Bumped fmt to version 6.0.0

include/spdlog/fmt/bundled/LICENSE.rst

-Copyright (c) 2012 - 2016, Victor Zverovich
+Copyright (c) 2012 - present, Victor Zverovich
 
-All rights reserved.
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
 
-Redistribution and use in source and binary forms, with or without
-modification, are permitted provided that the following conditions are met:
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
 
-1. Redistributions of source code must retain the above copyright notice, this
-   list of conditions and the following disclaimer.
-2. Redistributions in binary form must reproduce the above copyright notice,
-   this list of conditions and the following disclaimer in the documentation
-   and/or other materials provided with the distribution.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
-ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
-DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
-ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
-SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+--- Optional exception to the license ---
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into a machine-executable object form of such
+source code, you may redistribute such embedded portions in such object form
+without including the above copyright and permission notices.

include/spdlog/fmt/bundled/locale.h

@@ -8,65 +8,65 @@
 #ifndef FMT_LOCALE_H_
 #define FMT_LOCALE_H_
 
-#include "format.h"
 #include <locale>
+#include "format.h"
 
 FMT_BEGIN_NAMESPACE
 
 namespace internal {
 template <typename Char>
-typename buffer_context<Char>::type::iterator vformat_to(
-    const std::locale &loc, basic_buffer<Char> &buf,
+typename buffer_context<Char>::iterator vformat_to(
+    const std::locale& loc, buffer<Char>& buf,
     basic_string_view<Char> format_str,
-    basic_format_args<typename buffer_context<Char>::type> args) {
-  typedef back_insert_range<basic_buffer<Char> > range;
-  return vformat_to<arg_formatter<range>>(
-    buf, to_string_view(format_str), args, internal::locale_ref(loc));
+    basic_format_args<buffer_context<Char>> args) {
+  using range = buffer_range<Char>;
+  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str), args,
+                                          internal::locale_ref(loc));
 }
 
 template <typename Char>
-std::basic_string<Char> vformat(
-    const std::locale &loc, basic_string_view<Char> format_str,
-    basic_format_args<typename buffer_context<Char>::type> args) {
+std::basic_string<Char> vformat(const std::locale& loc,
+                                basic_string_view<Char> format_str,
+                                basic_format_args<buffer_context<Char>> args) {
   basic_memory_buffer<Char> buffer;
   internal::vformat_to(loc, buffer, format_str, args);
   return fmt::to_string(buffer);
 }
-}
+}  // namespace internal
 
-template <typename S, typename Char = FMT_CHAR(S)>
+template <typename S, typename Char = char_t<S>>
 inline std::basic_string<Char> vformat(
-    const std::locale &loc, const S &format_str,
-    basic_format_args<typename buffer_context<Char>::type> args) {
+    const std::locale& loc, const S& format_str,
+    basic_format_args<buffer_context<Char>> args) {
   return internal::vformat(loc, to_string_view(format_str), args);
 }
 
-template <typename S, typename... Args>
-inline std::basic_string<FMT_CHAR(S)> format(
-    const std::locale &loc, const S &format_str, const Args &... args) {
+template <typename S, typename... Args, typename Char = char_t<S>>
+inline std::basic_string<Char> format(const std::locale& loc,
+                                      const S& format_str, Args&&... args) {
   return internal::vformat(
       loc, to_string_view(format_str),
-    *internal::checked_args<S, Args...>(format_str, args...));
+      {internal::make_args_checked<Args...>(format_str, args...)});
 }
 
-template <typename String, typename OutputIt, typename... Args>
-inline typename std::enable_if<internal::is_output_iterator<OutputIt>::value,
-                               OutputIt>::type
-    vformat_to(OutputIt out, const std::locale &loc, const String &format_str,
-               typename format_args_t<OutputIt, FMT_CHAR(String)>::type args) {
-  typedef output_range<OutputIt, FMT_CHAR(String)> range;
+template <typename S, typename OutputIt, typename... Args,
+          typename Char = enable_if_t<
+              internal::is_output_iterator<OutputIt>::value, char_t<S>>>
+inline OutputIt vformat_to(OutputIt out, const std::locale& loc,
+                           const S& format_str,
+                           format_args_t<OutputIt, Char> args) {
+  using range = internal::output_range<OutputIt, Char>;
   return vformat_to<arg_formatter<range>>(
       range(out), to_string_view(format_str), args, internal::locale_ref(loc));
 }
 
