QString: fix comparisons to null strings in ucstricmp

Commit 8f52ad9fe084eee26869e4a94a678076845a6f58 ("ucstricmp: compare
null and empty strings equal") made sure empties and nulls would compare
equally, but may have broken the null vs non-empty comparison (which was
not tested). The commit message also said that it expected all callers
to handle null before calling into those functions, but that's not the
case for QStringView created from a null QString: the incoming "a"
pointer was null.

So just remove the checks for null pointers and rely on the size checks
doing the right thing.

[ChangeLog][QtCore][QString] Fixed a regression from 5.9 that caused
comparing default-constructed QStrings to be sorted after non-empty
strings.

Task-number: QTBUG-65939
Change-Id: I56b444f9d6274221a3b7fffd150c83ad46c599b6
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 7 insertions, 1 deletions

diff --git a/tests/auto/corelib/tools/qstring/tst_qstring.cpp b/tests/auto/corelib/tools/qstring/tst_qstring.cpp
index 70ccc72630..a028391b06 100644
--- a/tests/auto/corelib/tools/qstring/tst_qstring.cpp
+++ b/tests/auto/corelib/tools/qstring/tst_qstring.cpp
@@ -6043,8 +6043,14 @@ void tst_QString::compare_data()
     QTest::addColumn<int>("csr"); // case sensitive result
     QTest::addColumn<int>("cir"); // case insensitive result
 
-
     // null strings
+    QTest::newRow("null-null") << QString() << QString() << 0 << 0;
+    QTest::newRow("text-null") << QString("a") << QString() << 1 << 1;
+    QTest::newRow("null-text") << QString() << QString("a") << -1 << -1;
+    QTest::newRow("null-empty") << QString() << QString("") << 0 << 0;
+    QTest::newRow("empty-null") << QString("") << QString() << 0 << 0;
+
+    // empty strings
     QTest::newRow("data0") << QString("") << QString("") << 0 << 0;
     QTest::newRow("data1") << QString("a") << QString("") << 1 << 1;
     QTest::newRow("data2") << QString("") << QString("a") << -1 << -1;