diff --git a/CMakeLists.txt b/CMakeLists.txt
index e4a48b0d..3bf80f80 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -81,6 +81,7 @@ option(FMT_FUZZ "Generate the fuzz target." OFF)
 option(FMT_CUDA_TEST "Generate the cuda-test target." OFF)
 option(FMT_OS "Include core requiring OS (Windows/Posix) " ON)
 option(FMT_MODULE "Build a module instead of a traditional library." OFF)
+option(FMT_SYSTEM_HEADERS "Expose headers with marking them as system." OFF)
 
 set(FMT_CAN_MODULE OFF)
 if (CMAKE_CXX_STANDARD GREATER 17 AND
@@ -96,6 +97,10 @@ if (FMT_TEST AND FMT_MODULE)
   # The tests require {fmt} to be compiled as traditional library
   message(STATUS "Testing is incompatible with build mode 'module'.")
 endif ()
+set(FMT_SYSTEM_HEADERS_ATTRIBUTE "")
+if (FMT_SYSTEM_HEADERS)
+  set(FMT_SYSTEM_HEADERS_ATTRIBUTE SYSTEM)
+endif ()
 
 # Get version from core.h
 file(READ include/fmt/core.h core_h)
@@ -262,7 +267,7 @@ endif ()
 
 target_compile_features(fmt INTERFACE ${FMT_REQUIRED_FEATURES})
 
-target_include_directories(fmt PUBLIC
+target_include_directories(fmt ${FMT_SYSTEM_HEADERS_ATTRIBUTE} PUBLIC
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
@@ -298,7 +303,7 @@ add_library(fmt::fmt-header-only ALIAS fmt-header-only)
 target_compile_definitions(fmt-header-only INTERFACE FMT_HEADER_ONLY=1)
 target_compile_features(fmt-header-only INTERFACE ${FMT_REQUIRED_FEATURES})
 
-target_include_directories(fmt-header-only INTERFACE
+target_include_directories(fmt-header-only ${FMT_SYSTEM_HEADERS_ATTRIBUTE} INTERFACE
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
diff --git a/ChangeLog.rst b/ChangeLog.rst
index d0a1aa1d..4b88f4a6 100644
--- a/ChangeLog.rst
+++ b/ChangeLog.rst
@@ -281,6 +281,9 @@
   This doesn't introduce a dependency on ``<locale>`` so there is virtually no
   compile time effect.
 
+* Deprecated an undocumented ``format_to`` overload that takes
+  ``basic_memory_buffer``.
+
 * Made parameter order in ``vformat_to`` consistent with ``format_to``
   (`#2327 <https://github.com/fmtlib/fmt/issues/2327>`_).
 
diff --git a/include/fmt/args.h b/include/fmt/args.h
index 36f62220..99060040 100644
--- a/include/fmt/args.h
+++ b/include/fmt/args.h
@@ -146,14 +146,7 @@ class dynamic_format_arg_store
   constexpr dynamic_format_arg_store() = default;
 
   constexpr dynamic_format_arg_store(
-      const dynamic_format_arg_store<Context>& store)
-      :
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-        basic_format_args<Context>(),
-#endif
-        data_(store.data_),
-        named_info_(store.named_info_) {
-  }
+      const dynamic_format_arg_store<Context>& store) = delete;
 
   /**
     \rst
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index d54c8ae7..5285d420 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -11,14 +11,29 @@
 #include <algorithm>
 #include <chrono>
 #include <ctime>
+#include <iterator>
 #include <locale>
-#include <sstream>
+#include <ostream>
 #include <type_traits>
 
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
 
+// Enable tzset.
+#ifndef FMT_USE_TZSET
+// UWP doesn't provide _tzset.
+#  if FMT_HAS_INCLUDE("winapifamily.h")
+#    include <winapifamily.h>
+#  endif
+#  if defined(_WIN32) && (!defined(WINAPI_FAMILY) || \
+                          (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#    define FMT_USE_TZSET 1
+#  else
+#    define FMT_USE_TZSET 0
+#  endif
+#endif
+
 // Enable safe chrono durations, unless explicitly disabled.
 #ifndef FMT_SAFE_DURATION_CAST
 #  define FMT_SAFE_DURATION_CAST 1
@@ -290,36 +305,42 @@ inline null<> localtime_s(...) { return null<>(); }
 inline null<> gmtime_r(...) { return null<>(); }
 inline null<> gmtime_s(...) { return null<>(); }
 
-template <typename Char>
-inline auto do_write(const std::tm& time, const std::locale& loc, char format,
-                     char modifier) -> std::basic_string<Char> {
-  auto&& os = std::basic_ostringstream<Char>();
-  os.imbue(loc);
-  using iterator = std::ostreambuf_iterator<Char>;
-  const auto& facet = std::use_facet<std::time_put<Char, iterator>>(loc);
-  auto end = facet.put(os, os, Char(' '), &time, format, modifier);
-  if (end.failed()) FMT_THROW(format_error("failed to format time"));
-  return std::move(os).str();
-}
-
-template <typename Char, typename OutputIt,
-          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
-auto write(OutputIt out, const std::tm& time, const std::locale& loc,
-           char format, char modifier = 0) -> OutputIt {
-  auto str = do_write<Char>(time, loc, format, modifier);
-  return std::copy(str.begin(), str.end(), out);
-}
-
 inline const std::locale& get_classic_locale() {
   static const auto& locale = std::locale::classic();
   return locale;
 }
 
-template <typename Char, typename OutputIt,
-          FMT_ENABLE_IF(std::is_same<Char, char>::value)>
-auto write(OutputIt out, const std::tm& time, const std::locale& loc,
-           char format, char modifier = 0) -> OutputIt {
-  auto str = do_write<char>(time, loc, format, modifier);
+template <typename CodeUnit> struct codecvt_result {
+  static constexpr const size_t max_size = 32;
+  CodeUnit buf[max_size];
+  CodeUnit* end;
+};
+template <typename CodeUnit>
+constexpr const size_t codecvt_result<CodeUnit>::max_size;
+
+template <typename CodeUnit>
+void write_codecvt(codecvt_result<CodeUnit>& out, string_view in_buf,
+                   const std::locale& loc) {
+  using codecvt = std::codecvt<CodeUnit, char, std::mbstate_t>;
+#if FMT_CLANG_VERSION
+#  pragma clang diagnostic push
+#  pragma clang diagnostic ignored "-Wdeprecated"
+  auto& f = std::use_facet<codecvt>(loc);
+#  pragma clang diagnostic pop
+#else
+  auto& f = std::use_facet<codecvt>(loc);
+#endif
+  auto mb = std::mbstate_t();
+  const char* from_next = nullptr;
+  auto result = f.in(mb, in_buf.begin(), in_buf.end(), from_next,
+                     std::begin(out.buf), std::end(out.buf), out.end);
+  if (result != std::codecvt_base::ok)
+    FMT_THROW(format_error("failed to format time"));
+}
+
+template <typename OutputIt>
+auto write_encoded_tm_str(OutputIt out, string_view in, const std::locale& loc)
+    -> OutputIt {
   if (detail::is_utf8() && loc != get_classic_locale()) {
     // char16_t and char32_t codecvts are broken in MSVC (linkage errors) and
     // gcc-4.
@@ -332,56 +353,89 @@ auto write(OutputIt out, const std::tm& time, const std::locale& loc,
     using code_unit = char32_t;
 #endif
 
