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Re: ridiculous warning or not?

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Tim Rentsch <txr@alumni.caltech.edu> writes:
> Keith Thompson <kst-u@mib.org> writes:
>> Tim Rentsch <txr@alumni.caltech.edu> writes:
>>> Keith Thompson <kst-u@mib.org> writes:
>> [...snip-a-lot...]
>>>> So this:
>>>>
>>>>     char f[];
>>>>
>>>> is treated as:
>>>>
>>>>     char f[] = 0;
>>>
>>> No, it would be  'char f[] = {0};'  as the implementation is
>>> obliged to do by 6.7.9p16 -- implementations are obliged to
>>> follow "shall" directives.
>>
>> Implementations are obliged to follow *all* normative requirements
>> in the standard.  6.9.2p2 requires an implicit "initializer equal
>> to 0".  I wouldn't say that `{0}` is "equal to 0".
>>
>>[...snip-some-more...]
>>
>>>> Apparently we have to interpret the "initializer equal to 0" to mean
>>>> `{ 0 }` rather than `0` in this case.  And we're supposed to infer
>>>> from that that `f` has exactly one element; apparently `{ 0 }` is
>>>> "equal to 0" but `{ 0, 0 }` isn't.
>>>
>>> { 0, 0 } is two initializers, not one.
>>
>> { 0, 0 } is one initializer, which contains two more initializers.
>> [...snip elaboration...]
>
> My comments were kind of half frivolous, because I find
> it hard to believe someone would take this question so
> seriously, when it seems perfectly obvious what is
> intended.  I do think my comments have some degree of
> merit (and yours also), but not sufficient to overcome
> the level of silliness present (for which I am more
> to blame than you).
>
> Therefore, rather than continuing on the particular
> points above, I would like to quote from Defect Report #11
> (slightly reformatted):
>
[snip]
>     Response
>     --------
>     Subclause 6.7.2 External object definitions contains the
>     following excerpt:
>
>         If a translation unit contains one or more tentative
>         definitions for an identifier, and the translation unit
>         contains no external definition for that identifier,
>         then the behavior is exactly as if the translation unit
>         contains a file scope declaration of that identifier,
>         with the composite type as of the end of the
>         translation unit, with an initializer equal to 0.
>
>     This statement describes an effect and not a literal token
>     sequence.  Therefore, this example does not contain an
>     error.
>
> Please note the first sentence in the last paragraph.

Interesting.  That's
    http://www.open-std.org/JTC1/SC22/WG14/www/docs/dr_011.html
submitted 1992-12-10 against C90; it resulted in the addition of
the footnote in question.

Personally, I'm not satisfied with the statement that it "describes
an effect and not a literal token sequence", or with the conclusion
that an initializer "equal to 0" implies that the array has 1
element.  The standard isn't a mathematically formal document, but
this is one of those cases where I think it needs to be more precise.
The phrase "equal to 0" has an exact meaning; I dislike the standard
using it so loosely.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
    Will write code for food.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Thread

ridiculous warning or not? kerravon <kerravon@w3.to> - 2012-08-20 02:41 -0700
  Re: ridiculous warning or not? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-08-20 07:55 -0400
  Re: ridiculous warning or not? army1987 <army1987@ask-for-it.invalid> - 2012-08-20 19:11 +0000
  Re: ridiculous warning or not? Kenneth Brody <kenbrody@spamcop.net> - 2012-08-20 16:09 -0400
    Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 07:29 -0700
  Re: ridiculous warning or not? Andrew Cooper <amc96@cam.ac.uk> - 2012-08-21 00:36 +0100
  Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-21 01:41 +0100
    Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-08-20 18:59 -0700
      Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 08:03 -0700
        Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-09-07 14:37 -0700
          Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 19:17 -0700
            Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-09-07 19:56 -0700
              Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-08 06:30 -0700
    Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 07:57 -0700
      Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-09-08 00:25 +0100
        Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 18:58 -0700
          Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-09-07 19:26 -0700
            Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-08 06:26 -0700
              Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-09-08 11:33 -0700
                Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 14:39 -0800
                Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-12-17 15:56 -0800
                Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-20 10:31 -0800
                Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-12-20 16:57 -0800
                Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-12-21 03:11 +0000
                Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-21 09:06 -0800
          Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-09-08 03:42 +0100
            Re: ridiculous warning or not? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-08 06:01 -0700
              Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-09-08 14:45 +0100
                Re: ridiculous warning or not? Keith Thompson <kst-u@mib.org> - 2012-09-08 11:28 -0700
                Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-09-08 22:53 +0100
  Re: ridiculous warning or not? kerravon <kerravon@w3.to> - 2012-08-21 03:25 -0700
    Re: ridiculous warning or not? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-21 11:20 -0700
      Re: ridiculous warning or not? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-21 21:07 +0100
        Re: ridiculous warning or not? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-21 14:39 -0700
          Re: ridiculous warning or not? Ike Naar <ike@iceland.freeshell.org> - 2012-08-21 22:09 +0000
            Re: ridiculous warning or not? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-21 15:13 -0700
              Re: ridiculous warning or not? Fred K <fred.l.kleinschmidt@gmail.com> - 2012-08-22 07:17 -0700

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