Fix 'libstdc++-v3/src/c++20/tzdb.cc' build for '__GTHREADS && !__GTHREADS_CXX0X' configurations

[François Dumont]

On 20/02/2025 18:28, Thomas Schwinge wrote:
> Hi!
>
> On 2025-02-20T16:36:56+0000, Jonathan Wakely <jwakely@redhat.com> wrote:
>> On 20/02/25 15:50 +0100, Thomas Schwinge wrote:
>> >From 820e015494e25187c9a5ffbd69911ec6ce612789 Mon Sep 17 00:00:00 2001
>>> From: Jonathan Wakely <jwakely@redhat.com>
>>> Date: Thu, 20 Feb 2025 14:08:11 +0000
>>> Subject: [PATCH] Fix 'libstdc++-v3/src/c++20/tzdb.cc' build for '__GTHREADS &&
>>> !__GTHREADS_CXX0X' configurations
>>>
>>> 	libstdc++-v3/
>>> 	* src/c++20/tzdb.cc [__GTHREADS && !__GTHREADS_CXX0X]: Use
>>> 	'__gnu_cxx::__mutex'.
>>>
>>> Co-authored-by: Thomas Schwinge <tschwinge@baylibre.com>
>>> ---
>>> libstdc++-v3/src/c++20/tzdb.cc | 8 +++++++-
>>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
>>> index 7e8cce7ce8c..70ba7b0ef53 100644
>>> --- a/libstdc++-v3/src/c++20/tzdb.cc
>>> +++ b/libstdc++-v3/src/c++20/tzdb.cc
>>> @@ -35,6 +35,9 @@
>>> #include <atomic>     // atomic<T*>, atomic<int>
>>> #include <memory>     // atomic<shared_ptr<T>>
>>> #include <mutex>      // mutex
>>> +#if defined __GTHREADS && ! defined _GLIBCXX_HAS_GHTREADS
>>> +# include <ext/concurrence.h> // __gnu_cxx::__mutex
>>> +#endif
>>> #include <filesystem> // filesystem::read_symlink
>>>
>>> #ifndef _AIX
>>> @@ -97,11 +100,14 @@ namespace std::chrono
>>> {
>>>    namespace
>>>    {
>>> -#if ! USE_ATOMIC_SHARED_PTR
>>> #ifndef __GTHREADS
>>>      // Dummy no-op mutex type for single-threaded targets.
>>>      struct mutex { void lock() { } void unlock() { } };
>>> +#elif ! defined _GLIBCXX_HAS_GHTREADS
>> This still has my GHTREADS typo.
> Eh.  I had fixed that, but apparently lost it.  Re-fixed.
>
>> A comment here would be good too:
>>
>>       // Use __gnu_cxx::__mutex is std::mutex isn't available.
> Added.

Minor but comment was added with alas the small typo to say 'if' rather 
than 'is':

      // Use __gnu_cxx::__mutex if std::mutex isn't available.