fix doctree leak

HTML like

<div>hello</div>
</body>
</html>
<div>hello</div>

currently causes the document tree to be a forest with
two root nodes.
To ensure we don't leak the first tree, an additional root node is
introduced to hold all document trees.

Catched by: Jeremy's valgrind logs
Reported by: corvid <corvid@lavabit.com>

2 files changed, 25 insertions, 16 deletions

diff --git a/src/css.cc b/src/css.cc
index aa799002..e9a8eb56 100644
--- a/src/css.cc
+++ b/src/css.cc
@@ -150,7 +150,7 @@ bool CssSelector::match (Doctree *docTree, const DoctreeNode *node) {
                if (sel->match (node))
                   break;
 
-               node = node->parent;
+               node = docTree->parent (node);
             }
             break;
          default:
@@ -160,9 +160,9 @@ bool CssSelector::match (Doctree *docTree, const DoctreeNode *node) {
       comb = cs->combinator;
 
       if (comb == ADJACENT_SIBLING)
-         node = node->sibling;
+         node = docTree->sibling (node);
       else 
-         node = node->parent;
+         node = docTree->parent (node);
    }
 
    return true;
diff --git a/src/doctree.hh b/src/doctree.hh
index c46a5a10..92cf6f0d 100644
--- a/src/doctree.hh
+++ b/src/doctree.hh
@@ -53,37 +53,46 @@ class Doctree {
 
    public:
       Doctree () {
-         topNode = NULL;
-         rootNode = NULL;
+         rootNode = new DoctreeNode;
+         topNode = rootNode;
          num = 0;
       };
 
       ~Doctree () { 
-         if (rootNode)
-            delete rootNode;
+         delete rootNode;
       };
 
       DoctreeNode *push () {
          DoctreeNode *dn = new DoctreeNode ();
          dn->parent = topNode;
-         if (dn->parent) {
-            dn->sibling = dn->parent->lastChild;
-            dn->parent->lastChild = dn;
-         }
+         dn->sibling = dn->parent->lastChild;
+         dn->parent->lastChild = dn;
          dn->num = num++;
-         if (!rootNode)
-            rootNode = dn;
          topNode = dn;
          return dn;
       };
 
       void pop () {
-         if (topNode)
-            topNode = topNode->parent;
+         assert (topNode != rootNode); // never pop the root node
+         topNode = topNode->parent;
       };
 
       inline DoctreeNode *top () {
-         return topNode;
+         if (topNode != rootNode)
+            return topNode;
+         else
+            return NULL;
+      };
+
+      inline DoctreeNode *parent (const DoctreeNode *node) {
+         if (node->parent != rootNode) 
+            return node->parent;
+         else
+            return NULL;
+      };
+
+      inline DoctreeNode *sibling (const DoctreeNode *node) {
+         return node->sibling;
       };
 };