QVariant: make many more QtCore types nothrow-copyable

All of those are implicitly-shared Qt data types whose copy constructors
can't throw and have wide contracts (there aren't even any assertions
for validity in any of them). These are all types with a QVariant
implicit constructor, except for QCborValue, which is updated on this
list so QJsonValue (which has a QVariant constructor) is also
legitimately noexcept.

To ensure we haven't made a mistake, the Private constructor checks
again.

Change-Id: I3859764fed084846bcb0fffd17044d8319a45e1f
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

18 files changed, 71 insertions, 94 deletions

diff --git a/src/corelib/io/qurl.cpp b/src/corelib/io/qurl.cpp
index c3122e27f2..14d89a9ea8 100644
--- a/src/corelib/io/qurl.cpp
+++ b/src/corelib/io/qurl.cpp
@@ -1837,7 +1837,7 @@ QUrl::QUrl() : d(nullptr)
 /*!
     Constructs a copy of \a other.
 */
-QUrl::QUrl(const QUrl &other) : d(other.d)
+QUrl::QUrl(const QUrl &other) noexcept : d(other.d)
 {
     if (d)
         d->ref.ref();
@@ -3227,7 +3227,7 @@ bool QUrl::operator !=(const QUrl &url) const
 /*!
     Assigns the specified \a url to this object.
 */
-QUrl &QUrl::operator =(const QUrl &url)
+QUrl &QUrl::operator =(const QUrl &url) noexcept
 {
     if (!d) {
         if (url.d) {
diff --git a/src/corelib/io/qurl.h b/src/corelib/io/qurl.h
index 918c3e5831..7922149bd8 100644
--- a/src/corelib/io/qurl.h
+++ b/src/corelib/io/qurl.h
@@ -143,8 +143,8 @@ public:
 #endif
 
     QUrl();
-    QUrl(const QUrl &copy);
-    QUrl &operator =(const QUrl &copy);
+    QUrl(const QUrl &copy) noexcept;
+    QUrl &operator =(const QUrl &copy) noexcept;
 #ifdef QT_NO_URL_CAST_FROM_STRING
     explicit QUrl(const QString &url, ParsingMode mode = TolerantMode);
 #else
diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index 1b37e689f5..be7be78d51 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -335,13 +335,21 @@ template <typename T> inline
 QVariant::Private::Private(std::piecewise_construct_t, const T &t)
     : is_shared(!CanUseInternalSpace<T>), is_null(std::is_same_v<T, std::nullptr_t>)
 {
+    // confirm noexceptness
+    static constexpr bool isNothrowQVariantConstructible = noexcept(QVariant(t));
+    static constexpr bool isNothrowCopyConstructible = std::is_nothrow_copy_constructible_v<T>;
+    static constexpr bool isNothrowCopyAssignable = std::is_nothrow_copy_assignable_v<T>;
+
     const QtPrivate::QMetaTypeInterface *iface = QtPrivate::qMetaTypeInterfaceForType<T>();
     Q_ASSERT((quintptr(iface) & 0x3) == 0);
     packedType = quintptr(iface) >> 2;
 
     if constexpr (CanUseInternalSpace<T>) {
+        static_assert(isNothrowQVariantConstructible == isNothrowCopyConstructible);
+        static_assert(isNothrowQVariantConstructible == isNothrowCopyAssignable);
         new (data.data) T(t);
     } else {
+        static_assert(!isNothrowQVariantConstructible); // we allocate memory, even if T doesn't
         data.shared = QVariant::PrivateShared::create(QtPrivate::qMetaTypeInterfaceForType<T>());
         new (data.shared->data()) T(t);
     }
@@ -705,7 +713,7 @@ QVariant::QVariant(const QVariant &p)
 */
 
 /*!
-  \fn QVariant::QVariant(const QBitArray &val)
+  \fn QVariant::QVariant(const QBitArray &val) noexcept
 
     Constructs a new variant with a bitarray value, \a val.
 */
@@ -759,7 +767,7 @@ QVariant::QVariant(const QVariant &p)
  */
 
 /*!
-  \fn QVariant::QVariant(const QUrl &val)
+  \fn QVariant::QVariant(const QUrl &val) noexcept
 
