Make updateSystemPrivate() local to qlocale.cpp

It's not thread-safe so should only be used within systemData()'s
locked code.  This eliminates the last callers of it by making it a
local function of the compilation unit, exposing a method from
QSystemLocale() to get round its use of private parts.  Make the
constructor for QSystemLocale only stomp its _systemLocale global if
previously unset, but let instantiation still clear
globalLocaleData.m_language_id, so that it can be used as a way to
trigger an update to system locale data.

Change-Id: I908dca9fd30bbf20f42321ab8f9094f2fa37b7b0
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qlocale.cpp

@@ -620,13 +620,18 @@ static QLocalePrivate *c_private()
 */
 
 /*!
-  Constructs a QSystemLocale object. The constructor will automatically
-  install this object as the system locale and remove any earlier installed
-  system locales.
+  Constructs a QSystemLocale object.
+
+  The constructor will automatically install this object as the system locale,
+  if there's not one active.  It also resets the flag that'll prompt
+  QLocale::system() to re-initialize its data, so that instantiating a
+  QSystemLocale transiently (doesn't install the transient as system locale if
+  there was one already and) triggers an update to the system locale's data.
 */
 QSystemLocale::QSystemLocale()
 {
-    _systemLocale = this;
+    if (!_systemLocale)
+        _systemLocale = this;
 
     globalLocaleData.m_language_id = 0;
 }
@@ -656,15 +661,17 @@ static const QSystemLocale *systemLocale()
     return QSystemLocale_globalSystemLocale();
 }
 
-void QLocalePrivate::updateSystemPrivate()
+static void updateSystemPrivate()
 {
-    // this function is NOT thread-safe!
+    // This function is NOT thread-safe!
+    // It *should not* be called by anything but systemData()
     const QSystemLocale *sys_locale = systemLocale();
 
     // tell the object that the system locale has changed.
     sys_locale->query(QSystemLocale::LocaleChanged, QVariant());
 
-    globalLocaleData = *sys_locale->fallbackUiLocale().d->m_data;
+    // Populate global with fallback as basis:
+    globalLocaleData = *sys_locale->fallbackUiLocaleData();
 
     QVariant res = sys_locale->query(QSystemLocale::LanguageId, QVariant());
     if (!res.isNull()) {
@@ -715,7 +722,7 @@ static const QLocaleData *systemData()
         static QBasicMutex systemDataMutex;
         systemDataMutex.lock();
         if (globalLocaleData.m_language_id == 0)
-            QLocalePrivate::updateSystemPrivate();
+            updateSystemPrivate();
         systemDataMutex.unlock();
     }
 
@@ -2351,7 +2358,6 @@ QString QLocale::toString(double i, char f, int prec) const
 
 QLocale QLocale::system()
 {
-    // this function is NOT thread-safe!
     QT_PREPEND_NAMESPACE(systemData)(); // trigger updating of the system data if necessary
     return QLocale(*systemLocalePrivate->data());
 }

src/corelib/tools/qlocale.h

@@ -1096,6 +1096,7 @@ public:
 private:
     QLocale(QLocalePrivate &dd);
     friend class QLocalePrivate;
+    friend class QSystemLocale;
     friend Q_CORE_EXPORT uint qHash(const QLocale &key, uint seed) Q_DECL_NOTHROW;
 
     QSharedDataPointer<QLocalePrivate> d;

src/corelib/tools/qlocale_p.h

@@ -66,6 +66,7 @@
 QT_BEGIN_NAMESPACE
 
 #ifndef QT_NO_SYSTEMLOCALE
+struct QLocaleData;
 class Q_CORE_EXPORT QSystemLocale
 {
 public:
@@ -126,6 +127,7 @@ public:
     virtual QVariant query(QueryType type, QVariant in) const;
     virtual QLocale fallbackUiLocale() const;
 
+    inline const QLocaleData *fallbackUiLocaleData() const;
 private:
     QSystemLocale(bool);
     friend class QSystemLocaleSingleton;
@@ -364,8 +366,6 @@ public:
 
     QLocale::MeasurementSystem measurementSystem() const;
 
-    static void updateSystemPrivate();
-
     QString dateTimeToString(QStringView format, const QDateTime &datetime,
                              const QDate &dateOnly, const QTime &timeOnly,
                              const QLocale *q) const;
@@ -375,6 +375,10 @@ public:
     QLocale::NumberOptions m_numberOptions;
 };
 
+#ifndef QT_NO_SYSTEMLOCALE
+const QLocaleData *QSystemLocale::fallbackUiLocaleData() const { return fallbackUiLocale().d->m_data; }
+#endif
+
 template <>
 inline QLocalePrivate *QSharedDataPointer<QLocalePrivate>::clone()
 {

tests/auto/corelib/tools/qlocale/tst_qlocale.cpp

@@ -1870,9 +1870,11 @@ static void setWinLocaleInfo(LCTYPE type, const QString &value)
 #  define LOCALE_SSHORTTIME 0x00000079
 #endif
 
-class RestoreLocaleHelper {
+class RestoreLocaleHelper
+{
 public:
-    RestoreLocaleHelper() {
+    RestoreLocaleHelper()
+    {
         m_decimal = getWinLocaleInfo(LOCALE_SDECIMAL);
         m_thousand = getWinLocaleInfo(LOCALE_STHOUSAND);
         m_sdate = getWinLocaleInfo(LOCALE_SSHORTDATE);
@@ -1880,7 +1882,8 @@ public:
         m_time = getWinLocaleInfo(LOCALE_SSHORTTIME);
     }
 
-    ~RestoreLocaleHelper() {
+    ~RestoreLocaleHelper()
+    {
         // restore these, or the user will get a surprise
         setWinLocaleInfo(LOCALE_SDECIMAL, m_decimal);
         setWinLocaleInfo(LOCALE_STHOUSAND, m_thousand);
@@ -1888,12 +1891,10 @@ public:
         setWinLocaleInfo(LOCALE_SLONGDATE, m_ldate);
         setWinLocaleInfo(LOCALE_SSHORTTIME, m_time);
 
-        // make sure QLocale::system() gets updated
-        QLocalePrivate::updateSystemPrivate();
+        QSystemLocale dummy; // to provoke a refresh of the system locale
     }
 
     QString m_decimal, m_thousand, m_sdate, m_ldate, m_time;
-
 };
 
 void tst_QLocale::windowsDefaultLocale()
@@ -1909,8 +1910,7 @@ void tst_QLocale::windowsDefaultLocale()
     const QString shortTimeFormat = QStringLiteral("h^m^s");
     setWinLocaleInfo(LOCALE_SSHORTTIME, shortTimeFormat);
 
-    // make sure QLocale::system() gets updated
-    QLocalePrivate::updateSystemPrivate();
+    QSystemLocale dummy; // to provoke a refresh of the system locale
     QLocale locale = QLocale::system();
 
     // make sure we are seeing the system's format strings