Re: [musl] setlocale() behaviour

[Alastair Houghton <ahoughton@apple.com>]

Rich, any chance of some input from you on this, since it was you that wrote about it previously?

Kind regards,

Alastair.

On 19 Jul 2023, at 18:10, Alastair Houghton <ahoughton@apple.com> wrote:
> 
> As Rich Felker noted previously about this behaviour:
> 
>> Unfortunately this turns out to have been something of a tradeoff,
>> since there's no way for applications (and, as it turns out,
>> especially tests/test suites) to query whether a particular locale is
>> "really" available. I've been asked to change the behavior to fail on
>> unknown locale names, but of course that's not a working option in
>> light of the above.
> 
> 
> He then went on in a subsequent message to the list to suggest
> 
>> 1. setlocale(cat, explicit_locale_name) - succeeds if the locale
>>   actually has a definition file, fails and returns a null pointer
>>   otherwise.
>> 
>> 2. setlocale(cat, "") - always succeeds, honoring the environment
>>   variable for the category if a locale definition file by that name
>>   exists, but otherwise (the unspecified behavior) treating it as if
>>   it were C.UTF-8.
> 
> Which would work just fine for libc++.  What it’s trying to do is to check whether e.g. fr_FR is supported, then it can enable additional tests that rely on the French localisation being present.  I appreciate that, per the POSIX standard, you don’t *technically* know what fr_FR means, but in practice that isn’t really true --- an implementation that had a locale installed called fr_FR that *wasn’t* French would be pretty silly.  Unfortunately, because of musl’s current behaviour, it *looks like* such an implementation, even though it actually isn’t (and it totally could have a genuine fr_FR locale if you had the right data in the right place).
> 
> I can, of course, check whether setlocale(LC_ALL, “something ridiculous”) succeeds and returns “something ridiculous”, then disable all locales except for POSIX, C and C.UTF-8.  That will work around the current musl behaviour without causing trouble with other C libraries, but libc++’s maintainer isn’t terribly keen on it and would rather we explore the possibility of musl changing its implementation.
> 
> TL/DR: What I’m really enquiring about here is the fact that there was discussion about changing it to work in a more useful manner, but nothing changed (and I don’t see anything in that email thread to explain that it was decided to not make the proposed change; but maybe I missed it?)
> 
> Kind regards,
> 
> Alastair.
> 
> 
>