QTimeZone - Fix dateForLocalTime() to check validity of next transition

The private method dateForLocalTime() was not checking that transitions
were valid, resulting in infinite looping when a time zone didn't have
any future transitions.

Change-Id: I0e5d07063861778dd86056a80c36fdd9f9d36133
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

3 files changed, 16 insertions, 3 deletions

diff --git a/src/corelib/tools/qtimezoneprivate.cpp b/src/corelib/tools/qtimezoneprivate.cpp
index dd4e18e01f..08a5ce0861 100644
--- a/src/corelib/tools/qtimezoneprivate.cpp
+++ b/src/corelib/tools/qtimezoneprivate.cpp
@@ -264,7 +264,8 @@ QTimeZonePrivate::Data QTimeZonePrivate::dataForLocalTime(qint64 forLocalMSecs)
     // If the local msecs is less than the real local time of the transition
     // then get the previous transition to use instead
     if (forLocalMSecs < tran.atMSecsSinceEpoch + (tran.offsetFromUtc * 1000)) {
-        while (forLocalMSecs < tran.atMSecsSinceEpoch + (tran.offsetFromUtc * 1000)) {
+        while (tran.atMSecsSinceEpoch != invalidMSecs()
+               && forLocalMSecs < tran.atMSecsSinceEpoch + (tran.offsetFromUtc * 1000)) {
             nextTran = tran;
             tran = previousTransition(tran.atMSecsSinceEpoch);
         }
@@ -272,7 +273,8 @@ QTimeZonePrivate::Data QTimeZonePrivate::dataForLocalTime(qint64 forLocalMSecs)
         // The zone msecs is after the transition, so check it is before the next tran
         // If not try use the next transition instead
         nextTran = nextTransition(tran.atMSecsSinceEpoch);
-        while (forLocalMSecs >= nextTran.atMSecsSinceEpoch + (nextTran.offsetFromUtc * 1000)) {
+        while (nextTran.atMSecsSinceEpoch != invalidMSecs()
+               && forLocalMSecs >= nextTran.atMSecsSinceEpoch + (nextTran.offsetFromUtc * 1000)) {
             tran = nextTran;
             nextTran = nextTransition(tran.atMSecsSinceEpoch);
         }
@@ -292,7 +294,8 @@ QTimeZonePrivate::Data QTimeZonePrivate::dataForLocalTime(qint64 forLocalMSecs)
             // then use the prev tran as we default to the FirstOccurrence
             // TODO Check if faster to just always get prev tran, or if faster using 6 hour check.
             Data dstTran = previousTransition(tran.atMSecsSinceEpoch);
-            if (dstTran.daylightTimeOffset > 0 && diffPrevTran < (dstTran.daylightTimeOffset * 1000))
+            if (dstTran.atMSecsSinceEpoch != invalidMSecs()
+                && dstTran.daylightTimeOffset > 0 && diffPrevTran < (dstTran.daylightTimeOffset * 1000))
                 tran = dstTran;
         } else if (diffNextTran >= 0 && diffNextTran <= (nextTran.daylightTimeOffset * 1000)) {
             // If time falls within last hour of standard time then is actually the missing hour
diff --git a/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp b/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
index 1e2b0ed649..6c80c5ff47 100644
--- a/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
+++ b/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
@@ -2903,6 +2903,12 @@ void tst_QDateTime::timeZones() const
     // - Test 03:00:00 = 1 hour after tran
     hourAfterStd = QDateTime(QDate(2013, 10, 27), QTime(3, 0, 0), cet);
     QCOMPARE(hourAfterStd.toMSecsSinceEpoch(), dstToStdMSecs + 3600000);
+
+    // Test Time Zone that has transitions but no future transitions afer a given date
+    QTimeZone sgt("Asia/Singapore");
+    QDateTime future(QDate(2015, 1, 1), QTime(0, 0, 0), sgt);
+    QVERIFY(future.isValid());
+    QCOMPARE(future.offsetFromUtc(), 28800);
 }
 
 void tst_QDateTime::invalid() const
diff --git a/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp b/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp
index cfb20f51e4..d7643ff55d 100644
--- a/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp
+++ b/tests/auto/corelib/tools/qtimezone/tst_qtimezone.cpp
@@ -409,6 +409,10 @@ void tst_QTimeZone::stressTest()
             qDebug() << "Stress test calculating transistions for" << testZone.id();
             testZone.transitions(lowDate1, highDate1);
         }
+        testDate.setTimeZone(testZone);
+        testDate.isValid();
+        testDate.offsetFromUtc();
+        testDate.timeZoneAbbreviation();
     }
 }