Reject overwrites by the same index in QPromise::addResult()

One can call addResult(value, index) twice and consequently set the
value twice by the same index. This seems rather strange and probably
should not be allowed. This commit rejects setting results when there's
already a valid result by that index. Consequently, this fixes memory
leaks caused by N-times-called addResult(..., index)

Fixes: QTBUG-86828
Change-Id: I77494f2cb73ce727ffad721cfcdcaa420899eb25
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

6 files changed, 244 insertions, 14 deletions

diff --git a/src/corelib/thread/qfutureinterface.h b/src/corelib/thread/qfutureinterface.h
index 6c7c511cc0..9296c63f0b 100644
--- a/src/corelib/thread/qfutureinterface.h
+++ b/src/corelib/thread/qfutureinterface.h
@@ -270,11 +270,12 @@ inline void QFutureInterface<T>::reportResult(const T *result, int index)
 
     if (store.filterMode()) {
         const int resultCountBefore = store.count();
-        store.addResult<T>(index, result);
-        this->reportResultsReady(resultCountBefore, store.count());
+        if (store.addResult<T>(index, result) != -1)
+            this->reportResultsReady(resultCountBefore, store.count());
     } else {
         const int insertIndex = store.addResult<T>(index, result);
-        this->reportResultsReady(insertIndex, insertIndex + 1);
+        if (insertIndex != -1)
+            this->reportResultsReady(insertIndex, insertIndex + 1);
     }
 }
 
@@ -289,7 +290,8 @@ void QFutureInterface<T>::reportAndMoveResult(T &&result, int index)
 
     const int oldResultCount = store.count();
     const int insertIndex = store.moveResult(index, std::forward<T>(result));
-    if (!store.filterMode() || oldResultCount < store.count()) // Let's make sure it's not in pending results.
+    // Let's make sure it's not in pending results.
+    if (insertIndex != -1 && (!store.filterMode() || oldResultCount < store.count()))
         reportResultsReady(insertIndex, store.count());
 }
 
@@ -317,11 +319,12 @@ inline void QFutureInterface<T>::reportResults(const QList<T> &_results, int beg
 
     if (store.filterMode()) {
         const int resultCountBefore = store.count();
-        store.addResults(beginIndex, &_results, count);
-        this->reportResultsReady(resultCountBefore, store.count());
+        if (store.addResults(beginIndex, &_results, count) != -1)
+            this->reportResultsReady(resultCountBefore, store.count());
     } else {
         const int insertIndex = store.addResults(beginIndex, &_results, count);
-        this->reportResultsReady(insertIndex, insertIndex + _results.count());
+        if (insertIndex != -1)
+            this->reportResultsReady(insertIndex, insertIndex + _results.count());
     }
 }
 
diff --git a/src/corelib/thread/qpromise.qdoc b/src/corelib/thread/qpromise.qdoc
index 9c7925da95..4b7b497b3f 100644
--- a/src/corelib/thread/qpromise.qdoc
+++ b/src/corelib/thread/qpromise.qdoc
@@ -112,6 +112,9 @@
     Adds \a result to the internal result collection at \a index position. If
     index is unspecified, \a result is added to the end of the collection.
 
+    \note addResult() rejects \a result if there's already another result in the
+    collection stored at the same index.
+
     You can get a result at a specific index by calling QFuture::resultAt().
 
     \note It is possible to specify an arbitrary index and request result at
diff --git a/src/corelib/thread/qresultstore.cpp b/src/corelib/thread/qresultstore.cpp
index b6af27dfa9..a239954dbe 100644
--- a/src/corelib/thread/qresultstore.cpp
+++ b/src/corelib/thread/qresultstore.cpp
@@ -144,6 +144,11 @@ bool ResultIteratorBase::canIncrementVectorIndex() const
     return (m_vectorIndex + 1 < mapIterator.value().m_count);
 }
 
+bool ResultIteratorBase::isValid() const
+{
+    return mapIterator.value().isValid();
+}
+
 ResultStoreBase::ResultStoreBase()
     : insertIndex(0), resultCount(0), m_filterMode(false), filteredResults(0) { }
 
