fix: namespace nodes behave with compaction (backport to v1.13.x)

ext/nokogiri/nokogiri.h

@@ -171,6 +171,7 @@ int noko_io_write(void *ctx, char *buffer, int len);
 int noko_io_close(void *ctx);
 
 #define Noko_Node_Get_Struct(obj,type,sval) ((sval) = (type*)DATA_PTR(obj))
+#define Noko_Namespace_Get_Struct(obj,type,sval) ((sval) = (type*)DATA_PTR(obj))
 
 VALUE noko_xml_node_wrap(VALUE klass, xmlNodePtr node) ;
 VALUE noko_xml_node_wrap_node_set_result(xmlNodePtr node, VALUE node_set) ;

ext/nokogiri/xml_document.c

@@ -104,7 +104,11 @@ recursively_remove_namespaces_from_node(xmlNodePtr node)
        (node->type == XML_XINCLUDE_START) ||
        (node->type == XML_XINCLUDE_END)) &&
       node->nsDef) {
-    xmlFreeNsList(node->nsDef);
+    xmlNsPtr curr = node->nsDef;
+    while (curr) {
+      noko_xml_document_pin_namespace(curr, node->doc);
+      curr = curr->next;
+    }
     node->nsDef = NULL;
   }
 

ext/nokogiri/xml_namespace.c

@@ -25,13 +25,15 @@
 VALUE cNokogiriXmlNamespace ;
 
 static void
-dealloc_namespace(xmlNsPtr ns)
+_xml_namespace_dealloc(void *ptr)
 {
   /*
    * this deallocator is only used for namespace nodes that are part of an xpath
    * node set. see noko_xml_namespace_wrap().
    */
+  xmlNsPtr ns = ptr;
   NOKOGIRI_DEBUG_START(ns) ;
+
   if (ns->href) {
     xmlFree(DISCARD_CONST_QUAL_XMLCHAR(ns->href));
   }
@@ -42,6 +44,36 @@ dealloc_namespace(xmlNsPtr ns)
   NOKOGIRI_DEBUG_END(ns) ;
 }
 
+#ifdef HAVE_RB_GC_LOCATION
+static void
+_xml_namespace_update_references(void *ptr)
+{
+  xmlNsPtr ns = ptr;
+  if (ns->_private) {
+    ns->_private = (void *)rb_gc_location((VALUE)ns->_private);
+  }
+}
+#else
+#  define _xml_namespace_update_references 0
+#endif
+
+static const rb_data_type_t nokogiri_xml_namespace_type_with_dealloc = {
+  "Nokogiri/XMLNamespace/WithDealloc",
+  {0, _xml_namespace_dealloc, 0, _xml_namespace_update_references},
+  0, 0,
+#ifdef RUBY_TYPED_FREE_IMMEDIATELY
+  RUBY_TYPED_FREE_IMMEDIATELY,
+#endif
+};
+
+static const rb_data_type_t nokogiri_xml_namespace_type_without_dealloc = {
+  "Nokogiri/XMLNamespace/WithoutDealloc",
+  {0, 0, 0, _xml_namespace_update_references},
+  0, 0,
+#ifdef RUBY_TYPED_FREE_IMMEDIATELY
+  RUBY_TYPED_FREE_IMMEDIATELY,
+#endif
+};
 
 /*
  * call-seq:
@@ -54,7 +86,7 @@ prefix(VALUE self)
 {
   xmlNsPtr ns;
 
-  Data_Get_Struct(self, xmlNs, ns);
+  Noko_Namespace_Get_Struct(self, xmlNs, ns);
   if (!ns->prefix) { return Qnil; }
 
   return NOKOGIRI_STR_NEW2(ns->prefix);
@@ -71,7 +103,7 @@ href(VALUE self)
 {
   xmlNsPtr ns;
 
-  Data_Get_Struct(self, xmlNs, ns);
+  Noko_Namespace_Get_Struct(self, xmlNs, ns);
   if (!ns->href) { return Qnil; }
 
   return NOKOGIRI_STR_NEW2(ns->href);
@@ -87,14 +119,18 @@ noko_xml_namespace_wrap(xmlNsPtr c_namespace, xmlDocPtr c_document)
   }
 
   if (c_document) {
-    rb_namespace = Data_Wrap_Struct(cNokogiriXmlNamespace, 0, 0, c_namespace);
+    rb_namespace = TypedData_Wrap_Struct(cNokogiriXmlNamespace,
+                                         &nokogiri_xml_namespace_type_without_dealloc,
+                                         c_namespace);
 
     if (DOC_RUBY_OBJECT_TEST(c_document)) {
       rb_iv_set(rb_namespace, "@document", DOC_RUBY_OBJECT(c_document));
       rb_ary_push(DOC_NODE_CACHE(c_document), rb_namespace);
     }
   } else {
-    rb_namespace = Data_Wrap_Struct(cNokogiriXmlNamespace, 0, dealloc_namespace, c_namespace);
+    rb_namespace = TypedData_Wrap_Struct(cNokogiriXmlNamespace,
+                                         &nokogiri_xml_namespace_type_with_dealloc,
+                                         c_namespace);
   }
 
   c_namespace->_private = (void *)rb_namespace;