-    using codecvt = std::codecvt<code_unit, char, std::mbstate_t>;
-#if FMT_CLANG_VERSION
-#  pragma clang diagnostic push
-#  pragma clang diagnostic ignored "-Wdeprecated"
-    auto& f = std::use_facet<codecvt>(loc);
-#  pragma clang diagnostic pop
-#else
-    auto& f = std::use_facet<codecvt>(loc);
-#endif
-
-    auto mb = std::mbstate_t();
-    const char* from_next = nullptr;
-    code_unit* to_next = nullptr;
-    constexpr size_t buf_size = 32;
-    code_unit buf[buf_size] = {};
-    auto result = f.in(mb, str.data(), str.data() + str.size(), from_next, buf,
-                       buf + buf_size, to_next);
-    if (result != std::codecvt_base::ok)
-      FMT_THROW(format_error("failed to format time"));
-    str.clear();
-    for (code_unit* p = buf; p != to_next; ++p) {
+    using unit_t = codecvt_result<code_unit>;
+    unit_t unit;
+    write_codecvt(unit, in, loc);
+    // In UTF-8 is used one to four one-byte code units.
+    auto&& buf = basic_memory_buffer<char, unit_t::max_size * 4>();
+    for (code_unit* p = unit.buf; p != unit.end; ++p) {
       uint32_t c = static_cast<uint32_t>(*p);
       if (sizeof(code_unit) == 2 && c >= 0xd800 && c <= 0xdfff) {
         // surrogate pair
         ++p;
-        if (p == to_next || (c & 0xfc00) != 0xd800 || (*p & 0xfc00) != 0xdc00) {
+        if (p == unit.end || (c & 0xfc00) != 0xd800 ||
+            (*p & 0xfc00) != 0xdc00) {
           FMT_THROW(format_error("failed to format time"));
         }
         c = (c << 10) + static_cast<uint32_t>(*p) - 0x35fdc00;
       }
       if (c < 0x80) {
-        str.push_back(static_cast<char>(c));
+        buf.push_back(static_cast<char>(c));
       } else if (c < 0x800) {
-        str.push_back(static_cast<char>(0xc0 | (c >> 6)));
-        str.push_back(static_cast<char>(0x80 | (c & 0x3f)));
+        buf.push_back(static_cast<char>(0xc0 | (c >> 6)));
+        buf.push_back(static_cast<char>(0x80 | (c & 0x3f)));
       } else if ((c >= 0x800 && c <= 0xd7ff) || (c >= 0xe000 && c <= 0xffff)) {
-        str.push_back(static_cast<char>(0xe0 | (c >> 12)));
-        str.push_back(static_cast<char>(0x80 | ((c & 0xfff) >> 6)));
-        str.push_back(static_cast<char>(0x80 | (c & 0x3f)));
+        buf.push_back(static_cast<char>(0xe0 | (c >> 12)));
+        buf.push_back(static_cast<char>(0x80 | ((c & 0xfff) >> 6)));
+        buf.push_back(static_cast<char>(0x80 | (c & 0x3f)));
       } else if (c >= 0x10000 && c <= 0x10ffff) {
-        str.push_back(static_cast<char>(0xf0 | (c >> 18)));
-        str.push_back(static_cast<char>(0x80 | ((c & 0x3ffff) >> 12)));
-        str.push_back(static_cast<char>(0x80 | ((c & 0xfff) >> 6)));
-        str.push_back(static_cast<char>(0x80 | (c & 0x3f)));
+        buf.push_back(static_cast<char>(0xf0 | (c >> 18)));
+        buf.push_back(static_cast<char>(0x80 | ((c & 0x3ffff) >> 12)));
+        buf.push_back(static_cast<char>(0x80 | ((c & 0xfff) >> 6)));
+        buf.push_back(static_cast<char>(0x80 | (c & 0x3f)));
       } else {
         FMT_THROW(format_error("failed to format time"));
       }
     }
+    return copy_str<char>(buf.data(), buf.data() + buf.size(), out);
   }
-  return std::copy(str.begin(), str.end(), out);
+  return copy_str<char>(in.data(), in.data() + in.size(), out);
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+auto write_tm_str(OutputIt out, string_view sv, const std::locale& loc)
+    -> OutputIt {
+  codecvt_result<Char> unit;
+  write_codecvt(unit, sv, loc);
+  return copy_str<Char>(unit.buf, unit.end, out);
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(std::is_same<Char, char>::value)>
+auto write_tm_str(OutputIt out, string_view sv, const std::locale& loc)
+    -> OutputIt {
+  return write_encoded_tm_str(out, sv, loc);
+}
+
+template <typename Char>
+inline void do_write(buffer<Char>& buf, const std::tm& time,
+                     const std::locale& loc, char format, char modifier) {
+  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
+  auto&& os = std::basic_ostream<Char>(&format_buf);
+  os.imbue(loc);
+  using iterator = std::ostreambuf_iterator<Char>;
+  const auto& facet = std::use_facet<std::time_put<Char, iterator>>(loc);
+  auto end = facet.put(os, os, Char(' '), &time, format, modifier);
+  if (end.failed()) FMT_THROW(format_error("failed to format time"));
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+auto write(OutputIt out, const std::tm& time, const std::locale& loc,
+           char format, char modifier = 0) -> OutputIt {
+  auto&& buf = get_buffer<Char>(out);
+  do_write<Char>(buf, time, loc, format, modifier);
+  return buf.out();
+}
+
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(std::is_same<Char, char>::value)>
+auto write(OutputIt out, const std::tm& time, const std::locale& loc,
+           char format, char modifier = 0) -> OutputIt {
+  auto&& buf = basic_memory_buffer<Char>();
+  do_write<char>(buf, time, loc, format, modifier);
+  return write_encoded_tm_str(out, string_view(buf.data(), buf.size()), loc);
 }
 
 }  // namespace detail
@@ -878,7 +932,13 @@ template <typename T>
 struct has_member_data_tm_gmtoff<T, void_t<decltype(T::tm_gmtoff)>>
     : std::true_type {};
 