   Constructs a new variant with a url value of \a val.
  */
@@ -821,13 +829,13 @@ QVariant::QVariant(const QVariant &p)
 */
 
 /*!
-  \fn QVariant::QVariant(const QLocale &l)
+  \fn QVariant::QVariant(const QLocale &l) noexcept
 
   Constructs a new variant with a locale value, \a l.
 */
 
 /*!
-  \fn QVariant::QVariant(const QRegularExpression &re)
+  \fn QVariant::QVariant(const QRegularExpression &re) noexcept
 
   \since 5.0
 
@@ -876,7 +884,7 @@ QVariant::QVariant(double val) noexcept : d(std::piecewise_construct_t{}, val) {
 QVariant::QVariant(float val) noexcept : d(std::piecewise_construct_t{}, val) {}
 
 QVariant::QVariant(const QByteArray &val) noexcept : d(std::piecewise_construct_t{}, val) {}
-QVariant::QVariant(const QBitArray &val) : d(std::piecewise_construct_t{}, val) {}
+QVariant::QVariant(const QBitArray &val) noexcept : d(std::piecewise_construct_t{}, val) {}
 QVariant::QVariant(const QString &val) noexcept : d(std::piecewise_construct_t{}, val) {}
 QVariant::QVariant(QChar val) noexcept : d(std::piecewise_construct_t{}, val) {}
 QVariant::QVariant(const QStringList &val) noexcept : d(std::piecewise_construct_t{}, val) {}
@@ -913,17 +921,19 @@ QVariant::QVariant(QSizeF s) noexcept(Private::FitsInInternalSize<sizeof(qreal)
     : d(std::piecewise_construct_t{}, s) {}
 #endif
 #ifndef QT_BOOTSTRAPPED
-QVariant::QVariant(const QUrl &u) : d(std::piecewise_construct_t{}, u) {}
+QVariant::QVariant(const QUrl &u) noexcept : d(std::piecewise_construct_t{}, u) {}
 #endif
-QVariant::QVariant(const QLocale &l) : d(std::piecewise_construct_t{}, l) {}
+QVariant::QVariant(const QLocale &l) noexcept : d(std::piecewise_construct_t{}, l) {}
 #if QT_CONFIG(regularexpression)
-QVariant::QVariant(const QRegularExpression &re) : d(std::piecewise_construct_t{}, re) {}
+QVariant::QVariant(const QRegularExpression &re) noexcept : d(std::piecewise_construct_t{}, re) {}
 #endif // QT_CONFIG(regularexpression)
 QVariant::QVariant(QUuid uuid) noexcept(Private::FitsInInternalSize<16>) : d(std::piecewise_construct_t{}, uuid) {}
 #ifndef QT_BOOTSTRAPPED
-QVariant::QVariant(const QJsonValue &jsonValue) : d(std::piecewise_construct_t{}, jsonValue) {}
-QVariant::QVariant(const QJsonObject &jsonObject) : d(std::piecewise_construct_t{}, jsonObject) {}
-QVariant::QVariant(const QJsonArray &jsonArray) : d(std::piecewise_construct_t{}, jsonArray) {}
+QVariant::QVariant(const QJsonValue &jsonValue) noexcept(Private::FitsInInternalSize<sizeof(CborValueStandIn)>)
+    : d(std::piecewise_construct_t{}, jsonValue)
+{ static_assert(sizeof(CborValueStandIn) == sizeof(QJsonValue)); }
+QVariant::QVariant(const QJsonObject &jsonObject) noexcept : d(std::piecewise_construct_t{}, jsonObject) {}
+QVariant::QVariant(const QJsonArray &jsonArray) noexcept : d(std::piecewise_construct_t{}, jsonArray) {}
 QVariant::QVariant(const QJsonDocument &jsonDocument) : d(std::piecewise_construct_t{}, jsonDocument) {}
 #endif // QT_BOOTSTRAPPED
 #if QT_CONFIG(itemmodel)
diff --git a/src/corelib/kernel/qvariant.h b/src/corelib/kernel/qvariant.h
index 7b45123fb6..3841fa5760 100644
--- a/src/corelib/kernel/qvariant.h
+++ b/src/corelib/kernel/qvariant.h
@@ -56,6 +56,7 @@ inline T qvariant_cast(const QVariant &);
 
 class Q_CORE_EXPORT QVariant
 {
+    struct CborValueStandIn { qint64 n; void *c; int t; };
 public:
     struct PrivateShared
     {
@@ -206,7 +207,7 @@ public:
     QVariant(float f) noexcept;
 
