[PATCH] libstdc++: Make syncbuf _S_get_mutex instantiation extern.

[Nathan Myers]

Thank you.

On 8/28/25 1:48 PM, Jonathan Wakely wrote:
> On Thu, 28 Aug 2025 at 18:35, Nathan Myers wrote:
>>
>> [Note: do we need entries in config/abi/pre/gnu.ver for these?]
> 
> Aren't there test failures without them?

I probably should have labeled this [RFC], because I haven't run
tests yet.

>> This declares and defines explicit instantiations of std::syncbuf<T>::
>> __mutex::_S_get_mutex for T=char and T=wchar_t, where the function
>> is defined at all, the wchar_t case gated on _GLIBCXX_USE_WCHAR_T.
> 
> I was thinking we'd just have one set of mutexes for all basic_syncbuf
> specializations, e.g. in a non-dependent base class.

Ah, of course.