From 43c964b8ada63942b5d239f60fdbca6f5773f678 Mon Sep 17 00:00:00 2001
From: Sona Kurazyan <sona.kurazyan@qt.io>
Date: Mon, 4 Nov 2019 10:18:41 +0100
Subject: [PATCH] Fix converting a null QStringRef to QString

The assumption when calling QStringRef::toString() on a null
QStringRef (i.e. when QStringRef::isNull() is true) is that
QStringRef::toString().isNull() will also return true. With the
current implementation we return a null QString() only when the
QStringRef references a nullptr QString. We need to do the same
also when QStringRef references a QString with null private data.

Change-Id: I4177a5ea187ae758d7c46fe76a9d0583140e90cb
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/text/qstring.cpp                        |  2 +-
 .../auto/corelib/text/qstringref/tst_qstringref.cpp | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index 51aa0b7512..edce0ff720 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -10506,7 +10506,7 @@ ownership of it, no memory is freed when instances are destroyed.
 */
 
 QString QStringRef::toString() const {
-    if (!m_string)
+    if (isNull())
         return QString();
     if (m_size && m_position == 0 && m_size == m_string->size())
         return *m_string;
diff --git a/tests/auto/corelib/text/qstringref/tst_qstringref.cpp b/tests/auto/corelib/text/qstringref/tst_qstringref.cpp
index 6f01947131..20d5426bf7 100644
--- a/tests/auto/corelib/text/qstringref/tst_qstringref.cpp
+++ b/tests/auto/corelib/text/qstringref/tst_qstringref.cpp
@@ -87,6 +87,7 @@ private slots:
     void mid();
     void split_data();
     void split();
+    void nullToString();
 };
 
 static QStringRef emptyRef()
@@ -2177,6 +2178,18 @@ void tst_QStringRef::split()
     }
 }
 
+void tst_QStringRef::nullToString()
+{
+    QStringRef nullRef;
+    QVERIFY(nullRef.isNull());
+    QVERIFY(nullRef.toString().isNull());
+
+    QString str;
+    nullRef = &str;
+    QVERIFY(nullRef.isNull());
+    QVERIFY(nullRef.toString().isNull());
+}
+
 QTEST_APPLESS_MAIN(tst_QStringRef)
 
 #include "tst_qstringref.moc"