-#if defined(_WIN32)
+template <typename T, typename = void>
+struct has_member_data_tm_zone : std::false_type {};
+template <typename T>
+struct has_member_data_tm_zone<T, void_t<decltype(T::tm_zone)>>
+    : std::true_type {};
+
+#if FMT_USE_TZSET
 inline void tzset_once() {
   static bool init = []() -> bool {
     _tzset();
@@ -1021,7 +1081,9 @@ template <typename OutputIt, typename Char> class tm_writer {
   }
   void format_utc_offset_impl(std::false_type) {
 #if defined(_WIN32)
+#  if FMT_USE_TZSET
     tzset_once();
+#  endif
     long offset = 0;
     _get_timezone(&offset);
     if (tm_.tm_isdst) {
@@ -1035,6 +1097,14 @@ template <typename OutputIt, typename Char> class tm_writer {
 #endif
   }
 
+  void format_tz_name_impl(std::true_type) {
+    if (is_classic_)
+      out_ = write_tm_str<Char>(out_, tm_.tm_zone, loc_);
+    else
+      format_localized('Z');
+  }
+  void format_tz_name_impl(std::false_type) { format_localized('Z'); }
+
   void format_localized(char format, char modifier = 0) {
     out_ = write<Char>(out_, tm_, loc_, format, modifier);
   }
@@ -1144,7 +1214,7 @@ template <typename OutputIt, typename Char> class tm_writer {
   void on_utc_offset() {
     format_utc_offset_impl(has_member_data_tm_gmtoff<std::tm>{});
   }
-  void on_tz_name() { format_localized('Z'); }
+  void on_tz_name() { format_tz_name_impl(has_member_data_tm_zone<std::tm>{}); }
 
   void on_year(numeric_system ns) {
     if (is_classic_ || ns == numeric_system::standard)
@@ -1318,21 +1388,21 @@ inline bool isfinite(T) {
   return true;
 }
 
-// Converts value to int and checks that it's in the range [0, upper).
-template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
-inline int to_nonnegative_int(T value, int upper) {
+// Converts value to Int and checks that it's in the range [0, upper).
+template <typename T, typename Int, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline Int to_nonnegative_int(T value, Int upper) {
   FMT_ASSERT(value >= 0 && to_unsigned(value) <= to_unsigned(upper),
              "invalid value");
   (void)upper;
-  return static_cast<int>(value);
+  return static_cast<Int>(value);
 }
-template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
-inline int to_nonnegative_int(T value, int upper) {
+template <typename T, typename Int, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+inline Int to_nonnegative_int(T value, Int upper) {
   FMT_ASSERT(
       std::isnan(value) || (value >= 0 && value <= static_cast<T>(upper)),
       "invalid value");
   (void)upper;
-  return static_cast<int>(value);
+  return static_cast<Int>(value);
 }
 
 template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
@@ -1389,15 +1459,37 @@ inline std::chrono::duration<Rep, std::milli> get_milliseconds(
 #endif
 }
 
-template <typename Rep, typename Period,
-          FMT_ENABLE_IF(std::is_floating_point<Rep>::value)>
-inline std::chrono::duration<Rep, std::milli> get_milliseconds(
+// Returns the number of fractional digits in the range [0, 18] according to the
+// C++20 spec. If more than 18 fractional digits are required then returns 6 for
+// microseconds precision.
+constexpr int count_fractional_digits(long long num, long long den, int n = 0) {
+  return num % den == 0
+             ? n
+             : (n > 18 ? 6 : count_fractional_digits(num * 10, den, n + 1));
+}
+
+constexpr long long pow10(std::uint32_t n) {
+  return n == 0 ? 1 : 10 * pow10(n - 1);
+}
+
+template <class Rep, class Period,
+          FMT_ENABLE_IF(std::numeric_limits<Rep>::is_signed)>
+constexpr std::chrono::duration<Rep, Period> abs(
     std::chrono::duration<Rep, Period> d) {
-  using common_type = typename std::common_type<Rep, std::intmax_t>::type;
-  auto ms = mod(d.count() * static_cast<common_type>(Period::num) /
-                    static_cast<common_type>(Period::den) * 1000,
-                1000);
-  return std::chrono::duration<Rep, std::milli>(static_cast<Rep>(ms));
+  // We need to compare the duration using the count() method directly
+  // due to a compiler bug in clang-11 regarding the spaceship operator,
+  // when -Wzero-as-null-pointer-constant is enabled.
+  // In clang-12 the bug has been fixed. See
+  // https://bugs.llvm.org/show_bug.cgi?id=46235 and the reproducible example:
+  // https://www.godbolt.org/z/Knbb5joYx.
+  return d.count() >= d.zero().count() ? d : -d;
+}
+
+template <class Rep, class Period,
+          FMT_ENABLE_IF(!std::numeric_limits<Rep>::is_signed)>
+constexpr std::chrono::duration<Rep, Period> abs(
+    std::chrono::duration<Rep, Period> d) {
+  return d;
 }
 
 template <typename Char, typename Rep, typename OutputIt,
@@ -1560,6 +1652,36 @@ struct chrono_formatter {
     out = format_decimal<char_type>(out, n, num_digits).end;
   }
 
+  template <class Duration> void write_fractional_seconds(Duration d) {
+    constexpr auto num_fractional_digits =
+        count_fractional_digits(Duration::period::num, Duration::period::den);
+
+    using subsecond_precision = std::chrono::duration<
+        typename std::common_type<typename Duration::rep,
+                                  std::chrono::seconds::rep>::type,
+        std::ratio<1, detail::pow10(num_fractional_digits)>>;
+    if (std::ratio_less<typename subsecond_precision::period,
+                        std::chrono::seconds::period>::value) {
+      *out++ = '.';
+      const auto subseconds =
+          std::chrono::treat_as_floating_point<
+              typename subsecond_precision::rep>::value
+              ? (detail::abs(d) -
+                 std::chrono::duration_cast<std::chrono::seconds>(d))
+                    .count()
+              : std::chrono::duration_cast<subsecond_precision>(
+                    detail::abs(d) -
+                    std::chrono::duration_cast<std::chrono::seconds>(d))
+                    .count();
+      uint32_or_64_or_128_t<long long> n =
+          to_unsigned(to_nonnegative_int(subseconds, max_value<long long>()));
+      int num_digits = detail::count_digits(n);
+      if (num_fractional_digits > num_digits)
+        out = std::fill_n(out, num_fractional_digits - num_digits, '0');
+      out = format_decimal<char_type>(out, n, num_digits).end;
+    }
+  }
+
   void write_nan() { std::copy_n("nan", 3, out); }
   void write_pinf() { std::copy_n("inf", 3, out); }
   void write_ninf() { std::copy_n("-inf", 4, out); }
@@ -1637,19 +1759,7 @@ struct chrono_formatter {
 
