libstdc++: Search for tzdata on Windows (msys)

Windows does not provide a tzdata.zi, but msys does. Use this, if
available, instead of the embedded (and possibly outdated) database.

libstdc++-v3/Changelog:

	Use msys provided time zone information.

	* src/c++20/tzdb.cc (zoneinfo_file): On Windows look relative
	from the DLL path for the time zone information.

Signed-off-by: Björn Schäpers <bjoern@hazardy.de>

diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index 6e244dc656d850398ba24f4d5a2823b711ab8acd..9923d14b7a75453e82a76198dadba2a74f7ef57d 100644 (file)
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -44,6 +44,12 @@
 # include <cstdlib>   // getenv
 #endif
 
+#if _GLIBCXX_HAVE_WINDOWS_H
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+# include <psapi.h>
+#endif
+
 #if defined __GTHREADS && ATOMIC_POINTER_LOCK_FREE == 2
 # define USE_ATOMIC_LIST_HEAD 1
 // TODO benchmark atomic<shared_ptr<>> vs mutex.
@@ -1144,6 +1150,34 @@ namespace std::chrono
 #ifdef _GLIBCXX_ZONEINFO_DIR
       else
        path = _GLIBCXX_ZONEINFO_DIR;
+#endif
+#ifdef _GLIBCXX_HAVE_WINDOWS_H
+      if (path.empty())
+       {
+         HMODULE dll_module;
+         if (GetModuleHandleExA(
+                 GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
+                     | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+                 reinterpret_cast<const char *>(&zoneinfo_file), &dll_module))
+           {
+             char dll_path[MAX_PATH];
+             if (GetModuleFileNameA(dll_module, dll_path, MAX_PATH) != 0)
+               {
+                 string_view dll_path_view = dll_path;
+                 auto pos = dll_path_view.find_last_of('\\');
+                 dll_path_view = dll_path_view.substr(0, pos);
+                 if (dll_path_view.ends_with("\\bin"))
+                   {
+                     constexpr string_view remaining_path = "share\\zoneinfo";
+                     dll_path_view.remove_suffix(3); // Remove bin
+                     path.reserve(dll_path_view.size()
+                                  + remaining_path.size());
+                     path = dll_path_view;
+                     path += remaining_path;
+                   }
+               }
+           }
+       }
 #endif
       if (!path.empty())
        path.append(filename);