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Re: When is the complete type of an external definition known?

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In article <a9f1hmFe4bU1@mid.individual.net>,
Wojtek Lerch  <wojtek_l@yahoo.ca> wrote:
>On 19-Aug-12 10:22 PM, Keith Thompson wrote:
>> Vlad from Moscow <vlad.moscow@mail.ru> writes:
>>> понедельник, 20 августа 2012 г., 1:56:49 UTC+4
>пользователь Ike Naar написал:
>>>> On 2012-08-19, Vlad from Moscow <vlad.moscow@mail.ru> wrote:
>> [...]
>>>>    static int a[];
>>>>
>>>> violates 6.9.2 p3:
>>>>
>>>> "If the declaration of an identifier for an object is a tentative
>>>> definition and has internal linkage, the declared type shall not be
>>>> an incomplete type."
>>
>> ... (more precisely a constraint violation).
>
>Actually that paragraph is in a Semantics section, not in a Constraints 
>section.  It's plain undefined behaviour without a promise of a diagnostic.
>
>Out of curiosity, does anybody know the reason for this restriction?  It 
>sounds like a useful thing to be able to do.  (And I have to admit that 
>did it more than once, before I knew about this.)  Is it because 
>different compilers used to interpret it differently back in the day, 
>and the standard didn't want to break them?  The Rationale doesn't seem 
>to mention "tentative" at all.

When I asked this question before, the most believable answer was that
ancient compilers didn't handle this case because it would have required a
second compiler pass. Without the static keyword, the linker could finish up
whatever the compiler couldn't do in its single pass. With static, the linker
didn't get enough information.

Assuming the last of the single-pass compilers has finally died out, it
should be possible to get this fixed. It needs someone who cares enough to
make it an official proposal.

-- 
Alan Curry

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When is the complete type of an external definition known? Vlad from Moscow <vlad.moscow@mail.ru> - 2012-08-19 13:40 -0700
  Re: When is the complete type of an external definition known? Keith Thompson <kst-u@mib.org> - 2012-08-19 14:06 -0700
    Re: When is the complete type of an external definition known? Vlad from Moscow <vlad.moscow@mail.ru> - 2012-08-19 14:30 -0700
      Re: When is the complete type of an external definition known? Ike Naar <ike@iceland.freeshell.org> - 2012-08-19 21:56 +0000
        Re: When is the complete type of an external definition known? Vlad from Moscow <vlad.moscow@mail.ru> - 2012-08-19 16:42 -0700
          Re: When is the complete type of an external definition known? Keith Thompson <kst-u@mib.org> - 2012-08-19 19:22 -0700
            Re: When is the complete type of an external definition known? Wojtek Lerch <wojtek_l@yahoo.ca> - 2012-08-20 10:57 -0400
              Re: When is the complete type of an external definition known? Keith Thompson <kst-u@mib.org> - 2012-08-20 13:01 -0700
                Re: When is the complete type of an external definition known? Wojtek Lerch <wojtek_l@yahoo.ca> - 2012-08-20 16:58 -0400
              Re: When is the complete type of an external definition known? pacman@kosh.dhis.org (Alan Curry) - 2012-08-21 00:44 +0000
          Re: When is the complete type of an external definition known? Ike Naar <ike@sverige.freeshell.org> - 2012-08-20 05:57 +0000
            Re: When is the complete type of an external definition known? Vlad from Moscow <vlad.moscow@mail.ru> - 2012-08-20 03:22 -0700
              Re: When is the complete type of an external definition known? Ike Naar <ike@sverige.freeshell.org> - 2012-08-20 12:27 +0000
                Re: When is the complete type of an external definition known? Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-20 17:04 +0200
                Re: When is the complete type of an external definition known? Ike Naar <ike@iceland.freeshell.org> - 2012-08-20 16:35 +0000
                Re: When is the complete type of an external definition known? Jens Gustedt <jens.gustedt@loria.fr> - 2012-08-20 20:43 +0200
          Re: When is the complete type of an external definition known? James Kuyper <jameskuyper@verizon.net> - 2012-08-20 08:46 -0400
  Re: When is the complete type of an external definition known? Vlad from Moscow <vlad.moscow@mail.ru> - 2012-08-19 14:24 -0700
  Re: When is the complete type of an external definition known? "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2012-08-19 23:36 +0200
    Re: When is the complete type of an external definition known? Vlad from Moscow <vlad.moscow@mail.ru> - 2012-08-19 14:46 -0700

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