     if (ns == numeric_system::standard) {
       write(second(), 2);
-#if FMT_SAFE_DURATION_CAST
-      // convert rep->Rep
-      using duration_rep = std::chrono::duration<rep, Period>;
-      using duration_Rep = std::chrono::duration<Rep, Period>;
-      auto tmpval = fmt_safe_duration_cast<duration_Rep>(duration_rep{val});
-#else
-      auto tmpval = std::chrono::duration<Rep, Period>(val);
-#endif
-      auto ms = get_milliseconds(tmpval);
-      if (ms != std::chrono::milliseconds(0)) {
-        *out++ = '.';
-        write(ms.count(), 3);
-      }
+      write_fractional_seconds(std::chrono::duration<rep, Period>{val});
       return;
     }
     auto time = tm();
@@ -1678,7 +1788,7 @@ struct chrono_formatter {
     on_24_hour_time();
     *out++ = ':';
     if (handle_nan_inf()) return;
-    write(second(), 2);
+    on_second(numeric_system::standard);
   }
 
   void on_am_pm() {
diff --git a/include/fmt/core.h b/include/fmt/core.h
index e87b706c..6f75b353 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -8,7 +8,8 @@
 #ifndef FMT_CORE_H_
 #define FMT_CORE_H_
 
-#include <cstdio>  // std::FILE
+#include <cstddef>  // std::byte
+#include <cstdio>   // std::FILE
 #include <cstring>
 #include <iterator>
 #include <limits>
@@ -367,6 +368,12 @@ FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
 #  endif
 #endif
 
+#ifdef __cpp_lib_byte
+using byte = std::byte;
+#else
+enum class byte : unsigned char {};
+#endif
+
 #if defined(FMT_USE_STRING_VIEW)
 template <typename Char> using std_string_view = std::basic_string_view<Char>;
 #elif defined(FMT_USE_EXPERIMENTAL_STRING_VIEW)
@@ -560,7 +567,7 @@ constexpr auto to_string_view(const S& s)
 FMT_BEGIN_DETAIL_NAMESPACE
 
 void to_string_view(...);
-using fmt::v8::to_string_view;
+using fmt::to_string_view;
 
 // Specifies whether S is a string type convertible to fmt::basic_string_view.
 // It should be a constexpr function but MSVC 2017 fails to compile it in
@@ -1102,6 +1109,11 @@ template <typename... Args> constexpr auto count_named_args() -> size_t {
   return count<is_named_arg<Args>::value...>();
 }
 
+template <typename... Args>
+constexpr auto count_statically_named_args() -> size_t {
+  return count<is_statically_named_arg<Args>::value...>();
+}
+
 enum class type {
   none_type,
   // Integer types should go first,
@@ -1357,20 +1369,21 @@ template <typename Context> struct arg_mapper {
       -> basic_string_view<char_type> {
     return std_string_view<char_type>(val);
   }
-  FMT_CONSTEXPR FMT_INLINE auto map(const signed char* val)
-      -> decltype(this->map("")) {
+
+  using cstring_result = conditional_t<std::is_same<char_type, char>::value,
+                                       const char*, unformattable_pointer>;
+
+  FMT_CONSTEXPR FMT_INLINE auto map(const signed char* val) -> cstring_result {
     return map(reinterpret_cast<const char*>(val));
   }
   FMT_CONSTEXPR FMT_INLINE auto map(const unsigned char* val)
-      -> decltype(this->map("")) {
+      -> cstring_result {
     return map(reinterpret_cast<const char*>(val));
   }
-  FMT_CONSTEXPR FMT_INLINE auto map(signed char* val)
-      -> decltype(this->map("")) {
+  FMT_CONSTEXPR FMT_INLINE auto map(signed char* val) -> cstring_result {
     return map(reinterpret_cast<const char*>(val));
   }
-  FMT_CONSTEXPR FMT_INLINE auto map(unsigned char* val)
-      -> decltype(this->map("")) {
+  FMT_CONSTEXPR FMT_INLINE auto map(unsigned char* val) -> cstring_result {
     return map(reinterpret_cast<const char*>(val));
   }
 
@@ -1402,15 +1415,20 @@ template <typename Context> struct arg_mapper {
   }
 
   template <typename T,
-            FMT_ENABLE_IF(std::is_enum<T>::value &&
-                          !has_formatter<T, Context>::value &&
-                          !has_fallback_formatter<T, char_type>::value)>
+            FMT_ENABLE_IF(
+                std::is_enum<T>::value&& std::is_convertible<T, int>::value &&
+                !has_formatter<T, Context>::value &&
+                !has_fallback_formatter<T, char_type>::value)>
   FMT_CONSTEXPR FMT_INLINE auto map(const T& val)
       -> decltype(std::declval<arg_mapper>().map(
           static_cast<typename std::underlying_type<T>::type>(val))) {
     return map(static_cast<typename std::underlying_type<T>::type>(val));
   }
 
+  FMT_CONSTEXPR FMT_INLINE auto map(detail::byte val) -> unsigned {
+    return map(static_cast<unsigned char>(val));
+  }
+
   template <typename T, typename U = remove_cvref_t<T>>
   struct formattable
       : bool_constant<has_const_formatter<U, Context>() ||
@@ -1482,14 +1500,11 @@ class appender : public std::back_insert_iterator<detail::buffer<char>> {
   using _Unchecked_type = appender;  // Mark iterator as checked.
 
   auto operator++() -> appender& {
-    base::operator++();
     return *this;
   }
 
   auto operator++(int) -> appender {
-    auto tmp = *this;
-    ++*this;
-    return tmp;
+    return *this;
   }
 };
 
@@ -2472,7 +2487,7 @@ FMT_CONSTEXPR FMT_INLINE auto parse_format_specs(const Char* begin,
                                                  const Char* end,
                                                  SpecHandler&& handler)
     -> const Char* {
-  if (begin + 1 < end && begin[1] == '}' && is_ascii_letter(*begin) &&
+  if (1 < end - begin && begin[1] == '}' && is_ascii_letter(*begin) &&
       *begin != 'L') {
     presentation_type type = parse_presentation_type(*begin++);
     if (type == presentation_type::none)
@@ -3033,7 +3048,8 @@ template <typename Char, typename... Args> class basic_format_string {
              std::is_reference<Args>::value)...>() == 0,
         "passing views as lvalues is disallowed");
 #ifdef FMT_HAS_CONSTEVAL
-    if constexpr (detail::count_named_args<Args...>() == 0) {
+    if constexpr (detail::count_named_args<Args...>() ==
+                  detail::count_statically_named_args<Args...>()) {
       using checker = detail::format_string_checker<Char, detail::error_handler,
                                                     remove_cvref_t<Args>...>;
       detail::parse_format_string<true>(str_, checker(s, {}));
diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index f4ffeb67..04ded482 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -704,7 +704,12 @@ FMT_INLINE FMT_CONSTEXPR20 digits::result grisu_gen_digits(
   if (handler.fixed) {
     // Adjust fixed precision by exponent because it is relative to decimal
     // point.
-    handler.precision += exp + handler.exp10;
+    int precision_offset = exp + handler.exp10;
+    if (precision_offset > 0 &&
+        handler.precision > max_value<int>() - precision_offset) {
+      FMT_THROW(format_error("number is too big"));
+    }
+    handler.precision += precision_offset;
     // Check if precision is satisfied just by leading zeros, e.g.
     // format("{:.2f}", 0.001) gives "0.00" without generating any digits.
     if (handler.precision <= 0) {
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 3cf123ee..ea5b9ece 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -265,6 +265,38 @@ FMT_END_NAMESPACE
 
