[libcxx-commits] [libcxx] 4167fec - [libc++][chrono] Completes the tzdb class. (#82157)
via libcxx-commits
libcxx-commits at lists.llvm.org
Thu Apr 4 10:03:05 PDT 2024
Author: Mark de Wever
Date: 2024-04-04T19:03:01+02:00
New Revision: 4167fec40768fb05b411bcefa186fe2b106ca7e4
URL: https://github.com/llvm/llvm-project/commit/4167fec40768fb05b411bcefa186fe2b106ca7e4
DIFF: https://github.com/llvm/llvm-project/commit/4167fec40768fb05b411bcefa186fe2b106ca7e4.diff
LOG: [libc++][chrono] Completes the tzdb class. (#82157)
It adds the missing member functions of the tzdb class and adds the free
functions that use these member functions.
Implements parts of:
- P0355 Extending <chrono> to Calendars and Time Zones
Added:
libcxx/test/libcxx/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp
libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/current_zone.pass.cpp
libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/locate_zone.pass.cpp
libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/current_zone.pass.cpp
libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp
Modified:
libcxx/include/__chrono/tzdb.h
libcxx/include/__chrono/tzdb_list.h
libcxx/include/chrono
libcxx/modules/std/chrono.inc
libcxx/src/tzdb.cpp
libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.compile.pass.cpp
libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.verify.cpp
Removed:
################################################################################
diff --git a/libcxx/include/__chrono/tzdb.h b/libcxx/include/__chrono/tzdb.h
index 45c20f279f9c96..e0bfedf0d78239 100644
--- a/libcxx/include/__chrono/tzdb.h
+++ b/libcxx/include/__chrono/tzdb.h
@@ -16,6 +16,7 @@
// Enable the contents of the header only when libc++ was built with experimental features enabled.
#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_TZDB)
+# include <__algorithm/ranges_lower_bound.h>
# include <__chrono/leap_second.h>
# include <__chrono/time_zone.h>
# include <__chrono/time_zone_link.h>
@@ -43,6 +44,40 @@ struct tzdb {
vector<time_zone_link> links;
vector<leap_second> leap_seconds;
+
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI const time_zone* __locate_zone(string_view __name) const {
+ if (const time_zone* __result = __find_in_zone(__name))
+ return __result;
+
+ if (auto __it = ranges::lower_bound(links, __name, {}, &time_zone_link::name);
+ __it != links.end() && __it->name() == __name)
+ if (const time_zone* __result = __find_in_zone(__it->target()))
+ return __result;
+
+ return nullptr;
+ }
+
+ _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI const time_zone* locate_zone(string_view __name) const {
+ if (const time_zone* __result = __locate_zone(__name))
+ return __result;
+
+ std::__throw_runtime_error("tzdb: requested time zone not found");
+ }
+
+ _LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI const time_zone* current_zone() const {
+ return __current_zone();
+ }
+
+private:
+ _LIBCPP_HIDE_FROM_ABI const time_zone* __find_in_zone(string_view __name) const noexcept {
+ if (auto __it = ranges::lower_bound(zones, __name, {}, &time_zone::name);
+ __it != zones.end() && __it->name() == __name)
+ return std::addressof(*__it);
+
+ return nullptr;
+ }
+
+ [[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI const time_zone* __current_zone() const;
};
} // namespace chrono
diff --git a/libcxx/include/__chrono/tzdb_list.h b/libcxx/include/__chrono/tzdb_list.h
index e8aaf31e36316c..693899d372112d 100644
--- a/libcxx/include/__chrono/tzdb_list.h
+++ b/libcxx/include/__chrono/tzdb_list.h
@@ -17,6 +17,7 @@
#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_TZDB)