@@ -196,6 +201,15 @@ int ResultStoreBase::insertResultItem(int index, ResultItem &resultItem)
     return storeIndex;
 }
 
+bool ResultStoreBase::containsValidResultItem(int index) const
+{
+    // index might refer to either visible or pending result
+    const bool inPending = m_filterMode && index != -1 && index > insertIndex;
+    const auto &store = inPending ? pendingResults : m_results;
+    auto it = findResult(store, index);
+    return it != ResultIteratorBase(store.end()) && it.isValid();
+}
+
 void ResultStoreBase::syncPendingResults()
 {
     // check if we can insert any of the pending results:
diff --git a/src/corelib/thread/qresultstore.h b/src/corelib/thread/qresultstore.h
index 5f8c7f150a..0a1382fd79 100644
--- a/src/corelib/thread/qresultstore.h
+++ b/src/corelib/thread/qresultstore.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -87,6 +87,8 @@ public:
     bool operator!=(const ResultIteratorBase &other) const;
     bool isVector() const;
     bool canIncrementVectorIndex() const;
+    bool isValid() const;
+
 protected:
     QMap<int, ResultItem>::const_iterator mapIterator;
     int m_vectorIndex;
@@ -139,6 +141,7 @@ public:
 protected:
     int insertResultItem(int index, ResultItem &resultItem);
     void insertResultItemIfValid(int index, ResultItem &resultItem);
+    bool containsValidResultItem(int index) const;
     void syncPendingResults();
     void syncResultCount();
     int updateInsertIndex(int index, int _count);
@@ -169,6 +172,9 @@ public:
     template <typename T>
     int addResult(int index, const T *result)
     {
+        if (containsValidResultItem(index)) // reject if already present
+            return -1;
+
         if (result == nullptr)
             return addResult(index, static_cast<void *>(nullptr));
 
@@ -178,18 +184,27 @@ public:
     template <typename T>
     int moveResult(int index, T &&result)
     {
+        if (containsValidResultItem(index)) // reject if already present
+            return -1;
+
         return addResult(index, static_cast<void *>(new T(std::move_if_noexcept(result))));
     }
 
     template<typename T>
     int addResults(int index, const QList<T> *results)
     {
+        if (containsValidResultItem(index)) // reject if already present
+            return -1;
+
         return addResults(index, new QList<T>(*results), results->count(), results->count());
     }
 
     template<typename T>
     int addResults(int index, const QList<T> *results, int totalCount)
     {
+        if (containsValidResultItem(index)) // reject if already present
+            return -1;
+
         if (m_filterMode == true && results->count() != totalCount && 0 == results->count())
             return addResults(index, nullptr, 0, totalCount);
 
@@ -198,12 +213,18 @@ public:
 
     int addCanceledResult(int index)
     {
+        if (containsValidResultItem(index)) // reject if already present
+            return -1;
+
         return addResult(index, static_cast<void *>(nullptr));
     }
 
     template <typename T>
     int addCanceledResults(int index, int _count)
     {
+        if (containsValidResultItem(index)) // reject if already present
+            return -1;
+
         QList<T> empty;
         return addResults(index, &empty, _count);
     }
diff --git a/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp b/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
index 23ff646fb7..99f2144528 100644
--- a/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
+++ b/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
@@ -149,6 +149,11 @@ private slots:
     void signalConnect();
     void waitForFinished();
 
+    void rejectResultOverwrite_data();
+    void rejectResultOverwrite();
+    void rejectPendingResultOverwrite_data() { rejectResultOverwrite_data(); }
+    void rejectPendingResultOverwrite();
+
 private:
     using size_type = std::vector<int>::size_type;
 
@@ -3109,5 +3114,182 @@ void tst_QFuture::waitForFinished()
     QVERIFY(waitingThread->isFinished());
 }
 
