QTypeRevision: fix support for 8-bit signed segments

The logic in the isValidSegment() function was failing for 8-bit signed
because for them Integer(SegmentUnknown) is -1, so
  (std::numeric_limits<Integer>::max)() < Integer(SegmentUnknown)
was always false (127 < -1) and the function would only return true on
the impossible condition of
  segment >= 0 && segment < -1

Fixes: QTBUG-128848
Pick-to: 6.5 6.8
Change-Id: I8d17b93afd6c2982a099fffdcaeccf126b7a9d02
Reviewed-by: Ulf Hermann <[email protected]>

src/corelib/tools/qtyperevision.h

@@ -45,9 +45,11 @@ class QTypeRevision
     static constexpr bool isValidSegment(Integer segment)
     {
         // using extra parentheses around max to avoid expanding it if it is a macro
+        // and adding zero to cause it to be promoted
+        constexpr auto Max = (std::numeric_limits<Integer>::max)() + 0;
+        constexpr bool HasSufficientRange = Max >= SegmentUnknown;
         return segment >= Integer(0)
-                && ((std::numeric_limits<Integer>::max)() < Integer(SegmentUnknown)
-                    || segment < Integer(SegmentUnknown));
+                && (!HasSufficientRange || segment < Integer(SegmentUnknown));
     }
 
     template<typename Major, typename Minor,

tests/auto/corelib/tools/qtyperevision/tst_qtyperevision.cpp

@@ -95,7 +95,7 @@ void tst_QTypeRevision::qTypeRevision()
 void tst_QTypeRevision::qTypeRevisionTypes()
 {
     compileTestRevision<quint8>();
-    // compileTestRevision<qint8>();
+    compileTestRevision<qint8>();
     compileTestRevision<quint16>();
     compileTestRevision<qint16>();
     compileTestRevision<quint32>();
@@ -104,7 +104,7 @@ void tst_QTypeRevision::qTypeRevisionTypes()
     compileTestRevision<qint64>();
     compileTestRevision<long>();
     compileTestRevision<ulong>();
-    // compileTestRevision<char>();
+    compileTestRevision<char>();
 
     QVERIFY(!QTypeRevision::isValidSegment(0xff));
     QVERIFY(!QTypeRevision::isValidSegment(-1));