# include <__availability>
+# include <__chrono/time_zone.h>
# include <__chrono/tzdb.h>
# include <__config>
# include <__fwd/string.h>
@@ -84,6 +85,15 @@ _LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline con
return get_tzdb_list().front();
}
+_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline const time_zone*
+locate_zone(string_view __name) {
+ return get_tzdb().locate_zone(__name);
+}
+
+_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_HIDE_FROM_ABI inline const time_zone* current_zone() {
+ return get_tzdb().current_zone();
+}
+
_LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI const tzdb& reload_tzdb();
_LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI string remote_version();
diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index 4dd43137b71820..8fdc30a3624dfc 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -689,6 +689,9 @@ struct tzdb {
vector<time_zone> zones;
vector<time_zone_link> links;
vector<leap_second> leap_seconds;
+
+ const time_zone* locate_zone(string_view tz_name) const;
+ const time_zone* current_zone() const;
};
class tzdb_list { // C++20
@@ -714,6 +717,8 @@ public:
// [time.zone.db.access], time zone database access
const tzdb& get_tzdb(); // C++20
tzdb_list& get_tzdb_list(); // C++20
+const time_zone* locate_zone(string_view tz_name); // C++20
+const time_zone* current_zone() // C++20
// [time.zone.db.remote], remote time zone database support
const tzdb& reload_tzdb(); // C++20
diff --git a/libcxx/modules/std/chrono.inc b/libcxx/modules/std/chrono.inc
index 2c0bd3f98a67d7..e14228043d3b84 100644
--- a/libcxx/modules/std/chrono.inc
+++ b/libcxx/modules/std/chrono.inc
@@ -199,10 +199,10 @@ export namespace std {
using std::chrono::tzdb_list;
// [time.zone.db.access], time zone database access
- // using std::chrono::current_zone;
+ using std::chrono::current_zone;
using std::chrono::get_tzdb;
using std::chrono::get_tzdb_list;
- // using std::chrono::locate_zone;
+ using std::chrono::locate_zone;
// [time.zone.db.remote], remote time zone database support
using std::chrono::reload_tzdb;
diff --git a/libcxx/src/tzdb.cpp b/libcxx/src/tzdb.cpp
index 7ba5ceb7ada3d2..2c82a4a4317a81 100644
--- a/libcxx/src/tzdb.cpp
+++ b/libcxx/src/tzdb.cpp
@@ -675,6 +675,57 @@ void __init_tzdb(tzdb& __tzdb, __tz::__rules_storage_type& __rules) {
std::ranges::sort(__tzdb.leap_seconds);
}
+#ifdef _WIN32
+[[nodiscard]] static const time_zone* __current_zone_windows(const tzdb& tzdb) {
+ // TODO TZDB Implement this on Windows.
+ std::__throw_runtime_error("unknown time zone");
+}
+#else // ifdef _WIN32
+[[nodiscard]] static const time_zone* __current_zone_posix(const tzdb& tzdb) {
+ // On POSIX systems there are several ways to configure the time zone.
+ // In order of priority they are:
+ // - TZ environment variable
+ // https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08
+ // The documentation is unclear whether or not it's allowed to
+ // change time zone information. For example the TZ string
+ // MST7MDT
+ // this is an entry in tzdata.zi. The value
+ // MST
+ // is also an entry. Is it allowed to use the following?
+ // MST-3
+ // Even when this is valid there is no time_zone record in the
+ // database. Since the library would need to return a valid pointer,
+ // this means the library needs to allocate and leak a pointer.
+ //
+ // - The time zone name is the target of the symlink /etc/localtime
+ // relative to /usr/share/zoneinfo/
+
+ // The algorithm is like this:
+ // - If the environment variable TZ is set and points to a valid
+ // record use this value.
+ // - Else use the name based on the `/etc/localtime` symlink.
