Review remarks v3

- Moved auto_id back on its place.
- Reverted pointer_from FMT_CONSTEXPR_DECL changes.
- Made NameRefCreator a dynamic_specs_handler's base class.

include/fmt/core.h

@@ -776,8 +776,6 @@ enum : unsigned long long { is_unpacked_bit = 1ull << 63 };
 
 template <typename Context>
 class arg_map;
-
-struct auto_id {};
 }  // namespace internal
 
 // A formatting argument. It is a trivially copyable/constructible type to

include/fmt/format.h

@@ -618,7 +618,7 @@ template <typename Char>
 class null_terminating_iterator;
 
 template <typename Char>
-FMT_CONSTEXPR const Char *pointer_from(null_terminating_iterator<Char> it);
+FMT_CONSTEXPR_DECL const Char *pointer_from(null_terminating_iterator<Char> it);
 
 // An iterator that produces a null terminator on *end. This simplifies parsing
 // and allows comparing the performance of processing a null-terminated string
@@ -696,7 +696,7 @@ class null_terminating_iterator {
   // This should be a friend specialization pointer_from<Char> but the latter
   // doesn't compile by gcc 5.1 due to a compiler bug.
   template <typename CharT>
-  friend FMT_CONSTEXPR const CharT *pointer_from(
+  friend FMT_CONSTEXPR_DECL const CharT *pointer_from(
       null_terminating_iterator<CharT> it);
 
  private:
@@ -1804,6 +1804,8 @@ FMT_CONSTEXPR void set_dynamic_spec(
   value = static_cast<T>(big_value);
 }
 
+struct auto_id {};
+
 // The standard format specifier handler with checking.
 template <typename Context>
 class specs_handler: public specs_setter<typename Context::char_type> {
@@ -1942,7 +1944,8 @@ template <typename Specs, typename ParseContext,
           typename NameRefCreator = string_value_name_arg_ref_creator<
               typename ParseContext::char_type>>
 class dynamic_specs_handler
-    : public specs_setter<typename ParseContext::char_type> {
+    : private NameRefCreator,
+      public specs_setter<typename ParseContext::char_type> {
  protected:
   typedef typename NameRefCreator::arg_ref_type arg_ref_type;
 
@@ -1952,10 +1955,10 @@ class dynamic_specs_handler
   FMT_CONSTEXPR dynamic_specs_handler(
       Specs &specs, ParseContext &ctx,
       NameRefCreator name_ref_creator = NameRefCreator())
-      : specs_setter<char_type>(specs),
+      : NameRefCreator(name_ref_creator),
+        specs_setter<char_type>(specs),
         specs_(specs),
-        context_(ctx),
-        name_ref_creator_(name_ref_creator) {}
+        context_(ctx) {}
 
   template <typename Id>
   FMT_CONSTEXPR void on_dynamic_width(Id arg_id) {
@@ -1992,7 +1995,7 @@ class dynamic_specs_handler
   FMT_CONSTEXPR arg_ref_type
   make_name_arg_ref(basic_string_view<char_type> arg_id) {
     context_.check_arg_id(arg_id);
-    return name_ref_creator_.make_name_arg_ref(arg_id);
+    return NameRefCreator::make_name_arg_ref(arg_id);
   }
 
   template <typename Id>
@@ -2003,7 +2006,6 @@ class dynamic_specs_handler
  private:
   Specs &specs_;
   ParseContext &context_;
-  NameRefCreator name_ref_creator_;
 };
 
 template <typename Char>