 FMT_BEGIN_NAMESPACE
 namespace detail {
+
+template <typename Streambuf> class formatbuf : public Streambuf {
+ private:
+  using char_type = typename Streambuf::char_type;
+  using streamsize = decltype(std::declval<Streambuf>().sputn(nullptr, 0));
+  using int_type = typename Streambuf::int_type;
+  using traits_type = typename Streambuf::traits_type;
+
+  buffer<char_type>& buffer_;
+
+ public:
+  explicit formatbuf(buffer<char_type>& buf) : buffer_(buf) {}
+
+ protected:
+  // The put area is always empty. This makes the implementation simpler and has
+  // the advantage that the streambuf and the buffer are always in sync and
+  // sputc never writes into uninitialized memory. A disadvantage is that each
+  // call to sputc always results in a (virtual) call to overflow. There is no
+  // disadvantage here for sputn since this always results in a call to xsputn.
+
+  auto overflow(int_type ch) -> int_type override {
+    if (!traits_type::eq_int_type(ch, traits_type::eof()))
+      buffer_.push_back(static_cast<char_type>(ch));
+    return ch;
+  }
+
+  auto xsputn(const char_type* s, streamsize count) -> streamsize override {
+    buffer_.append(s, s + count);
+    return count;
+  }
+};
+
 // An equivalent of `*reinterpret_cast<Dest*>(&source)` that doesn't have
 // undefined behavior (e.g. due to type aliasing).
 // Example: uint64_t d = bit_cast<uint64_t>(2.718);
@@ -2574,6 +2606,7 @@ FMT_FORMAT_AS(unsigned long, unsigned long long);
 FMT_FORMAT_AS(Char*, const Char*);
 FMT_FORMAT_AS(std::basic_string<Char>, basic_string_view<Char>);
 FMT_FORMAT_AS(std::nullptr_t, const void*);
+FMT_FORMAT_AS(detail::byte, unsigned char);
 FMT_FORMAT_AS(detail::std_string_view<Char>, basic_string_view<Char>);
 
 template <typename Char>
@@ -3016,16 +3049,14 @@ constexpr auto operator"" _a(const char* s, size_t) -> detail::udl_arg<char> {
 #  endif
 
 /**
-  \rst
-  User-defined literal equivalent of :func:`fmt::format`.
+  DEPRECATED! User-defined literal equivalent of fmt::format.
 
   **Example**::
 
     using namespace fmt::literals;
     std::string message = "The answer is {}"_format(42);
-  \endrst
  */
-constexpr auto operator"" _format(const char* s, size_t n)
+FMT_DEPRECATED constexpr auto operator"" _format(const char* s, size_t n)
     -> detail::udl_formatter<char> {
   return {{s, n}};
 }
diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index dd005fa1..3d716ece 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -18,36 +18,6 @@ template <typename OutputIt, typename Char> class basic_printf_context;
 
 namespace detail {
 
-template <class Char> class formatbuf : public std::basic_streambuf<Char> {
- private:
-  using int_type = typename std::basic_streambuf<Char>::int_type;
-  using traits_type = typename std::basic_streambuf<Char>::traits_type;
-
-  buffer<Char>& buffer_;
-
- public:
-  explicit formatbuf(buffer<Char>& buf) : buffer_(buf) {}
-
- protected:
-  // The put area is always empty. This makes the implementation simpler and has
-  // the advantage that the streambuf and the buffer are always in sync and
-  // sputc never writes into uninitialized memory. A disadvantage is that each
-  // call to sputc always results in a (virtual) call to overflow. There is no
-  // disadvantage here for sputn since this always results in a call to xsputn.
-
-  auto overflow(int_type ch = traits_type::eof()) -> int_type override {
-    if (!traits_type::eq_int_type(ch, traits_type::eof()))
-      buffer_.push_back(static_cast<Char>(ch));
-    return ch;
-  }
-
-  auto xsputn(const Char* s, std::streamsize count)
-      -> std::streamsize override {
-    buffer_.append(s, s + count);
-    return count;
-  }
-};
-
 // Checks if T has a user-defined operator<<.
 template <typename T, typename Char, typename Enable = void>
 class is_streamable {
@@ -75,6 +45,8 @@ struct is_streamable<
     enable_if_t<
         std::is_arithmetic<T>::value || std::is_array<T>::value ||
         std::is_pointer<T>::value || std::is_same<T, char8_type>::value ||
+        std::is_same<T, std::basic_string<Char>>::value ||
+        std::is_same<T, std_string_view<Char>>::value ||
         (std::is_convertible<T, int>::value && !std::is_enum<T>::value)>>
     : std::false_type {};
 
@@ -97,7 +69,7 @@ void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
 template <typename Char, typename T>
 void format_value(buffer<Char>& buf, const T& value,
                   locale_ref loc = locale_ref()) {
-  auto&& format_buf = formatbuf<Char>(buf);
+  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
   auto&& output = std::basic_ostream<Char>(&format_buf);
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
   if (loc) output.imbue(loc.get<std::locale>());
diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index ee12bd95..71474f32 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -19,21 +19,6 @@
 
 FMT_BEGIN_NAMESPACE
 
-template <typename Char, typename Enable = void> struct formatting_range {
-#ifdef FMT_DEPRECATED_BRACED_RANGES
-  Char prefix = '{';
-  Char postfix = '}';
-#else
-  Char prefix = '[';
-  Char postfix = ']';
-#endif
-
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-};
-
 template <typename Char, typename Enable = void> struct formatting_tuple {
   Char prefix = '(';
   Char postfix = ')';
@@ -71,7 +56,7 @@ OutputIterator copy(wchar_t ch, OutputIterator out) {
   return out;
 }
 
