Don't leak memory when canceling Type Hierarchy

Add QFutureSynchronizer for collecting all running
futures (including those already canceled, but not finished yet).
It could happen, that we cancel the future, while
the associated task still needs some time in order
to catch the cancel request. When a d'tor of synchronizer
is run it cancels and waits for all pending futures
to be finished.

Add extra check for isCanceled() after a call to
updateDependencyTable(). In case the cancel was detected
inside updateDependencyTable(), we should return immediately.

Don't leak CppClass object inside handleLookupItemMatch()
when the task was canceled.

Amends: c400923308f5c4df4e8d96a04d12dc54322f7ade

Change-Id: I709e14a0c8b563d522a8e8c32b087e5f83310b24
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/plugins/cpptools/cppelementevaluator.cpp b/src/plugins/cpptools/cppelementevaluator.cpp
index 208f75433d..0e739ddeab 100644
--- a/src/plugins/cpptools/cppelementevaluator.cpp
+++ b/src/plugins/cpptools/cppelementevaluator.cpp
@@ -214,6 +214,8 @@ void CppClass::lookupDerived(QFutureInterfaceBase &futureInterface,
     using Data = QPair<CppClass*, CppTools::TypeHierarchy>;
 
     snapshot.updateDependencyTable(futureInterface);
+    if (futureInterface.isCanceled())
+        return;
     CppTools::TypeHierarchyBuilder builder(declaration, snapshot);
     const CppTools::TypeHierarchy &completeHierarchy = builder.buildDerivedTypeHierarchy(futureInterface);
 
@@ -531,7 +533,7 @@ static void handleLookupItemMatch(QFutureInterface<QSharedPointer<CppElement>> &
 
             if (futureInterface.isCanceled())
                 return;
-            auto cppClass = new CppClass(declaration);
+            QSharedPointer<CppClass> cppClass(new CppClass(declaration));
             if (lookupBaseClasses)
                 cppClass->lookupBases(futureInterface, declaration, contextToUse);
             if (futureInterface.isCanceled())
@@ -540,7 +542,7 @@ static void handleLookupItemMatch(QFutureInterface<QSharedPointer<CppElement>> &
                 cppClass->lookupDerived(futureInterface, declaration, snapshot);
             if (futureInterface.isCanceled())
                 return;
-            element = QSharedPointer<CppElement>(cppClass);
+            element = cppClass;
         } else if (Enum *enumDecl = declaration->asEnum()) {
             element = QSharedPointer<CppElement>(new CppEnum(enumDecl));
         } else if (auto enumerator = dynamic_cast<EnumeratorDeclaration *>(declaration)) {