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Re: Random thought -- EOF and errno

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Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> James Kuyper <jameskuyper@verizon.net> writes:
>> On 08/12/2011 12:04 PM, Kenneth Brody wrote:
>>> A stray thought wandered into my head this morning...
>>> 
>>> Given that 7.5p4 reserves macros that begin with E+digit or
>>> E+capital-letter for error codes, what allows the Standard to also
>>> define EOF in a manner unrelated to <errno.h>?  (Aside from "duh,
>>> it's the Standard, and it can do whatever it likes", that is.)
>>
>> Those macros are reserved for use by the implementation; EOF is
>> #defined by the implementation; there's no conflict. In principle,
>> EOF could even be a valid errno value.
>
> I'm not sure it could be (or at least not in a useful way).  7.5p3 says
> that errno "is set to a positive error number by several library
> functions" but EOF must have a negative value (7.19.1p3).  It certainly
> seems as if setting errno to EOF would not be confirming to the spirit
> of the standard.

If an implementation defined EOF with a positive value in <errno.h>, I
presume it would violate the standard, but what clause would it violate?

Such an implementation would fail to compile this:

#include <errno.h>
#include <stdio.h>
int main(void){}

which clearlyi would be A Bad Thing, but does the standard actually
require it to be accepted?

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

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Random thought -- EOF and errno Kenneth Brody <kenbrody@spamcop.net> - 2011-08-12 12:04 -0400
  Re: Random thought -- EOF and errno James Kuyper <jameskuyper@verizon.net> - 2011-08-12 12:27 -0400
    Re: Random thought -- EOF and errno Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 00:12 +0100
      Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-12 16:30 -0700
        Re: Random thought -- EOF and errno Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 01:27 +0100
          Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-12 18:28 -0700
            Re: Random thought -- EOF and errno Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 14:38 +0100
              Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-13 11:50 -0700
                Re: Random thought -- EOF and errno Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-13 17:45 -0400
                Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-13 18:04 -0700
                Re: Random thought -- EOF and errno Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 22:53 +0100
                Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-13 17:57 -0700
                Re: Random thought -- EOF and errno Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-13 21:06 -0400
                Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-13 18:39 -0700
                Re: Random thought -- EOF and errno Tim Rentsch <txr@alumni.caltech.edu> - 2011-09-04 12:59 -0700
      Re: Random thought -- EOF and errno James Kuyper <jameskuyper@verizon.net> - 2011-08-12 20:51 -0400
        Re: Random thought -- EOF and errno Nobody <nobody@nowhere.com> - 2011-08-13 05:55 +0100
          Re: Random thought -- EOF and errno Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-13 14:49 +0100
        Re: Random thought -- EOF and errno Kenneth Brody <kenbrody@spamcop.net> - 2011-08-15 15:02 -0400
          Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-15 12:18 -0700
          Re: Random thought -- EOF and errno James Kuyper <jameskuyper@verizon.net> - 2011-08-15 21:54 -0400
            Re: Random thought -- EOF and errno Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-08-16 04:21 +0100
        Re: Random thought -- EOF and errno William Ahern <william@wilbur.25thandClement.com> - 2011-08-15 12:56 -0700
  Re: Random thought -- EOF and errno Seebs <usenet-nospam@seebs.net> - 2011-08-12 18:37 +0000
  Re: Random thought -- EOF and errno Nobody <nobody@nowhere.com> - 2011-08-13 06:00 +0100
    Re: Random thought -- EOF and errno Kenneth Brody <kenbrody@spamcop.net> - 2011-08-15 15:05 -0400
      Re: Random thought -- EOF and errno Keith Thompson <kst-u@mib.org> - 2011-08-15 12:14 -0700
      Re: Random thought -- EOF and errno gordonb.gl0ml@burditt.org (Gordon Burditt) - 2011-08-16 04:31 -0500

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