4 files changed, 90 insertions, 47 deletions
diff --git a/src/qml/qml/qqmlincubator.cpp b/src/qml/qml/qqmlincubator.cpp
index f0ef5360b0..d9c965d3ea 100644
--- a/src/qml/qml/qqmlincubator.cpp
+++ b/src/qml/qml/qqmlincubator.cpp
@@ -410,14 +410,39 @@ void QQmlIncubationController::incubateFor(int msecs)
     } while (d && d->incubatorCount != 0 && !i.shouldInterrupt());
 }
 
+#if QT_DEPRECATED_SINCE(5, 15)
 /*!
-Incubate objects while the bool pointed to by \a flag is true, or until there are no
-more objects to incubate, or up to \a msecs if \a msecs is not zero.
+\obsolete
+
+\warning Do not use this function.
+Use the overload taking a \c{std::atomic<bool>} instead.
+*/
+void QQmlIncubationController::incubateWhile(volatile bool *flag, int msecs)
+{
+    if (!d || !d->incubatorCount)
+        return;
+
+    QQmlInstantiationInterrupt i(flag, msecs * 1000000);
+    i.reset();
+    do {
+        static_cast<QQmlIncubatorPrivate*>(d->incubatorList.first())->incubate(i);
+    } while (d && d->incubatorCount != 0 && !i.shouldInterrupt());
+}
+#endif
+
+/*!
+\since 5.15
+
+Incubate objects while the atomic bool pointed to by \a flag is true,
+or until there are no more objects to incubate, or up to \a msecs if \a
+msecs is not zero.
 
 Generally this method is used in conjunction with a thread or a UNIX signal that sets
 the bool pointed to by \a flag to false when it wants incubation to be interrupted.
+
+\note \a flag is read using acquire memory ordering.
 */
-void QQmlIncubationController::incubateWhile(volatile bool *flag, int msecs)
+void QQmlIncubationController::incubateWhile(std::atomic<bool> *flag, int msecs)
 {
     if (!d || !d->incubatorCount)
         return;
diff --git a/src/qml/qml/qqmlincubator.h b/src/qml/qml/qqmlincubator.h
index f075407e73..6e47ca2173 100644
--- a/src/qml/qml/qqmlincubator.h
+++ b/src/qml/qml/qqmlincubator.h
@@ -42,6 +42,7 @@
 
 #include <QtQml/qtqmlglobal.h>
 #include <QtQml/qqmlerror.h>
+#include <atomic>
 
 QT_BEGIN_NAMESPACE
 
@@ -112,7 +113,11 @@ public:
     int incubatingObjectCount() const;
 
     void incubateFor(int msecs);
+#if QT_DEPRECATED_SINCE(5, 15)
+    QT_DEPRECATED_VERSION_X(5, 15, "Use the overload that takes a std::atomic<bool>")
     void incubateWhile(volatile bool *flag, int msecs=0);
+#endif
+    void incubateWhile(std::atomic<bool> *flag, int msecs = 0);
 
 protected:
     virtual void incubatingObjectCountChanged(int);
diff --git a/src/qml/qml/qqmlvme_p.h b/src/qml/qml/qqmlvme_p.h
index 13c5524d96..32b1631271 100644
--- a/src/qml/qml/qqmlvme_p.h
+++ b/src/qml/qml/qqmlvme_p.h
@@ -64,6 +64,8 @@
 #include <private/qqmlengine_p.h>
 #include <private/qfinitestack_p.h>
 
+#include <atomic>
+
 QT_BEGIN_NAMESPACE
 
 class QObject;
@@ -97,17 +99,20 @@ class QTypeInfo<QQmlVMETypes::State> : public QTypeInfoMerger<QQmlVMETypes::Stat
 class QQmlInstantiationInterrupt {
 public:
     inline QQmlInstantiationInterrupt();
+    // ### Qt 6: remove
     inline QQmlInstantiationInterrupt(volatile bool *runWhile, int nsecs=0);
+    inline QQmlInstantiationInterrupt(std::atomic<bool> *runWhile, int nsecs = 0);
     inline QQmlInstantiationInterrupt(int nsecs);
 
     inline void reset();
     inline bool shouldInterrupt() const;
 private:
-    enum Mode { None, Time, Flag };
+    enum Mode { None, Time, LegacyFlag, Flag }; // ### Qt 6: remove LegacyFlag
     Mode mode;
     QElapsedTimer timer;
-    int nsecs;
-    volatile bool *runWhile;
+    int nsecs = 0;
+    volatile bool *runWhileLegacy = nullptr; // ### Qt 6: remove
+    std::atomic<bool> *runWhile = nullptr;
 };
 
 class Q_QML_PRIVATE_EXPORT QQmlVME
@@ -147,17 +152,22 @@ private:
 };
 