     QVariant(const QByteArray &bytearray) noexcept;
-    QVariant(const QBitArray &bitarray);
+    QVariant(const QBitArray &bitarray) noexcept;
     QVariant(const QString &string) noexcept;
     QVariant(const QStringList &stringlist) noexcept;
     QVariant(QChar qchar) noexcept;
@@ -226,19 +227,19 @@ public:
     QVariant(QRect rect) noexcept(Private::FitsInInternalSize<sizeof(int) * 4>);
     QVariant(QRectF rect) noexcept(Private::FitsInInternalSize<sizeof(qreal) * 4>);
 #endif
-    QVariant(const QLocale &locale);
+    QVariant(const QLocale &locale) noexcept;
 #if QT_CONFIG(regularexpression)
-    QVariant(const QRegularExpression &re);
+    QVariant(const QRegularExpression &re) noexcept;
 #endif // QT_CONFIG(regularexpression)
 #if QT_CONFIG(easingcurve)
     QVariant(const QEasingCurve &easing);
 #endif
     QVariant(QUuid uuid) noexcept(Private::FitsInInternalSize<16>);
 #ifndef QT_BOOTSTRAPPED
-    QVariant(const QUrl &url);
-    QVariant(const QJsonValue &jsonValue);
-    QVariant(const QJsonObject &jsonObject);
-    QVariant(const QJsonArray &jsonArray);
+    QVariant(const QUrl &url) noexcept;
+    QVariant(const QJsonValue &jsonValue) noexcept(Private::FitsInInternalSize<sizeof(CborValueStandIn)>);
+    QVariant(const QJsonObject &jsonObject) noexcept;
+    QVariant(const QJsonArray &jsonArray) noexcept;
     QVariant(const QJsonDocument &jsonDocument);
 #endif // QT_BOOTSTRAPPED
 #if QT_CONFIG(itemmodel)
diff --git a/src/corelib/serialization/qcborvalue.cpp b/src/corelib/serialization/qcborvalue.cpp
index 056e8c07b6..c136e80755 100644
--- a/src/corelib/serialization/qcborvalue.cpp
+++ b/src/corelib/serialization/qcborvalue.cpp
@@ -1805,7 +1805,7 @@ QCborValue::QCborValue(QCborTag tag, const QCborValue &tv)
 /*!
     Copies the contents of \a other into this object.
  */
-QCborValue::QCborValue(const QCborValue &other)
+QCborValue::QCborValue(const QCborValue &other) noexcept
     : n(other.n), container(other.container), t(other.t)
 {
     if (container)
@@ -1899,7 +1899,7 @@ void QCborValue::dispose()
 /*!
     Replaces the contents of this QCborObject with a copy of \a other.
  */
-QCborValue &QCborValue::operator=(const QCborValue &other)
+QCborValue &QCborValue::operator=(const QCborValue &other) noexcept
 {
     n = other.n;
     assignContainer(container, other.container);
diff --git a/src/corelib/serialization/qcborvalue.h b/src/corelib/serialization/qcborvalue.h
index a83a36a3d8..ff4a0fd104 100644
--- a/src/corelib/serialization/qcborvalue.h
+++ b/src/corelib/serialization/qcborvalue.h
@@ -139,12 +139,12 @@ public:
     // make sure const char* doesn't go call the bool constructor
     QCborValue(const void *) = delete;
 
