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Always cancel unfinished QPromises on destruction 

If the QPromise is being destroyed, we should signal the associated
futures to stop waiting. No matter in which state the promise is, if
it's not finished, we should always cancel to avoid infinite waits.
This is also what docs state:

"The promise implicitly transitions to a canceled state on destruction
unless finish() is called beforehand by the user."

Fixes: QTBUG-101284
Pick-to: 6.3 6.2
Change-Id: I65ebfefe03b79b41afacda78a4f49938c54d8b37
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
bb10
Sona Kurazyan 2022-03-23 09:30:23 +01:00
parent 837bfd6f14
commit 76a1c060ac
2 changed files with 16 additions and 8 deletions
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10
src/corelib/thread/qpromise.h
View File

@ -71,15 +71,9 @@ public:
QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QPromise)
~QPromise()
{
const int state = d.loadState();
// If QFutureInterface has no state, there is nothing to be done
if (state == static_cast<int>(QFutureInterfaceBase::State::NoState)) {
d.cleanContinuation();
return;
}
// Otherwise, if computation is not finished at this point, cancel
// If computation is not finished at this point, cancel
// potential waits
if (!(state & QFutureInterfaceBase::State::Finished)) {
if (d.d && !(d.loadState() & QFutureInterfaceBase::State::Finished)) {
d.cancelAndFinish(); // cancel and finalize the state
d.cleanContinuation();
}

14
tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
View File

@ -64,6 +64,7 @@ private slots:
void cancelWhenDestroyed();
#endif
void cancelWhenReassigned();
void cancelWhenDestroyedWithoutStarting();
void finishWhenSwapped();
void cancelWhenMoved();
void waitUntilResumed();
@ -505,6 +506,19 @@ void tst_QPromise::cancelWhenReassigned()
#endif
}
void tst_QPromise::cancelWhenDestroyedWithoutStarting()
{
QFuture<void> future;
{
QPromise<void> promise;
future = promise.future();
}
future.waitForFinished();
QVERIFY(!future.isStarted());
QVERIFY(future.isCanceled());
QVERIFY(future.isFinished());
}
void tst_QPromise::finishWhenSwapped()
{
#if !QT_CONFIG(cxx11_future)