Compatibility with old clang versions (clang 3.6, 3.7 C++11).

tests/test_class_sh_factory_constructors.cpp

@@ -59,6 +59,12 @@ std::unique_ptr<atyp_udcp const, sddc> rtrn_udcp() { return std::unique_ptr<atyp
 struct with_alias {
 struct with_alias {
     int val               = 0;
     int val               = 0;
     virtual ~with_alias() = default;
     virtual ~with_alias() = default;
+    // Some compilers complain about implicitly defined versions of some of the following:
+    with_alias()                   = default;
+    with_alias(const with_alias &) = default;
+    with_alias(with_alias &&)      = default;
+    with_alias &operator=(const with_alias &) = default;
+    with_alias &operator=(with_alias &&) = default;
 };
 };
 struct with_alias_alias : with_alias {};
 struct with_alias_alias : with_alias {};
 struct sddwaa : std::default_delete<with_alias_alias> {};
 struct sddwaa : std::default_delete<with_alias_alias> {};