-    QCborValue(const QCborValue &other);
+    QCborValue(const QCborValue &other) noexcept;
     QCborValue(QCborValue &&other) noexcept
         : n(other.n), container(qExchange(other.container, nullptr)), t(qExchange(other.t, Undefined))
     {
     }
-    QCborValue &operator=(const QCborValue &other);
+    QCborValue &operator=(const QCborValue &other) noexcept;
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QCborValue)
 
     void swap(QCborValue &other) noexcept
diff --git a/src/corelib/serialization/qjsonarray.cpp b/src/corelib/serialization/qjsonarray.cpp
index 167b6a3a77..33f4d51b5f 100644
--- a/src/corelib/serialization/qjsonarray.cpp
+++ b/src/corelib/serialization/qjsonarray.cpp
@@ -138,11 +138,13 @@ QJsonArray::QJsonArray(std::initializer_list<QJsonValue> args)
     Since QJsonArray is implicitly shared, the copy is shallow
     as long as the object doesn't get modified.
  */
-QJsonArray::QJsonArray(const QJsonArray &other)
-{
-    a = other.a;
-}
+QJsonArray::QJsonArray(const QJsonArray &other) noexcept = default;
+
+/*!
+    \since 5.10
 
+    Move-constructs a QJsonArray from \a other.
+*/
 QJsonArray::QJsonArray(QJsonArray &&other) noexcept
     : a(other.a)
 {
@@ -152,18 +154,7 @@ QJsonArray::QJsonArray(QJsonArray &&other) noexcept
 /*!
     Assigns \a other to this array.
  */
-QJsonArray &QJsonArray::operator =(const QJsonArray &other)
-{
-    a = other.a;
-    return *this;
-}
-
-/*!
-    \fn QJsonArray::QJsonArray(QJsonArray &&other)
-    \since 5.10
-
-    Move-constructs a QJsonArray from \a other.
-*/
+QJsonArray &QJsonArray::operator =(const QJsonArray &other) noexcept = default;
 
 /*!
     \fn QJsonArray &QJsonArray::operator =(QJsonArray &&other)
diff --git a/src/corelib/serialization/qjsonarray.h b/src/corelib/serialization/qjsonarray.h
index ec36d384f6..af4ac9fd37 100644
--- a/src/corelib/serialization/qjsonarray.h
+++ b/src/corelib/serialization/qjsonarray.h
@@ -23,8 +23,8 @@ public:
 
     ~QJsonArray();
 
-    QJsonArray(const QJsonArray &other);
-    QJsonArray &operator =(const QJsonArray &other);
+    QJsonArray(const QJsonArray &other) noexcept;
+    QJsonArray &operator =(const QJsonArray &other) noexcept;
 
     QJsonArray(QJsonArray &&other) noexcept;
 
diff --git a/src/corelib/serialization/qjsonobject.cpp b/src/corelib/serialization/qjsonobject.cpp
index 0a5bafd1cb..7737244a2c 100644
--- a/src/corelib/serialization/qjsonobject.cpp
+++ b/src/corelib/serialization/qjsonobject.cpp
@@ -122,11 +122,13 @@ QJsonObject::QJsonObject(std::initializer_list<QPair<QString, QJsonValue> > args
     Since QJsonObject is implicitly shared, the copy is shallow
     as long as the object does not get modified.
  */
-QJsonObject::QJsonObject(const QJsonObject &other)
-{
-    o = other.o;
-}
+QJsonObject::QJsonObject(const QJsonObject &other) noexcept = default;
 
+/*!
+    \since 5.10
+
+    Move-constructs a QJsonObject from \a other.
+*/
 QJsonObject::QJsonObject(QJsonObject &&other) noexcept
     : o(other.o)
 {
@@ -136,18 +138,8 @@ QJsonObject::QJsonObject(QJsonObject &&other) noexcept
 /*!
     Assigns \a other to this object.
  */
-QJsonObject &QJsonObject::operator =(const QJsonObject &other)
-{
-    o = other.o;
-    return *this;
-}
+QJsonObject &QJsonObject::operator =(const QJsonObject &other) noexcept = default;
 
-/*!
-    \fn QJsonObject::QJsonObject(QJsonObject &&other)
-    \since 5.10
-
-    Move-constructs a QJsonObject from \a other.
-*/
 
