QCborValue: fix sorting of UTF8-to-UTF16 strings

We must compare the raw string length in UTF-8, not the UTF-16 one.

[ChangeLog][QtCore][QCborValue] Fixed a bug that caused certain
non-US-ASCII string comparisons to produce results not in line with the
CBOR specifications.

Pick-to: 6.5 6.6 6.7
Change-Id: I5f663c2f9f4149af84fefffd17c05d1c0f1bbc3a
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

2 files changed, 44 insertions, 6 deletions

diff --git a/src/corelib/serialization/qcborvalue.cpp b/src/corelib/serialization/qcborvalue.cpp
index 123d62168b..07150e5d8c 100644
--- a/src/corelib/serialization/qcborvalue.cpp
+++ b/src/corelib/serialization/qcborvalue.cpp
@@ -1190,16 +1190,18 @@ static int compareElementRecursive(const QCborContainerPrivate *c1, const Elemen
 
         if (!(e1.flags & Element::StringIsAscii) || !(e2.flags & Element::StringIsAscii)) {
             // Case 2: one of them is UTF-8 and the other is UTF-16, so lengths
-            // are NOT comparable. We need to convert to UTF-16 first...
+            // are NOT comparable. We need to convert to UTF-8 first...
             // (we can't use QUtf8::compareUtf8 because we need to compare lengths)
-            auto string = [](const Element &e, const ByteData *b) {
-                return e.flags & Element::StringIsUtf16 ? b->asQStringRaw() : b->toUtf8String();
+            auto string = [](const Element &e, const ByteData *b) -> QByteArray {
+                if (e.flags & Element::StringIsUtf16)
+                    return b->asStringView().toUtf8();
+                return b->asByteArrayView();    // actually a QByteArray::fromRaw
             };
 
-            QString s1 = string(e1, b1);
-            QString s2 = string(e2, b2);
+            QByteArray s1 = string(e1, b1);
+            QByteArray s2 = string(e2, b2);
             if (s1.size() == s2.size())
-                return s1.compare(s2);
+                return memcmp(s1.constData(), s2.constData(), s1.size());
             return s1.size() < s2.size() ? -1 : 1;
         }
 
diff --git a/tests/auto/corelib/serialization/qcborvalue/tst_qcborvalue.cpp b/tests/auto/corelib/serialization/qcborvalue/tst_qcborvalue.cpp
index 37f1569bbc..2e06251ac4 100644
--- a/tests/auto/corelib/serialization/qcborvalue/tst_qcborvalue.cpp
+++ b/tests/auto/corelib/serialization/qcborvalue/tst_qcborvalue.cpp
@@ -16,6 +16,8 @@ Q_DECLARE_METATYPE(QCborKnownTags)
 Q_DECLARE_METATYPE(QCborValue)
 Q_DECLARE_METATYPE(QCborValue::EncodingOptions)
 
+using namespace Qt::StringLiterals;
+
 class tst_QCborValue : public QObject
 {
     Q_OBJECT
@@ -1895,6 +1897,40 @@ void tst_QCborValue::sorting()
     // which shows all doubles sorted after integrals
     QT_TEST_ALL_COMPARISON_OPS(vint2, vdouble1, Qt::strong_ordering::less);
     QVERIFY(vint2.toInteger() > vdouble1.toDouble());
+
+    // Add some non-US-ASCII strings. In the current implementation, QCborValue
+    // can store a string as either US-ASCII, UTF-8, or UTF-16, so let's exercise
+    // those comparisons.
+
+    // we don't have a QUtf8StringView constructor, so work around it
+    auto utf8string = [](QByteArray str) {
+        Q_ASSERT(str.size() < 24);
+        str.prepend(char(QCborValue::String) + str.size());
+        return QCborValue::fromCbor(str);
+    };
+    // 5 code units in UTF-8
+    QCborValue vs4_utf16(u"Mørk"_s);
+    QCborValue vs4_utf8 = utf8string("Mørk");
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf8, vs4_utf8, Qt::strong_ordering::equal);
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf16, vs4_utf16, Qt::strong_ordering::equal);
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf16, vs4_utf8, Qt::strong_ordering::equal);
+
+    // 5 code units in UTF-16
+    QCborValue vs5_utf16(u"Først"_s);
+    QCborValue vs5_utf8 = utf8string("Først");
+    QT_TEST_ALL_COMPARISON_OPS(vs5_utf8, vs5_utf8, Qt::strong_ordering::equal);
+    QT_TEST_ALL_COMPARISON_OPS(vs5_utf16, vs5_utf16, Qt::strong_ordering::equal);
+    QT_TEST_ALL_COMPARISON_OPS(vs5_utf16, vs5_utf8, Qt::strong_ordering::equal);
+
+    // sorted by UTF-8 length first, so "Mørk" < "World" < "Først" (!!)
+    QT_TEST_ALL_COMPARISON_OPS(vs3, vs4_utf8, Qt::strong_ordering::greater);
+    QT_TEST_ALL_COMPARISON_OPS(vs3, vs4_utf16, Qt::strong_ordering::greater);
+    QT_TEST_ALL_COMPARISON_OPS(vs3, vs5_utf8, Qt::strong_ordering::less);
+    QT_TEST_ALL_COMPARISON_OPS(vs3, vs5_utf16, Qt::strong_ordering::less);
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf8, vs5_utf8, Qt::strong_ordering::less);
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf8, vs5_utf16, Qt::strong_ordering::less);
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf16, vs5_utf8, Qt::strong_ordering::less);
+    QT_TEST_ALL_COMPARISON_OPS(vs4_utf16, vs5_utf16, Qt::strong_ordering::less);
 }
 
 void tst_QCborValue::comparison_data()