Fix excessive memory usage in ModuleMerger.

No need to clone the prototype item for every single list property.

Change-Id: Iccde5172aa093ca1df25d93fbf3c336ed3445ab0
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

2 files changed, 12 insertions, 9 deletions

diff --git a/src/lib/corelib/language/modulemerger.cpp b/src/lib/corelib/language/modulemerger.cpp
index b32361b79..85405d21a 100644
--- a/src/lib/corelib/language/modulemerger.cpp
+++ b/src/lib/corelib/language/modulemerger.cpp
@@ -193,7 +193,7 @@ void ModuleMerger::pullListProperties(Item::PropertyMap *dst, Item *instance)
 }
 
 void ModuleMerger::appendPrototypeValueToNextChain(Item *moduleProto, const QString &propertyName,
-        const ValuePtr &sv) const
+        const ValuePtr &sv)
 {
     const PropertyDeclaration pd = m_mergedModuleItem->propertyDeclaration(propertyName);
     if (pd.isScalar())
@@ -201,14 +201,16 @@ void ModuleMerger::appendPrototypeValueToNextChain(Item *moduleProto, const QStr
     ValuePtr protoValue = moduleProto->property(propertyName);
     if (!protoValue)
         return;
-    Item * const clonedModulePrototype = moduleProto->clone();
-    Item * const scope = Item::create(clonedModulePrototype->pool());
-    scope->setFile(clonedModulePrototype->file());
-    m_mergedModuleItem->scope()->copyProperty(QLatin1String("project"), scope);
-    m_mergedModuleItem->scope()->copyProperty(QLatin1String("product"), scope);
-    clonedModulePrototype->setScope(scope);
+    if (!m_clonedModulePrototype) {
+        m_clonedModulePrototype = moduleProto->clone();
+        Item * const scope = Item::create(m_clonedModulePrototype->pool());
+        scope->setFile(m_clonedModulePrototype->file());
+        m_mergedModuleItem->scope()->copyProperty(QLatin1String("project"), scope);
+        m_mergedModuleItem->scope()->copyProperty(QLatin1String("product"), scope);
+        m_clonedModulePrototype->setScope(scope);
+    }
     const ValuePtr clonedValue = protoValue->clone();
-    clonedValue->setDefiningItem(clonedModulePrototype);
+    clonedValue->setDefiningItem(m_clonedModulePrototype);
     lastInNextChain(sv)->setNext(clonedValue);
 }
 
diff --git a/src/lib/corelib/language/modulemerger.h b/src/lib/corelib/language/modulemerger.h
index 3b417191b..32614bc18 100644
--- a/src/lib/corelib/language/modulemerger.h
+++ b/src/lib/corelib/language/modulemerger.h
@@ -54,12 +54,13 @@ private:
     void mergeOutProps(Item::PropertyMap *dst, const Item::PropertyMap &src);
     void pullListProperties(Item::PropertyMap *dst, Item *instance);
     void appendPrototypeValueToNextChain(Item *moduleProto, const QString &propertyName,
-            const ValuePtr &sv) const;
+            const ValuePtr &sv);
     static ValuePtr lastInNextChain(const ValuePtr &v);
 
     const Logger &m_logger;
     Item * const m_rootItem;
     Item *m_mergedModuleItem;
+    Item *m_clonedModulePrototype = nullptr;
     const QualifiedId m_moduleName;
     QHash<ValuePtr, PropertyDeclaration> m_decls;
     QSet<const Item *> m_seenInstancesTopDown;