Simplify locale handling

fmtlib · Sep 22, 2024 · ff92223 · ff92223
1 parent 80c4d42
commit ff92223
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Showing 6 changed files with 38 additions and 51 deletions.
diff --git a/doc/api.md b/doc/api.md
@@ -410,11 +410,11 @@ locale:
 that take `std::locale` as a parameter. The locale type is a template
 parameter to avoid the expensive `<locale>` include.
 
-::: format(const Locale&, format_string<T...>, T&&...)
+::: format(detail::locale_ref, format_string<T...>, T&&...)
 
-::: format_to(OutputIt, const Locale&, format_string<T...>, T&&...)
+::: format_to(OutputIt, detail::locale_ref, format_string<T...>, T&&...)
 
-::: formatted_size(const Locale&, format_string<T...>, T&&...)
+::: formatted_size(detail::locale_ref, format_string<T...>, T&&...)
 
 <a id="legacy-checks"></a>
 ### Legacy Compile-Time Checks

diff --git a/include/fmt/base.h b/include/fmt/base.h
@@ -2220,9 +2220,12 @@ struct locale_ref {
 
  public:
   constexpr locale_ref() : locale_(nullptr) {}
-  template <typename Locale> explicit locale_ref(const Locale& loc);
+
+  template <typename Locale, FMT_ENABLE_IF(sizeof(Locale::collate) != 0)>
+  locale_ref(const Locale& loc);
+
   explicit operator bool() const noexcept { return locale_ != nullptr; }
-#endif
+#endif  // FMT_USE_LOCALE
 
   template <typename Locale> auto get() const -> Locale;
 };

diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
@@ -84,7 +84,7 @@ using std::locale;
 using std::numpunct;
 using std::use_facet;
 
-template <typename Locale>
+template <typename Locale, enable_if_t<(sizeof(Locale::collate) != 0), int>>
 locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
   static_assert(std::is_same<Locale, locale>::value, "");
 }

diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -796,11 +796,6 @@ using is_double_double = bool_constant<std::numeric_limits<T>::digits == 106>;
 #  define FMT_USE_FULL_CACHE_DRAGONBOX 0
 #endif
 
-template <typename T, typename Enable = void>
-struct is_locale : std::false_type {};
-template <typename T>
-struct is_locale<T, void_t<decltype(T::classic())>> : std::true_type {};
-
 // An allocator that uses malloc/free to allow removing dependency on the C++
 // standard libary runtime.
 template <typename T> struct allocator {
@@ -4213,47 +4208,41 @@ FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
 // Can be used to report errors from destructors.
 FMT_API void report_system_error(int error_code, const char* message) noexcept;
 
-template <typename Locale, FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
-auto vformat(const Locale& loc, string_view fmt, format_args args)
+inline auto vformat(detail::locale_ref loc, string_view fmt, format_args args)
     -> std::string {
   auto buf = memory_buffer();
-  detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
+  detail::vformat_to(buf, fmt, args, loc);
   return {buf.data(), buf.size()};
 }
 
-template <typename Locale, typename... T,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
-FMT_INLINE auto format(const Locale& loc, format_string<T...> fmt, T&&... args)
-    -> std::string {
-  return fmt::vformat(loc, fmt.str, vargs<T...>{{args...}});
+template <typename... T>
+FMT_INLINE auto format(detail::locale_ref loc, format_string<T...> fmt,
+                       T&&... args) -> std::string {
+  return vformat(loc, fmt.str, vargs<T...>{{args...}});
 }
 
-template <typename OutputIt, typename Locale,
-          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value&&
-                            detail::is_locale<Locale>::value)>
-auto vformat_to(OutputIt out, const Locale& loc, string_view fmt,
+template <typename OutputIt,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+auto vformat_to(OutputIt out, detail::locale_ref loc, string_view fmt,
                 format_args args) -> OutputIt {
   auto&& buf = detail::get_buffer<char>(out);
-  detail::vformat_to(buf, fmt, args, detail::locale_ref(loc));
+  detail::vformat_to(buf, fmt, args, loc);
   return detail::get_iterator(buf, out);
 }
 
-template <typename OutputIt, typename Locale, typename... T,
-          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value&&
-                            detail::is_locale<Locale>::value)>
-FMT_INLINE auto format_to(OutputIt out, const Locale& loc,
+template <typename OutputIt, typename... T,
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
+FMT_INLINE auto format_to(OutputIt out, detail::locale_ref loc,
                           format_string<T...> fmt, T&&... args) -> OutputIt {
   return fmt::vformat_to(out, loc, fmt.str, vargs<T...>{{args...}});
 }
 
