[committed] libstdc++: Support single components in name of chrono::current_zone() [PR108211]

[Jonathan Wakely via Gcc-patches]

Tested x86_64-linux. Pushed to trunk.

-- >8 --

We currently only handle the case where /etc/localtime is a symlink to a
path like ".../Etc/UTC" and fail for ".../UTC". This makes both work.

libstdc++-v3/ChangeLog:

        PR libstdc++/108211
        * src/c++20/tzdb.cc (chrono::current_zone()): Check for zone
        using only last component of the name.
---
 libstdc++-v3/src/c++20/tzdb.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index 6772517d55a..9103b159400 100644
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -1501,8 +1501,11 @@ namespace std::chrono
        if (std::distance(first, last) > 2)
          {
            --last;
-           string name = std::prev(last)->string() + '/';
-           name += last->string();
+           string name = last->string();
+           if (auto tz = do_locate_zone(this->zones, this->links, name))
+             return tz;
+           --last;
+           name = last->string() + '/' + name;
            if (auto tz = do_locate_zone(this->zones, this->links, name))
              return tz;
          }
-- 
2.39.0