 /*!
     \fn QJsonObject &QJsonObject::operator =(QJsonObject &&other)
diff --git a/src/corelib/serialization/qjsonobject.h b/src/corelib/serialization/qjsonobject.h
index f5f4d1f47e..d7d3fe549b 100644
--- a/src/corelib/serialization/qjsonobject.h
+++ b/src/corelib/serialization/qjsonobject.h
@@ -25,8 +25,8 @@ public:
 
     ~QJsonObject();
 
-    QJsonObject(const QJsonObject &other);
-    QJsonObject &operator =(const QJsonObject &other);
+    QJsonObject(const QJsonObject &other) noexcept;
+    QJsonObject &operator =(const QJsonObject &other) noexcept;
 
     QJsonObject(QJsonObject &&other) noexcept;
 
diff --git a/src/corelib/serialization/qjsonvalue.cpp b/src/corelib/serialization/qjsonvalue.cpp
index ef07dcdc3b..5383addb70 100644
--- a/src/corelib/serialization/qjsonvalue.cpp
+++ b/src/corelib/serialization/qjsonvalue.cpp
@@ -247,15 +247,12 @@ QJsonValue::~QJsonValue() = default;
 /*!
     Creates a copy of \a other.
  */
-QJsonValue::QJsonValue(const QJsonValue &other)
-    : value(other.value)
-{
-}
+QJsonValue::QJsonValue(const QJsonValue &other) noexcept = default;
 
 /*!
     Assigns the value stored in \a other to this object.
  */
-QJsonValue &QJsonValue::operator =(const QJsonValue &other)
+QJsonValue &QJsonValue::operator =(const QJsonValue &other) noexcept
 {
     QJsonValue copy(other);
     swap(copy);
diff --git a/src/corelib/serialization/qjsonvalue.h b/src/corelib/serialization/qjsonvalue.h
index 3aecaa6126..dddc8a0c30 100644
--- a/src/corelib/serialization/qjsonvalue.h
+++ b/src/corelib/serialization/qjsonvalue.h
@@ -51,8 +51,8 @@ public:
 
     ~QJsonValue();
 
-    QJsonValue(const QJsonValue &other);
-    QJsonValue &operator =(const QJsonValue &other);
+    QJsonValue(const QJsonValue &other) noexcept;
+    QJsonValue &operator =(const QJsonValue &other) noexcept;
 
     QJsonValue(QJsonValue &&other) noexcept;
 
diff --git a/src/corelib/text/qlocale.cpp b/src/corelib/text/qlocale.cpp
index c42fa645c3..b19e4498d3 100644
--- a/src/corelib/text/qlocale.cpp
+++ b/src/corelib/text/qlocale.cpp
@@ -1072,10 +1072,7 @@ QLocale::QLocale(Language language, Script script, Territory territory)
     Constructs a QLocale object as a copy of \a other.
 */
 
-QLocale::QLocale(const QLocale &other)
-{
-    d = other.d;
-}
+QLocale::QLocale(const QLocale &other) noexcept = default;
 
 /*!
     Destructor
@@ -1090,11 +1087,7 @@ QLocale::~QLocale()
     to this QLocale object.
 */
 
-QLocale &QLocale::operator=(const QLocale &other)
-{
-    d = other.d;
-    return *this;
-}
+QLocale &QLocale::operator=(const QLocale &other) noexcept = default;
 
 /*!
     \internal
diff --git a/src/corelib/text/qlocale.h b/src/corelib/text/qlocale.h
index 599cd79232..72c98685fa 100644
--- a/src/corelib/text/qlocale.h
+++ b/src/corelib/text/qlocale.h
@@ -896,9 +896,9 @@ public:
     explicit QLocale(QStringView name);
     QLocale(Language language, Territory territory);
     QLocale(Language language, Script script = AnyScript, Territory territory = AnyTerritory);
-    QLocale(const QLocale &other);
+    QLocale(const QLocale &other) noexcept;
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QLocale)
-    QLocale &operator=(const QLocale &other);
+    QLocale &operator=(const QLocale &other) noexcept;
     ~QLocale();
 
     void swap(QLocale &other) noexcept { d.swap(other.d); }
diff --git a/src/corelib/text/qregularexpression.cpp b/src/corelib/text/qregularexpression.cpp
index f736f47059..2e5eabbbc8 100644
--- a/src/corelib/text/qregularexpression.cpp
+++ b/src/corelib/text/qregularexpression.cpp
@@ -1354,10 +1354,7 @@ QRegularExpression::QRegularExpression(const QString &pattern, PatternOptions op
 
