Re: [boost] [locale] Documentation correction

Subject: Re: [boost] [locale] Documentation correction
From: Artyom Beilis (artyomtnk_at_[hidden])
Date: 2011-07-18 01:45:30

----- Original Message ----
> From: Beman Dawes <bdawes_at_[hidden]>
> To: Boost Developers List <boost_at_[hidden]>
> Sent: Mon, July 18, 2011 12:09:17 AM
> Subject: [boost] [locale] Documentation correction
> 
> The last bullet item on page libs/locale/doc/html/index.html says:
> 
>       Many standard libraries provide only the C and POSIX locales,
>       thus GCC supports localization only under Linux. On all other
>       platforms, attempting to create locales other than "C" or  "POSIX"
>      would fail.
> 
> Actually, locale("") works on most  platforms, including PC-BSD and
> Open Solaris, so needs to be added to the  above list of locales that
> do work.  Look at the trunk filesystem  regression first test,
> "locale_info", and click on the Pass link to see the  output.
> locale("") is working pretty much across the board, even on the  Darwin
> tests.
> 

I had actually tested this, AFAIR
it had thrown both on Solaris with gcc-3.4 and FreeBSD with gcc-4.2
if the current locale (LANG/LC_ALL) was not C (like en_US.UTF-8) but
I may recheck (need to get to my virtual machines)

Even if locale("") does not throw it does not mean
that it does anything useful.

For example with gcc-4.5.3/mingw on Windows, this code

#include <iostream>
#include <locale>
#include <locale.h>

int main()
{
    try {
        std::locale l("");
        std::cout << "Ok: " << l.name() << std::endl;
    }
    catch(std::exception const &e) {
        std::cerr <<"Error:"<< e.what() << std::endl;
    }
    std::cout << "C Locale:"<< setlocale(LC_ALL,"") << std::endl;
}

Prints

  Ok: C
  C Locale:Hebrew_Israel.1255

And behaves like POSIX locale.

> Mac OS X is of particular interest because by default  locale("") does
> fall, and the Apple folks have said in the past that they  won't fix
> it. It fails on my Mac mini in the default configuration.  Presumably
> the Darwin regression test machine has something beyond the  default
> configuration.
> 

This is why Boost.Locale exists.

> Also, would it be possible to use locales from  the Apache library?  See
> http://stdcxx.apache.org/doc/stdlibref/locale.html#Table%C2%A021
> 

I know this library but I have never tested with it. If you
know how to switch the standard library by Apache's one you
may try to run Boost.Locale's tests and see how it goes.

In any case I'd recommend to use ICU as localization backend
as even when standard library works well it still provides
quite low quality support. See:

  
http://cppcms.sourceforge.net/boost_locale/html/using_localization_backends.html

So it is always better to use ICU unless you want to keep 
as few dependencies as possible and the standard library support suits you.

Artyom Beilis
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