Clang: Fix crash after cancelled completion request

Amends

  commit 755de9f86a
  Editor: delete processor after canceling

Ensure to update the bookkeeping in BackendReceiver on

  CodeAssistantPrivate::cancelCurrentRequest()

as otherwise we run into a use-after-free.

Change-Id: Ic5abdc9d743dc0b76eb050a9e3e00f85d2c5bc96
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangbackendcommunicator.cpp

@@ -513,5 +513,10 @@ void BackendCommunicator::requestCompletions(ClangCompletionAssistProcessor *ass
     m_receiver.addExpectedCompletionsMessage(message.ticketNumber, assistProcessor);
 }
 
+void BackendCommunicator::cancelCompletions(TextEditor::IAssistProcessor *processor)
+{
+    m_receiver.cancelProcessor(processor);
+}
+
 } // namespace Internal
 } // namespace ClangCodeModel

src/plugins/clangcodemodel/clangbackendcommunicator.h

@@ -43,6 +43,8 @@ class IEditor;
 class IDocument;
 }
 
+namespace TextEditor { class IAssistProcessor; }
+
 namespace ClangCodeModel {
 namespace Internal {
 
@@ -88,6 +90,7 @@ public:
                             quint32 column,
                             qint32 funcNameStartLine = -1,
                             qint32 funcNameStartColumn = -1);
+    void cancelCompletions(TextEditor::IAssistProcessor *processor);
     void requestAnnotations(const ClangBackEnd::FileContainer &fileContainer);
     QFuture<CppTools::CursorInfo> requestReferences(
             const FileContainer &fileContainer,

src/plugins/clangcodemodel/clangbackendreceiver.cpp

@@ -84,6 +84,18 @@ void BackendReceiver::addExpectedCompletionsMessage(
     m_assistProcessorsTable.insert(ticket, processor);
 }
 
+void BackendReceiver::cancelProcessor(TextEditor::IAssistProcessor *processor)
+{
+    for (auto it = m_assistProcessorsTable.cbegin(), end = m_assistProcessorsTable.cend();
+            it != end; ++it)
+    {
+        if (it.value() == processor) {
+            m_assistProcessorsTable.erase(it);
+            return;
+        }
+    }
+}
+
 void BackendReceiver::deleteProcessorsOfEditorWidget(TextEditor::TextEditorWidget *textEditorWidget)
 {
     QList<quint64> toRemove;

src/plugins/clangcodemodel/clangbackendreceiver.h

@@ -35,7 +35,10 @@
 #include <QPointer>
 #include <QTextDocument>
 
-namespace TextEditor { class TextEditorWidget; }
+namespace TextEditor {
+class IAssistProcessor;
+class TextEditorWidget;
+} // namespace TextEditor
 
 namespace ClangCodeModel {
 namespace Internal {
@@ -52,6 +55,7 @@ public:
     void setAliveHandler(const AliveHandler &handler);
 
     void addExpectedCompletionsMessage(quint64 ticket, ClangCompletionAssistProcessor *processor);
+    void cancelProcessor(TextEditor::IAssistProcessor *processor);
     void deleteProcessorsOfEditorWidget(TextEditor::TextEditorWidget *textEditorWidget);
 
     QFuture<CppTools::CursorInfo>

src/plugins/clangcodemodel/clangcompletionassistprocessor.cpp

@@ -697,6 +697,10 @@ IAssistProposal *ClangCompletionAssistProcessor::createFunctionHintProposal(
     return new FunctionHintProposal(m_positionForProposal, model);
 }
 
+void ClangCompletionAssistProcessor::cancel()
+{
+    m_interface->communicator().cancelCompletions(this);
+}
+
 } // namespace Internal
 } // namespace ClangCodeModel
-

src/plugins/clangcodemodel/clangcompletionassistprocessor.h

@@ -56,6 +56,7 @@ public:
     const TextEditor::TextEditorWidget *textEditorWidget() const;
 
 private:
+    void cancel() override;
     TextEditor::IAssistProposal *startCompletionHelper();
     int startOfOperator(int pos, unsigned *kind, bool wantFunctionCall) const;
     int findStartOfName(int pos = -1) const;