tst_QByteArray: fix UB (signed overflow)

The first case is simple, as it's a static overflow. Theoretically,
the compiler would be allowed to just remove the complete function as
dead code. This is an error left from the port from int to qsizetype:
Qt 5.15 there has uint(MaxAllocSize) + 1, so use quint here again,
qint64 is wrong.

In the second case, we _may_ reach alloc == MaxAllocSize. Check that,
if we do, we don't then add 1 to it.

Pick-to: 6.3 6.2
Change-Id: I93044ed6f1b77559642fa1e4e8f313cf59eeeb79
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 3 insertions, 2 deletions

diff --git a/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp b/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp
index 0f1f00bf6c..cecd0f1584 100644
--- a/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp
+++ b/tests/auto/corelib/text/qbytearray/tst_qbytearray.cpp
@@ -1386,7 +1386,7 @@ void tst_QByteArray::blockSizeCalculations()
     QCOMPARE(qCalculateGrowingBlockSize(MaxAllocSize/2, 2, 1).elementCount, qsizetype(MaxAllocSize)/2);
 
     // error conditions
-    QCOMPARE(qCalculateBlockSize(qint64(MaxAllocSize) + 1, 1), qsizetype(-1));
+    QCOMPARE(qCalculateBlockSize(quint64(MaxAllocSize) + 1, 1), qsizetype(-1));
     QCOMPARE(qCalculateBlockSize(qsizetype(-1), 1), qsizetype(-1));
     QCOMPARE(qCalculateBlockSize(MaxAllocSize, 1, 1), qsizetype(-1));
     QCOMPARE(qCalculateBlockSize(MaxAllocSize/2 + 1, 2), qsizetype(-1));
@@ -1443,7 +1443,8 @@ void tst_QByteArray::blockSizeCalculations()
         QVERIFY(checkSize(alloc, qsizetype(MaxAllocSize) / elementSize));
 
         // the next allocation should be invalid
-        QCOMPARE(qCalculateGrowingBlockSize(alloc + 1, elementSize).size, qsizetype(-1));
+        if (alloc < MaxAllocSize) // lest alloc + 1 overflows (= UB)
+            QCOMPARE(qCalculateGrowingBlockSize(alloc + 1, elementSize).size, qsizetype(-1));
     }
 }