QLinkedList - fix erase with iterator when the list is shared.

Before a call to erase on a shared instance would imply that the
item was removed from the shared data (i.e all instances)

This patch improves the behavior to detach and erase the item
specified by the iterator (i.e same behavior as QVector)

Change-Id: Ib3cfb5363c86b400886c80b75b0c20ca854ce801
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 32 insertions, 2 deletions

diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index b9ca1b964a..99be770ae9 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -91,7 +91,7 @@ public:
 
     inline int size() const { return d->size; }
     inline void detach()
-    { if (d->ref.isShared()) detach_helper(); }
+    { if (d->ref.isShared()) detach_helper2(this->e); }
     inline bool isDetached() const { return !d->ref.isShared(); }
     inline void setSharable(bool sharable) { if (!sharable) detach(); if (d != &QLinkedListData::shared_null) d->sharable = sharable; }
     inline bool isSharedWith(const QLinkedList<T> &other) const { return d == other.d; }
@@ -232,6 +232,7 @@ public:
 
 private:
     void detach_helper();
+    iterator detach_helper2(iterator);
     void freeData(QLinkedListData*);
 };
 
@@ -245,6 +246,14 @@ inline QLinkedList<T>::~QLinkedList()
 template <typename T>
 void QLinkedList<T>::detach_helper()
 {
+    detach_helper2(this->e);
+}
+
+template <typename T>
+typename QLinkedList<T>::iterator QLinkedList<T>::detach_helper2(iterator orgite)
+{
+    // detach and convert orgite to an iterator in the detached instance
+    bool isEndIterator = (orgite.i == this->e);
     union { QLinkedListData *d; Node *e; } x;
     x.d = new QLinkedListData;
     x.d->ref.initializeOwned();
@@ -252,6 +261,22 @@ void QLinkedList<T>::detach_helper()
     x.d->sharable = true;
     Node *original = e->n;
     Node *copy = x.e;
+    Node *org = orgite.i;
+
+    while (original != org) {
+        QT_TRY {
+            copy->n = new Node(original->t);
+            copy->n->p = copy;
+            original = original->n;
+            copy = copy->n;
+        } QT_CATCH(...) {
+            copy->n = x.e;
+            Q_ASSERT(!x.d->ref.deref()); // Don't trigger assert in free
+            freeData(x.d);
+            QT_RETHROW;
+        }
+    }
+    iterator r(copy);
     while (original != e) {
         QT_TRY {
             copy->n = new Node(original->t);
@@ -270,6 +295,9 @@ void QLinkedList<T>::detach_helper()
     if (!d->ref.deref())
         freeData(d);
     d = x.d;
+    if (!isEndIterator)
+        ++r; // since we stored the element right before the original node.
+    return r;
 }
 
 template <typename T>
@@ -448,7 +476,9 @@ typename QLinkedList<T>::iterator QLinkedList<T>::erase(typename QLinkedList<T>:
 template <typename T>
 typename QLinkedList<T>::iterator QLinkedList<T>::erase(iterator pos)
 {
-    detach();
+    if (d->ref.isShared())
+        pos = detach_helper2(pos);
+
     Node *i = pos.i;
     if (i != e) {
         Node *n = i;