[boost] Re: Lexical cast suggestion

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-09-21 05:21:12

Martin wrote:

>> It's already the case, because config file do not contain the information
>> about the used locale. Further, even if it did, the set of locales on
>> different computers is not the same, and on different OS even the naming
>> may be different, so moving configuration files is hard already.
>> This might mean I need to set classic locale for parsing, to make sure
>> config files are really portable.
> 
> I am not familiar with the code layout for program options but with a
> quick look it seems like you can do it the the same way as in the streams?
> Add a locale reference member to the value_semantics class and an imbue
> method to the options_description class which specifies the default.

So every library which uses lexical_cast would have to provide the 'imbue'
and store the locale everywhere? I think per-thread global variable is
better.

>> That's not convenient, so probably global
>> "lexical_cast_locale" is better. But for MT environment you need to store
>> that global state in TSS.
> 
> The global locale can already be used so there is no need for another
> global locale.

Nope, there's only one global locale, it's not per-thread. If it's
per-thread, you can do

    std::locale::tss_global(std::locale("koi8-r"));
    // do some work with program_options
    std::locale::tss_global(std::locale(""));

> const std::locale old = std::locale::global(std::locale::classic());
> double x = lexical_cast<double>(str);
> std::locale::global(old);

But that does not prevent other threads to change the locale again one CPU
tick before you you call lexical_cast.

- Volodya