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Re: gcc and 'include'

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From Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups comp.lang.c
Subject Re: gcc and 'include'
Date Mon, 30 Mar 2026 07:20:29 -0700
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Michael S <already5chosen@yahoo.com> writes:

> On Fri, 27 Mar 2026 22:05:24 +0000
> Bart <bc@freeuk.com> wrote:
>
>> But, yeah, some C aspect being unintuitive is nothing new:
>>
>>    extern int abc;
>>    int abc = 123;
>>
>> Or:
>>
>>    static int abc;
>>    extern int abc;
>>
>> Both are valid C, but this isn't:
>>
>>    extern int abc;
>>    static int abc;
>>
>>
>> I dare not ask what the rules are;  I'm sure they exist, but they
>> still don't make sense.  I can only find out which of these are
>> valid or not by trial and error.  A HLL shouldn't be like that.
>
> Why do you care?
> As C programmer, all you have to know is to never use either 2nd or
> 3rd, because even if one of them can be legal according to Standard,
> both of them certainly make no sense.

There are situations where an 'extern' declaration might reasonably
be preceded by a 'static' declaration (or definition).  These days I
expect such situations don't arise very often, so people don't think
about it, but the rule is there for a reason.

> For your first example, it sometimes make sense, typically as result
> of #inclyde and/or marcro substitution.  What exactly do you find
> unintuitive about it?

For global symbols, in 99+ percent of all cases, there should be
an 'extern' declaration in a .h file, and a definition without
the 'extern' in exactly one .c file.  Informally, 'extern' means
"is defined somewhere but I'm not saying where", and leaving off
the 'extern' means "I'm defining it here".  Speaking for myself I
don't find anything hard to understand or unintuitive about that.

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Thread

gcc and 'include' Bart <bc@freeuk.com> - 2026-03-26 22:36 +0000
  Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-26 16:12 -0700
    Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-27 10:55 +0000
      Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-27 13:49 +0100
      Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-27 10:51 -0700
      Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-27 21:27 +0000
        Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-27 22:05 +0000
          Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-27 17:03 -0700
          Re: gcc and 'include' Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-03-28 05:10 +0100
          Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-28 20:37 +0300
            Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-28 18:33 +0000
              Re: gcc and 'include' antispam@fricas.org (Waldek Hebisch) - 2026-03-29 00:53 +0000
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-29 22:37 +0100
                Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 05:33 -0700
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 14:42 +0100
                Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-30 16:53 +0300
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 18:11 +0100
                Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 08:27 -0700
                Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-30 11:54 -0700
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 21:54 +0100
                Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-30 18:07 -0700
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-31 11:39 +0100
                Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-03-31 13:56 -0700
                Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-06 20:56 -0700
                Re: gcc and 'include' Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-04-06 23:12 -0700
                Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-30 21:06 -0400
              Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-29 11:24 +0200
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-29 12:44 +0100
                Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-31 15:57 +0200
            Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 07:20 -0700
          Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 05:07 -0700
  Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-27 00:25 +0000
    Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-30 07:13 +0000
      Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-30 07:54 -0700
        Re: gcc and 'include' Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-03-31 01:46 +0000
          Re: gcc and 'include' antispam@fricas.org (Waldek Hebisch) - 2026-03-31 05:28 +0000
  Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-27 04:10 +0300
    Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-26 19:08 -0700
      Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-27 16:47 +0300
        Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-27 16:43 +0100
        Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-27 09:03 -0700
          Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-29 11:46 +0300
            Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 08:19 -0700
              Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-30 20:08 +0300
                Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-31 00:26 -0700
                Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-31 11:27 +0300
                Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-04-07 09:45 -0700
        Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-28 10:25 -0700
          Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-29 10:37 +0300
            Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-29 11:30 +0200
            Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-29 07:22 -0700
            Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-29 13:56 -0400
              Re: gcc and 'include' Michael S <already5chosen@yahoo.com> - 2026-03-29 21:39 +0300
                Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-29 20:08 -0400
                Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-30 01:58 +0100
                Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 07:59 -0700
  Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-26 19:06 -0700
  Re: gcc and 'include' Bart <bc@freeuk.com> - 2026-03-27 16:20 +0000
    Re: gcc and 'include' David Brown <david.brown@hesbynett.no> - 2026-03-27 18:07 +0100
    Re: gcc and 'include' James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-03-28 18:48 -0400
  Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-27 22:38 -0700
    Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-28 00:30 -0700
      Re: gcc and 'include' Andrey Tarasevich <noone@noone.net> - 2026-03-29 16:15 -0700
        Re: gcc and 'include' Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-03-30 00:41 -0700

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