+
+ if (const char* __tz = getenv("TZ"))
+ if (const time_zone* __result = tzdb.__locate_zone(__tz))
+ return __result;
+
+ filesystem::path __path = "/etc/localtime";
+ if (!std::filesystem::exists(__path))
+ std::__throw_runtime_error("tzdb: the symlink '/etc/localtime' does not exist");
+
+ if (!std::filesystem::is_symlink(__path))
+ std::__throw_runtime_error("tzdb: the path '/etc/localtime' is not a symlink");
+
+ filesystem::path __tz = filesystem::read_symlink(__path);
+ string __name = filesystem::relative(__tz, "/usr/share/zoneinfo/");
+
+ if (const time_zone* __result = tzdb.__locate_zone(__name))
+ return __result;
+
+ std::__throw_runtime_error(("tzdb: the time zone '" + __name + "' is not found in the database").c_str());
+}
+#endif // ifdef _WIN32
+
//===----------------------------------------------------------------------===//
// Public API
//===----------------------------------------------------------------------===//
@@ -684,6 +735,14 @@ _LIBCPP_NODISCARD_EXT _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI tzdb_l
return __result;
}
+[[nodiscard]] _LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI const time_zone* tzdb::__current_zone() const {
+#ifdef _WIN32
+ return chrono::__current_zone_windows(*this);
+#else
+ return chrono::__current_zone_posix(*this);
+#endif
+}
+
_LIBCPP_AVAILABILITY_TZDB _LIBCPP_EXPORTED_FROM_ABI const tzdb& reload_tzdb() {
if (chrono::remote_version() == chrono::get_tzdb().version)
return chrono::get_tzdb();
diff --git a/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.compile.pass.cpp b/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.compile.pass.cpp
index c868832ea74ada..9acb57fa05f75c 100644
--- a/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.compile.pass.cpp
+++ b/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.compile.pass.cpp
@@ -38,8 +38,16 @@ void test() {
std::chrono::get_tzdb_list();
std::chrono::get_tzdb();
+ std::chrono::locate_zone("name");
+ std::chrono::current_zone();
std::chrono::remote_version();
+ {
+ const std::chrono::tzdb& t = list.front();
+ t.locate_zone("name");
+ t.current_zone();
+ }
+
{
tz.name();
operator==(tz, tz);
diff --git a/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.verify.cpp b/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.verify.cpp
index 4d26b46a89c91b..8795a4eb3c6c13 100644
--- a/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/chrono.nodiscard_extensions.verify.cpp
@@ -33,9 +33,17 @@ void test() {
list.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
list.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ {
+ const std::chrono::tzdb& t = list.front();
+ t.locate_zone("name"); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ t.current_zone(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ }
+
namespace crno = std::chrono;
crno::get_tzdb_list(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
crno::get_tzdb(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ crno::locate_zone("n"); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ crno::current_zone(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
crno::remote_version(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
{
diff --git a/libcxx/test/libcxx/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp b/libcxx/test/libcxx/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp
new file mode 100644
index 00000000000000..971f7f04c49a8a
--- /dev/null
+++ b/libcxx/test/libcxx/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp
@@ -0,0 +1,84 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// <chrono>
+
+// struct tzdb
+
+// const time_zone* locate_zone(string_view tz_name) const;
+
+#include <cassert>
+#include <chrono>
+#include <fstream>
+#include <string_view>
+
+#include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
+#include "filesystem_test_helper.h"
+#include "test_tzdb.h"
+
+scoped_test_env env;
+[[maybe_unused]] const std::filesystem::path dir = env.create_dir("zoneinfo");
+const std::filesystem::path file = env.create_file("zoneinfo/tzdata.zi");
+
+std::string_view std::chrono::__libcpp_tzdb_directory() {
+ static std::string result = dir.string();
+ return result;
+}
+
+void write(std::string_view input) {
+ static int version = 0;
+
+ std::ofstream f{file};
+ f << "# version " << version++ << '\n';
+ f.write(input.data(), input.size());
+}
+
+static const std::chrono::tzdb& parse(std::string_view input) {
+ write(input);
+ return std::chrono::reload_tzdb();
+}
+
+int main(int, const char**) {
+ const std::chrono::tzdb& tzdb = parse(
+ R"(
+Z zone 0 r f
+L zone link
+L link link_to_link
+)");
+
+ {
+ const std::chrono::time_zone* tz = tzdb.locate_zone("zone");
+ assert(tz);
+ assert(tz->name() == "zone");
+ }
+ {
+ const std::chrono::time_zone* tz = tzdb.locate_zone("link");
+ assert(tz);
+ assert(tz->name() == "zone");
+ }
+
+ TEST_VALIDATE_EXCEPTION(
+ std::runtime_error,
+ [&]([[maybe_unused]] const std::runtime_error& e) {
+ std::string_view what{"tzdb: requested time zone not found"};
+ TEST_LIBCPP_REQUIRE(
+ e.what() == what,
+ TEST_WRITE_CONCATENATED("\nExpected exception ", what, "\nActual exception ", e.what(), '\n'));
+ },
+ TEST_IGNORE_NODISCARD tzdb.locate_zone("link_to_link"));
+
+ return 0;
+}
diff --git a/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/current_zone.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/current_zone.pass.cpp
new file mode 100644
index 00000000000000..d85c8ba52622a0
--- /dev/null
+++ b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/current_zone.pass.cpp
@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// <chrono>
+
+// const time_zone* current_zone();
+
+#include <cassert>
+#include <chrono>
+#include <string_view>
+#include <stdlib.h>
+
+#include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
+
+#ifdef _WIN32
+static void set_tz(std::string zone) {
+ // Note Windows does not have setenv, only putenv
+ // https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/putenv-s-wputenv-s?view=msvc-170
+ // Unlike POSIX it does not mention the string of putenv becomes part
+ // of the environment.
