QVariant: don't do fuzzy comparisons with NaN and infinities

There was a test that tested this, but was wrong.

[ChangeLog][QtCore][QVariant] Fixed a bug that caused wrong results for
comparisons of QVariants containing either NaN or infinite numbers.

Task-number: QTBUG-56073
Change-Id: I33dc971f005a4848bb8ffffd1475d29d00dd1b7f
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 24 insertions, 3 deletions

diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index 9476ab3f5b..7c9df5b46f 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -74,6 +74,7 @@
 #include "qline.h"
 #endif
 
+#include <cmath>
 #include <float.h>
 #include <cstring>
 
@@ -3472,8 +3473,17 @@ static int numericCompare(const QVariant::Private *d1, const QVariant::Private *
     Q_ASSERT(ok);
     qreal r2 = qConvertToRealNumber(d2, &ok);
     Q_ASSERT(ok);
-    if (r1 == r2 || qFuzzyCompare(r1, r2))
+    if (r1 == r2)
         return 0;
+
+    // only do fuzzy comparisons for finite, non-zero numbers
+    int c1 = std::fpclassify(r1);
+    int c2 = std::fpclassify(r2);
+    if ((c1 == FP_NORMAL || c1 == FP_SUBNORMAL) && (c2 == FP_NORMAL || c2 == FP_SUBNORMAL)) {
+        if (qFuzzyCompare(r1, r2))
+            return 0;
+    }
+
     return r1 < r2 ? -1 : 1;
 }
 
diff --git a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
index 3a51e67768..442f7e80d1 100644
--- a/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
+++ b/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp
@@ -1755,6 +1755,10 @@ void tst_QVariant::compareNumbers_data() const
     QTest::newRow("double5") << qVariantFromValue(0.) << qVariantFromValue(-qInf()) << +1;
     QTest::newRow("double6") << qVariantFromValue(-double(qInf())) << qVariantFromValue(-qInf()) << 0;
     QTest::newRow("double7") << qVariantFromValue(qInf()) << qVariantFromValue(qInf()) << 0;
+    QTest::newRow("double8") << qVariantFromValue(-qInf()) << qVariantFromValue(qInf()) << -1;
+    QTest::newRow("double9") << qVariantFromValue(qQNaN()) << qVariantFromValue(0.) << INT_MAX;
+    QTest::newRow("double10") << qVariantFromValue(0.) << qVariantFromValue(qQNaN()) << INT_MAX;
+    QTest::newRow("double11") << qVariantFromValue(qQNaN()) << qVariantFromValue(qQNaN()) << INT_MAX;
 
     // mixed comparisons
     // fp + fp
@@ -1763,8 +1767,12 @@ void tst_QVariant::compareNumbers_data() const
     QTest::newRow("float+double3") << qVariantFromValue(0.f) << qVariantFromValue(-1.) << +1;
     QTest::newRow("float+double4") << qVariantFromValue(-float(qInf())) << qVariantFromValue(0.) << -1;
     QTest::newRow("float+double5") << qVariantFromValue(0.f) << qVariantFromValue(-qInf()) << +1;
-    QTest::newRow("float+double6") << qVariantFromValue(-float(qInf())) << qVariantFromValue(qInf()) << 0;
+    QTest::newRow("float+double6") << qVariantFromValue(-float(qInf())) << qVariantFromValue(-qInf()) << 0;
     QTest::newRow("float+double7") << qVariantFromValue(float(qInf())) << qVariantFromValue(qInf()) << 0;
+    QTest::newRow("float+double8") << qVariantFromValue(-float(qInf())) << qVariantFromValue(qInf()) << -1;
+    QTest::newRow("float+double9") << qVariantFromValue(qQNaN()) << qVariantFromValue(0.) << INT_MAX;
+    QTest::newRow("float+double10") << qVariantFromValue(0.) << qVariantFromValue(qQNaN()) << INT_MAX;
+    QTest::newRow("float+double11") << qVariantFromValue(qQNaN()) << qVariantFromValue(qQNaN()) << INT_MAX;
 
     // fp + int
     QTest::newRow("float+int1") << qVariantFromValue(0.f) << qVariantFromValue(0) << 0;
@@ -1978,7 +1986,7 @@ void tst_QVariant::compareNumbers() const
         QCOMPARE(v2, v1);
         QVERIFY(v2 >= v1);
         QVERIFY(!(v2 > v1));
-    } else {
+    } else if (expected == +1) {
         QVERIFY(!(v1 < v2));
         QVERIFY(!(v1 <= v2));
         QVERIFY(!(v1 == v2));
@@ -1990,6 +1998,9 @@ void tst_QVariant::compareNumbers() const
         QVERIFY(!(v2 == v1));
         QVERIFY(!(v2 >= v1));
         QVERIFY(!(v2 > v1));
+    } else {
+        // unorderable (NaN)
+        QVERIFY(!(v1 == v2));
     }
 }