how to set locale with C++

[Václav Zeman]

On 9 February 2012 15:24, marco atzeri wrote:
> On 2/9/2012 1:37 PM, Corinna Vinschen wrote:
>>
>> On Feb  9 12:13, marco atzeri wrote:
>>>
>>> Attached a small example taken from Bruce Eckel Thinking in C++
>>>
>>> On cygwin both this call
>>>
>>>   cout.imbue(locale("en_US.UTF-8"));
>>>
>>>   cout.imbue(locale("fr_FR.UTF-8"));
>>>
>>> raise exception
>>>
>>> "terminate called after throwing an instance of 'std::runtime_error'
>>>   what():  locale::facet::_S_create_c_locale name not valid
>>> Aborted (core dumped)"
>>>
>>> I could understand eventually the second one, but "English (US)" is
>>> the current windows locale so I expected that at least "en_US.UTF-8"
>>> is accepted.
>>>
>>> What I am missing ?
>>
>>
>> This doesn't look like a Cygwin issue.  The above error
>> "locale::facet::_S_create_c_locale name not valid" points to some
>> problem in the library implementing the locale call.  The underlying
>> plain C call setlocale should work fine.
>>
>>
>> Corinna
>>
>
> g++ 4.5.3 seems to have a problem on cygwin.
>
> setlocale on pure C is working
> (modified from
> http://www.cplusplus.com/reference/clibrary/clocale/setlocale/)
>
> $ ./setlocale.exe
> Locale is: C
> Date is: Thu Feb  9 14:52:45 2012
> Currency symbol is:
> -
> Locale is: fr_FR.UTF-8
> Date is: jeu.  9 févr. 2012 14:52:45
> Currency symbol is: €
> -
>
>
> Dave,
> it could be related to libstdc++ built with a different
> --enable-clocale option ?
The problem is that Cygwin/newlib does not have good enough locale
support.  C99 locale support is not good enough for std::locale
implementation.  Mainly because the functions that change the locale
affect the whole process.  It is necessary to have at least per thread
locale for std::locale to be implementable; it is better to have some
sort of locale structure to pass around.  AFAIK this can be
implemented using functions provided by xlocale.h (MacOS X, [1]).

>
> http://gcc.gnu.org/onlinedocs/libstdc++/manual/build.html
>
> Or that functionality is not available on cygwin ?

[1] <http://developer.apple.com/documentation/Darwin/Reference/ManPages/man3/xlocale.3.html>

-- 
VZ

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