+void tst_QFuture::rejectResultOverwrite_data()
+{
+    QTest::addColumn<bool>("filterMode");
+    QTest::addColumn<QList<int>>("initResults");
+
+    QTest::addRow("filter-mode-on-1-result") << true << QList<int>({ 456 });
+    QTest::addRow("filter-mode-on-N-results") << true << QList<int>({ 456, 789 });
+    QTest::addRow("filter-mode-off-1-result") << false << QList<int>({ 456 });
+    QTest::addRow("filter-mode-off-N-results") << false << QList<int>({ 456, 789 });
+}
+
+void tst_QFuture::rejectResultOverwrite()
+{
+    QFETCH(bool, filterMode);
+    QFETCH(QList<int>, initResults);
+
+    QFutureInterface<int> iface;
+    iface.setFilterMode(filterMode);
+    auto f = iface.future();
+    QFutureWatcher<int> watcher;
+    watcher.setFuture(f);
+
+    QTestEventLoop eventProcessor;
+    // control the loop by suspend
+    connect(&watcher, &QFutureWatcher<int>::suspending, &eventProcessor, &QTestEventLoop::exitLoop);
+    // internal machinery always emits resultsReadyAt
+    QSignalSpy resultCounter(&watcher, &QFutureWatcher<int>::resultsReadyAt);
+
+    // init
+    if (initResults.size() == 1)
+        iface.reportResult(initResults[0]);
+    else
+        iface.reportResults(initResults);
+    QCOMPARE(f.resultCount(), initResults.size());
+    QCOMPARE(f.resultAt(0), initResults[0]);
+    QCOMPARE(f.results(), initResults);
+
+    QTimer::singleShot(50, [&f]() {
+        f.suspend(); // should exit the loop
+    });
+    // Run event loop, QCoreApplication::postEvent is in use
+    // in QFutureInterface:
+    eventProcessor.enterLoopMSecs(2000);
+    QVERIFY(!eventProcessor.timeout());
+    QCOMPARE(resultCounter.count(), 1);
+    f.resume();
+
+    // overwrite with lvalue
+    {
+        int result = -1;
+        const auto originalCount = f.resultCount();
+        iface.reportResult(result, 0);
+        QCOMPARE(f.resultCount(), originalCount);
+        QCOMPARE(f.resultAt(0), initResults[0]);
+    }
+    // overwrite with rvalue
+    {
+        const auto originalCount = f.resultCount();
+        iface.reportResult(-1, 0);
+        QCOMPARE(f.resultCount(), originalCount);
+        QCOMPARE(f.resultAt(0), initResults[0]);
+    }
+    // overwrite with array
+    {
+        const auto originalCount = f.resultCount();
+        iface.reportResults(QList<int> { -1, -2, -3 }, 0);
+        QCOMPARE(f.resultCount(), originalCount);
+        QCOMPARE(f.resultAt(0), initResults[0]);
+    }
+
+    // special case: add result by different index, overlapping with the vector
+    if (initResults.size() > 1) {
+        const auto originalCount = f.resultCount();
+        iface.reportResult(-1, 1);
+        QCOMPARE(f.resultCount(), originalCount);
+        QCOMPARE(f.resultAt(1), initResults[1]);
+    }
+
+    QTimer::singleShot(50, [&f]() {
+        f.suspend(); // should exit the loop
+    });
+    eventProcessor.enterLoopMSecs(2000);
+    QVERIFY(!eventProcessor.timeout());
+    QCOMPARE(resultCounter.count(), 1);
+    f.resume();
+    QCOMPARE(f.results(), initResults);
+}
+
+void tst_QFuture::rejectPendingResultOverwrite()
+{
+    QFETCH(bool, filterMode);
+    QFETCH(QList<int>, initResults);
+
+    QFutureInterface<int> iface;
+    iface.setFilterMode(filterMode);
+    auto f = iface.future();
+    QFutureWatcher<int> watcher;
+    watcher.setFuture(f);
+
+    QTestEventLoop eventProcessor;
+    // control the loop by suspend
+    connect(&watcher, &QFutureWatcher<int>::suspending, &eventProcessor, &QTestEventLoop::exitLoop);
+    // internal machinery always emits resultsReadyAt
+    QSignalSpy resultCounter(&watcher, &QFutureWatcher<int>::resultsReadyAt);
+
+    // init
+    if (initResults.size() == 1)
+        iface.reportResult(initResults[0], 1);
+    else
+        iface.reportResults(initResults, 1);
+    QCOMPARE(f.resultCount(), 0); // not visible yet
+    if (!filterMode) {
+        QCOMPARE(f.resultAt(1), initResults[0]);
+        QCOMPARE(f.results(), initResults);
+
+        QTimer::singleShot(50, [&f]() {
+            f.suspend(); // should exit the loop
+        });
+        // Run event loop, QCoreApplication::postEvent is in use
+        // in QFutureInterface:
+        eventProcessor.enterLoopMSecs(2000);
+        QVERIFY(!eventProcessor.timeout());
+        QCOMPARE(resultCounter.count(), 1);
+        f.resume();
+    }
+
+    // overwrite with lvalue
+    {
+        int result = -1;
+        const auto originalCount = f.resultCount();
+        iface.reportResult(result, 1);
+        QCOMPARE(f.resultCount(), originalCount);
+        if (!filterMode)
+            QCOMPARE(f.resultAt(1), initResults[0]);
+    }
+    // overwrite with rvalue
+    {
+        const auto originalCount = f.resultCount();
+        iface.reportResult(-1, 1);
+        QCOMPARE(f.resultCount(), originalCount);
+        if (!filterMode)
+            QCOMPARE(f.resultAt(1), initResults[0]);
+    }
+    // overwrite with array
+    {
+        const auto originalCount = f.resultCount();
+        iface.reportResults(QList<int> { -1, -2 }, 1);
+        QCOMPARE(f.resultCount(), originalCount);
+        if (!filterMode)
+            QCOMPARE(f.resultAt(1), initResults[0]);
+    }
+    // special case: add result by different index, overlapping with the vector
+    if (initResults.size() > 1) {
+        const auto originalCount = f.resultCount();
+        iface.reportResult(-1, 2);
+        QCOMPARE(f.resultCount(), originalCount);
+        if (!filterMode)
+            QCOMPARE(f.resultAt(2), initResults[1]);
+    }
+
+    if (!filterMode) {
+        QTimer::singleShot(50, [&f]() {
+            f.suspend(); // should exit the loop
+        });
+        eventProcessor.enterLoopMSecs(2000);
+        QVERIFY(!eventProcessor.timeout());
+        QCOMPARE(resultCounter.count(), 1);
+        f.resume();
+    }
+
+    iface.reportResult(123, 0); // make results at 0 and 1 accessible
+    QCOMPARE(f.resultCount(), initResults.size() + 1);
+    QCOMPARE(f.resultAt(1), initResults[0]);
+    initResults.prepend(123);
+    QCOMPARE(f.results(), initResults);
+}
+
 QTEST_MAIN(tst_QFuture)
 #include "tst_qfuture.moc"
diff --git a/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp b/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
index 2b8853ccd7..62e3711d42 100644
--- a/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
+++ b/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
@@ -169,12 +169,12 @@ void tst_QPromise::addResult()
     auto f = promise.future();
 