 QQmlInstantiationInterrupt::QQmlInstantiationInterrupt()
-    : mode(None), nsecs(0), runWhile(nullptr)
+    : mode(None)
 {
 }
 
 QQmlInstantiationInterrupt::QQmlInstantiationInterrupt(volatile bool *runWhile, int nsecs)
+    : mode(LegacyFlag), nsecs(nsecs), runWhileLegacy(runWhile)
+{
+}
+
+QQmlInstantiationInterrupt::QQmlInstantiationInterrupt(std::atomic<bool> *runWhile, int nsecs)
     : mode(Flag), nsecs(nsecs), runWhile(runWhile)
 {
 }
 
 QQmlInstantiationInterrupt::QQmlInstantiationInterrupt(int nsecs)
-    : mode(Time), nsecs(nsecs), runWhile(nullptr)
+    : mode(Time), nsecs(nsecs)
 {
 }
 
@@ -169,15 +179,18 @@ void QQmlInstantiationInterrupt::reset()
 
 bool QQmlInstantiationInterrupt::shouldInterrupt() const
 {
-    if (mode == None) {
+    switch (mode) {
+    case None:
         return false;
-    } else if (mode == Time) {
+    case Time:
         return timer.nsecsElapsed() > nsecs;
-    } else if (mode == Flag) {
-        return !*runWhile || (nsecs && timer.nsecsElapsed() > nsecs);
-    } else {
-        return false;
+    case LegacyFlag:
+        return !*runWhileLegacy || (nsecs && timer.nsecsElapsed() > nsecs);
+    case Flag:
+        return !runWhile->load(std::memory_order_acquire) || (nsecs && timer.nsecsElapsed() > nsecs);
     }
+    Q_UNREACHABLE();
+    return false;
 }
 
 QT_END_NAMESPACE
diff --git a/tests/auto/qml/qqmlincubator/tst_qqmlincubator.cpp b/tests/auto/qml/qqmlincubator/tst_qqmlincubator.cpp
index 756b3b1d7c..549aae8c2b 100644
--- a/tests/auto/qml/qqmlincubator/tst_qqmlincubator.cpp
+++ b/tests/auto/qml/qqmlincubator/tst_qqmlincubator.cpp
@@ -149,7 +149,7 @@ void tst_qqmlincubator::objectDeleted()
         QVERIFY(!SelfRegisteringType::me());
 
         while (SelfRegisteringOuterType::me() == nullptr && incubator.isLoading()) {
-            bool b = false;
+            std::atomic<bool> b{false};
             controller.incubateWhile(&b);
         }
 
@@ -157,14 +157,14 @@ void tst_qqmlincubator::objectDeleted()
         QVERIFY(incubator.isLoading());
 
         while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-            bool b = false;
+            std::atomic<bool> b{false};
             controller.incubateWhile(&b);
         }
 
         delete SelfRegisteringType::me();
 
         {
-            bool b = true;
+            std::atomic<bool> b{true};
             controller.incubateWhile(&b);
         }
 
@@ -205,7 +205,7 @@ void tst_qqmlincubator::clear()
     component.create(incubator);
 
     while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -224,7 +224,7 @@ void tst_qqmlincubator::clear()
     component.create(incubator);
 
     {
-        bool b = true;
+        std::atomic<bool> b{true};
         controller.incubateWhile(&b);
     }
 
@@ -318,7 +318,7 @@ void tst_qqmlincubator::forceCompletion()
     QVERIFY(incubator.isLoading());
 
     while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -377,7 +377,7 @@ void tst_qqmlincubator::setInitialState()
     MyIncubator incubator(QQmlIncubator::Asynchronous);
     component.create(incubator);
     QVERIFY(incubator.isLoading());
-    bool b = true;
+    std::atomic<bool> b{true};
     controller.incubateWhile(&b);
     QVERIFY(incubator.isReady());
     QVERIFY(incubator.object());
@@ -414,7 +414,7 @@ void tst_qqmlincubator::clearDuringCompletion()
     QVERIFY(!CompletionRegisteringType::me());
 
     while (CompletionRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -453,7 +453,7 @@ void tst_qqmlincubator::objectDeletionAfterInit()
     component.create(incubator);
 
     while (!incubator.obj && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -552,7 +552,7 @@ void tst_qqmlincubator::statusChanged()
     QCOMPARE(incubator.statuses.at(0), int(QQmlIncubator::Loading));
 
     {
-    bool b = true;
+    std::atomic<bool> b{true};
     controller.incubateWhile(&b);
     }
 
@@ -574,7 +574,7 @@ void tst_qqmlincubator::statusChanged()
     QCOMPARE(incubator.statuses.at(0), int(QQmlIncubator::Loading));
 
     {
-    bool b = true;
+    std::atomic<bool> b{true};
     controller.incubateWhile(&b);
     }
 
