Try to fix crash on MacOS

Author: cfis

ext/libxml/ruby_xml_xpath_context.c

@@ -90,14 +90,15 @@ static VALUE rxml_xpath_context_initialize(VALUE self, VALUE document)
   if (wrapper == NULL)
   {
     wrapper = ALLOC(rxml_xpath_context);
+    wrapper->xctxt = NULL;
+    wrapper->document = document;
     RTYPEDDATA_DATA(self) = wrapper;
   }
   else if (wrapper->xctxt)
   {
     xmlXPathFreeContext(wrapper->xctxt);
   }
 
-  wrapper->document = document;
   wrapper->xctxt = xmlXPathNewContext(xdoc);
 
   return self;

ext/libxml/ruby_xml_xpath_object.c

@@ -73,6 +73,7 @@ static const rb_data_type_t rxml_xpath_object_data_type = {
 VALUE rxml_xpath_object_wrap(VALUE document, xmlDocPtr xdoc, xmlXPathObjectPtr xpop)
 {
   int i;
+  VALUE result;
   rxml_xpath_object *rxpopp = ALLOC(rxml_xpath_object);
 
   /* Make sure Ruby's GC can find the array in the stack */
@@ -106,7 +107,9 @@ VALUE rxml_xpath_object_wrap(VALUE document, xmlDocPtr xdoc, xmlXPathObjectPtr x
   }
 
   rxpopp->nsnodes = nsnodes;
-  return TypedData_Wrap_Struct(cXMLXPathObject, &rxml_xpath_object_data_type, rxpopp);
+  result = TypedData_Wrap_Struct(cXMLXPathObject, &rxml_xpath_object_data_type, rxpopp);
+  RB_GC_GUARD(nsnodes);
+  return result;
 }
 
 static VALUE rxml_xpath_object_tabref(xmlXPathObjectPtr xpop, int index)