ext/nokogiri/xml_node.c

@@ -1353,7 +1353,7 @@ set_namespace(VALUE self, VALUE namespace)
   Noko_Node_Get_Struct(self, xmlNode, node);
 
   if (!NIL_P(namespace)) {
-    Data_Get_Struct(namespace, xmlNs, ns);
+    Noko_Namespace_Get_Struct(namespace, xmlNs, ns);
   }
 
   xmlSetNs(node, ns);

test/test_compaction.rb

@@ -3,19 +3,63 @@
 require "helper"
 
 describe "compaction" do
-  it "https://github.com/sparklemotion/nokogiri/pull/2579" do
-    skip unless GC.respond_to?(:verify_compaction_references)
+  describe Nokogiri::XML::Node do
+    it "compacts safely" do # https://github.com/sparklemotion/nokogiri/pull/2579
+      skip unless GC.respond_to?(:verify_compaction_references)
 
-    big_doc = "<root>" + ("a".."zz").map { |x| "<#{x}>#{x}</#{x}>" }.join + "</root>"
-    doc = Nokogiri.XML(big_doc)
+      big_doc = "<root>" + ("a".."zz").map { |x| "<#{x}>#{x}</#{x}>" }.join + "</root>"
+      doc = Nokogiri.XML(big_doc)
 
-    # ensure a bunch of node objects have been wrapped
-    doc.root.children.each(&:inspect)
+      # ensure a bunch of node objects have been wrapped
+      doc.root.children.each(&:inspect)
 
-    # compact the heap and try to get the node wrappers to move
-    GC.verify_compaction_references(double_heap: true, toward: :empty)
+      # compact the heap and try to get the node wrappers to move
+      GC.verify_compaction_references(double_heap: true, toward: :empty)
 
-    # access the node wrappers and make sure they didn't move
-    doc.root.children.each(&:inspect)
+      # access the node wrappers and make sure they didn't move
+      doc.root.children.each(&:inspect)
+    end
+  end
+
+  describe Nokogiri::XML::Namespace do
+    it "namespace_scopes" do
+      skip unless GC.respond_to?(:verify_compaction_references)
+
+      doc = Nokogiri::XML(<<~EOF)
+        <root xmlns="http://example.com/root" xmlns:bar="http://example.com/bar">
+          <first/>
+          <second xmlns="http://example.com/child"/>
+          <third xmlns:foo="http://example.com/foo"/>
+        </root>
+      EOF
+
+      doc.at_xpath("//root:first", "root" => "http://example.com/root").namespace_scopes.inspect
+
+      GC.verify_compaction_references(double_heap: true, toward: :empty)
+
+      doc.at_xpath("//root:first", "root" => "http://example.com/root").namespace_scopes.inspect
+    end
+
+    it "remove_namespaces!" do
+      skip unless GC.respond_to?(:verify_compaction_references)
+
+      doc = Nokogiri::XML(<<~XML)
+        <root xmlns:a="http://a.flavorjon.es/" xmlns:b="http://b.flavorjon.es/">
+          <a:foo>hello from a</a:foo>
+          <b:foo>hello from b</b:foo>
+          <container xmlns:c="http://c.flavorjon.es/">
+            <c:foo c:attr='attr-value'>hello from c</c:foo>
+          </container>
+        </root>
+      XML
+
+      namespaces = doc.root.namespaces
+      namespaces.each(&:inspect)
+      doc.remove_namespaces!
+
+      GC.verify_compaction_references(double_heap: true, toward: :empty)
+
+      namespaces.each(&:inspect)
+    end
   end
 end

test/test_memory_leak.rb

@@ -191,6 +191,47 @@ def test_leaking_namespace_node_strings_with_prefix
       end
     end
 
+    def test_document_remove_namespaces_with_ruby_objects
+      xml = <<~XML
+        <root xmlns:a="http://a.flavorjon.es/" xmlns:b="http://b.flavorjon.es/">
+          <a:foo>hello from a</a:foo>
+          <b:foo>hello from b</b:foo>
+          <container xmlns:c="http://c.flavorjon.es/">
+            <c:foo c:attr='attr-value'>hello from c</c:foo>
+          </container>
+        </root>
+      XML
+
+      20.times do
+        10_000.times do
+          doc = Nokogiri::XML::Document.parse(xml)
+          doc.namespaces.each(&:inspect)
+          doc.remove_namespaces!
+        end
+        puts MemInfo.rss
+      end
+    end
+
+    def test_document_remove_namespaces_without_ruby_objects
+      xml = <<~XML
+        <root xmlns:a="http://a.flavorjon.es/" xmlns:b="http://b.flavorjon.es/">
+          <a:foo>hello from a</a:foo>
+          <b:foo>hello from b</b:foo>
+          <container xmlns:c="http://c.flavorjon.es/">
+            <c:foo c:attr='attr-value'>hello from c</c:foo>
+          </container>
+        </root>
+      XML
+
+      20.times do
+        20_000.times do
+          doc = Nokogiri::XML::Document.parse(xml)
+          doc.remove_namespaces!
+        end
+        puts MemInfo.rss
+      end
+    end
+
     def test_leaking_dtd_nodes_after_internal_subset_removal
       # see https://github.com/sparklemotion/nokogiri/issues/1784
       100_000.times do |i|