-template <typename OutputIt, typename S, typename... Args>
-inline typename std::enable_if<
-    internal::is_string<S>::value &&
-    internal::is_output_iterator<OutputIt>::value, OutputIt>::type
-    format_to(OutputIt out, const std::locale &loc, const S &format_str,
-              const Args &... args) {
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value&&
+                            internal::is_string<S>::value)>
+inline OutputIt format_to(OutputIt out, const std::locale& loc,
+                          const S& format_str, Args&&... args) {
   internal::check_format_string<Args...>(format_str);
-  typedef typename format_context_t<OutputIt, FMT_CHAR(S)>::type context;
+  using context = format_context_t<OutputIt, char_t<S>>;
   format_arg_store<context, Args...> as{args...};
   return vformat_to(out, loc, to_string_view(format_str),
                     basic_format_args<context>(as));

include/spdlog/fmt/bundled/ostream.h

@@ -8,22 +8,21 @@
 #ifndef FMT_OSTREAM_H_
 #define FMT_OSTREAM_H_
 
-#include "format.h"
 #include <ostream>
+#include "format.h"
 
 FMT_BEGIN_NAMESPACE
 namespace internal {
 
-template <class Char>
-class formatbuf : public std::basic_streambuf<Char> {
+template <class Char> class formatbuf : public std::basic_streambuf<Char> {
  private:
-  typedef typename std::basic_streambuf<Char>::int_type int_type;
-  typedef typename std::basic_streambuf<Char>::traits_type traits_type;
+  using int_type = typename std::basic_streambuf<Char>::int_type;
+  using traits_type = typename std::basic_streambuf<Char>::traits_type;
 
-  basic_buffer<Char> &buffer_;
+  buffer<Char>& buffer_;
 
  public:
-  formatbuf(basic_buffer<Char> &buffer) : buffer_(buffer) {}
+  formatbuf(buffer<Char>& buf) : buffer_(buf) {}
 
  protected:
   // The put-area is actually always empty. This makes the implementation
@@ -39,33 +38,32 @@ class formatbuf : public std::basic_streambuf<Char> {
     return ch;
   }
 
-  std::streamsize xsputn(const Char *s, std::streamsize count) FMT_OVERRIDE {
+  std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
     buffer_.append(s, s + count);
     return count;
   }
 };
 
-template <typename Char>
-struct test_stream : std::basic_ostream<Char> {
+template <typename Char> struct test_stream : std::basic_ostream<Char> {
  private:
   struct null;
   // Hide all operator<< from std::basic_ostream<Char>.
   void operator<<(null);
 };
 
-// Checks if T has a user-defined operator<< (e.g. not a member of std::ostream).
-template <typename T, typename Char>
-class is_streamable {
+// Checks if T has a user-defined operator<< (e.g. not a member of
+// std::ostream).
+template <typename T, typename Char> class is_streamable {
  private:
   template <typename U>
-  static decltype(
-    internal::declval<test_stream<Char>&>()
-      << internal::declval<U>(), std::true_type()) test(int);
+  static decltype((void)(std::declval<test_stream<Char>&>()
+                         << std::declval<U>()),
+                  std::true_type())
+  test(int);
 
-  template <typename>
-  static std::false_type test(...);
+  template <typename> static std::false_type test(...);
 
-  typedef decltype(test<T>(0)) result;
+  using result = decltype(test<T>(0));
 
  public:
   static const bool value = result::value;
@@ -73,65 +71,51 @@ class is_streamable {
 
