dns: make ctor private

This ensures one can't instanciate a DNSResolver object by
mistake, but uses the singleton. A separate create static
function is added for cases where a new object is explicitely
needed.

src/common/dns_utils.cpp

@@ -334,6 +334,11 @@ DNSResolver& DNSResolver::instance()
   return *staticInstance;
 }
 
+DNSResolver DNSResolver::create()
+{
+  return DNSResolver();
+}
+
 bool DNSResolver::check_address_syntax(const char *addr)
 {
   // if string doesn't contain a dot, we won't consider it a url for now.

src/common/dns_utils.h

@@ -49,7 +49,7 @@ struct DNSResolverData;
  */
 class DNSResolver
 {
-public:
+private:
 
   /**
    * @brief Constructs an instance of DNSResolver
@@ -58,6 +58,8 @@ public:
    */
   DNSResolver();
 
+public:
+
   /**
    * @brief takes care of freeing C pointers and such
    */
@@ -119,6 +121,13 @@ public:
    */
   static DNSResolver& instance();
 
+  /**
+   * @brief Gets a new instance of DNSResolver
+   *
+   * @return returns a pointer to the new object
+   */
+  static DNSResolver create();
+
 private:
 
   /**

tests/unit_tests/dns_resolver.cpp

@@ -35,7 +35,7 @@
 
 TEST(DNSResolver, IPv4Success)
 {
-  tools::DNSResolver resolver;
+  tools::DNSResolver resolver = tools::DNSResolver::create();
 
   bool avail, valid;
 
@@ -55,7 +55,7 @@ TEST(DNSResolver, IPv4Success)
 TEST(DNSResolver, IPv4Failure)
 {
   // guaranteed by IANA/ICANN/RFC to be invalid
-  tools::DNSResolver resolver;
+  tools::DNSResolver resolver = tools::DNSResolver::create();
 
   bool avail, valid;
 
@@ -70,7 +70,7 @@ TEST(DNSResolver, IPv4Failure)
 
 TEST(DNSResolver, DNSSECSuccess)
 {
-  tools::DNSResolver resolver;
+  tools::DNSResolver resolver = tools::DNSResolver::create();
 
   bool avail, valid;
 
@@ -86,7 +86,7 @@ TEST(DNSResolver, DNSSECSuccess)
 
 TEST(DNSResolver, DNSSECFailure)
 {
-  tools::DNSResolver resolver;
+  tools::DNSResolver resolver = tools::DNSResolver::create();
 
   bool avail, valid;
 
@@ -103,7 +103,7 @@ TEST(DNSResolver, DNSSECFailure)
 // It would be great to include an IPv6 test and assume it'll pass, but not every ISP / resolver plays nicely with IPv6;)
 /*TEST(DNSResolver, IPv6Success)
 {
-  tools::DNSResolver resolver;
+  tools::DNSResolver resolver = tools::DNSResolver::create();
 
   bool avail, valid;
 
@@ -123,7 +123,7 @@ TEST(DNSResolver, DNSSECFailure)
 TEST(DNSResolver, IPv6Failure)
 {
   // guaranteed by IANA/ICANN/RFC to be invalid
-  tools::DNSResolver resolver;
+  tools::DNSResolver resolver = tools::DNSResolver::create();
 
   bool avail, valid;