cssrbtree: Fix a crasher

After removing elements, there were a few cases where the tree wasn't
properly balanced which could further down violate assumptions about the
layout.

Attached is the original testcase that triggered it. I didn't bother
simplifying it.

gtk/gtkcssrbtree.c

@@ -353,7 +353,7 @@ gtk_css_rb_tree_remove_node_fixup (GtkCssRbTree *tree,
                                    GtkCssRbNode *node,
                                    GtkCssRbNode *parent)
 {
-  while (node->parent && is_black (node))
+  while (node != tree->root && is_black (node))
     {
       if (node == parent->left)
 	{
@@ -664,7 +664,7 @@ gtk_css_rb_tree_remove (GtkCssRbTree *tree,
 
   /* We need to clean up the validity of the tree.
    */
-  if (x && is_black (y))
+  if (is_black (y))
     gtk_css_rb_tree_remove_node_fixup (tree, x, y->parent);
 
   if (y != real_node)

testsuite/gtk/cssrbtree-crash.c

@@ -0,0 +1,286 @@
+/* GtkRBTree tests.
+ *
+ * Copyright (C) 2011, Red Hat, Inc.
+ * Authors: Benjamin Otte <otte@gnome.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <locale.h>
+
+#include <gtk/gtk.h>
+
+#include "gtk/gtkcssrbtreeprivate.h"
+
+typedef struct _Node Node;
+typedef struct _Aug Aug;
+
+struct _Node {
+  guint unused;
+};
+
+struct _Aug {
+  guint n_items;
+};
+
+static void
+augment (GtkCssRbTree *tree,
+         gpointer      _aug,
+         gpointer      _node,
+         gpointer      left,
+         gpointer      right)
+{
+  Aug *aug = _aug;
+  
+  aug->n_items = 1;
+
+  if (left)
+    {
+      Aug *left_aug = gtk_css_rb_tree_get_augment (tree, left);
+
+      aug->n_items += left_aug->n_items;
+    }
+
+  if (right)
+    {
+      Aug *right_aug = gtk_css_rb_tree_get_augment (tree, right);
+
+      aug->n_items += right_aug->n_items;
+    }
+}
+
+static Node *
+get (GtkCssRbTree *tree,
+     guint         pos)
+{
+  Node *node, *tmp;
+
+  node = gtk_css_rb_tree_get_root (tree);
+
+  while (node)
+    {
+      tmp = gtk_css_rb_tree_get_left (tree, node);
+      if (tmp)
+        {
+          Aug *aug = gtk_css_rb_tree_get_augment (tree, tmp);
+          if (pos < aug->n_items)
+            {
+              node = tmp;
+              continue;
+            }
+          pos -= aug->n_items;
+        }
+
+      if (pos < 1)
+        break;
+      pos--;
+
+      node = gtk_css_rb_tree_get_right (tree, node);
+    }
+
+  return node;
+}
+
+static void
+add (GtkCssRbTree *tree,
+     guint         pos)
+{
+  Node *node = get (tree, pos);
+
+  gtk_css_rb_tree_insert_before (tree, node);
+}
+
+static void
+delete (GtkCssRbTree *tree,
+        guint         pos)
+{
+  Node *node = get (tree, pos);
+
+  gtk_css_rb_tree_remove (tree, node);
+}
+
+static guint
+print_node (GtkCssRbTree *tree,
+            Node         *node,
+            guint         depth,
+            const char   *prefix,
+            guint         n)
+{
+  Node *child;
+
+  child = gtk_css_rb_tree_get_left (tree, node);
+  if (child)
+    n = print_node (tree, child, depth + 1, "/", n);
+  g_print ("%*s %u\n", 2 * depth, prefix, n);
+  n++;
+  child = gtk_css_rb_tree_get_right (tree, node);
+  if (child)
+    n = print_node (tree, child, depth + 1, "\\", n);
+
+  return n;
+}
+
+static void
+print (GtkCssRbTree *tree)
+{
+  print_node (tree, gtk_css_rb_tree_get_root (tree), 0, "", 0);
