Autotest: Fix QDateTime failure if the test got run West of Greenwich

There was a comment about the test failing for max() because of an
overflow. That happens if you're at UTC or ahead of it (to the East of
the Prime Meridian), which is how this test usually gets run (UTC,
Europe/Oslo, Europe/Helsinki, Pacific/Auckland). But if you're behind
UTC (to the West of the Prime Meridian), then the overflow happens for
min().

Change-Id: Iebba49d1303e9f18f5038f5cf23c77bf83e5fd4b
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>

1 files changed, 42 insertions, 2 deletions

diff --git a/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp b/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
index 6c80c5ff47..5d1fe0784f 100644
--- a/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
+++ b/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
@@ -61,6 +61,7 @@ public:
     static QString str( int y, int month, int d, int h, int min, int s );
     static QDateTime dt( const QString& str );
 public slots:
+    void initTestCase();
     void init();
 private slots:
     void ctor();
@@ -150,6 +151,7 @@ private slots:
     void invalid() const;
 
 private:
+    enum { LocalTimeIsUtc = 0, LocalTimeAheadOfUtc = 1, LocalTimeBehindUtc = -1} localTimeType;
     bool europeanTimeZone;
     QDate defDate() const { return QDate(1900, 1, 1); }
     QTime defTime() const { return QTime(0, 0, 0); }
@@ -169,6 +171,42 @@ tst_QDateTime::tst_QDateTime()
     uint x1 = QDateTime(QDate(1990, 1, 1), QTime()).toTime_t();
     uint x2 = QDateTime(QDate(1990, 6, 1), QTime()).toTime_t();
     europeanTimeZone = (x1 == 631148400 && x2 == 644191200);
+
+    QDateTime dt1 = QDateTime::fromTime_t(0);
+    QDateTime dt2 = QDateTime::fromTime_t(181 * 86400); // six months later, Jul 1
+    if (dt1.date().year() < 1970 || dt2.date().month() < 7) {
+        localTimeType = LocalTimeBehindUtc;
+    } else if (dt1.time().hour() > 0 || dt1.date().day() > 1) {
+        localTimeType = LocalTimeAheadOfUtc;
+    } else if (dt2.time().hour() > 0 || dt2.date().day() > 1) {
+        localTimeType = LocalTimeAheadOfUtc;
+    } else {
+        localTimeType = LocalTimeIsUtc;
+    }
+}
+
+void tst_QDateTime::initTestCase()
+{
+    // Never construct a message like this in an i18n context...
+    const char *typemsg1, *typemsg2 = "and therefore not";
+    switch (localTimeType) {
+    case LocalTimeIsUtc:
+        typemsg1 = "exactly";
+        break;
+    case LocalTimeBehindUtc:
+        typemsg1 = "behind";
+        break;
+    case LocalTimeAheadOfUtc:
+        typemsg1 = "ahead of";
+        typemsg2 = europeanTimeZone ? "and is" : "but isn't";
+        break;
+    }
+
+    qDebug() << "Current local time detected to be"
+             << typemsg1
+             << "UTC"
+             << typemsg2
+             << "the Central European timezone";
 }
 
 void tst_QDateTime::init()
@@ -610,8 +648,10 @@ void tst_QDateTime::fromMSecsSinceEpoch()
     QDateTime dtUtc = QDateTime::fromMSecsSinceEpoch(msecs, Qt::UTC);
     QDateTime dtOffset = QDateTime::fromMSecsSinceEpoch(msecs, Qt::OffsetFromUTC, 60*60);
 
-    // LocalTime will overflow for max
-    if (msecs != std::numeric_limits<qint64>::max())
+    // LocalTime will overflow for min or max, depending on whether you're
+    // East or West of Greenwich. The test passes at GMT.
+    if (localTimeType == LocalTimeIsUtc
+            || msecs != std::numeric_limits<qint64>::max() * localTimeType)
         QCOMPARE(dtLocal, utc);
 
     QCOMPARE(dtUtc, utc);