QString: Fix severals bugs when comparing with QStringRef

the internal ucstricmp and ucstrcmp contains different bugs if the
strings are not 0-terminated, as it is with QStringRef.

- in ucstricmp, even if the pointer are the same, the lenght could
  be different
- we used to deference the 'end' pointer, that would be 0 if the
  string ends with 0, but we cannot do that in the general case

Task-number: QTBUG-10404
Reviewed-by: Denis
(cherry picked from commit cd003bfcf9a05967893099e8948ba3d8f281aa7d)

2 files changed, 40 insertions, 4 deletions

diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index 01d3825529..3f472d33b6 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -111,7 +111,7 @@ int qFindStringBoyerMoore(const QChar *haystack, int haystackLen, int from,
 static int ucstricmp(const ushort *a, const ushort *ae, const ushort *b, const ushort *be)
 {
     if (a == b)
-        return 0;
+        return (ae - be);
     if (a == 0)
         return 1;
     if (b == 0)
@@ -123,7 +123,7 @@ static int ucstricmp(const ushort *a, const ushort *ae, const ushort *b, const u
 
     uint alast = 0;
     uint blast = 0;
-    while (a != e) {
+    while (a < e) {
 //         qDebug() << hex << alast << blast;
 //         qDebug() << hex << "*a=" << *a << "alast=" << alast << "folded=" << foldCase (*a, alast);
 //         qDebug() << hex << "*b=" << *b << "blast=" << blast << "folded=" << foldCase (*b, blast);
@@ -152,7 +152,7 @@ static int ucstricmp(const ushort *a, const ushort *ae, const uchar *b)
     if (b == 0)
         return -1;
 
-    while (a != ae && *b) {
+    while (a < ae && *b) {
         int diff = foldCase(*a) - foldCase(*b);
         if ((diff))
             return diff;
@@ -4532,9 +4532,12 @@ int QString::compare_helper(const QChar *data1, int length1, QLatin1String s2,
         return length1;
 
     if (cs == Qt::CaseSensitive) {
-        while (uc != e && *c && *uc == *c)
+        while (uc < e && *c && *uc == *c)
             uc++, c++;
 
+        if (uc == e)
+            return -*c;
+
         return *uc - *c;
     } else {
         return ucstricmp(uc, e, c);
diff --git a/tests/auto/qstring/tst_qstring.cpp b/tests/auto/qstring/tst_qstring.cpp
index 26de04e183..5a153dede9 100644
--- a/tests/auto/qstring/tst_qstring.cpp
+++ b/tests/auto/qstring/tst_qstring.cpp
@@ -202,6 +202,7 @@ private slots:
     void repeated() const;
     void repeated_data() const;
     void task262677remove();
+    void QTBUG10404_compareRef();
 };
 
 typedef QList<int> IntList;
@@ -4680,6 +4681,38 @@ void tst_QString::task262677remove()
     QVERIFY(driveName == QLatin1String("V:"));
 }
 
+void tst_QString::QTBUG10404_compareRef()
+{
+    QString a = "ABCDEFGH";
+
+    QCOMPARE(QStringRef(&a, 1, 2).compare(QLatin1String("BC")), 0);
+    QVERIFY(QStringRef(&a, 1, 2).compare(QLatin1String("BCD")) < 0);
+    QCOMPARE(QStringRef(&a, 1, 2).compare(QLatin1String("Bc"), Qt::CaseInsensitive), 0);
+    QVERIFY(QStringRef(&a, 1, 2).compare(QLatin1String("bCD"), Qt::CaseInsensitive) < 0);
+
+    QCOMPARE(QStringRef(&a, 1, 2).compare(QString::fromLatin1("BC")), 0);
+    QVERIFY(QStringRef(&a, 1, 2).compare(QString::fromLatin1("BCD")) < 0);
+    QCOMPARE(QStringRef(&a, 1, 2).compare(QString::fromLatin1("Bc"), Qt::CaseInsensitive), 0);
+    QVERIFY(QStringRef(&a, 1, 2).compare(QString::fromLatin1("bCD"), Qt::CaseInsensitive) < 0);
+
+    QCOMPARE(QString::fromLatin1("BC").compare(QStringRef(&a, 1, 2)), 0);
+    QVERIFY(QString::fromLatin1("BCD").compare(QStringRef(&a, 1, 2)) > 0);
+    QCOMPARE(QString::fromLatin1("Bc").compare(QStringRef(&a, 1, 2), Qt::CaseInsensitive), 0);
+    QVERIFY(QString::fromLatin1("bCD").compare(QStringRef(&a, 1, 2), Qt::CaseInsensitive) > 0);
+
+    QCOMPARE(QStringRef(&a, 1, 2).compare(QStringRef(&a, 1, 2)), 0);
+    QVERIFY(QStringRef(&a, 1, 2).compare(QStringRef(&a, 1, 3)) < 0);
+    QCOMPARE(QStringRef(&a, 1, 2).compare(QStringRef(&a, 1, 2), Qt::CaseInsensitive), 0);
+    QVERIFY(QStringRef(&a, 1, 2).compare(QStringRef(&a, 1, 3), Qt::CaseInsensitive) < 0);
+
+    QString a2 = "ABCDEFGh";
+    QCOMPARE(QStringRef(&a2, 1, 2).compare(QStringRef(&a, 1, 2)), 0);
+    QVERIFY(QStringRef(&a2, 1, 2).compare(QStringRef(&a, 1, 3)) < 0);
+    QCOMPARE(QStringRef(&a2, 1, 2).compare(QStringRef(&a, 1, 2), Qt::CaseInsensitive), 0);
+    QVERIFY(QStringRef(&a2, 1, 2).compare(QStringRef(&a, 1, 3), Qt::CaseInsensitive) < 0);
+}
+
+
 
 QTEST_APPLESS_MAIN(tst_QString)