LibC: Implement tzset with time zone awareness in accordance with POSIX

1 files changed, 64 insertions, 0 deletions

diff --git a/Tests/LibC/TestLibCTime.cpp b/Tests/LibC/TestLibCTime.cpp
index fcf2327639..4fa829e2a2 100644
--- a/Tests/LibC/TestLibCTime.cpp
+++ b/Tests/LibC/TestLibCTime.cpp
@@ -10,6 +10,25 @@
 
 const auto expected_epoch = "Thu Jan  1 00:00:00 1970\n"sv;
 
+class TimeZoneGuard {
+public:
+    TimeZoneGuard()
+        : m_tz(getenv("TZ"))
+    {
+    }
+
+    ~TimeZoneGuard()
+    {
+        if (m_tz)
+            setenv("TZ", m_tz, 1);
+        else
+            unsetenv("TZ");
+    }
+
+private:
+    char const* m_tz { nullptr };
+};
+
 TEST_CASE(asctime)
 {
     time_t epoch = 0;
@@ -41,3 +60,48 @@ TEST_CASE(ctime_r)
 
     EXPECT_EQ(expected_epoch, StringView(result));
 }
+
+TEST_CASE(tzset)
+{
+    TimeZoneGuard guard;
+
+    auto set_tz = [](char const* tz) {
+        setenv("TZ", tz, 1);
+        tzset();
+    };
+
+    set_tz("UTC");
+    EXPECT_EQ(timezone, 0);
+    EXPECT_EQ(altzone, 0);
+    EXPECT_EQ(daylight, 0);
+    EXPECT_EQ(tzname[0], "UTC"sv);
+    EXPECT_EQ(tzname[1], "UTC"sv);
+
+    set_tz("America/New_York");
+    EXPECT_EQ(timezone, 5 * 60 * 60);
+    EXPECT_EQ(altzone, 4 * 60 * 60);
+    EXPECT_EQ(daylight, 1);
+    EXPECT_EQ(tzname[0], "EST"sv);
+    EXPECT_EQ(tzname[1], "EDT"sv);
+
+    set_tz("America/Phoenix");
+    EXPECT_EQ(timezone, 7 * 60 * 60);
+    EXPECT_EQ(altzone, 7 * 60 * 60);
+    EXPECT_EQ(daylight, 0);
+    EXPECT_EQ(tzname[0], "MST"sv);
+    EXPECT_EQ(tzname[1], "MST"sv);
+
+    set_tz("America/Asuncion");
+    EXPECT_EQ(timezone, 4 * 60 * 60);
+    EXPECT_EQ(altzone, 3 * 60 * 60);
+    EXPECT_EQ(daylight, 1);
+    EXPECT_EQ(tzname[0], "-04"sv);
+    EXPECT_EQ(tzname[1], "-03"sv);
+
+    set_tz("CET");
+    EXPECT_EQ(timezone, -1 * 60 * 60);
+    EXPECT_EQ(altzone, -2 * 60 * 60);
+    EXPECT_EQ(daylight, 1);
+    EXPECT_EQ(tzname[0], "CET"sv);
+    EXPECT_EQ(tzname[1], "CEST"sv);
+}