From afdae3618a08da9f2c41b7c4ea57219f444ee324 Mon Sep 17 00:00:00 2001
From: Sona Kurazyan <sona.kurazyan@qt.io>
Date: Tue, 18 Jan 2022 13:35:24 +0100
Subject: [PATCH] Create QFutures returned by QtFuture::when* methods via
 QPromise
MIME-Version: 1.0
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This is required to ensure that the continuation attached to a
QFuture returned by QtFuture::when* methods is cleaned in the destructor
of the associated QPromise, so that it doesn't keep any ref-counted
copies to the shared data, thus preventing it from being deleted.

Task-number: QTBUG-99534
Pick-to: 6.3
Change-Id: If4e2929b2e638d6b48c95f0aef9dc886066cedbe
Reviewed-by: Andrei Golubev <andrei.golubev@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
---
 src/corelib/thread/qfuture_impl.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/corelib/thread/qfuture_impl.h b/src/corelib/thread/qfuture_impl.h
index 112ac21f9e8..69f57652ea0 100644
--- a/src/corelib/thread/qfuture_impl.h
+++ b/src/corelib/thread/qfuture_impl.h
@@ -1006,13 +1006,13 @@ struct WhenAllContext
         futures[index] = std::forward<T>(future);
         Q_ASSERT(count > 0);
         if (--count <= 0) {
-            promise.reportResult(futures);
-            promise.reportFinished();
+            promise.addResult(futures);
+            promise.finish();
         }
     }
 
     QAtomicInteger<qsizetype> count;
-    QFutureInterface<ResultFutures> promise;
+    QPromise<ResultFutures> promise;
     ResultFutures futures;
 };
 
@@ -1025,13 +1025,13 @@ struct WhenAnyContext
     void checkForCompletion(qsizetype, T &&result)
     {
         if (!ready.fetchAndStoreRelaxed(true)) {
-            promise.reportResult(std::forward<T>(result));
-            promise.reportFinished();
+            promise.addResult(std::forward<T>(result));
+            promise.finish();
         }
     }
 
     QAtomicInt ready = false;
-    QFutureInterface<ResultType> promise;
+    QPromise<ResultType> promise;
 };
 
 template<qsizetype Index, typename ContextType, typename... Ts>
@@ -1066,7 +1066,7 @@ QFuture<OutputSequence> whenAllImpl(InputIt first, InputIt last)
 
     auto context = QSharedPointer<QtPrivate::WhenAllContext<OutputSequence>>::create(size);
     context->futures.resize(size);
-    context->promise.reportStarted();
+    context->promise.start();
 
     qsizetype idx = 0;
     for (auto it = first; it != last; ++it, ++idx) {
@@ -1085,7 +1085,7 @@ QFuture<OutputSequence> whenAllImpl(Futures &&... futures)
     constexpr qsizetype size = sizeof...(Futures);
     auto context = QSharedPointer<QtPrivate::WhenAllContext<OutputSequence>>::create(size);
     context->futures.resize(size);
-    context->promise.reportStarted();
+    context->promise.start();
 
     QtPrivate::addCompletionHandlers(context, std::make_tuple(std::forward<Futures>(futures)...));
 
@@ -1106,7 +1106,7 @@ QFuture<QtFuture::WhenAnyResult<typename Future<ValueType>::type>> whenAnyImpl(I
     }
 
     auto context = QSharedPointer<QtPrivate::WhenAnyContext<ResultType>>::create();
-    context->promise.reportStarted();
+    context->promise.start();
 
     qsizetype idx = 0;
     for (auto it = first; it != last; ++it, ++idx) {
@@ -1125,7 +1125,7 @@ QFuture<std::variant<std::decay_t<Futures>...>> whenAnyImpl(Futures &&... future
     using ResultType = std::variant<std::decay_t<Futures>...>;
 
     auto context = QSharedPointer<QtPrivate::WhenAnyContext<ResultType>>::create();
-    context->promise.reportStarted();
+    context->promise.start();
 
     QtPrivate::addCompletionHandlers(context, std::make_tuple(std::forward<Futures>(futures)...));