Fix crashes when cyclic inheritance

Task-number: QTCREATORBUG-7933

Change-Id: I98469a092ff3ff0acc69800e9aade4ebb268332a
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/libs/cplusplus/LookupContext.cpp

@@ -708,11 +708,22 @@ ClassOrNamespace *ClassOrNamespace::nestedType(const Name *name, ClassOrNamespac
     if (!referenceClass)
         return reference;
 
+    const TemplateNameId *templId = name->asTemplateNameId();
+    if (_alreadyConsideredClasses.contains(referenceClass) ||
+            (templId &&
+            _alreadyConsideredTemplates.contains(templId))) {
+            return reference;
+    }
+
+    if (!name->isTemplateNameId())
+        _alreadyConsideredClasses.insert(referenceClass);
+
     QSet<ClassOrNamespace *> knownUsings = reference->usings().toSet();
 
     // If we are dealling with a template type, more work is required, since we need to
     // construct all instantiation data.
-    if (const TemplateNameId *templId = name->asTemplateNameId()) {
+    if (templId) {
+        _alreadyConsideredTemplates.insert(templId);
         ClassOrNamespace *instantiation = _factory->allocClassOrNamespace(reference);
         instantiation->_templateId = templId;
         instantiation->_instantiationOrigin = origin;
@@ -786,6 +797,7 @@ ClassOrNamespace *ClassOrNamespace::nestedType(const Name *name, ClassOrNamespac
             }
         }
 
+        _alreadyConsideredTemplates.clear(templId);
         return instantiation;
     }
 
@@ -828,6 +840,7 @@ ClassOrNamespace *ClassOrNamespace::nestedType(const Name *name, ClassOrNamespac
         }
     }
 
+    _alreadyConsideredClasses.clear(referenceClass);
     return reference;
 }
 

src/libs/cplusplus/LookupContext.h

@@ -45,6 +45,33 @@
 namespace CPlusPlus {
 
 class CreateBindings;
+class Class;
+template<typename T>
+class AlreadyConsideredClassContainer
+{
+public:
+    AlreadyConsideredClassContainer() : _class(0) {}
+    void insert(const T *item)
+    {
+        if (_container.isEmpty())
+            _class = item;
+        _container.insert(item);
+    }
+    bool contains(const T *item)
+    {
+        return _container.contains(item);
+    }
+
+    void clear(const T *item)
+    {
+        if (_class != item)
+            _container.clear();
+    }
+
+private:
+    QSet<const T *> _container;
+    const T * _class;
+};
 
 class CPLUSPLUS_EXPORT ClassOrNamespace
 {
@@ -112,6 +139,9 @@ private:
     const TemplateNameId *_templateId;
     ClassOrNamespace *_instantiationOrigin;
 
+    AlreadyConsideredClassContainer<Class> _alreadyConsideredClasses;
+    AlreadyConsideredClassContainer<TemplateNameId> _alreadyConsideredTemplates;
+
     friend class CreateBindings;
 };