From d54f9df1bd2d83aa259e2597bbdacd98216574d8 Mon Sep 17 00:00:00 2001
From: Sona Kurazyan <sona.kurazyan@qt.io>
Date: Mon, 26 Jul 2021 17:03:37 +0200
Subject: [PATCH] Don't report results when the results list is empty
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When inserting items into the result store, a ResultItem is created,
which stores a pointer to the results list and their size. If the size
of the ResultItem is set to 0, it means that a single result is stored.
In case of trying to report results via an empty list, the size is 0, so
result store treats it as a single result.

Added checks before storing the results to make sure that the result
list isn't empty. Note that empty lists are allowed in some cases for
the filter mode, because ResultStoreBase::addResults() knows how to
handle those cases correctly.

Task-number: QTBUG-80957
Change-Id: I399af4c3eef6adf82fea5df031fe9a9075006b1f
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
(cherry picked from commit 08de1fb28153d8170b592796a84032897afa4206)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/thread/qresultstore.cpp           |  1 +
 src/corelib/thread/qresultstore.h             |  7 +++++++
 .../corelib/thread/qfuture/tst_qfuture.cpp    | 20 +++++++++++++++++++
 .../thread/qresultstore/tst_qresultstore.cpp  | 16 +++++++++++++++
 4 files changed, 44 insertions(+)

diff --git a/src/corelib/thread/qresultstore.cpp b/src/corelib/thread/qresultstore.cpp
index a239954dbe0..5982ae54541 100644
--- a/src/corelib/thread/qresultstore.cpp
+++ b/src/corelib/thread/qresultstore.cpp
@@ -235,6 +235,7 @@ int ResultStoreBase::addResult(int index, const void *result)
 int ResultStoreBase::addResults(int index, const void *results, int vectorSize, int totalCount)
 {
     if (m_filterMode == false || vectorSize == totalCount) {
+        Q_ASSERT(vectorSize != 0);
         ResultItem resultItem(results, vectorSize);
         return insertResultItem(index, resultItem);
     } else {
diff --git a/src/corelib/thread/qresultstore.h b/src/corelib/thread/qresultstore.h
index 0a1382fd796..0967b89123b 100644
--- a/src/corelib/thread/qresultstore.h
+++ b/src/corelib/thread/qresultstore.h
@@ -193,6 +193,9 @@ public:
     template<typename T>
     int addResults(int index, const QList<T> *results)
     {
+        if (results->empty()) // reject if results are empty
+            return -1;
+
         if (containsValidResultItem(index)) // reject if already present
             return -1;
 
@@ -202,6 +205,10 @@ public:
     template<typename T>
     int addResults(int index, const QList<T> *results, int totalCount)
     {
+        // reject if results are empty, and nothing is filtered away
+        if ((m_filterMode == false || results->count() == totalCount) && results->empty())
+            return -1;
+
         if (containsValidResultItem(index)) // reject if already present
             return -1;
 
diff --git a/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp b/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
index 5f6267ec7d6..435e44c05b0 100644
--- a/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
+++ b/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
@@ -730,6 +730,26 @@ void tst_QFuture::futureInterface()
         QCOMPARE(i1.resultReference(0), 2);
         QCOMPARE(i2.resultReference(0), 1);
     }
+
+    {
+        QFutureInterface<int> fi;
+        fi.reportStarted();
+        QVERIFY(!fi.reportResults(QList<int> {}));
+        fi.reportFinished();
+
+        QVERIFY(fi.results().empty());
+    }
+
+    {
+        QFutureInterface<int> fi;
+        fi.reportStarted();
+        QList<int> values = { 1, 2, 3 };
+        QVERIFY(fi.reportResults(values));
+        QVERIFY(!fi.reportResults(QList<int> {}));
+        fi.reportFinished();
+
+        QCOMPARE(fi.results(), values);
+    }
 }
 
 template <typename T>
diff --git a/tests/auto/corelib/thread/qresultstore/tst_qresultstore.cpp b/tests/auto/corelib/thread/qresultstore/tst_qresultstore.cpp
index 10ac19137e1..48b0eaf1eb2 100644
--- a/tests/auto/corelib/thread/qresultstore/tst_qresultstore.cpp
+++ b/tests/auto/corelib/thread/qresultstore/tst_qresultstore.cpp
@@ -177,6 +177,14 @@ void tst_QtConcurrentResultStore::addResults()
 
     ++it;
     QCOMPARE(it, store.end());
+
+    QList<int> empty;
+    const auto countBefore = store.count();
+    QCOMPARE(store.addResults(countBefore, &empty), -1);
+    QCOMPARE(store.count(), countBefore);
+
+    QCOMPARE(store.addResults(countBefore, &vec1), countBefore);
+    QCOMPARE(store.count(), countBefore + vec1.size());
 }
 
 void tst_QtConcurrentResultStore::resultIndex()
@@ -340,6 +348,14 @@ void tst_QtConcurrentResultStore::filterMode()
     QCOMPARE(store.contains(6), true);
     QCOMPARE(store.contains(7), true);
     QCOMPARE(store.contains(8), false);
+
+    QList<int> empty;
+    const auto countBefore = store.count();
+    QCOMPARE(store.addResults(countBefore, &empty), -1);
+    QCOMPARE(store.count(), countBefore);
+
+    QCOMPARE(store.addResult(countBefore, &int2), countBefore);
+    QCOMPARE(store.count(), countBefore + 1);
 }
 
 void tst_QtConcurrentResultStore::addCanceledResult()