Use RAII to handle setting of default locale in tst_QString

Various tests were setting the default locale and relying on cleanup()
to "restore" the C locale; which needn't actually be the locale we
started out in and, in any case, was the wrong locale for some tests.
So handle this via an RAII class that records the actual prior locale
and restores it on destruction.

Fixes: QTBUG-73116
Change-Id: If44f7cb8c6e0ce81be396ac1ea8bab7038a86729
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

tests/auto/corelib/tools/qstring/tst_qstring.cpp

@@ -319,10 +319,18 @@ class tst_QString : public QObject
     template <typename ArgType>
     void insert_impl() const { insert_impl<ArgType, QString &(QString::*)(int, const ArgType&)>(); }
     void insert_data(bool emptyIsNoop = false);
+
+    class TransientDefaultLocale
+    {
+        const QLocale prior; // Records what *was* the default before we set it.
+    public:
+        TransientDefaultLocale(const QLocale &transient) { revise(transient); }
+        void revise(const QLocale &transient) { QLocale::setDefault(transient); }
+        ~TransientDefaultLocale() { QLocale::setDefault(prior); }
+    };
+
 public:
     tst_QString();
-public slots:
-    void cleanup();
 private slots:
     void fromStdString();
     void toStdString();
@@ -654,11 +662,6 @@ tst_QString::tst_QString()
     QTextCodec::setCodecForLocale(QTextCodec::codecForName("ISO 8859-1"));
 }
 
-void tst_QString::cleanup()
-{
-    QLocale::setDefault(QString("C"));
-}
-
 void tst_QString::remove_uint_uint_data()
 {
     replace_uint_uint_data();
@@ -4750,7 +4753,7 @@ void tst_QString::arg()
     is all messed up, because Qt Test itself uses QString::arg().
 */
 
-    QLocale::setDefault(QString("de_DE"));
+    TransientDefaultLocale transient(QString("de_DE"));
 
     QString s4( "[%0]" );
     QString s5( "[%1]" );
@@ -4898,13 +4901,11 @@ void tst_QString::arg()
     QCOMPARE(QString("%1").arg(-1., 3, 'g', -1, QChar('x')), QLatin1String("x-1"));
     QCOMPARE(QString("%1").arg(-100., 3, 'g', -1, QChar('x')), QLatin1String("-100"));
 
-    QLocale::setDefault(QString("ar"));
+    transient.revise(QString("ar"));
     QCOMPARE( QString("%L1").arg(12345.6789, 10, 'g', 7, QLatin1Char('0')),
               QString::fromUtf8("\xd9\xa0\xd9\xa1\xd9\xa2\xd9\xac\xd9\xa3\xd9\xa4\xd9\xa5\xd9\xab\xd9\xa6\xd9\xa8") ); // "٠١٢٬٣٤٥٫٦٨"
     QCOMPARE( QString("%L1").arg(123456789, 13, 10, QLatin1Char('0')),
               QString("\xd9\xa0\xd9\xa0\xd9\xa1\xd9\xa2\xd9\xa3\xd9\xac\xd9\xa4\xd9\xa5\xd9\xa6\xd9\xac\xd9\xa7\xd9\xa8\xd9\xa9") ); // ٠٠١٢٣٬٤٥٦٬٧٨٩
-
-    QLocale::setDefault(QLocale::system());
 }
 
 void tst_QString::number()
@@ -6594,14 +6595,14 @@ void tst_QString::arg_locale()
     QLocale l(QLocale::English, QLocale::UnitedKingdom);
     QString str("*%L1*%L2*");
 
-    QLocale::setDefault(l);
+    TransientDefaultLocale transient(l);
     QCOMPARE(str.arg(123456).arg(1234.56), QString::fromLatin1("*123,456*1,234.56*"));
 
     l.setNumberOptions(QLocale::OmitGroupSeparator);
-    QLocale::setDefault(l);
+    transient.revise(l);
     QCOMPARE(str.arg(123456).arg(1234.56), QString::fromLatin1("*123456*1234.56*"));
 
-    QLocale::setDefault(QLocale::C);
+    transient.revise(QLocale::C);
     QCOMPARE(str.arg(123456).arg(1234.56), QString::fromLatin1("*123456*1234.56*"));
 }
 
@@ -6615,7 +6616,7 @@ void tst_QString::toUpperLower_icu()
     QCOMPARE(s.toUpper(), QString::fromLatin1("I"));
     QCOMPARE(s.toLower(), QString::fromLatin1("i"));
 
-    QLocale::setDefault(QLocale(QLocale::Turkish, QLocale::Turkey));
+    TransientDefaultLocale transient(QLocale(QLocale::Turkish, QLocale::Turkey));
 
     QCOMPARE(s.toUpper(), QString::fromLatin1("I"));
     QCOMPARE(s.toLower(), QString::fromLatin1("i"));
@@ -6639,8 +6640,6 @@ void tst_QString::toUpperLower_icu()
     // nothing should happen here
     QCOMPARE(l.toLower(sup), sup);
     QCOMPARE(l.toLower(QString::fromLatin1("i")), QString::fromLatin1("i"));
-
-    // the cleanup function will restore the default locale
 }
 #endif