QtQml: Extract method to create the inline storage for Sequence

We will get a different kind of storage in addition.

The unification of the different init() methods uncovers a bug: The
storage can indeed be nullptr when querying the size later. If you
construct a detached sequence from a null container, there is no reason
to create the internal storage. The size is evidently 0 in that case.
Fix sizeInline() to tell us as much.

Pick-to: 6.8
Task-number: QTBUG-129972
Task-number: QTBUG-139025
Change-Id: I33347805fc79f81c69c3191a76ff9167186b43f0
Reviewed-by: Olivier De Cannière <olivier.decanniere@qt.io>
(cherry picked from commit 706e479e3b7a71f070ef6c05f00143e1842f2ec8)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 06d100df8dfbadbbe6877d7c010e28c2ab50ccf4)

2 files changed, 20 insertions, 9 deletions

diff --git a/src/qml/jsruntime/qv4sequenceobject.cpp b/src/qml/jsruntime/qv4sequenceobject.cpp
index ae0ab27371..d9744dac14 100644
--- a/src/qml/jsruntime/qv4sequenceobject.cpp
+++ b/src/qml/jsruntime/qv4sequenceobject.cpp
@@ -80,8 +80,13 @@ static void generateWarning(QV4::ExecutionEngine *v4, const QString& description
 
 static qsizetype sizeInline(const Heap::Sequence *p)
 {
-    Q_ASSERT(p->storagePointer()); // Must readReference() before
-    return p->metaSequence().size(p->storagePointer());
+    if (const void *container = p->storagePointer())
+        return p->metaSequence().size(container);
+
+    // It can be stored inline, and the container can still be nullptr.
+    // This happens if we construct it from a nullptr in the first place and never update it.
+    // It means it's empty.
+    return 0;
 }
 
 struct SequenceOwnPropertyKeyIterator : ObjectOwnPropertyKeyIterator
@@ -121,16 +126,13 @@ void Heap::Sequence::initTypes(QMetaType listType, QMetaSequence metaSequence)
     Q_ASSERT(m_listType);
     m_metaSequence = metaSequence.iface();
     Q_ASSERT(m_metaSequence);
-    QV4::Scope scope(internalClass->engine);
-    QV4::Scoped<QV4::Sequence> o(scope, this);
-    o->setArrayType(Heap::ArrayData::Custom);
 }
 
 void Heap::Sequence::init(QMetaType listType, QMetaSequence metaSequence, const void *container)
 {
     ReferenceObject::init(nullptr, -1, NoFlag);
     initTypes(listType,  metaSequence);
-    m_container = listType.create(container);
+    createInlineStorage(container);
 }
 
 void Heap::Sequence::init(
@@ -142,12 +144,20 @@ void Heap::Sequence::init(
 
     if (CppStackFrame *frame = internalClass->engine->currentStackFrame)
         setLocation(frame->v4Function, frame->statementNumber());
-    if (container)
-        m_container = listType.create(container);
-    else if (flags & EnforcesLocation)
+    createInlineStorage(container);
+    if (!container && (flags & EnforcesLocation))
         QV4::ReferenceObject::readReference(this);
 }
 
+void Heap::Sequence::createInlineStorage(const void *container)
+{
+    QV4::Scope scope(internalClass->engine);
+    QV4::Scoped<QV4::Sequence> o(scope, this);
+    o->setArrayType(Heap::ArrayData::Custom);
+    if (container)
+        m_container = listType().create(container);
+}
+
 Heap::Sequence *Heap::Sequence::detached() const
 {
     return internalClass->engine->memoryManager->allocate<QV4::Sequence>(
diff --git a/src/qml/jsruntime/qv4sequenceobject_p.h b/src/qml/jsruntime/qv4sequenceobject_p.h
index fb9e9ff5ea..a3d920c144 100644
--- a/src/qml/jsruntime/qv4sequenceobject_p.h
+++ b/src/qml/jsruntime/qv4sequenceobject_p.h
@@ -96,6 +96,7 @@ private:
     friend struct QV4::SequenceOwnPropertyKeyIterator;
 
     void initTypes(QMetaType listType, QMetaSequence metaSequence);
+    void createInlineStorage(const void *container);
 
     bool loadReference();
     bool storeReference();