fix crash when deallocating sibling Element proxies that do not have a parent

2 files changed, 47 insertions, 3 deletions

diff --git a/src/lxml/proxy.pxi b/src/lxml/proxy.pxi
index 52909f69..e3b78165 100644
--- a/src/lxml/proxy.pxi
+++ b/src/lxml/proxy.pxi
@@ -167,6 +167,7 @@ cdef int attemptDeallocation(xmlNode* c_node):
 cdef xmlNode* getDeallocationTop(xmlNode* c_node):
     u"""Return the top of the tree that can be deallocated, or NULL.
     """
+    cdef xmlNode* c_next
     #print "trying to do deallocating:", c_node.type
     if hasProxy(c_node):
         #print "Not freeing: proxies still exist"
@@ -183,10 +184,22 @@ cdef xmlNode* getDeallocationTop(xmlNode* c_node):
             #print "Not freeing: proxies still exist"
             return NULL
     # see whether we have children to deallocate
-    if canDeallocateChildNodes(c_node):
-        return c_node
-    else:
+    if not canDeallocateChildNodes(c_node):
         return NULL
+    # see whether we have siblings to deallocate
+    c_next = c_node.prev
+    while c_next:
+        if _isElement(c_next):
+            if hasProxy(c_next) or not canDeallocateChildNodes(c_next):
+                return NULL
+        c_next = c_next.prev
+    c_next = c_node.next
+    while c_next:
+        if _isElement(c_next):
+            if hasProxy(c_next) or not canDeallocateChildNodes(c_next):
+                return NULL
+        c_next = c_next.next
+    return c_node
 
 cdef int canDeallocateChildNodes(xmlNode* c_parent):
     cdef xmlNode* c_node
diff --git a/src/lxml/tests/test_etree.py b/src/lxml/tests/test_etree.py
index 41d6571f..132e2ce9 100644
--- a/src/lxml/tests/test_etree.py
+++ b/src/lxml/tests/test_etree.py
@@ -3557,6 +3557,37 @@ class ETreeOnlyTestCase(HelperTestCase):
         gc.collect()
         # not really testing anything here, but it shouldn't crash
 
+    def test_proxy_collect_siblings(self):
+        root = etree.Element('parent')
+        c1 = etree.SubElement(root, 'child1')
+        c2 = etree.SubElement(root, 'child2')
+
+        root.remove(c1)
+        root.remove(c2)
+        c1.addnext(c2)
+        del c1
+        # trigger deallocation attempt of c1
+        c2.getprevious()
+        # make sure it wasn't deallocated
+        self.assertEqual('child1', c2.getprevious().tag)
+
+    def test_proxy_collect_siblings_text(self):
+        root = etree.Element('parent')
+        c1 = etree.SubElement(root, 'child1')
+        c2 = etree.SubElement(root, 'child2')
+
+        root.remove(c1)
+        root.remove(c2)
+        c1.addnext(c2)
+        c1.tail = 'abc'
+        c2.tail = 'xyz'
+        del c1
+        # trigger deallocation attempt of c1
+        c2.getprevious()
+        # make sure it wasn't deallocated
+        self.assertEqual('child1', c2.getprevious().tag)
+        self.assertEqual('abc', c2.getprevious().tail)
+
     # helper methods
 
     def _writeElement(self, element, encoding='us-ascii', compression=0):