QtConcurrent: filter/map reduction without default ctor

Previously a default constructor was required for the result type
of mappedReduced() and filteredReduced(), even if a default value
was provided.

This patch fixes the problem.

The issue was in the ResultReporter type, that was calling
QList::resize() to adjust the size of expected reported results.
A default-value parameter was added to the class, so that
a corresponding overload of QList::resize could be invoked.

Task-number: QTBUG-88452
Change-Id: I51113753e314d76aa74d201b5a7e327a6ca75f47
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

1 files changed, 9 insertions, 11 deletions

diff --git a/src/concurrent/qtconcurrentfilterkernel.h b/src/concurrent/qtconcurrentfilterkernel.h
index ede775e9bd..379ea5a946 100644
--- a/src/concurrent/qtconcurrentfilterkernel.h
+++ b/src/concurrent/qtconcurrentfilterkernel.h
@@ -160,21 +160,19 @@ template <typename ReducedResultType,
                                           typename qValueType<Iterator>::value_type> >
 class FilteredReducedKernel : public IterateKernel<Iterator, ReducedResultType>
 {
-    ReducedResultType reducedResult;
+    ReducedResultType &reducedResult;
     KeepFunctor keep;
     ReduceFunctor reduce;
     Reducer reducer;
     typedef IterateKernel<Iterator, ReducedResultType> IterateKernelType;
 
 public:
-    template <typename Keep = KeepFunctor, typename Reduce = ReduceFunctor>
-    FilteredReducedKernel(QThreadPool *pool,
-                          Iterator begin,
-                          Iterator end,
-                          Keep &&_keep,
-                          Reduce &&_reduce,
-                          ReduceOptions reduceOption)
-        : IterateKernelType(pool, begin, end), reducedResult(), keep(std::forward<Keep>(_keep)),
+    template<typename Keep = KeepFunctor, typename Reduce = ReduceFunctor>
+    FilteredReducedKernel(QThreadPool *pool, Iterator begin, Iterator end, Keep &&_keep,
+                          Reduce &&_reduce, ReduceOptions reduceOption)
+        : IterateKernelType(pool, begin, end),
+          reducedResult(this->defaultValue.value),
+          keep(std::forward<Keep>(_keep)),
           reduce(std::forward<Reduce>(_reduce)),
           reducer(pool, reduceOption)
     { }
@@ -183,8 +181,8 @@ public:
     FilteredReducedKernel(QThreadPool *pool, Iterator begin, Iterator end, Keep &&_keep,
                           Reduce &&_reduce, ReducedResultType &&initialValue,
                           ReduceOptions reduceOption)
-        : IterateKernelType(pool, begin, end),
-          reducedResult(std::forward<ReducedResultType>(initialValue)),
+        : IterateKernelType(pool, begin, end, std::forward<ReducedResultType>(initialValue)),
+          reducedResult(this->defaultValue.value),
           keep(std::forward<Keep>(_keep)),
           reduce(std::forward<Reduce>(_reduce)),
           reducer(pool, reduceOption)