 // Write the content of buf to os.
 template <typename Char>
-void write(std::basic_ostream<Char> &os, basic_buffer<Char> &buf) {
-  const Char *data = buf.data();
-  typedef std::make_unsigned<std::streamsize>::type UnsignedStreamSize;
-  UnsignedStreamSize size = buf.size();
-  UnsignedStreamSize max_size =
-      internal::to_unsigned((std::numeric_limits<std::streamsize>::max)());
+void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
+  const Char* buf_data = buf.data();
+  using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
+  unsigned_streamsize size = buf.size();
+  unsigned_streamsize max_size =
+      to_unsigned((std::numeric_limits<std::streamsize>::max)());
   do {
-    UnsignedStreamSize n = size <= max_size ? size : max_size;
-    os.write(data, static_cast<std::streamsize>(n));
-    data += n;
+    unsigned_streamsize n = size <= max_size ? size : max_size;
+    os.write(buf_data, static_cast<std::streamsize>(n));
+    buf_data += n;
     size -= n;
   } while (size != 0);
 }
 
 template <typename Char, typename T>
-void format_value(basic_buffer<Char> &buffer, const T &value) {
-  internal::formatbuf<Char> format_buf(buffer);
+void format_value(buffer<Char>& buf, const T& value) {
+  formatbuf<Char> format_buf(buf);
   std::basic_ostream<Char> output(&format_buf);
   output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
   output << value;
-  buffer.resize(buffer.size());
+  buf.resize(buf.size());
 }
-}  // namespace internal
-
-// Disable conversion to int if T has an overloaded operator<< which is a free
-// function (not a member of std::ostream).
-template <typename T, typename Char>
-struct convert_to_int<T, Char, void> {
-  static const bool value =
-    convert_to_int<T, Char, int>::value &&
-    !internal::is_streamable<T, Char>::value;
-};
 
 // Formats an object of type T that has an overloaded ostream operator<<.
 template <typename T, typename Char>
-struct formatter<T, Char,
-    typename std::enable_if<
-      internal::is_streamable<T, Char>::value &&
-      !internal::format_type<
-        typename buffer_context<Char>::type, T>::value>::type>
+struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
     : formatter<basic_string_view<Char>, Char> {
-
   template <typename Context>
-  auto format(const T &value, Context &ctx) -> decltype(ctx.out()) {
+  auto format(const T& value, Context& ctx) -> decltype(ctx.out()) {
     basic_memory_buffer<Char> buffer;
-    internal::format_value(buffer, value);
+    format_value(buffer, value);
     basic_string_view<Char> str(buffer.data(), buffer.size());
     return formatter<basic_string_view<Char>, Char>::format(str, ctx);
   }
 };
+}  // namespace internal
 
 template <typename Char>
-inline void vprint(std::basic_ostream<Char> &os,
-                   basic_string_view<Char> format_str,
-                   basic_format_args<typename buffer_context<Char>::type> args) {
+void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
+            basic_format_args<buffer_context<Char>> args) {
   basic_memory_buffer<Char> buffer;
   internal::vformat_to(buffer, format_str, args);
   internal::write(os, buffer);
 }
+
 /**
   \rst
   Prints formatted data to the stream *os*.
@@ -141,12 +125,11 @@ inline void vprint(std::basic_ostream<Char> &os,
     fmt::print(cerr, "Don't {}!", "panic");
   \endrst
  */
-template <typename S, typename... Args>
-inline typename std::enable_if<internal::is_string<S>::value>::type
-print(std::basic_ostream<FMT_CHAR(S)> &os, const S &format_str,
-      const Args & ... args) {
-  internal::checked_args<S, Args...> ca(format_str, args...);
-  vprint(os, to_string_view(format_str), *ca);
+template <typename S, typename... Args,
+          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
+  vprint(os, to_string_view(format_str),
+         {internal::make_args_checked<Args...>(format_str, args...)});
 }
 FMT_END_NAMESPACE
 

include/spdlog/fmt/bundled/posix.h

@@ -69,7 +69,7 @@ FMT_BEGIN_NAMESPACE
   A reference to a null-terminated string. It can be constructed from a C
   string or ``std::string``.
 