-template <typename Locale, typename... T,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value)>
-FMT_NODISCARD FMT_INLINE auto formatted_size(const Locale& loc,
+template <typename... T>
+FMT_NODISCARD FMT_INLINE auto formatted_size(detail::locale_ref loc,
                                              format_string<T...> fmt,
                                              T&&... args) -> size_t {
   auto buf = detail::counting_buffer<>();
-  detail::vformat_to(buf, fmt.str, vargs<T...>{{args...}},
-                     detail::locale_ref(loc));
+  detail::vformat_to(buf, fmt.str, vargs<T...>{{args...}}, loc);
   return buf.count();
 }
 

diff --git a/include/fmt/std.h b/include/fmt/std.h
@@ -433,8 +433,8 @@ template <> struct formatter<std::error_code> {
   }
 
   template <typename FormatContext>
-  FMT_CONSTEXPR20 auto format(const std::error_code& ec, FormatContext& ctx) const
-      -> decltype(ctx.out()) {
+  FMT_CONSTEXPR20 auto format(const std::error_code& ec,
+                              FormatContext& ctx) const -> decltype(ctx.out()) {
     auto specs = specs_;
     detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
                                 ctx);

diff --git a/include/fmt/xchar.h b/include/fmt/xchar.h
@@ -191,11 +191,9 @@ auto format(const S& fmt, T&&... args) -> std::basic_string<Char> {
                  fmt::make_format_args<buffered_context<Char>>(args...));
 }
 
-template <typename Locale, typename S,
-          typename Char = detail::format_string_char_t<S>,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
-                            detail::is_exotic_char<Char>::value)>
-inline auto vformat(const Locale& loc, const S& fmt,
+template <typename S, typename Char = detail::format_string_char_t<S>,
+          FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
+inline auto vformat(detail::locale_ref loc, const S& fmt,
                     typename detail::vformat_args<Char>::type args)
     -> std::basic_string<Char> {
   auto buf = basic_memory_buffer<Char>();
@@ -204,11 +202,10 @@ inline auto vformat(const Locale& loc, const S& fmt,
   return {buf.data(), buf.size()};
 }
 
-template <typename Locale, typename S, typename... T,
+template <typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
-          FMT_ENABLE_IF(detail::is_locale<Locale>::value&&
-                            detail::is_exotic_char<Char>::value)>
-inline auto format(const Locale& loc, const S& fmt, T&&... args)
+          FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
+inline auto format(detail::locale_ref loc, const S& fmt, T&&... args)
     -> std::basic_string<Char> {
   return vformat(loc, detail::to_string_view(fmt),
                  fmt::make_format_args<buffered_context<Char>>(args...));
@@ -235,25 +232,23 @@ inline auto format_to(OutputIt out, const S& fmt, T&&... args) -> OutputIt {
                     fmt::make_format_args<buffered_context<Char>>(args...));
 }
 
-template <typename Locale, typename S, typename OutputIt, typename... Args,
+template <typename S, typename OutputIt, typename... Args,
           typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
-                            detail::is_locale<Locale>::value&&
-                                detail::is_exotic_char<Char>::value)>
-inline auto vformat_to(OutputIt out, const Locale& loc, const S& fmt,
+                            detail::is_exotic_char<Char>::value)>
+inline auto vformat_to(OutputIt out, detail::locale_ref loc, const S& fmt,
                        typename detail::vformat_args<Char>::type args)
     -> OutputIt {
   auto&& buf = detail::get_buffer<Char>(out);
   vformat_to(buf, detail::to_string_view(fmt), args, detail::locale_ref(loc));
   return detail::get_iterator(buf, out);
 }
 
-template <typename OutputIt, typename Locale, typename S, typename... T,
+template <typename OutputIt, typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
           bool enable = detail::is_output_iterator<OutputIt, Char>::value &&
-                        detail::is_locale<Locale>::value &&
                         detail::is_exotic_char<Char>::value>
-inline auto format_to(OutputIt out, const Locale& loc, const S& fmt,
+inline auto format_to(OutputIt out, detail::locale_ref loc, const S& fmt,
                       T&&... args) ->
     typename std::enable_if<enable, OutputIt>::type {
   return vformat_to(out, loc, detail::to_string_view(fmt),