     \sa operator=()
 */
-QRegularExpression::QRegularExpression(const QRegularExpression &re)
-    : d(re.d)
-{
-}
+QRegularExpression::QRegularExpression(const QRegularExpression &re) noexcept = default;
 
 /*!
     \fn QRegularExpression::QRegularExpression(QRegularExpression &&re)
@@ -1386,11 +1383,7 @@ QT_DEFINE_QESDP_SPECIALIZATION_DTOR(QRegularExpressionPrivate)
     Assigns the regular expression \a re to this object, and returns a reference
     to the copy. Both the pattern and the pattern options are copied.
 */
-QRegularExpression &QRegularExpression::operator=(const QRegularExpression &re)
-{
-    d = re.d;
-    return *this;
-}
+QRegularExpression &QRegularExpression::operator=(const QRegularExpression &re) noexcept = default;
 
 /*!
     \fn void QRegularExpression::swap(QRegularExpression &other)
diff --git a/src/corelib/text/qregularexpression.h b/src/corelib/text/qregularexpression.h
index fc0f1302e3..4f1ad8d13f 100644
--- a/src/corelib/text/qregularexpression.h
+++ b/src/corelib/text/qregularexpression.h
@@ -50,10 +50,10 @@ public:
 
     QRegularExpression();
     explicit QRegularExpression(const QString &pattern, PatternOptions options = NoPatternOption);
-    QRegularExpression(const QRegularExpression &re);
+    QRegularExpression(const QRegularExpression &re) noexcept;
     QRegularExpression(QRegularExpression &&re) = default;
     ~QRegularExpression();
-    QRegularExpression &operator=(const QRegularExpression &re);
+    QRegularExpression &operator=(const QRegularExpression &re) noexcept;
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QRegularExpression)
 
     void swap(QRegularExpression &other) noexcept { d.swap(other.d); }
diff --git a/src/corelib/tools/qbitarray.cpp b/src/corelib/tools/qbitarray.cpp
index ecd12d095c..5c48b3b608 100644
--- a/src/corelib/tools/qbitarray.cpp
+++ b/src/corelib/tools/qbitarray.cpp
@@ -453,7 +453,7 @@ quint32 QBitArray::toUInt32(QSysInfo::Endian endianness, bool *ok) const noexcep
     \overload
 */
 
-/*! \fn QBitArray::QBitArray(const QBitArray &other)
+/*! \fn QBitArray::QBitArray(const QBitArray &other) noexcept
 
     Constructs a copy of \a other.
 
@@ -465,7 +465,7 @@ quint32 QBitArray::toUInt32(QSysInfo::Endian endianness, bool *ok) const noexcep
     \sa operator=()
 */
 
-/*! \fn QBitArray &QBitArray::operator=(const QBitArray &other)
+/*! \fn QBitArray &QBitArray::operator=(const QBitArray &other) noexcept
 
     Assigns \a other to this bit array and returns a reference to
     this bit array.
diff --git a/src/corelib/tools/qbitarray.h b/src/corelib/tools/qbitarray.h
index 8e19725339..e724aea598 100644
--- a/src/corelib/tools/qbitarray.h
+++ b/src/corelib/tools/qbitarray.h
@@ -21,8 +21,8 @@ class Q_CORE_EXPORT QBitArray
 public:
     inline QBitArray() noexcept {}
     explicit QBitArray(qsizetype size, bool val = false);
-    QBitArray(const QBitArray &other) : d(other.d) {}
-    inline QBitArray &operator=(const QBitArray &other) { d = other.d; return *this; }
+    QBitArray(const QBitArray &other) noexcept : d(other.d) {}
+    inline QBitArray &operator=(const QBitArray &other) noexcept { d = other.d; return *this; }
     inline QBitArray(QBitArray &&other) noexcept : d(std::move(other.d)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QBitArray)