Fix capacity reservation for shared QByteArray

We can squeeze, but not by discarding elements. Make sure the size of
the object stays intact after changing the reserved capacity.

I've also added unit tests for other containers, just to be sure.

Task-number: QTBUG-37750
Change-Id: I5135b095943b7589423c51cebcb52af792468e61
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>

4 files changed, 53 insertions, 0 deletions

diff --git a/tests/auto/corelib/tools/qbytearray/tst_qbytearray.cpp b/tests/auto/corelib/tools/qbytearray/tst_qbytearray.cpp
index b06741b23e..6e183f3212 100644
--- a/tests/auto/corelib/tools/qbytearray/tst_qbytearray.cpp
+++ b/tests/auto/corelib/tools/qbytearray/tst_qbytearray.cpp
@@ -1855,6 +1855,21 @@ void tst_QByteArray::reserve()
         QVERIFY(data == qba.data());
     }
 
+    qba.resize(capacity);
+
+    QByteArray copy = qba;
+    qba.reserve(capacity / 2);
+    QCOMPARE(qba.size(), capacity); // we didn't shrink the size!
+    QCOMPARE(qba.capacity(), capacity);
+    QCOMPARE(copy.capacity(), capacity);
+
+    copy = qba;
+    qba.reserve(capacity * 2);
+    QCOMPARE(qba.size(), capacity);
+    QCOMPARE(qba.capacity(), capacity * 2);
+    QCOMPARE(copy.capacity(), capacity);
+    QVERIFY(qba.constData() != data);
+
     QByteArray nil1, nil2;
     nil1.reserve(0);
     nil2.squeeze();
diff --git a/tests/auto/corelib/tools/qlist/tst_qlist.cpp b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
index 2c9bf9d4c9..d77cc4a37c 100644
--- a/tests/auto/corelib/tools/qlist/tst_qlist.cpp
+++ b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
@@ -278,6 +278,8 @@ private slots:
     void setSharableComplex() const;
     void eraseValidIteratorsOnSharedList() const;
     void insertWithValidIteratorsOnSharedList() const;
+
+    void reserve() const;
 private:
     template<typename T> void length() const;
     template<typename T> void append() const;
@@ -1669,5 +1671,31 @@ void tst_QList::insertWithValidIteratorsOnSharedList() const
     QCOMPARE(a.at(1), 15);
 }
 
+void tst_QList::reserve() const
+{
+    // Note:
+    // This test depends on QList's current behavior that ints are stored in the array itself.
+    // This test would not work for QList<Complex>.
+    int capacity = 100;
+    QList<int> list;
+    list.reserve(capacity);
+    list << 0;
+    int *data = &list[0];
+
+    for (int i = 1; i < capacity; i++) {
+        list << i;
+        QCOMPARE(&list.at(0), data);
+    }
+
+    QList<int> copy = list;
+    list.reserve(capacity / 2);
+    QCOMPARE(list.size(), capacity); // we didn't shrink the size!
+
+    copy = list;
+    list.reserve(capacity * 2);
+    QCOMPARE(list.size(), capacity);
+    QVERIFY(&list.at(0) != data);
+}
+
 QTEST_APPLESS_MAIN(tst_QList)
 #include "tst_qlist.moc"
diff --git a/tests/auto/corelib/tools/qstring/tst_qstring.cpp b/tests/auto/corelib/tools/qstring/tst_qstring.cpp
index 5655d9f529..d9d6b985b7 100644
--- a/tests/auto/corelib/tools/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/tools/qstring/tst_qstring.cpp
@@ -4277,14 +4277,23 @@ void tst_QString::capacity()
     QVERIFY( (int)s2.capacity() >= res );
     QCOMPARE( s2, s1 );
 
+    s2 = s1;    // share again
     s2.reserve( res * 2 );
     QVERIFY( (int)s2.capacity() >=  res * 2 );
+    QVERIFY(s2.constData() != s1.constData());
     QCOMPARE( s2, s1 );
 
+    // don't share again -- s2 must be detached for squeeze() to do anything
     s2.squeeze();
     QVERIFY( (int)s2.capacity() == res );
     QCOMPARE( s2, s1 );
 
+    s2 = s1;    // share again
+    int oldsize = s1.size();
+    s2.reserve( res / 2 );
+    QVERIFY( (int)s2.capacity() >=  res / 2 );
+    QVERIFY( (int)s2.capacity() >=  oldsize );
+    QCOMPARE( s2, s1 );
 }
 
 void tst_QString::section_data()
diff --git a/tests/auto/corelib/tools/qvector/tst_qvector.cpp b/tests/auto/corelib/tools/qvector/tst_qvector.cpp
index 59956e33cf..c9545c8eb4 100644
--- a/tests/auto/corelib/tools/qvector/tst_qvector.cpp
+++ b/tests/auto/corelib/tools/qvector/tst_qvector.cpp
@@ -1942,6 +1942,7 @@ void tst_QVector::reserve()
         a.resize(2);
         QVector<Foo> b(a);
         b.reserve(1);
+        QCOMPARE(b.size(), a.size());
     }
     QCOMPARE(fooCtor, fooDtor);
 }