6 files changed, 40 insertions, 5 deletions
diff --git a/src/gui/kernel/qboxlayout.cpp b/src/gui/kernel/qboxlayout.cpp
index 91393ed..444cea2 100644
--- a/src/gui/kernel/qboxlayout.cpp
+++ b/src/gui/kernel/qboxlayout.cpp
@@ -1001,7 +1001,8 @@ void QBoxLayout::insertSpacerItem(int index, QSpacerItem *spacerItem)
 void QBoxLayout::insertLayout(int index, QLayout *layout, int stretch)
 {
     Q_D(QBoxLayout);
-    addChildLayout(layout);
+    if (!adoptLayout(layout))
+        return;
     if (index < 0)                                // append
         index = d->list.count();
     QBoxLayoutItem *it = new QBoxLayoutItem(layout, stretch);
diff --git a/src/gui/kernel/qformlayout.cpp b/src/gui/kernel/qformlayout.cpp
index ba88211..8f97d1c 100644
--- a/src/gui/kernel/qformlayout.cpp
+++ b/src/gui/kernel/qformlayout.cpp
@@ -976,8 +976,8 @@ void QFormLayoutPrivate::setLayout(int row, QFormLayout::ItemRole role, QLayout
 {
     if (layout) {
         Q_Q(QFormLayout);
-        q->addChildLayout(layout);
-        setItem(row, role, layout);
+        if (q->adoptLayout(layout))
+            setItem(row, role, layout);
     }
 }
 
diff --git a/src/gui/kernel/qgridlayout.cpp b/src/gui/kernel/qgridlayout.cpp
index c9550de..731d5cd9 100644
--- a/src/gui/kernel/qgridlayout.cpp
+++ b/src/gui/kernel/qgridlayout.cpp
@@ -1609,7 +1609,8 @@ void QGridLayout::addWidget(QWidget *widget, int fromRow, int fromColumn,
 void QGridLayout::addLayout(QLayout *layout, int row, int column, Qt::Alignment alignment)
 {
     Q_D(QGridLayout);
-    addChildLayout(layout);
+    if (!adoptLayout(layout))
+        return;
     QGridBox *b = new QGridBox(layout);
     b->setAlignment(alignment);
     d->add(b, row, column);
@@ -1628,7 +1629,8 @@ void QGridLayout::addLayout(QLayout *layout, int row, int column,
                                       int rowSpan, int columnSpan, Qt::Alignment alignment)
 {
     Q_D(QGridLayout);
-    addChildLayout(layout);
+    if (!adoptLayout(layout))
+        return;
     QGridBox *b = new QGridBox(layout);
     b->setAlignment(alignment);
     d->add(b, row, (rowSpan < 0) ? -1 : row + rowSpan - 1, column, (columnSpan < 0) ? -1 : column + columnSpan - 1);
diff --git a/src/gui/kernel/qlayout.cpp b/src/gui/kernel/qlayout.cpp
index 1f7b34c..ce8322b 100644
--- a/src/gui/kernel/qlayout.cpp
+++ b/src/gui/kernel/qlayout.cpp
@@ -935,6 +935,16 @@ void QLayout::addChildLayout(QLayout *l)
 
 }
 
+/*!
+   \internal
+ */
+bool QLayout::adoptLayout(QLayout *layout)
+{
+    const bool ok = !layout->parent();
+    addChildLayout(layout);
+    return ok;
+}
+
 #ifdef QT_DEBUG
 static bool layoutDebug()
 {
diff --git a/src/gui/kernel/qlayout.h b/src/gui/kernel/qlayout.h
index d4a79d9..09f0e33 100644
--- a/src/gui/kernel/qlayout.h
+++ b/src/gui/kernel/qlayout.h
@@ -189,6 +189,7 @@ protected:
     void childEvent(QChildEvent *e);
     void addChildLayout(QLayout *l);
     void addChildWidget(QWidget *w);
+    bool adoptLayout(QLayout *layout);
 #ifdef QT3_SUPPORT
     QT3_SUPPORT void deleteAllItems();
 #endif
diff --git a/tests/auto/qboxlayout/tst_qboxlayout.cpp b/tests/auto/qboxlayout/tst_qboxlayout.cpp
index 0f9bbce..466be31 100644
--- a/tests/auto/qboxlayout/tst_qboxlayout.cpp
+++ b/tests/auto/qboxlayout/tst_qboxlayout.cpp
@@ -62,6 +62,7 @@ public slots:
 
 private slots:
     void insertSpacerItem();
+    void insertLayout();
     void sizeHint();
     void sizeConstraints();
     void setGeometry();
@@ -160,6 +161,26 @@ void tst_QBoxLayout::insertSpacerItem()
     window->show();
 }
 
+void tst_QBoxLayout::insertLayout()
+{
+    QWidget *window = new QWidget;
+    QVBoxLayout *vbox = new QVBoxLayout(window);
+    QVBoxLayout *dummyParentLayout = new QVBoxLayout;
+    QHBoxLayout *subLayout = new QHBoxLayout;
+    dummyParentLayout->addLayout(subLayout);
+    QCOMPARE(subLayout->parent(), dummyParentLayout);
+    QCOMPARE(dummyParentLayout->count(), 1);
+
+    // add subLayout to another layout
+    QTest::ignoreMessage(QtWarningMsg, "QLayout::addChildLayout: layout \"\" already has a parent");
+    vbox->addLayout(subLayout);
+    QCOMPARE((subLayout->parent() == vbox), (vbox->count() == 1));
+
+    delete dummyParentLayout;
+    delete window;
+}
+
+
 void tst_QBoxLayout::sizeHint()
 {
     QWidget *window = new QWidget;