              Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 14:57 +0000
                Re: C Translator fir <profesor.fir@gmail.com> - 2019-03-29 15:08 -0700
                Re: C Translator fir <profesor.fir@gmail.com> - 2019-03-29 15:42 -0700
              Re: C Translator scott@slp53.sl.home (Scott Lurndal) - 2019-03-29 15:16 +0000
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 15:30 +0000
                Re: C Translator fir <profesor.fir@gmail.com> - 2019-03-29 14:47 -0700
        Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-29 10:42 +0000
          Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 11:57 +0000
            Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 13:04 +0000
            Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-03-29 14:58 +0100
              Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 14:29 +0000
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-29 20:06 +0000
            Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-29 20:02 +0000
              Re: C Translator Bart <bc@freeuk.com> - 2019-03-29 21:10 +0000
                Re: C Translator nobody@example.org (Scott) - 2019-03-30 04:52 +0000
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-30 11:03 +0000
                Re: C Translator nobody@example.org (Scott) - 2019-03-30 16:17 +0000
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-30 18:36 +0000
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-30 20:32 +0000
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-30 22:44 +0000
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-31 03:23 +0100
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-31 12:39 +0100
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-31 15:07 +0100
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-31 16:21 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-03-31 21:19 +0200
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-31 20:58 +0100
                Re: C Translator Ike Naar <ike@iceland.freeshell.org> - 2019-03-31 20:33 +0000
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-31 22:06 +0100
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-31 22:37 +0100
                Re: C Translator Bart <bc@freeuk.com> - 2019-03-31 23:33 +0100
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-01 02:35 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-01 11:33 +0200
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-03-31 23:54 +0200
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-01 02:16 +0100
                Re: C Translator Ike Naar <ike@iceland.freeshell.org> - 2019-04-01 06:42 +0000
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-01 11:35 +0200
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-01 16:54 +0100
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-01 21:01 +0100
                Re: C Translator Keith Thompson <kst-u@mib.org> - 2019-04-01 13:41 -0700
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-01 22:40 +0100
                Re: C Translator Keith Thompson <kst-u@mib.org> - 2019-04-01 16:25 -0700
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-02 00:50 +0100
                Re: C Translator Keith Thompson <kst-u@mib.org> - 2019-04-01 17:45 -0700
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-02 11:28 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-02 13:18 +0200
                Re: C Translator Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-04-02 19:15 +0000
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-02 21:14 +0100
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-02 13:28 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-02 10:49 +0200
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-02 01:58 +0100
                Re: C Translator Keith Thompson <kst-u@mib.org> - 2019-04-01 19:13 -0700
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-02 11:13 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-02 13:49 +0200
                Re: C Translator Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2019-04-02 05:15 -0700
                Re: C Translator Bart <bc@freeuk.com> - 2019-04-02 14:50 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-02 16:06 +0200
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-02 16:05 +0200
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-02 00:11 +0100
                Re: C Translator David Brown <david.brown@hesbynett.no> - 2019-04-02 10:35 +0200
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-02 00:06 +0100
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-31 21:36 +0100
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-31 16:32 +0100
              Re: C Translator Bart <bc@freeuk.com> - 2019-03-30 00:37 +0000
                Re: C Translator Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-03-30 01:00 +0000
                Re: C Translator fir <profesor.fir@gmail.com> - 2019-03-30 03:37 -0700
                Re: C Translator fir <profesor.fir@gmail.com> - 2019-03-30 06:15 -0700
        Re: C Translator James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-03-29 07:49 -0700

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