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Re: CVS commit: src/lib/libc/locale

On Tue, Apr 16, 2013 at 11:34:52PM +0000, YAMAMOTO Takashi wrote:
> > On Tue, Apr 16, 2013 at 11:39:50PM +0900, Takehiko NOZAKI wrote:
> >> so that the struct _locale __C_locale in libc is much more wasteful.
> > 
> > I should add that it is an internal detail and the way the composed C
> > locale is stored can and likely will change later. So the way it is
> > essentially a copy of (old) global locale is just a way to be minimally
> > intrusive.
> > 
> > Joerg
> i care the API.
> if you really want it be in libc, how about having libc provide a
> "locale_t get_static_c_locale();" style API rather than using NULL?
> it's better because 1) less code in *_l, 2) autoconf-like can detect
> the extension easily, and 3) a portable application can trivially
> have a fallback implementation using newlocale+pthread_once.

It adds more cost on the caller side. So far, there are three mechanisms
available (especially for libraries):

(1) Adhoc access to internal locale state. This is used with glibc.
(2) Explicit newlocale().
(3) Implicit access via 0 argument to *_l.

The first one is clearly a hack and not acceptable. Portable code can
always conditionally use (2), but it requires additional setup and
storage cost. (3) is used by Apple (which is where a large part of the
*_l interface originates from) and FreeBSD. It is orthogonal to (2) and
certainly easier to use. Exposing it via a special library call is also
possible and effectively a way to implement (2) by a static wrapper.
It still adds more cost to every caller and this is a classic case where
there are typically much more callers.


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