-  You can use one of the following typedefs for common character types:
+  You can use one of the following type aliases for common character types:
 
   +---------------+-----------------------------+
   | Type          | Definition                  |
@@ -89,28 +89,27 @@ FMT_BEGIN_NAMESPACE
     format(std::string("{}"), 42);
   \endrst
  */
-template <typename Char>
-class basic_cstring_view {
+template <typename Char> class basic_cstring_view {
  private:
-  const Char *data_;
+  const Char* data_;
 
  public:
   /** Constructs a string reference object from a C string. */
-  basic_cstring_view(const Char *s) : data_(s) {}
+  basic_cstring_view(const Char* s) : data_(s) {}
 
   /**
     \rst
     Constructs a string reference from an ``std::string`` object.
     \endrst
    */
-  basic_cstring_view(const std::basic_string<Char> &s) : data_(s.c_str()) {}
+  basic_cstring_view(const std::basic_string<Char>& s) : data_(s.c_str()) {}
 
   /** Returns the pointer to a C string. */
-  const Char *c_str() const { return data_; }
+  const Char* c_str() const { return data_; }
 };
 
-typedef basic_cstring_view<char> cstring_view;
-typedef basic_cstring_view<wchar_t> wcstring_view;
+using cstring_view = basic_cstring_view<char>;
+using wcstring_view = basic_cstring_view<wchar_t>;
 
 // An error code.
 class error_code {
@@ -126,33 +125,32 @@ class error_code {
 // A buffered file.
 class buffered_file {
  private:
-  FILE *file_;
+  FILE* file_;
 
   friend class file;
 
-  explicit buffered_file(FILE *f) : file_(f) {}
+  explicit buffered_file(FILE* f) : file_(f) {}
 
  public:
   // Constructs a buffered_file object which doesn't represent any file.
-  buffered_file() FMT_NOEXCEPT : file_(FMT_NULL) {}
+  buffered_file() FMT_NOEXCEPT : file_(nullptr) {}
 
   // Destroys the object closing the file it represents if any.
   FMT_API ~buffered_file() FMT_NOEXCEPT;
 
  private:
-  buffered_file(const buffered_file &) = delete;
-  void operator=(const buffered_file &) = delete;
-
+  buffered_file(const buffered_file&) = delete;
+  void operator=(const buffered_file&) = delete;
 
  public:
-  buffered_file(buffered_file &&other) FMT_NOEXCEPT : file_(other.file_) {
-    other.file_ = FMT_NULL;
+  buffered_file(buffered_file&& other) FMT_NOEXCEPT : file_(other.file_) {
+    other.file_ = nullptr;
   }
 
-  buffered_file& operator=(buffered_file &&other) {
+  buffered_file& operator=(buffered_file&& other) {
     close();
     file_ = other.file_;
-    other.file_ = FMT_NULL;
+    other.file_ = nullptr;
     return *this;
   }
 
@@ -163,18 +161,18 @@ class buffered_file {
   FMT_API void close();
 
   // Returns the pointer to a FILE object representing this file.
-  FILE *get() const FMT_NOEXCEPT { return file_; }
+  FILE* get() const FMT_NOEXCEPT { return file_; }
 
   // We place parentheses around fileno to workaround a bug in some versions
   // of MinGW that define fileno as a macro.
-  FMT_API int (fileno)() const;
+  FMT_API int(fileno)() const;
 
   void vprint(string_view format_str, format_args args) {
     fmt::vprint(file_, format_str, args);
   }
 
   template <typename... Args>
-  inline void print(string_view format_str, const Args & ... args) {
+  inline void print(string_view format_str, const Args&... args) {
     vprint(format_str, make_format_args(args...));
   }
 };
@@ -207,15 +205,13 @@ class file {
   FMT_API file(cstring_view path, int oflag);
 
  private:
-  file(const file &) = delete;
-  void operator=(const file &) = delete;
+  file(const file&) = delete;
+  void operator=(const file&) = delete;
 
  public:
-  file(file &&other) FMT_NOEXCEPT : fd_(other.fd_) {
-    other.fd_ = -1;
-  }
+  file(file&& other) FMT_NOEXCEPT : fd_(other.fd_) { other.fd_ = -1; }
 
-  file& operator=(file &&other) {
+  file& operator=(file&& other) {
     close();
     fd_ = other.fd_;
     other.fd_ = -1;
@@ -236,10 +232,10 @@ class file {
   FMT_API long long size() const;
 
   // Attempts to read count bytes from the file into the specified buffer.
-  FMT_API std::size_t read(void *buffer, std::size_t count);
+  FMT_API std::size_t read(void* buffer, std::size_t count);
 