+
+ int status = _putenv_s("TZ", zone.c_str(), 1);
+ assert(status == 0);
+}
+
+#else
+static void set_tz(const std::string& zone) {
+ int status = setenv("TZ", zone.c_str(), 1);
+ assert(status == 0);
+}
+#endif
+
+static void test_zone(const std::string& zone) {
+ set_tz(zone);
+ const std::chrono::time_zone* tz = std::chrono::current_zone();
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+static void test_link(const std::string& link, std::string_view zone) {
+ set_tz(link);
+ const std::chrono::time_zone* tz = std::chrono::current_zone();
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+int main(int, const char**) {
+ const std::chrono::time_zone* tz = std::chrono::current_zone();
+ // Returns a valid time zone, the value depends on the OS settings.
+ assert(tz);
+ // setting the environment to an invalid value returns the value of
+ // the OS setting.
+ set_tz("This is not a time zone");
+ assert(tz == std::chrono::current_zone());
+
+ const std::chrono::tzdb& db = std::chrono::get_tzdb();
+ for (const auto& zone : db.zones)
+ test_zone(std::string{zone.name()});
+
+ for (const auto& link : db.links)
+ test_link(std::string{link.name()}, link.target());
+
+ return 0;
+}
diff --git a/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/locate_zone.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/locate_zone.pass.cpp
new file mode 100644
index 00000000000000..c3142a86bf9d65
--- /dev/null
+++ b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.access/locate_zone.pass.cpp
@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// <chrono>
+
+// const time_zone* locate_zone(string_view tz_name);
+
+#include <cassert>
+#include <chrono>
+#include <string_view>
+
+#include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
+
+static void test_zone(std::string_view zone) {
+ const std::chrono::time_zone* tz = std::chrono::locate_zone(zone);
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+static void test_link(std::string_view link, std::string_view zone) {
+ const std::chrono::time_zone* tz = std::chrono::locate_zone(link);
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+static void test_exception([[maybe_unused]] std::string_view zone) {
+ TEST_VALIDATE_EXCEPTION(
+ std::runtime_error,
+ [&]([[maybe_unused]] const std::runtime_error& e) {
+ std::string_view what{"tzdb: requested time zone not found"};
+ TEST_LIBCPP_REQUIRE(
+ e.what() == what,
+ TEST_WRITE_CONCATENATED("\nExpected exception ", what, "\nActual exception ", e.what(), '\n'));
+ },
+ TEST_IGNORE_NODISCARD std::chrono::locate_zone(zone));
+}
+
+int main(int, const char**) {
+ const std::chrono::tzdb& db = std::chrono::get_tzdb();
+ for (const auto& zone : db.zones)
+ test_zone(zone.name());
+
+ for (const auto& link : db.links)
+ test_link(link.name(), link.target());
+
+ test_exception("This is not a time zone");
+
+ return 0;
+}
diff --git a/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/current_zone.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/current_zone.pass.cpp
new file mode 100644
index 00000000000000..7b4218cc8421b4
--- /dev/null
+++ b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/current_zone.pass.cpp
@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// <chrono>
+
+// struct tzdb
+
+// const time_zone* current_zone() const;
+
+#include <cassert>
+#include <chrono>
+#include <string_view>
+#include <stdlib.h>
+
+#include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
+
+#ifdef _WIN32
+static void set_tz(std::string zone) {
+ // Note Windows does not have setenv, only putenv
+ // https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/putenv-s-wputenv-s?view=msvc-170
+ // Unlike POSIX it does not mention the string of putenv becomes part
+ // of the environment.
