diff options
author | Marc Mutz <marc.mutz@kdab.com> | 2016-10-17 13:00:04 +0200 |
---|---|---|
committer | Marc Mutz <marc.mutz@kdab.com> | 2016-10-18 16:06:28 +0000 |
commit | e80faf3db61ca9c701cd86876e3bce8e33226576 (patch) | |
tree | 279ad81c075f711ea776f5cff37db88c9571d129 /tests/auto | |
parent | 3a1245fdace1b008018dfb6b6334d5ebaec81b5e (diff) |
QTimer: don't circumvent <chrono> safety net
By templating on the <chrono> types and unconditionally using
duration_cast to coerce the duration into a milliseconds, we
violate a principal design rule of <chrono>, namely that non-
narrowing conversions are implicit, but narrowing conversions
need duration_cast. By accepting any duration, we allow non-
sensical code such as
QTimer::singleShot(10us, ...)
to compile, which is misleading, since it's actually a zero-
timeout timer.
Overloading a non-template with a template also has adverse
effects: it breaks qOverload().
Fix by replacing the function templates with functions that
just take std::chrono::milliseconds. This way, benign code
such as
QTimer::singleShot(10s, ...)
QTimer::singleShot(10min, ...)
QTimer::singleShot(1h, ...)
work as expected, but attempts to use sub-millisecond
resolution fails to compile / needs an explicit user-
provided duration_cast.
To allow future extension to more precise timers, forcibly
inline the functions, so they don't partake in the ABI of the
class and we can later support sub-millisecond resolution by
simply taking micro- or nano- instead of milliseconds.
Change-Id: I12c9a98bdabefcd8ec18a9eb09f87ad908d889de
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'tests/auto')
-rw-r--r-- | tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp index 28df01cc16..fe97695d19 100644 --- a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp +++ b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp @@ -216,6 +216,16 @@ void tst_QTimer::remainingTimeDuringActivation() } } +namespace { + +#if QT_HAS_INCLUDE(<chrono>) + template <typename T> + std::chrono::milliseconds to_ms(T t) + { return std::chrono::duration_cast<std::chrono::milliseconds>(t); } +#endif + +} // unnamed namespace + void tst_QTimer::basic_chrono() { #if !QT_HAS_INCLUDE(<chrono>) @@ -225,7 +235,7 @@ void tst_QTimer::basic_chrono() using namespace std::chrono; TimerHelper helper; QTimer timer; - timer.setInterval(nanoseconds(0)); + timer.setInterval(to_ms(nanoseconds(0))); timer.start(); QCOMPARE(timer.intervalAsDuration().count(), milliseconds::rep(0)); QCOMPARE(timer.remainingTimeAsDuration().count(), milliseconds::rep(0)); @@ -248,7 +258,7 @@ void tst_QTimer::basic_chrono() QVERIFY(helper.count > oldCount); helper.count = 0; - timer.start(microseconds(200000)); + timer.start(to_ms(microseconds(200000))); QCOMPARE(timer.intervalAsDuration().count(), milliseconds::rep(200)); QTest::qWait(50); QCOMPARE(helper.count, 0); @@ -864,7 +874,7 @@ void tst_QTimer::singleShot_chrono() QCOMPARE(nhelper.count, 1); int count = 0; - QTimer::singleShot(microseconds(0), CountedStruct(&count)); + QTimer::singleShot(to_ms(microseconds(0)), CountedStruct(&count)); QCoreApplication::processEvents(); QCOMPARE(count, 1); |