QSqlField: add move ctor & move operator

Add the move ctor and move operator for QSqlField

Task-number: QTBUG-109938
Change-Id: Ib66eff76c3a920de9cfb3288f4219555005e7ae5
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/sql/kernel/qsqlfield.cpp

@@ -2,36 +2,20 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qsqlfield.h"
-#include "qatomic.h"
 #include "qdebug.h"
 
 QT_BEGIN_NAMESPACE
 
-class QSqlFieldPrivate
+class QSqlFieldPrivate : public QSharedData
 {
 public:
     QSqlFieldPrivate(const QString &name,
                      QMetaType type, const QString &tableName) :
-        ref(1), nm(name), table(tableName), def(QVariant()), type(type),
+        nm(name), table(tableName), def(QVariant()), type(type),
         req(QSqlField::Unknown), len(-1), prec(-1), tp(-1),
         ro(false), gen(true), autoval(false)
     {}
 
-    QSqlFieldPrivate(const QSqlFieldPrivate &other)
-        : ref(1),
-          nm(other.nm),
-          table(other.table),
-          def(other.def),
-          type(other.type),
-          req(other.req),
-          len(other.len),
-          prec(other.prec),
-          tp(other.tp),
-          ro(other.ro),
-          gen(other.gen),
-          autoval(other.autoval)
-    {}
-
     bool operator==(const QSqlFieldPrivate& other) const
     {
         return (nm == other.nm
@@ -46,7 +30,6 @@ public:
                 && autoval == other.autoval);
     }
 
-    QAtomicInt ref;
     QString nm;
     QString table;
     QVariant def;
@@ -59,6 +42,7 @@ public:
     bool gen: 1;
     bool autoval: 1;
 };
+QT_DEFINE_QESDP_SPECIALIZATION_DTOR(QSqlFieldPrivate)
 
 
 /*!
@@ -151,23 +135,14 @@ QSqlField::QSqlField(const QString &fieldName, QMetaType type, const QString &ta
 */
 
 QSqlField::QSqlField(const QSqlField &other)
-    : val(other.val),
-      d(other.d)
-{
-    d->ref.ref();
-}
+    = default;
 
 /*!
     Sets the field equal to \a other.
 */
 
 QSqlField& QSqlField::operator=(const QSqlField& other)
-{
-    qAtomicAssign(d, other.d);
-    val = other.val;
-    return *this;
-}
-
+    = default;
 
 /*! \fn bool QSqlField::operator!=(const QSqlField &other) const
     Returns \c true if the field is unequal to \a other; otherwise returns
@@ -189,10 +164,7 @@ bool QSqlField::operator==(const QSqlField& other) const
 */
 
 QSqlField::~QSqlField()
-{
-    if (!d->ref.deref())
-        delete d;
-}
+    = default;
 
 /*!
     Sets the required status of this field to \a required.
@@ -426,7 +398,7 @@ bool QSqlField::isNull() const
 */
 void QSqlField::detach()
 {
-    qAtomicDetach(d);
+    d.detach();
 }
 
 /*!

src/sql/kernel/qsqlfield.h

@@ -5,6 +5,7 @@
 #define QSQLFIELD_H
 
 #include <QtSql/qtsqlglobal.h>
+#include <QtCore/qshareddata.h>
 #include <QtCore/qvariant.h>
 #include <QtCore/qstring.h>
 
@@ -12,6 +13,7 @@ QT_BEGIN_NAMESPACE
 
 
 class QSqlFieldPrivate;
+QT_DECLARE_QESDP_SPECIALIZATION_DTOR_WITH_EXPORT(QSqlFieldPrivate, Q_SQL_EXPORT)
 
 class Q_SQL_EXPORT QSqlField
 {
@@ -22,9 +24,14 @@ public:
 
     QSqlField(const QSqlField& other);
     QSqlField& operator=(const QSqlField& other);
+    QSqlField(QSqlField &&other) noexcept = default;
+    QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QSqlField)
+    ~QSqlField();
+
+    void swap(QSqlField &other) noexcept { val.swap(other.val); d.swap(other.d); }
+
     bool operator==(const QSqlField& other) const;
     inline bool operator!=(const QSqlField &other) const { return !operator==(other); }
-    ~QSqlField();
 
     void setValue(const QVariant& value);
     inline QVariant value() const
@@ -76,8 +83,9 @@ public:
 
 private:
     void detach();
+    // ### Qt7: move to private class
     QVariant val;
-    QSqlFieldPrivate* d;
+    QExplicitlySharedDataPointer<QSqlFieldPrivate> d;
 };
 
 #ifndef QT_NO_DEBUG_STREAM

tests/auto/sql/kernel/qsqlfield/tst_qsqlfield.cpp

@@ -39,6 +39,7 @@ private slots:
     void clear();
     void setTableName_data();
     void setTableName();
+    void moveSemantics();
 };
 
 // Testing get/set functions
@@ -344,5 +345,24 @@ void tst_QSqlField::setTableName()
     QCOMPARE(field.tableName(), tableName);
 }
 
+void tst_QSqlField::moveSemantics()
+{
+    QSqlField field("test", QMetaType(QMetaType::QString), "testTable");
+    QSqlField empty;
+    field.setValue("string");
+    auto moved = std::move(field);
+    // `field` is now partially-formed
+
+    // moving transfers state:
+    QCOMPARE(moved.value().toString(), QLatin1String("string"));
+
+    // moved-from objects can be assigned-to:
+    field = empty;
+    QVERIFY(field.value().isNull());
+
+    // moved-from object can be destroyed:
+    moved = std::move(field);
+}
+
 QTEST_MAIN(tst_QSqlField)
 #include "tst_qsqlfield.moc"