QSemaphore: Fix futexMultiWaiterBit for 32bit systems

We don't actually need it in that case, but as the code that uses it is
disabled by a constant expression we cannot disable the variable itself
by a macro. The static_cast makes sure the compiler does not complain
about implicitly casting a 64bit value to a 32bit one.

 thread/qsemaphore.cpp:156:59: error: large integer implicitly truncated to unsigned type [-Werror=overflow]

Task-number: QTBUG-64261
Change-Id: I96f53e28b290e57033737b4f994f8af5b5666587
Reviewed-by: Liang Qi <liang.qi@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/corelib/thread/qsemaphore.cpp b/src/corelib/thread/qsemaphore.cpp
index 24f5769d05..21acc533a1 100644
--- a/src/corelib/thread/qsemaphore.cpp
+++ b/src/corelib/thread/qsemaphore.cpp
@@ -153,7 +153,8 @@ static QBasicAtomicInteger<quint32> *futexLow32(QBasicAtomicInteger<quintptr> *p
 }
 
 #ifdef FUTEX_OP
-static const quintptr futexMultiWaiterBit = Q_UINT64_C(1) << 63;
+// quintptr might be 32bit, in which case we want this to be 0, without implicitly casting.
+static const quintptr futexMultiWaiterBit = static_cast<quintptr>(Q_UINT64_C(1) << 63);
 static QBasicAtomicInteger<quint32> *futexHigh32(QBasicAtomicInteger<quintptr> *ptr)
 {
     auto result = reinterpret_cast<QBasicAtomicInteger<quint32> *>(ptr);