+}
+
+static void
+test_crash (void)
+{
+  GtkCssRbTree *tree;
+  guint i;
+
+  tree = gtk_css_rb_tree_new (Node, Aug, augment, NULL, NULL);
+
+  for (i = 0; i < 300; i++)
+    add (tree, i);
+  print (tree);
+  delete (tree, 144);
+  add (tree, 56);
+  delete (tree, 113);
+  delete (tree, 278);
+  delete (tree, 45);
+  delete (tree, 108);
+  delete (tree, 41);
+  add (tree, 56);
+  add (tree, 200);
+  delete (tree, 127);
+  delete (tree, 222);
+  add (tree, 80);
+  add (tree, 143);
+  add (tree, 216);
+  delete (tree, 177);
+  delete (tree, 193);
+  add (tree, 190);
+  delete (tree, 288);
+  add (tree, 45);
+  add (tree, 57);
+  add (tree, 211);
+  delete (tree, 103);
+  add (tree, 152);
+  delete (tree, 60);
+  add (tree, 185);
+  delete (tree, 167);
+  add (tree, 92);
+  delete (tree, 104);
+  delete (tree, 110);
+  delete (tree, 115);
+  add (tree, 32);
+  delete (tree, 44);
+  add (tree, 159);
+  add (tree, 271);
+  delete (tree, 35);
+  add (tree, 250);
+  delete (tree, 36);
+  add (tree, 284);
+  delete (tree, 82);
+  delete (tree, 248);
+  add (tree, 22);
+  delete (tree, 284);
+  add (tree, 88);
+  delete (tree, 182);
+  add (tree, 70);
+  add (tree, 55);
+  delete (tree, 6);
+  add (tree, 85);
+  delete (tree, 36);
+  delete (tree, 33);
+  delete (tree, 108);
+  add (tree, 229);
+  delete (tree, 269);
+  add (tree, 20);
+  add (tree, 170);
+  delete (tree, 154);
+  add (tree, 26);
+  add (tree, 211);
+  delete (tree, 167);
+  add (tree, 183);
+  add (tree, 292);
+  delete (tree, 2);
+  add (tree, 5);
+  delete (tree, 14);
+  delete (tree, 91);
+  add (tree, 172);
+  add (tree, 99);
+  delete (tree, 3);
+  delete (tree, 74);
+  delete (tree, 122);
+  add (tree, 87);
+  add (tree, 176);
+  delete (tree, 294);
+  add (tree, 169);
+  delete (tree, 41);
+  add (tree, 95);
+  delete (tree, 185);
+  add (tree, 218);
+  delete (tree, 62);
+  delete (tree, 175);
+  add (tree, 196);
+  delete (tree, 33);
+  delete (tree, 46);
+  add (tree, 30);
+  add (tree, 72);
+  delete (tree, 196);
+  delete (tree, 291);
+  add (tree, 198);
+  delete (tree, 181);
+  add (tree, 105);
+  delete (tree, 75);
+  add (tree, 30);
+  add (tree, 261);
+  delete (tree, 284);
+  delete (tree, 214);
+  delete (tree, 134);
+  add (tree, 153);
+  delete (tree, 46);
+  add (tree, 154);
+  add (tree, 266);
+  delete (tree, 272);
+  delete (tree, 150);
+  add (tree, 131);
+  delete (tree, 208);
+  add (tree, 241);
+  add (tree, 31);
+  add (tree, 151);
+  add (tree, 266);
+  delete (tree, 285);
+  add (tree, 178);
+  add (tree, 159);
+  add (tree, 203);
+  delete (tree, 266);
+  add (tree, 52);
+  delete (tree, 104);
+  add (tree, 243);
+  delete (tree, 12);
+  add (tree, 20);
+  delete (tree, 68);
+  print (tree);
+  delete (tree, 102);
+
+  gtk_css_rb_tree_unref (tree);
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+  setlocale (LC_ALL, "C");
+  g_test_bug_base ("http://bugzilla.gnome.org/show_bug.cgi?id=%s");
+
+  g_test_add_func ("/csrbtree/crash", test_crash);
+
+  return g_test_run ();
+}

testsuite/gtk/meson.build

@@ -17,6 +17,7 @@ tests = [
   ['cellarea'],
   ['check-icon-names'],
   ['cssprovider'],
+  ['cssrbtree-crash', ['../../gtk/gtkcssrbtree.c'], ['-DGTK_COMPILATION', '-UG_ENABLE_DEBUG']],
   ['defaultvalue'],
   ['entry'],
   ['filterlistmodel'],