Experiments: 1. disabling enable_shared_from_this, 2. using smart_holder in test_class_sh_shared_from_this.cpp

include/pybind11/pybind11.h

@@ -1577,6 +1577,7 @@ private:
     }
     // clang-format off
 
+#ifdef JUNK
     /// Initialize holder object, variant 1: object derives from enable_shared_from_this
     template <typename T>
     static void init_holder(detail::instance *inst, detail::value_and_holder &v_h,
@@ -1594,6 +1595,7 @@ private:
             v_h.set_holder_constructed();
         }
     }
+#endif
 
     static void init_holder_from_existing(const detail::value_and_holder &v_h,
             const holder_type *holder_ptr, std::true_type /*is_copy_constructible*/) {