+
+ int status = _putenv_s("TZ", zone.c_str(), 1);
+ assert(status == 0);
+}
+
+#else
+static void set_tz(const std::string& zone) {
+ int status = setenv("TZ", zone.c_str(), 1);
+ assert(status == 0);
+}
+#endif
+
+static void test_zone(const std::string& zone) {
+ set_tz(zone);
+ const std::chrono::time_zone* tz = std::chrono::get_tzdb().current_zone();
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+static void test_link(const std::string& link, std::string_view zone) {
+ set_tz(link);
+ const std::chrono::time_zone* tz = std::chrono::get_tzdb().current_zone();
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+int main(int, const char**) {
+ const std::chrono::time_zone* tz = std::chrono::get_tzdb().current_zone();
+ // Returns a valid time zone, the value depends on the OS settings.
+ assert(tz);
+ // setting the environment to an invalid value returns the value of
+ // the OS setting.
+ set_tz("This is not a time zone");
+ assert(tz == std::chrono::get_tzdb().current_zone());
+
+ const std::chrono::tzdb& db = std::chrono::get_tzdb();
+ for (const auto& zone : db.zones)
+ test_zone(std::string{zone.name()});
+
+ for (const auto& link : db.links)
+ test_link(std::string{link.name()}, link.target());
+
+ return 0;
+}
diff --git a/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp
new file mode 100644
index 00000000000000..12987f6c89d808
--- /dev/null
+++ b/libcxx/test/std/time/time.zone/time.zone.db/time.zone.db.tzdb/locate_zone.pass.cpp
@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-filesystem, no-localization, no-tzdb
+
+// XFAIL: libcpp-has-no-incomplete-tzdb
+// XFAIL: availability-tzdb-missing
+
+// <chrono>
+
+// struct tzdb
+
+// const time_zone* locate_zone(string_view tz_name) const;
+
+#include <cassert>
+#include <chrono>
+#include <string_view>
+
+#include "test_macros.h"
+#include "assert_macros.h"
+#include "concat_macros.h"
+
+static void test_zone(std::string_view zone) {
+ const std::chrono::time_zone* tz = std::chrono::get_tzdb().locate_zone(zone);
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+static void test_link(std::string_view link, std::string_view zone) {
+ const std::chrono::time_zone* tz = std::chrono::get_tzdb().locate_zone(link);
+ assert(tz);
+ assert(tz->name() == zone);
+}
+
+static void test_exception([[maybe_unused]] std::string_view zone) {
+ TEST_VALIDATE_EXCEPTION(
+ std::runtime_error,
+ [&]([[maybe_unused]] const std::runtime_error& e) {
+ std::string_view what{"tzdb: requested time zone not found"};
+ TEST_LIBCPP_REQUIRE(
+ e.what() == what,
+ TEST_WRITE_CONCATENATED("\nExpected exception ", what, "\nActual exception ", e.what(), '\n'));
+ },
+ TEST_IGNORE_NODISCARD std::chrono::get_tzdb().locate_zone(zone));
+}
+
+int main(int, const char**) {
+ const std::chrono::tzdb& db = std::chrono::get_tzdb();
+ for (const auto& zone : db.zones)
+ test_zone(zone.name());
+
+ for (const auto& link : db.links)
+ test_link(link.name(), link.target());
+
+ test_exception("This is not a time zone");
+
+ return 0;
+}
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