On 09/10/19 16:59 +0100, Jonathan Wakely wrote:
>If two threads see _M_index==0 concurrently they will both try to set
>it, potentially storing the facet at two different indices in the array.
>
>Either set the _M_index data member using an atomic compare-exchange
>operation or while holding a mutex.
>
>Also move the LONG_DOUBLE_COMPAT code into a separate function to remove
>the visual noise it creates.
>
>	PR libstdc++/91057
>	* src/c++98/locale.cc (locale::id::_M_id()) [__GTHREADS]: Use atomic
>	compare-exchange or double-checked lock to ensure only one thread sets
>	the _M_index variable.
>	[_GLIBCXX_LONG_DOUBLE_COMPAT]: Call find_ldbl_sync_facet to detect
>	facets that share another facet's ID.
>	[_GLIBCXX_LONG_DOUBLE_COMPAT] (find_ldbl_sync_facet): New function.
>
>Tested x86_64-linux, committed to trunk.

That patch was broken on powerpc and other targets with long double
compat symbols.

Tested powerpc64le-linux, committed to trunk.