   // Attempts to write count bytes from the specified buffer to the file.
-  FMT_API std::size_t write(const void *buffer, std::size_t count);
+  FMT_API std::size_t write(const void* buffer, std::size_t count);
 
   // Duplicates a file descriptor with the dup function and returns
   // the duplicate as a file object.
@@ -251,68 +247,59 @@ class file {
 
   // Makes fd be the copy of this file descriptor, closing fd first if
   // necessary.
-  FMT_API void dup2(int fd, error_code &ec) FMT_NOEXCEPT;
+  FMT_API void dup2(int fd, error_code& ec) FMT_NOEXCEPT;
 
   // Creates a pipe setting up read_end and write_end file objects for reading
   // and writing respectively.
-  FMT_API static void pipe(file &read_end, file &write_end);
+  FMT_API static void pipe(file& read_end, file& write_end);
 
   // Creates a buffered_file object associated with this file and detaches
   // this file object from the file.
-  FMT_API buffered_file fdopen(const char *mode);
+  FMT_API buffered_file fdopen(const char* mode);
 };
 
 // Returns the memory page size.
 long getpagesize();
 
-#if (defined(LC_NUMERIC_MASK) || defined(_MSC_VER)) && \
-    !defined(__ANDROID__) && !defined(__CYGWIN__) && !defined(__OpenBSD__) && \
-    !defined(__NEWLIB_H__)
-# define FMT_LOCALE
-#endif
-
 #ifdef FMT_LOCALE
 // A "C" numeric locale.
 class Locale {
  private:
-# ifdef _MSC_VER
-  typedef _locale_t locale_t;
+#  ifdef _WIN32
+  using locale_t = _locale_t;
 
   enum { LC_NUMERIC_MASK = LC_NUMERIC };
 
-  static locale_t newlocale(int category_mask, const char *locale, locale_t) {
+  static locale_t newlocale(int category_mask, const char* locale, locale_t) {
     return _create_locale(category_mask, locale);
   }
 
-  static void freelocale(locale_t locale) {
-    _free_locale(locale);
-  }
+  static void freelocale(locale_t locale) { _free_locale(locale); }
 
-  static double strtod_l(const char *nptr, char **endptr, _locale_t locale) {
+  static double strtod_l(const char* nptr, char** endptr, _locale_t locale) {
     return _strtod_l(nptr, endptr, locale);
   }
 #  endif
 
   locale_t locale_;
 
-  Locale(const Locale &) = delete;
-  void operator=(const Locale &) = delete;
+  Locale(const Locale&) = delete;
+  void operator=(const Locale&) = delete;
 
  public:
-  typedef locale_t Type;
+  using type = locale_t;
 
-  Locale() : locale_(newlocale(LC_NUMERIC_MASK, "C", FMT_NULL)) {
-    if (!locale_)
-      FMT_THROW(system_error(errno, "cannot create locale"));
+  Locale() : locale_(newlocale(LC_NUMERIC_MASK, "C", nullptr)) {
+    if (!locale_) FMT_THROW(system_error(errno, "cannot create locale"));
   }
   ~Locale() { freelocale(locale_); }
 
-  Type get() const { return locale_; }
+  type get() const { return locale_; }
 
   // Converts string to floating-point number and advances str past the end
   // of the parsed input.
-  double strtod(const char *&str) const {
-    char *end = FMT_NULL;
+  double strtod(const char*& str) const {
+    char* end = nullptr;
     double result = strtod_l(str, &end, locale_);
     str = end;
     return result;