     // add as lvalue
+    int resultAt0 = 456;
     {
-        int result = 456;
-        promise.addResult(result);
+        promise.addResult(resultAt0);
         QCOMPARE(f.resultCount(), 1);
-        QCOMPARE(f.result(), result);
-        QCOMPARE(f.resultAt(0), result);
+        QCOMPARE(f.result(), resultAt0);
+        QCOMPARE(f.resultAt(0), resultAt0);
     }
     // add as rvalue
     {
@@ -190,13 +190,20 @@ void tst_QPromise::addResult()
         QCOMPARE(f.resultCount(), 3);
         QCOMPARE(f.resultAt(2), result);
     }
-    // add at position and overwrite
+    // add as lvalue at position and overwrite
     {
         int result = -1;
         const auto originalCount = f.resultCount();
         promise.addResult(result, 0);
         QCOMPARE(f.resultCount(), originalCount);
-        QCOMPARE(f.resultAt(0), result);
+        QCOMPARE(f.resultAt(0), resultAt0); // overwrite does not work
+    }
+    // add as rvalue at position and overwrite
+    {
+        const auto originalCount = f.resultCount();
+        promise.addResult(-1, 0);
+        QCOMPARE(f.resultCount(), originalCount);
+        QCOMPARE(f.resultAt(0), resultAt0); // overwrite does not work
     }
 }