Fix integer overflows in QDeadlineTimer

If the deadline is far in the future, the conversions to nanoseconds
or internal arithmetic may overflow and give an invalid object, thus
the deadline may end up in the past. Added a test to the testlib
selftest for sleep.

[ChangeLog][QtCore][QDeadlineTimer] Fixed integer overflows
leading to immediate timeouts.

Task-number: QTBUG-69750
Change-Id: I9814eccdf9f9b3add9ca66ec3e27e10cd5ad54a8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 79 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp b/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
index 6ab24d2480..4ca68550b9 100644
--- a/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
+++ b/tests/auto/corelib/kernel/qdeadlinetimer/tst_qdeadlinetimer.cpp
@@ -29,6 +29,7 @@
 #include <QtCore/QString>
 #include <QtCore/QTime>
 #include <QtCore/QDeadlineTimer>
+#include <QtCore/QElapsedTimer>
 #include <QtTest/QtTest>
 
 #if QT_HAS_INCLUDE(<chrono>)
@@ -50,6 +51,7 @@ private Q_SLOTS:
     void current();
     void deadlines();
     void setDeadline();
+    void overflow();
     void expire();
     void stdchrono();
 };
@@ -417,6 +419,83 @@ void tst_QDeadlineTimer::setDeadline()
     QCOMPARE(deadline.deadlineNSecs(), nsec);
 }
 
+void tst_QDeadlineTimer::overflow()
+{
+    QFETCH_GLOBAL(Qt::TimerType, timerType);
+    // Check the constructor for overflows (should also cover saturating the result of the deadline() method if overflowing)
+    QDeadlineTimer now = QDeadlineTimer::current(timerType), deadline(std::numeric_limits<qint64>::max() - 1, timerType);
+    QVERIFY(deadline.isForever() || deadline.deadline() >= now.deadline());
+
+    // Check the setDeadline with milliseconds (should also cover implicitly setting the nanoseconds as qint64 max)
+    deadline.setDeadline(std::numeric_limits<qint64>::max() - 1, timerType);
+    QVERIFY(deadline.isForever() || deadline.deadline() >= now.deadline());
+
+    // Check the setRemainingTime with milliseconds (should also cover implicitly setting the nanoseconds as qint64 max)
+    deadline.setRemainingTime(std::numeric_limits<qint64>::max() - 1, timerType);
+    QVERIFY(deadline.isForever() || deadline.deadline() >= now.deadline());
+
+    // Check that the deadline gets saturated when the arguments of setPreciseDeadline are large
+    deadline.setPreciseDeadline(std::numeric_limits<qint64>::max() - 1, std::numeric_limits<qint64>::max() - 1, timerType);
+    QCOMPARE(deadline.deadline(), std::numeric_limits<qint64>::max());
+    QVERIFY(deadline.isForever());
+
+    // Check that remainingTime gets saturated if we overflow
+    deadline.setPreciseRemainingTime(std::numeric_limits<qint64>::max() - 1, std::numeric_limits<qint64>::max() - 1, timerType);
+    QCOMPARE(deadline.remainingTime(), qint64(-1));
+    QVERIFY(deadline.isForever());
+
+    // Check that we saturate the getter for nanoseconds
+    deadline.setPreciseDeadline(std::numeric_limits<qint64>::max() - 1, 0, timerType);
+    QCOMPARE(deadline.deadlineNSecs(), std::numeric_limits<qint64>::max());
+
+    // Check that adding nanoseconds and overflowing is consistent and saturates the timer
+    deadline = QDeadlineTimer::addNSecs(deadline, std::numeric_limits<qint64>::max() - 1);
+    QVERIFY(deadline.isForever());
+
+    // Make sure forever is forever, regardless of us subtracting time from it
+    deadline = QDeadlineTimer(QDeadlineTimer::Forever, timerType);
+    deadline = QDeadlineTimer::addNSecs(deadline, -10000);
+    QVERIFY(deadline.isForever());
+
+    // Make sure we get the correct result when moving the deadline back and forth in time
+    QDeadlineTimer current = QDeadlineTimer::current(timerType);
+    QDeadlineTimer takenNSecs = QDeadlineTimer::addNSecs(current, -1000);
+    QVERIFY(takenNSecs.deadlineNSecs() - current.deadlineNSecs() == -1000);
+    QDeadlineTimer addedNSecs = QDeadlineTimer::addNSecs(current, 1000);
+    QVERIFY(addedNSecs.deadlineNSecs() - current.deadlineNSecs() == 1000);
+
+    // Make sure the calculation goes as expected when we need to subtract nanoseconds
+    // We make use of an additional timer to be certain that
+    // even when the environment is under load we can track the
+    // time needed to do the calls
+    static constexpr qint64 nsExpected = 1000 * 1000 * 1000 - 1000;     // 1s - 1000ns, what we pass to setPreciseRemainingTime() later
+
+    QElapsedTimer callTimer;
+    callTimer.start();
+
+    deadline = QDeadlineTimer::current(timerType);
+    qint64 nsDeadline = deadline.deadlineNSecs();
+    // We adjust in relation to current() here, so we expect the difference to be a tad over the exact number.
+    // However we are tracking the elapsed time, so it shouldn't be a problem.
+    deadline.setPreciseRemainingTime(1, -1000, timerType);
+    qint64 difference = (deadline.deadlineNSecs() - nsDeadline) - nsExpected;
+    QVERIFY(difference >= 0);        // Should always be true, but just in case
+    QVERIFY(difference <= callTimer.nsecsElapsed()); // Ideally difference should be 0 exactly
+
+    // Make sure setRemainingTime underflows gracefully
+    deadline.setPreciseRemainingTime(std::numeric_limits<qint64>::min() / 10, 0, timerType);
+    QVERIFY(!deadline.isForever());     // On Win/macOS the above underflows, make sure we don't saturate to Forever
+    QVERIFY(deadline.remainingTime() == 0);
+    // If the timer is saturated we don't want to get a valid number of milliseconds
+    QVERIFY(deadline.deadline() == std::numeric_limits<qint64>::min());
+
+    // Check that the conversion to milliseconds and nanoseconds underflows gracefully
+    deadline.setPreciseDeadline(std::numeric_limits<qint64>::min() / 10, 0, timerType);
+    QVERIFY(!deadline.isForever());     // On Win/macOS the above underflows, make sure we don't saturate to Forever
+    QVERIFY(deadline.deadline() == std::numeric_limits<qint64>::min());
+    QVERIFY(deadline.deadlineNSecs() == std::numeric_limits<qint64>::min());
+}
+
 void tst_QDeadlineTimer::expire()
 {
     QFETCH_GLOBAL(Qt::TimerType, timerType);