@@ -622,7 +622,7 @@ void tst_qqmlincubator::asynchronousIfNested()
     QVERIFY(incubator.isLoading());
     QVERIFY(!SelfRegisteringType::me());
     while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -635,7 +635,7 @@ void tst_qqmlincubator::asynchronousIfNested()
 
     while (nested.isLoading()) {
         QVERIFY(incubator.isLoading());
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -643,7 +643,7 @@ void tst_qqmlincubator::asynchronousIfNested()
     QVERIFY(incubator.isLoading());
 
     {
-        bool b = true;
+        std::atomic<bool> b{true};
         controller.incubateWhile(&b);
     }
 
@@ -742,7 +742,7 @@ void tst_qqmlincubator::chainedAsynchronousIfNested()
     QVERIFY(!SelfRegisteringType::me());
 
     while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -779,7 +779,7 @@ void tst_qqmlincubator::chainedAsynchronousIfNested()
         QVERIFY(incubator1.isLoading());
         QVERIFY(incubator2.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -792,14 +792,14 @@ void tst_qqmlincubator::chainedAsynchronousIfNested()
         QVERIFY(incubator1.isReady());
         QVERIFY(incubator2.isLoading());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
     QVERIFY(incubator1.isReady());
     QVERIFY(incubator2.isReady());
     if (incubator.isLoading()) {
-        bool b = true;
+        std::atomic<bool> b{true};
         controller.incubateWhile(&b);
     }
 
@@ -856,7 +856,7 @@ void tst_qqmlincubator::chainedAsynchronousIfNestedOnCompleted()
     QVERIFY(!SelfRegisteringType::me());
 
     while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -876,7 +876,7 @@ void tst_qqmlincubator::chainedAsynchronousIfNestedOnCompleted()
         QVERIFY(incubator2.isNull());
         QVERIFY(incubator3.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -891,7 +891,7 @@ void tst_qqmlincubator::chainedAsynchronousIfNestedOnCompleted()
         QVERIFY(incubator2.isNull());
         QVERIFY(incubator3.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -906,7 +906,7 @@ void tst_qqmlincubator::chainedAsynchronousIfNestedOnCompleted()
         QVERIFY(incubator2.isLoading());
         QVERIFY(incubator3.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -921,12 +921,12 @@ void tst_qqmlincubator::chainedAsynchronousIfNestedOnCompleted()
         QVERIFY(incubator2.isReady());
         QVERIFY(incubator3.isLoading());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
     {
-    bool b = true;
+    std::atomic<bool> b{true};
     controller.incubateWhile(&b);
     }
 
@@ -984,7 +984,7 @@ void tst_qqmlincubator::chainedAsynchronousClear()
     QVERIFY(!SelfRegisteringType::me());
 
     while (SelfRegisteringType::me() == nullptr && incubator.isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -1004,7 +1004,7 @@ void tst_qqmlincubator::chainedAsynchronousClear()
         QVERIFY(incubator2.isNull());
         QVERIFY(incubator3.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -1019,7 +1019,7 @@ void tst_qqmlincubator::chainedAsynchronousClear()
         QVERIFY(incubator2.isNull());
         QVERIFY(incubator3.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -1034,7 +1034,7 @@ void tst_qqmlincubator::chainedAsynchronousClear()
         QVERIFY(incubator2.isLoading());
         QVERIFY(incubator3.isNull());
 
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -1078,7 +1078,7 @@ void tst_qqmlincubator::selfDelete()
 #define DELETE_TEST(status, mode) { \
     bool done = false; \
     component.create(*(new MyIncubator(&done, status, mode))); \
-    bool True = true; \
+    std::atomic<bool> True{true}; \
     controller.incubateWhile(&True); \
     QVERIFY(done == true); \
     }
@@ -1107,7 +1107,7 @@ void tst_qqmlincubator::selfDelete()
     QVERIFY(!SelfRegisteringType::me());
 
     while (SelfRegisteringType::me() == nullptr && incubator->isLoading()) {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 
@@ -1121,7 +1121,7 @@ void tst_qqmlincubator::selfDelete()
     delete SelfRegisteringType::me();
 
     {
-    bool b = true;
+    std::atomic<bool> b{true};
     controller.incubateWhile(&b);
     }
 
@@ -1142,7 +1142,7 @@ void tst_qqmlincubator::contextDelete()
     delete context;
 
     {
-        bool b = false;
+        std::atomic<bool> b{false};
         controller.incubateWhile(&b);
     }
 }
@@ -1155,7 +1155,7 @@ void tst_qqmlincubator::garbageCollection()
 
     engine.collectGarbage();
 
-    bool b = true;
+    std::atomic<bool> b{true};
     controller.incubateWhile(&b);
 
     // verify incubation completed (the incubator was not prematurely collected)