-/// Return true value if T has std::string interface, like std::string_view.
+// Returns true if T has a std::string-like interface, like std::string_view.
 template <typename T> class is_std_string_like {
   template <typename U>
   static auto check(U* p)
@@ -86,6 +71,32 @@ template <typename T> class is_std_string_like {
 template <typename Char>
 struct is_std_string_like<fmt::basic_string_view<Char>> : std::true_type {};
 
+template <typename T> class is_map {
+  template <typename U> static auto check(U*) -> typename U::mapped_type;
+  template <typename> static void check(...);
+
+ public:
+#ifdef FMT_FORMAT_MAP_AS_LIST
+  static FMT_CONSTEXPR_DECL const bool value = false;
+#else
+  static FMT_CONSTEXPR_DECL const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value;
+#endif
+};
+
+template <typename T> class is_set {
+  template <typename U> static auto check(U*) -> typename U::key_type;
+  template <typename> static void check(...);
+
+ public:
+#ifdef FMT_FORMAT_SET_AS_LIST
+  static FMT_CONSTEXPR_DECL const bool value = false;
+#else
+  static FMT_CONSTEXPR_DECL const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value && !is_map<T>::value;
+#endif
+};
+
 template <typename... Ts> struct conditional_helper {};
 
 template <typename T, typename _ = void> struct is_range_ : std::false_type {};
@@ -573,6 +584,7 @@ struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
 template <typename T, typename Char> struct is_range {
   static FMT_CONSTEXPR_DECL const bool value =
       detail::is_range_<T>::value && !detail::is_std_string_like<T>::value &&
+      !detail::is_map<T>::value &&
       !std::is_convertible<T, std::basic_string<Char>>::value &&
       !std::is_constructible<detail::std_string_view<Char>, T>::value;
 };
@@ -588,11 +600,9 @@ struct formatter<
             detail::has_fallback_formatter<detail::value_type<T>, Char>::value)
 #endif
         >> {
-  formatting_range<Char> formatting;
-
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return formatting.parse(ctx);
+    return ctx.begin();
   }
 
   template <
@@ -600,17 +610,64 @@ struct formatter<
       FMT_ENABLE_IF(
           std::is_same<U, conditional_t<detail::has_const_begin_end<T>::value,
                                         const T, T>>::value)>
-  auto format(U& values, FormatContext& ctx) -> decltype(ctx.out()) {
-    auto out = detail::copy(formatting.prefix, ctx.out());
-    size_t i = 0;
-    auto it = std::begin(values);
-    auto end = std::end(values);
+  auto format(U& range, FormatContext& ctx) -> decltype(ctx.out()) {
+#ifdef FMT_DEPRECATED_BRACED_RANGES
+    Char prefix = '{';
+    Char postfix = '}';
+#else
+    Char prefix = detail::is_set<T>::value ? '{' : '[';
+    Char postfix = detail::is_set<T>::value ? '}' : ']';
+#endif
+    auto out = ctx.out();
+    *out++ = prefix;
+    int i = 0;
+    auto it = std::begin(range);
+    auto end = std::end(range);
     for (; it != end; ++it) {
       if (i > 0) out = detail::write_delimiter(out);
       out = detail::write_range_entry<Char>(out, *it);
       ++i;
     }
-    return detail::copy(formatting.postfix, out);
+    *out++ = postfix;
+    return out;
+  }
+};
+
+template <typename T, typename Char>
+struct formatter<
+    T, Char,
+    enable_if_t<
+        detail::is_map<T>::value
+// Workaround a bug in MSVC 2019 and earlier.
+#if !FMT_MSC_VER
+        && (is_formattable<detail::value_type<T>, Char>::value ||
+            detail::has_fallback_formatter<detail::value_type<T>, Char>::value)
+#endif
+        >> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <
+      typename FormatContext, typename U,
+      FMT_ENABLE_IF(
+          std::is_same<U, conditional_t<detail::has_const_begin_end<T>::value,
+                                        const T, T>>::value)>
+  auto format(U& map, FormatContext& ctx) -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    *out++ = '{';
+    int i = 0;
+    for (const auto& item : map) {
+      if (i > 0) out = detail::write_delimiter(out);
+      out = detail::write_range_entry<Char>(out, item.first);
+      *out++ = ':';
+      *out++ = ' ';
+      out = detail::write_range_entry<Char>(out, item.second);
+      ++i;
+    }
+    *out++ = '}';
+    return out;
   }
 };
 
diff --git a/include/fmt/xchar.h b/include/fmt/xchar.h
index a0dd032f..55825077 100644
--- a/include/fmt/xchar.h
+++ b/include/fmt/xchar.h
@@ -5,8 +5,8 @@
 //
 // For the license information refer to format.h.
 
-#ifndef FMT_WCHAR_H_
-#define FMT_WCHAR_H_
+#ifndef FMT_XCHAR_H_
+#define FMT_XCHAR_H_
 
 #include <cwchar>
 #include <tuple>
@@ -217,11 +217,11 @@ inline void vprint(wstring_view fmt, wformat_args args) {
 
 template <typename... T>
 void print(std::FILE* f, wformat_string<T...> fmt, T&&... args) {
-  return vprint(f, wstring_view(fmt), make_wformat_args(args...));
+  return vprint(f, wstring_view(fmt), fmt::make_wformat_args(args...));
 }
 
 template <typename... T> void print(wformat_string<T...> fmt, T&&... args) {
-  return vprint(wstring_view(fmt), make_wformat_args(args...));
+  return vprint(wstring_view(fmt), fmt::make_wformat_args(args...));
 }
 
 /**
@@ -233,4 +233,4 @@ template <typename T> inline auto to_wstring(const T& value) -> std::wstring {
 FMT_MODULE_EXPORT_END
 FMT_END_NAMESPACE
 
-#endif  // FMT_WCHAR_H_
+#endif  // FMT_XCHAR_H_
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 6a27e33f..a0fbd05f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -8,19 +8,6 @@ target_link_libraries(test-main gtest)
 
 include(CheckCXXCompilerFlag)
 
-# Workaround GTest bug https://github.com/google/googletest/issues/705.
-check_cxx_compiler_flag(
-  -fno-delete-null-pointer-checks HAVE_FNO_DELETE_NULL_POINTER_CHECKS)
-if (HAVE_FNO_DELETE_NULL_POINTER_CHECKS)
-  target_compile_options(test-main PUBLIC -fno-delete-null-pointer-checks)
-endif ()
-
-# Use less strict pedantic flags for the tests because GMock doesn't compile
-# cleanly with -pedantic and -std=c++98.
-if (CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang"))
-    #set(PEDANTIC_COMPILE_FLAGS -Wall -Wextra -Wno-long-long -Wno-variadic-macros)
-endif ()
-
 function(add_fmt_executable name)
   add_executable(${name} ${ARGN})
   if (MINGW)
diff --git a/test/args-test.cc b/test/args-test.cc
index 2b1db8c8..e793cb5c 100644
--- a/test/args-test.cc
+++ b/test/args-test.cc
@@ -10,7 +10,7 @@
 #include "gtest/gtest.h"
 