include/spdlog/fmt/bundled/safe-duration-cast.h

+/*
+ * For conversion between std::chrono::durations without undefined
+ * behaviour or erroneous results.
+ * This is a stripped down version of duration_cast, for inclusion in fmt.
+ * See https://github.com/pauldreik/safe_duration_cast
+ *
+ * Copyright Paul Dreik 2019
+ *
+ * This file is licensed under the fmt license, see format.h
+ */
+
+#include <chrono>
+#include <cmath>
+#include <limits>
+#include <type_traits>
+
+#include "format.h"
+
+FMT_BEGIN_NAMESPACE
+
+namespace safe_duration_cast {
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
+                        std::numeric_limits<From>::is_signed ==
+                            std::numeric_limits<To>::is_signed)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  using F = std::numeric_limits<From>;
+  using T = std::numeric_limits<To>;
+  static_assert(F::is_integer, "From must be integral");
+  static_assert(T::is_integer, "To must be integral");
+
+  // A and B are both signed, or both unsigned.
+  if (F::digits <= T::digits) {
+    // From fits in To without any problem.
+  } else {
+    // From does not always fit in To, resort to a dynamic check.
+    if (from < T::min() || from > T::max()) {
+      // outside range.
+      ec = 1;
+      return {};
+    }
+  }
+  return static_cast<To>(from);
+}
+
+/**
+ * converts From to To, without loss. If the dynamic value of from
+ * can't be converted to To without loss, ec is set.
+ */
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value &&
+                        std::numeric_limits<From>::is_signed !=
+                            std::numeric_limits<To>::is_signed)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  using F = std::numeric_limits<From>;
+  using T = std::numeric_limits<To>;
+  static_assert(F::is_integer, "From must be integral");
+  static_assert(T::is_integer, "To must be integral");
+
+  if (F::is_signed && !T::is_signed) {
+    // From may be negative, not allowed!
+    if (from < 0) {
+      ec = 1;
+      return {};
+    }
+
+    // From is positive. Can it always fit in To?
+    if (F::digits <= T::digits) {
+      // yes, From always fits in To.
+    } else {
+      // from may not fit in To, we have to do a dynamic check
+      if (from > static_cast<From>(T::max())) {
+        ec = 1;
+        return {};
+      }
+    }
+  }
+
+  if (!F::is_signed && T::is_signed) {
+    // can from be held in To?
+    if (F::digits < T::digits) {
+      // yes, From always fits in To.
+    } else {
+      // from may not fit in To, we have to do a dynamic check
+      if (from > static_cast<From>(T::max())) {
+        // outside range.
+        ec = 1;
+        return {};
+      }
+    }
+  }
+
+  // reaching here means all is ok for lossless conversion.
+  return static_cast<To>(from);
+
+}  // function
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(std::is_same<From, To>::value)>
+FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
+  ec = 0;
+  return from;
+}  // function
+
+// clang-format off
+/**
+ * converts From to To if possible, otherwise ec is set.
+ *
+ * input                            |    output
+ * ---------------------------------|---------------
+ * NaN                              | NaN
+ * Inf                              | Inf
+ * normal, fits in output           | converted (possibly lossy)
+ * normal, does not fit in output   | ec is set
+ * subnormal                        | best effort
+ * -Inf                             | -Inf
+ */
+// clang-format on
+template <typename To, typename From,
+          FMT_ENABLE_IF(!std::is_same<From, To>::value)>
+FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+  ec = 0;
+  using T = std::numeric_limits<To>;
+  static_assert(std::is_floating_point<From>::value, "From must be floating");
+  static_assert(std::is_floating_point<To>::value, "To must be floating");
+
+  // catch the only happy case
+  if (std::isfinite(from)) {
+    if (from >= T::lowest() && from <= T::max()) {
+      return static_cast<To>(from);
+    }
+    // not within range.
+    ec = 1;
+    return {};
+  }
+
+  // nan and inf will be preserved
+  return static_cast<To>(from);
+}  // function
+
+template <typename To, typename From,
+          FMT_ENABLE_IF(std::is_same<From, To>::value)>
+FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
+  ec = 0;
+  static_assert(std::is_floating_point<From>::value, "From must be floating");
+  return from;
+}
+
+/**
+ * safe duration cast between integral durations
+ */
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_integral<FromRep>::value),
+          FMT_ENABLE_IF(std::is_integral<typename To::rep>::value)>
