QList: remove yet another iterator->pointer implicit conversion

The ranged constructor for QList has an optimization when the
iterators are QList's own iterators. In that case, it uses a
"contiguous append" shortcut by converting the iterators to pointers.
Avoid that conversion by extracting the pointers from the iterators.

Note that this is an optimization for C++17 only; in C++20
appendIteratorRange will deal with this case as well. Leave a note.

Change-Id: I761c36ff500dee95b4ae1b0a4479d22db0c8e3de
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index c1d59617c3..6f0e0931d4 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -130,6 +130,7 @@ public:
 #endif
 
     class iterator {
+        friend class QList<T>;
         T *i = nullptr;
     public:
         using difference_type = qsizetype;
@@ -178,6 +179,7 @@ public:
     };
 
     class const_iterator {
+        friend class QList<T>;
         const T *i = nullptr;
     public:
         using difference_type = qsizetype;
@@ -282,9 +284,11 @@ public:
             const auto distance = std::distance(i1, i2);
             if (distance) {
                 d = DataPointer(Data::allocate(distance));
+                // appendIteratorRange can deal with contiguous iterators on its own,
+                // this is an optimization for C++17 code.
                 if constexpr (std::is_same_v<std::decay_t<InputIterator>, iterator> ||
                               std::is_same_v<std::decay_t<InputIterator>, const_iterator>) {
-                    d->copyAppend(i1, i2);
+                    d->copyAppend(i1.i, i2.i);
                 } else {
                     d->appendIteratorRange(i1, i2);
                }