 TEST(args_test, basic) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   store.push_back(42);
   store.push_back("abc1");
   store.push_back(1.5f);
@@ -19,7 +19,7 @@ TEST(args_test, basic) {
 
 TEST(args_test, strings_and_refs) {
   // Unfortunately the tests are compiled with old ABI so strings use COW.
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   char str[] = "1234567890";
   store.push_back(str);
   store.push_back(std::cref(str));
@@ -48,7 +48,7 @@ template <> struct formatter<custom_type> {
 FMT_END_NAMESPACE
 
 TEST(args_test, custom_format) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   auto c = custom_type();
   store.push_back(c);
   ++c.i;
@@ -77,7 +77,7 @@ template <> struct formatter<to_stringable> {
 FMT_END_NAMESPACE
 
 TEST(args_test, to_string_and_formatter) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   auto s = to_stringable();
   store.push_back(s);
   store.push_back(std::cref(s));
@@ -85,13 +85,13 @@ TEST(args_test, to_string_and_formatter) {
 }
 
 TEST(args_test, named_int) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   store.push_back(fmt::arg("a1", 42));
   EXPECT_EQ("42", fmt::vformat("{a1}", store));
 }
 
 TEST(args_test, named_strings) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   char str[] = "1234567890";
   store.push_back(fmt::arg("a1", str));
   store.push_back(fmt::arg("a2", std::cref(str)));
@@ -100,7 +100,7 @@ TEST(args_test, named_strings) {
 }
 
 TEST(args_test, named_arg_by_ref) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   char band[] = "Rolling Stones";
   store.push_back(fmt::arg("band", std::cref(band)));
   band[9] = 'c';  // Changing band affects the output.
@@ -108,7 +108,7 @@ TEST(args_test, named_arg_by_ref) {
 }
 
 TEST(args_test, named_custom_format) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   auto c = custom_type();
   store.push_back(fmt::arg("c1", c));
   ++c.i;
@@ -121,7 +121,7 @@ TEST(args_test, named_custom_format) {
 }
 
 TEST(args_test, clear) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   store.push_back(42);
 
   auto result = fmt::vformat("{}", store);
@@ -138,7 +138,7 @@ TEST(args_test, clear) {
 }
 
 TEST(args_test, reserve) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   store.reserve(2, 1);
   store.push_back(1.5f);
   store.push_back(fmt::arg("a1", 42));
@@ -163,7 +163,7 @@ template <> struct formatter<copy_throwable> {
 FMT_END_NAMESPACE
 
 TEST(args_test, throw_on_copy) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
   store.push_back(std::string("foo"));
   try {
     store.push_back(copy_throwable());
@@ -171,16 +171,3 @@ TEST(args_test, throw_on_copy) {
   }
   EXPECT_EQ(fmt::vformat("{}", store), "foo");
 }
-
-TEST(args_test, copy_constructor) {
-  auto store = fmt::dynamic_format_arg_store<fmt::format_context>();
-  store.push_back(fmt::arg("test1", "value1"));
-  store.push_back(fmt::arg("test2", "value2"));
-  store.push_back(fmt::arg("test3", "value3"));
-
-  auto store2 = store;
-  store2.push_back(fmt::arg("test4", "value4"));
-
-  auto result = fmt::vformat("{test1} {test2} {test3} {test4}", store2);
-  EXPECT_EQ(result, "value1 value2 value3 value4");
-}
diff --git a/test/chrono-test.cc b/test/chrono-test.cc
index a2bc20c2..42360e5f 100644
--- a/test/chrono-test.cc
+++ b/test/chrono-test.cc
@@ -543,15 +543,12 @@ TEST(chrono_test, negative_durations) {
 }
 
 TEST(chrono_test, special_durations) {
-  EXPECT_EQ(
-      "40.",
-      fmt::format("{:%S}", std::chrono::duration<double>(1e20)).substr(0, 3));
+  auto value = fmt::format("{:%S}", std::chrono::duration<double>(1e20));
+  EXPECT_EQ(value, "40");
   auto nan = std::numeric_limits<double>::quiet_NaN();
   EXPECT_EQ(
       "nan nan nan nan nan:nan nan",
       fmt::format("{:%I %H %M %S %R %r}", std::chrono::duration<double>(nan)));
-  (void)fmt::format("{:%S}",
-                    std::chrono::duration<float, std::atto>(1.79400457e+31f));
   EXPECT_EQ(fmt::format("{}", std::chrono::duration<float, std::exa>(1)),
             "1Es");
   EXPECT_EQ(fmt::format("{}", std::chrono::duration<float, std::atto>(1)),
@@ -585,4 +582,44 @@ TEST(chrono_test, weekday) {
   }
 }
 
+TEST(chrono_test, cpp20_duration_subsecond_support) {
+  using attoseconds = std::chrono::duration<long long, std::atto>;
+  // Check that 18 digits of subsecond precision are supported.
+  EXPECT_EQ(fmt::format("{:%S}", attoseconds{999999999999999999}),
+            "00.999999999999999999");
+  EXPECT_EQ(fmt::format("{:%S}", attoseconds{673231113420148734}),
+            "00.673231113420148734");
+  EXPECT_EQ(fmt::format("{:%S}", attoseconds{-673231113420148734}),
+            "-00.673231113420148734");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::nanoseconds{13420148734}),
+            "13.420148734");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::nanoseconds{-13420148734}),
+            "-13.420148734");
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::milliseconds{1234}), "01.234");
+  {
+    // Check that {:%H:%M:%S} is equivalent to {:%T}.
+    auto dur = std::chrono::milliseconds{3601234};
+    auto formatted_dur = fmt::format("{:%T}", dur);
+    EXPECT_EQ(formatted_dur, "01:00:01.234");
+    EXPECT_EQ(fmt::format("{:%H:%M:%S}", dur), formatted_dur);
+  }
+  using nanoseconds_dbl = std::chrono::duration<double, std::nano>;
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{-123456789}), "-00.123456789");
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{9123456789}), "09.123456789");
+  // Verify that only the seconds part is extracted and printed.
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{99123456789}), "39.123456789");
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{99123000000}), "39.123000000");
+  {
+    // Now the hour is printed, and we also test if negative doubles work.
+    auto dur = nanoseconds_dbl{-99123456789};
+    auto formatted_dur = fmt::format("{:%T}", dur);
+    EXPECT_EQ(formatted_dur, "-00:01:39.123456789");
+    EXPECT_EQ(fmt::format("{:%H:%M:%S}", dur), formatted_dur);
+  }
+  // Check that durations with precision greater than std::chrono::seconds have
+  // fixed precision, and print zeros even if there is no fractional part.
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::microseconds{7000000}),
+            "07.000000");
+}
+
 #endif  // FMT_STATIC_THOUSANDS_SEPARATOR
diff --git a/test/core-test.cc b/test/core-test.cc
index decf31a7..78ec3de2 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -737,6 +737,8 @@ struct convertible_to_pointer {
   operator const int*() const { return nullptr; }
 };
 