+To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                      int& ec) {
+  using From = std::chrono::duration<FromRep, FromPeriod>;
+  ec = 0;
+  // the basic idea is that we need to convert from count() in the from type
+  // to count() in the To type, by multiplying it with this:
+  using Factor = std::ratio_divide<typename From::period, typename To::period>;
+
+  static_assert(Factor::num > 0, "num must be positive");
+  static_assert(Factor::den > 0, "den must be positive");
+
+  // the conversion is like this: multiply from.count() with Factor::num
+  // /Factor::den and convert it to To::rep, all this without
+  // overflow/underflow. let's start by finding a suitable type that can hold
+  // both To, From and Factor::num
+  using IntermediateRep =
+      typename std::common_type<typename From::rep, typename To::rep,
+                                decltype(Factor::num)>::type;
+
+  // safe conversion to IntermediateRep
+  IntermediateRep count =
+      lossless_integral_conversion<IntermediateRep>(from.count(), ec);
+  if (ec) {
+    return {};
+  }
+  // multiply with Factor::num without overflow or underflow
+  if (Factor::num != 1) {
+    constexpr auto max1 =
+        std::numeric_limits<IntermediateRep>::max() / Factor::num;
+    if (count > max1) {
+      ec = 1;
+      return {};
+    }
+    constexpr auto min1 =
+        std::numeric_limits<IntermediateRep>::min() / Factor::num;
+    if (count < min1) {
+      ec = 1;
+      return {};
+    }
+    count *= Factor::num;
+  }
+
+  // this can't go wrong, right? den>0 is checked earlier.
+  if (Factor::den != 1) {
+    count /= Factor::den;
+  }
+  // convert to the to type, safely
+  using ToRep = typename To::rep;
+  const ToRep tocount = lossless_integral_conversion<ToRep>(count, ec);
+  if (ec) {
+    return {};
+  }
+  return To{tocount};
+}
+
+/**
+ * safe duration_cast between floating point durations
+ */
+template <typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(std::is_floating_point<FromRep>::value),
+          FMT_ENABLE_IF(std::is_floating_point<typename To::rep>::value)>
+To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
+                      int& ec) {
+  using From = std::chrono::duration<FromRep, FromPeriod>;
+  ec = 0;
+  if (std::isnan(from.count())) {
+    // nan in, gives nan out. easy.
+    return To{std::numeric_limits<typename To::rep>::quiet_NaN()};
+  }
+  // maybe we should also check if from is denormal, and decide what to do about
+  // it.
+
+  // +-inf should be preserved.
+  if (std::isinf(from.count())) {
+    return To{from.count()};
+  }
+
+  // the basic idea is that we need to convert from count() in the from type
+  // to count() in the To type, by multiplying it with this:
+  using Factor = std::ratio_divide<typename From::period, typename To::period>;
+
+  static_assert(Factor::num > 0, "num must be positive");
+  static_assert(Factor::den > 0, "den must be positive");
+
+  // the conversion is like this: multiply from.count() with Factor::num
+  // /Factor::den and convert it to To::rep, all this without
+  // overflow/underflow. let's start by finding a suitable type that can hold
+  // both To, From and Factor::num
+  using IntermediateRep =
+      typename std::common_type<typename From::rep, typename To::rep,
+                                decltype(Factor::num)>::type;
+
+  // force conversion of From::rep -> IntermediateRep to be safe,
+  // even if it will never happen be narrowing in this context.
+  IntermediateRep count =
+      safe_float_conversion<IntermediateRep>(from.count(), ec);
+  if (ec) {
+    return {};
+  }
+
+  // multiply with Factor::num without overflow or underflow
+  if (Factor::num != 1) {
+    constexpr auto max1 = std::numeric_limits<IntermediateRep>::max() /
+                          static_cast<IntermediateRep>(Factor::num);
+    if (count > max1) {
+      ec = 1;
+      return {};
+    }
+    constexpr auto min1 = std::numeric_limits<IntermediateRep>::lowest() /
+                          static_cast<IntermediateRep>(Factor::num);
+    if (count < min1) {
+      ec = 1;
+      return {};
+    }
+    count *= static_cast<IntermediateRep>(Factor::num);
+  }
+
+  // this can't go wrong, right? den>0 is checked earlier.
+  if (Factor::den != 1) {
+    using common_t = typename std::common_type<IntermediateRep, intmax_t>::type;
+    count /= static_cast<common_t>(Factor::den);
+  }
+
+  // convert to the to type, safely
+  using ToRep = typename To::rep;
+
+  const ToRep tocount = safe_float_conversion<ToRep>(count, ec);
+  if (ec) {
+    return {};
+  }
+  return To{tocount};
+}
+
+}  // namespace safe_duration_cast
+
+FMT_END_NAMESPACE