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Date: Tue, 29 Dec 2009 06:41:33 -0700
From: Eric Blake <ebb9 AT byu DOT net>
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Subject: Re: gcc4[1.7] printf treats differently a string constant and a   	character array
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According to Andy Koppe on 12/29/2009 6:30 AM:
>> Remember, POSIX states that any use in a character context of bytes with
>> the 8th-bit set is specifically undefined in the C locale (whether that be
>> C.ASCII or C.UTF-8).
> 
> I very much disagree with that. C.ASCII and C.UTF-8 are different
> locales from plain "C", and the whole point of the explicitly stated
> charset is to define the meaning of bytes beyond 7-bit ASCII.

Point taken: an explicit "C.UTF-8" is a request of a specific charset
along with C semantics (such as no translation of output messages,
posix-mandated formatting for time and money, ...), but because the
charset is explicit, the use of 8-bit bytes is well-defined in our
implementation (and since POSIX does not specify C.UTF-8, you've already
left the realm of portability and gone into implementation-defined).

But my point remains: an explicit "C" is specified to be charset-agnostic,
so a portable program requesting "C" should not be expecting any
particular behavior of 8-bit bytes in character contexts.  Programs that
use LC_ALL=C to try to get 8-bit transparency from character contexts are
flat-out non-portable.  They get other well-defined benefits on 8-bit
bytes (such as sorting by strcmp instead of strcoll, fixed-format
messages, ...), but only insofar as those 8-bit bytes are in byte contexts
rather than character contexts.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9 AT byu DOT net
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