Cleanup QVariant::PrivateShared

Remove the additional indirection through ptr and replace
it with an offset calculation. Get rid of PrivateSharedEx
that was handling certain types differently.

This also fixes the support for overaligned types, by
using the alignment field from QMetaType to determine
the alignment requirements.

Change-Id: Icc6a78eb57f664c7747450578fe58dfee8f2863b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 15 insertions, 23 deletions

diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index a6b383d359..3c15287d12 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -229,13 +229,13 @@ static qlonglong qConvertToNumber(const QVariant::Private *d, bool *ok, bool all
         || d->type().id() == QMetaType::QCborSimpleType) {
         switch (typeInfo.sizeOf()) {
         case 1:
-            return d->is_shared ? *reinterpret_cast<signed char *>(d->data.shared->ptr) : d->data.sc;
+            return d->is_shared ? *reinterpret_cast<signed char *>(d->data.shared->data()) : d->data.sc;
         case 2:
-            return d->is_shared ? *reinterpret_cast<qint16 *>(d->data.shared->ptr) : d->data.s;
+            return d->is_shared ? *reinterpret_cast<qint16 *>(d->data.shared->data()) : d->data.s;
         case 4:
-            return d->is_shared ? *reinterpret_cast<qint32 *>(d->data.shared->ptr) : d->data.i;
+            return d->is_shared ? *reinterpret_cast<qint32 *>(d->data.shared->data()) : d->data.i;
         case 8:
-            return d->is_shared ? *reinterpret_cast<qint64 *>(d->data.shared->ptr) : d->data.ll;
+            return d->is_shared ? *reinterpret_cast<qint64 *>(d->data.shared->data()) : d->data.ll;
         }
     }
 
@@ -317,13 +317,13 @@ static qulonglong qConvertToUnsignedNumber(const QVariant::Private *d, bool *ok)
     if (typeInfo.flags() & QMetaType::IsEnumeration) {
         switch (typeInfo.sizeOf()) {
         case 1:
-            return d->is_shared ? *reinterpret_cast<uchar *>(d->data.shared->ptr) : d->data.uc;
+            return d->is_shared ? *reinterpret_cast<uchar *>(d->data.shared->data()) : d->data.uc;
         case 2:
-            return d->is_shared ? *reinterpret_cast<quint16 *>(d->data.shared->ptr) : d->data.us;
+            return d->is_shared ? *reinterpret_cast<quint16 *>(d->data.shared->data()) : d->data.us;
         case 4:
-            return d->is_shared ? *reinterpret_cast<quint32 *>(d->data.shared->ptr) : d->data.u;
+            return d->is_shared ? *reinterpret_cast<quint32 *>(d->data.shared->data()) : d->data.u;
         case 8:
-            return d->is_shared ? *reinterpret_cast<qint64 *>(d->data.shared->ptr) : d->data.ull;
+            return d->is_shared ? *reinterpret_cast<qint64 *>(d->data.shared->data()) : d->data.ull;
         }
     }
 
@@ -345,7 +345,7 @@ inline bool qt_convertToBool(const QVariant::Private *const d)
 
 static const void *constData(const QVariant::Private &d)
 {
-    return d.is_shared ? d.data.shared->ptr : reinterpret_cast<const void *>(&d.data.c);
+    return d.is_shared ? d.data.shared->data() : reinterpret_cast<const void *>(&d.data.c);
 }
 
 #ifndef QT_NO_QOBJECT
@@ -1402,16 +1402,9 @@ static void customConstruct(QVariant::Private *d, const void *copy)
         type.construct(&d->data, copy);
         d->is_shared = false;
     } else {
-        // Private::Data contains long long, and long double is the biggest standard type.
-        const size_t maxAlignment =
-            qMax(alignof(QVariant::Private::Data), alignof(long double));
-        const size_t s = sizeof(QVariant::PrivateShared);
-        const size_t offset = s + ((s * maxAlignment - s) % maxAlignment);
-        void *data = operator new(offset + size);
-        void *ptr = static_cast<char *>(data) + offset;
-        type.construct(ptr, copy);
+        d->data.shared = QVariant::PrivateShared::create(type);
+        type.construct(d->data.shared->data(), copy);
         d->is_shared = true;
-        d->data.shared = new (data) QVariant::PrivateShared(ptr);
     }
     // need to check for nullptr_t here, as this can get called by fromValue(nullptr). fromValue() uses
     // std::addressof(value) which in this case returns the address of the nullptr object.
@@ -1423,9 +1416,8 @@ static void customClear(QVariant::Private *d)
     if (!d->is_shared) {
         d->type().destruct(&d->data);
     } else {
-        d->type().destruct(d->data.shared->ptr);
-        d->data.shared->~PrivateShared();
-        operator delete(d->data.shared);
+        d->type().destruct(d->data.shared->data());
+        QVariant::PrivateShared::free(d->data.shared);
     }
 }
 
@@ -3885,7 +3877,7 @@ bool QVariant::equals(const QVariant &v) const
 
 const void *QVariant::constData() const
 {
-    return d.is_shared ? d.data.shared->ptr : reinterpret_cast<const void *>(&d.data);
+    return d.is_shared ? d.data.shared->data() : reinterpret_cast<const void *>(&d.data);
 }
 
 /*!
@@ -3922,7 +3914,7 @@ bool QVariant::isNull() const
     if (d.is_null || !metaType().isValid())
         return true;
     if (metaType().flags() & QMetaType::IsPointer) {
-        const void *d_ptr = d.is_shared ? d.data.shared->ptr : &(d.data);
+        const void *d_ptr = d.is_shared ? d.data.shared->data() : &(d.data);
         return *static_cast<void *const *>(d_ptr) == nullptr;
     }
     return false;