Reduce QtCoreLib size by not repeating "UTC" string too often.

It is a minor reduction, in release build it is ~200 bytes

Change-Id: I4f7972c95769f2e0ca1ddc935ff7a0a6b4379e2a
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

src/corelib/tools/qdatetime.cpp

@@ -3194,7 +3194,7 @@ QTimeZone QDateTime::timeZone() const
         return d->m_timeZone;
     case Qt::UTC:
         if (!d->m_timeZone.isValid())
-            d->m_timeZone = QTimeZone("UTC");
+            d->m_timeZone = QTimeZone(QTimeZonePrivate::utcQByteArray());
         return d->m_timeZone;
     case Qt::TimeZone :
         return d->m_timeZone;
@@ -3254,9 +3254,9 @@ QString QDateTime::timeZoneAbbreviation() const
 {
     switch (d->m_spec) {
     case Qt::UTC:
-        return QStringLiteral("UTC");
+        return QTimeZonePrivate::utcQString();
     case Qt::OffsetFromUTC:
-        return QLatin1String("UTC") + toOffsetString(Qt::ISODate, d->m_offsetFromUtc);
+        return QTimeZonePrivate::utcQString() + toOffsetString(Qt::ISODate, d->m_offsetFromUtc);
     case Qt::TimeZone:
 #ifndef QT_BOOTSTRAPPED
         return d->m_timeZone.d->abbreviation(d->toMSecsSinceEpoch());

src/corelib/tools/qtimezoneprivate.cpp

@@ -558,8 +558,8 @@ template<> QTimeZonePrivate *QSharedDataPointer<QTimeZonePrivate>::clone()
 // Create default UTC time zone
 QUtcTimeZonePrivate::QUtcTimeZonePrivate()
 {
-    const QString name = QStringLiteral("UTC");
-    init(QByteArrayLiteral("UTC"), 0, name, name, QLocale::AnyCountry, name);
+    const QString name = utcQString();
+    init(utcQByteArray(), 0, name, name, QLocale::AnyCountry, name);
 }
 
 // Create a named UTC time zone
@@ -583,7 +583,7 @@ QUtcTimeZonePrivate::QUtcTimeZonePrivate(qint32 offsetSeconds)
     QString utcId;
 
     if (offsetSeconds == 0)
-        utcId = QStringLiteral("UTC");
+        utcId = utcQString();
     else
         utcId = isoOffsetFormat(offsetSeconds);
 
@@ -675,7 +675,7 @@ qint32 QUtcTimeZonePrivate::daylightTimeOffset(qint64 atMSecsSinceEpoch) const
 
 QByteArray QUtcTimeZonePrivate::systemTimeZoneId() const
 {
-    return QByteArrayLiteral("UTC");
+    return utcQByteArray();
 }
 
 QSet<QByteArray> QUtcTimeZonePrivate::availableTimeZoneIds() const

src/corelib/tools/qtimezoneprivate_p.h

@@ -154,6 +154,17 @@ public:
     static QList<QByteArray> windowsIdToIanaIds(const QByteArray &windowsId,
                                                  QLocale::Country country);
 
+    // returns "UTC" QString and QByteArray
+    static inline QString utcQString() Q_REQUIRED_RESULT
+    {
+        return QStringLiteral("UTC");
+    }
+
+    static inline QByteArray utcQByteArray() Q_REQUIRED_RESULT
+    {
+        return QByteArrayLiteral("UTC");
+    }
+
 protected:
     QByteArray m_id;
 };

src/corelib/tools/qtimezoneprivate_tz.cpp

@@ -958,7 +958,7 @@ QByteArray QTzTimeZonePrivate::systemTimeZoneId() const
 
     // Give up for now and return UTC
     if (ianaId.isEmpty())
-        ianaId = QByteArrayLiteral("UTC");
+        ianaId = utcQByteArray();
 
     return ianaId;
 }

src/corelib/tools/qtimezoneprivate_win.cpp

@@ -249,7 +249,7 @@ static QByteArray windowsSystemZoneId()
     }
 
     // If we can't determine the current ID use UTC
-    return QByteArrayLiteral("UTC");
+    return QTimeZonePrivate::utcQByteArray();
 }
 
 static QDate calculateTransitionLocalDate(const SYSTEMTIME &rule, int year)
@@ -635,7 +635,7 @@ QByteArray QWinTimeZonePrivate::systemTimeZoneId() const
         ianaId = windowsIdToDefaultIanaId(windowsId);
         // If no global default then probably an unknown Windows ID so return UTC
         if (ianaId.isEmpty())
-            return QByteArrayLiteral("UTC");
+            return utcQByteArray();
     }
     return ianaId;
 }