+enum class test_scoped_enum {};
+
 TEST(core_test, is_formattable) {
   static_assert(fmt::is_formattable<signed char*>::value, "");
   static_assert(fmt::is_formattable<unsigned char*>::value, "");
@@ -777,6 +779,7 @@ TEST(core_test, is_formattable) {
 
   static_assert(!fmt::is_formattable<int(s::*)>::value, "");
   static_assert(!fmt::is_formattable<int (s::*)()>::value, "");
+  static_assert(!fmt::is_formattable<test_scoped_enum>::value, "");
 }
 
 TEST(core_test, format) { EXPECT_EQ(fmt::format("{}", 42), "42"); }
diff --git a/test/format-test.cc b/test/format-test.cc
index 9233a87b..952dbe20 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -934,6 +934,9 @@ TEST(format_test, precision) {
   EXPECT_THROW_MSG((void)fmt::format(runtime("{:.{}e}"), 42.0,
                                      fmt::detail::max_value<int>()),
                    format_error, "number is too big");
+  EXPECT_THROW_MSG(
+      (void)fmt::format("{:.2147483646f}", -2.2121295195081227E+304),
+      format_error, "number is too big");
 
   EXPECT_EQ("st", fmt::format("{0:.2}", "str"));
 }
@@ -1758,6 +1761,21 @@ TEST(format_test, custom_format_compile_time_string) {
 
 using namespace fmt::literals;
 
+#  if FMT_GCC_VERSION
+#    define FMT_CHECK_DEPRECATED_UDL_FORMAT 1
+#  elif FMT_CLANG_VERSION && defined(__has_warning)
+#    if __has_warning("-Wdeprecated-declarations")
+#      define FMT_CHECK_DEPRECATED_UDL_FORMAT 1
+#    endif
+#  endif
+#  ifndef FMT_CHECK_DEPRECATED_UDL_FORMAT
+#    define FMT_CHECK_DEPRECATED_UDL_FORMAT 0
+#  endif
+
+#  if FMT_CHECK_DEPRECATED_UDL_FORMAT
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
 TEST(format_test, format_udl) {
   EXPECT_EQ("{}c{}"_format("ab", 1), fmt::format("{}c{}", "ab", 1));
   EXPECT_EQ("foo"_format(), "foo");
@@ -1765,6 +1783,9 @@ TEST(format_test, format_udl) {
   EXPECT_EQ("{}"_format(date(2015, 10, 21)), "2015-10-21");
 }
 
+#    pragma GCC diagnostic pop
+#  endif
+
 TEST(format_test, named_arg_udl) {
   auto udl_a = fmt::format("{first}{second}{first}{third}", "first"_a = "abra",
                            "second"_a = "cad", "third"_a = 99);
diff --git a/test/fuzzing/float.cc b/test/fuzzing/float.cc
index b3780e1d..d4c9e4f5 100644
--- a/test/fuzzing/float.cc
+++ b/test/fuzzing/float.cc
@@ -12,7 +12,7 @@
 
 void check_round_trip(fmt::string_view format_str, double value) {
   auto buffer = fmt::memory_buffer();
-  fmt::format_to(buffer, format_str, value);
+  fmt::format_to(std::back_inserter(buffer), format_str, value);
 
   if (std::isnan(value)) {
     auto nan = std::signbit(value) ? "-nan" : "nan";
diff --git a/test/gtest/CMakeLists.txt b/test/gtest/CMakeLists.txt
index 1282d62a..0cc4e1aa 100644
--- a/test/gtest/CMakeLists.txt
+++ b/test/gtest/CMakeLists.txt
@@ -17,6 +17,13 @@ else ()
   target_compile_definitions(gtest PUBLIC GTEST_HAS_PTHREAD=0)
 endif ()
 
+# Workaround GTest bug https://github.com/google/googletest/issues/705.
+check_cxx_compiler_flag(
+  -fno-delete-null-pointer-checks HAVE_FNO_DELETE_NULL_POINTER_CHECKS)
+if (HAVE_FNO_DELETE_NULL_POINTER_CHECKS)
+  target_compile_options(gtest PUBLIC -fno-delete-null-pointer-checks)
+endif ()
+
 if (MSVC)
   # Disable MSVC warnings of _CRT_INSECURE_DEPRECATE functions.
   target_compile_definitions(gtest PRIVATE _CRT_SECURE_NO_WARNINGS)
diff --git a/test/ostream-test.cc b/test/ostream-test.cc
index a01182d1..f81039e5 100644
--- a/test/ostream-test.cc
+++ b/test/ostream-test.cc
@@ -294,3 +294,8 @@ struct abstract {
 void format_abstract_compiles(const abstract& a) {
   fmt::format(FMT_COMPILE("{}"), a);
 }
+
+TEST(ostream_test, is_formattable) {
+  EXPECT_TRUE(fmt::is_formattable<std::string>());
+  EXPECT_TRUE(fmt::is_formattable<fmt::detail::std_string_view<char>>());
+}
diff --git a/test/ranges-test.cc b/test/ranges-test.cc
index f8e67390..86dd5520 100644
--- a/test/ranges-test.cc
+++ b/test/ranges-test.cc
@@ -55,7 +55,12 @@ TEST(ranges_test, format_vector2) {
 
 TEST(ranges_test, format_map) {
   auto m = std::map<std::string, int>{{"one", 1}, {"two", 2}};
-  EXPECT_EQ(fmt::format("{}", m), "[(\"one\", 1), (\"two\", 2)]");
+  EXPECT_EQ(fmt::format("{}", m), "{\"one\": 1, \"two\": 2}");
+}
+
+TEST(ranges_test, format_set) {
+  EXPECT_EQ(fmt::format("{}", std::set<std::string>{"one", "two"}),
+            "{\"one\", \"two\"}");
 }
 
 TEST(ranges_test, format_pair) {
@@ -190,7 +195,7 @@ TEST(ranges_test, range) {
   EXPECT_EQ(fmt::format("{}", z), "[0, 0, 0]");
 }
 
-enum class test_enum { foo };
+enum test_enum { foo };
 
 TEST(ranges_test, enum_range) {
   auto v = std::vector<test_enum>{test_enum::foo};