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 /src/corelib/kernel/qtimer.cpp | |
| 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 'src/corelib/kernel/qtimer.cpp')
| -rw-r--r-- | src/corelib/kernel/qtimer.cpp | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/src/corelib/kernel/qtimer.cpp b/src/corelib/kernel/qtimer.cpp index 6d39233aa7..4a5738a6dc 100644 --- a/src/corelib/kernel/qtimer.cpp +++ b/src/corelib/kernel/qtimer.cpp @@ -533,7 +533,7 @@ void QTimer::singleShot(int msec, Qt::TimerType timerType, const QObject *receiv */ /*! - \fn void QTimer::singleShot(std::chrono::duration<Rep, Period> value, const QObject *receiver, const char *member) + \fn void QTimer::singleShot(std::chrono::milliseconds msec, const QObject *receiver, const char *member) \since 5.8 \overload \reentrant @@ -545,13 +545,13 @@ void QTimer::singleShot(int msec, Qt::TimerType timerType, const QObject *receiv create a local QTimer object. The \a receiver is the receiving object and the \a member is the slot. The - time interval is given in the duration object \a value. + time interval is given in the duration object \a msec. \sa start() */ /*! - \fn void QTimer::singleShot(std::chrono::duration<Rep, Period> value, Qt::TimerType timerType, const QObject *receiver, const char *member) + \fn void QTimer::singleShot(std::chrono::milliseconds msec, Qt::TimerType timerType, const QObject *receiver, const char *member) \since 5.8 \overload \reentrant @@ -563,18 +563,18 @@ void QTimer::singleShot(int msec, Qt::TimerType timerType, const QObject *receiv create a local QTimer object. The \a receiver is the receiving object and the \a member is the slot. The - time interval is given in the duration object \a value. The \a timerType affects the + time interval is given in the duration object \a msec. The \a timerType affects the accuracy of the timer. \sa start() */ /*! - \fn void QTimer::start(std::chrono::duration<Rep, Period> value) + \fn void QTimer::start(std::chrono::milliseconds msec) \since 5.8 \overload - Starts or restarts the timer with a timeout of duration \a value. + Starts or restarts the timer with a timeout of duration \a msec milliseconds. If the timer is already running, it will be \l{QTimer::stop()}{stopped} and restarted. |