Check for callback argument in DNS functions

src/node_dns.cc

@@ -332,6 +332,11 @@ static Handle<Value> ResolveA(int type, const Arguments& args) {
           String::New("Argument must be a string.")));
   }
 
+  if (!args[1]->IsFunction()) {
+    return ThrowException(Exception::Error(
+          String::New("Missing callback argument")));
+  }
+
   String::Utf8Value name(args[0]->ToString());
 
   struct dns_query *query;

test/disabled/test-dns.js

@@ -3,6 +3,14 @@ require("../common");
 var dns = require("dns"),
     sys = require("sys");
 
+
+// Try resolution without callback
+
+assert.throws(function () {
+  dns.resolve('google.com', 'A');
+})
+
+
 var hosts = ['example.com', 'example.org',
              'ietf.org', // AAAA
              'google.com', // MX, multiple A records