commit 7ba3c7e0a812cf8ec33605974c052e773a77d013
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Oct 2 12:47:45 2017 +0100

    C++17 P0067R5 std::to_chars and std::from_chars (partial)
    
    This adds the integral overloads of std::to_chars and std::from_chars,
    including the changes made by P0682R0. Support for floating point types
    is absent.
    
            * include/Makefile.am: Add new <charconv> header.
            * include/Makefile.in: Regenerate.
            * include/precompiled/stdc++.h: Include <charconv>.
            * include/std/charconv: New file.
            (to_chars_result, to_chars, from_chars_result, from_chars): Define.
            * testsuite/20_util/from_chars/1.cc: New test.
            * testsuite/20_util/from_chars/1_neg.cc: New test.
            * testsuite/20_util/from_chars/2.cc: New test.
            * testsuite/20_util/from_chars/requirements.cc: New test.
            * testsuite/20_util/to_chars/1.cc: New test.
            * testsuite/20_util/to_chars/1_neg.cc: New test.
            * testsuite/20_util/to_chars/2.cc: New test.
            * testsuite/20_util/to_chars/requirements.cc: New test.

diff --git a/libstdc++-v3/include/Makefile.am b/libstdc++-v3/include/Makefile.am
index 87a41f59027..236c2d6059f 100644
--- a/libstdc++-v3/include/Makefile.am
+++ b/libstdc++-v3/include/Makefile.am
@@ -31,6 +31,7 @@ std_headers = \
 	${std_srcdir}/array \
 	${std_srcdir}/atomic \
 	${std_srcdir}/bitset \
+	${std_srcdir}/charconv \
 	${std_srcdir}/chrono \
 	${std_srcdir}/codecvt \
 	${std_srcdir}/complex \
diff --git a/libstdc++-v3/include/precompiled/stdc++.h b/libstdc++-v3/include/precompiled/stdc++.h
index 262743a3c1b..b2993cd379f 100644
--- a/libstdc++-v3/include/precompiled/stdc++.h
+++ b/libstdc++-v3/include/precompiled/stdc++.h
@@ -121,3 +121,7 @@
 #if __cplusplus >= 201402L
 #include <shared_mutex>
 #endif
+
+#if __cplusplus > 201402L
+#include <charconv>
+#endif
diff --git a/libstdc++-v3/include/std/charconv b/libstdc++-v3/include/std/charconv
new file mode 100644
index 00000000000..b8221e4e434
--- /dev/null
+++ b/libstdc++-v3/include/std/charconv
@@ -0,0 +1,654 @@
+// Primitive numeric conversions (to_chars and from_chars) -*- C++ -*-
+
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file include/charconv
+ *  This is a Standard C++ Library header.
+ */
+
+#ifndef _GLIBCXX_CHARCONV
+#define _GLIBCXX_CHARCONV 1
+
+#pragma GCC system_header
+
+#if __cplusplus >= 201402L
+
+#include <type_traits>
+#include <limits>
+#include <cctype>
+#include <bits/error_constants.h> // for std::errc
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  /// Result type of std::to_chars
+  struct to_chars_result
+  {
+    char* ptr;
+    errc ec;
+  };
+
+  /// Result type of std::from_chars
+  struct from_chars_result
+  {
+    const char* ptr;
+    errc ec;
+  };
+
+namespace __detail
+{
+  template<typename _Tp, typename... _Types>
+    using __is_one_of = __or_<is_same<_Tp, _Types>...>;
+
+  template<typename _Tp>
+    using __is_int_to_chars_type = __and_<is_integral<_Tp>,
+	  __not_<__is_one_of<_Tp, bool, char16_t, char32_t
+#if _GLIBCXX_USE_WCHAR_T
+	  , wchar_t
+#endif
+	    >>>;
+
+  template<typename _Tp>
+    using __integer_to_chars_result_type
+      = enable_if_t<__is_int_to_chars_type<_Tp>::value, to_chars_result>;
+
+  template<typename _Tp>
+    using __unsigned_least_t
+      = conditional_t<(sizeof(_Tp) <= sizeof(int)), unsigned int,
+	conditional_t<(sizeof(_Tp) <= sizeof(long)), unsigned long,
+	conditional_t<(sizeof(_Tp) <= sizeof(long long)), unsigned long long,
+#if _GLIBCXX_USE_INT128
+	conditional_t<(sizeof(_Tp) <= sizeof(__int128)), unsigned __int128,
+#endif
+	void>>>>;
+
+  // Generic implementation for arbitrary bases.
+  template<typename _Tp>
+    constexpr unsigned
+    __to_chars_len(_Tp __value, int __base = 10) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      unsigned __n = 1;
+      const int __b2 = __base  * __base;
+      const int __b3 = __b2 * __base;
+      const int __b4 = __b3 * __base;
+      for (;;)
+	{
+	  if (__value < __base) return __n;
+	  if (__value < __b2) return __n + 1;
+	  if (__value < __b3) return __n + 2;
+	  if (__value < __b4) return __n + 3;
+	  __value /= (unsigned)__b4;
+	  __n += 4;
+	}
+    }
+
+  template<typename _Tp>
+    constexpr unsigned
+    __to_chars_len_2(_Tp __value) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);
+
+      // N.B. __builtin_clzll is undefined if __value == 0, but std::to_chars
+      // handles zero values directly.
+
+      // For sizeof(_Tp) > 1 this is an order of magnitude faster than
+      // the generic __to_chars_len.
+      return __nbits
+	- (__builtin_clzll(__value)
+	    - ((__CHAR_BIT__ * sizeof(long long)) - __nbits));
+    }
+
+  template<typename _Tp>
+    constexpr unsigned
+    __to_chars_len_8(_Tp __value) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      constexpr size_t __nbits = __CHAR_BIT__ * sizeof(_Tp);
+
+      if _GLIBCXX17_CONSTEXPR (__nbits <= 16)
+	{
+	  return __value > 077777u ? 6u
+	    : __value > 07777u ? 5u
+	    : __value > 0777u ? 4u
+	    : __value > 077u ? 3u
+	    : __value > 07u ? 2u
+	    : 1u;
+	}
+      else
+	return __to_chars_len(__value, 8);
+    }
+
+  // Generic implementation for arbitrary bases.
+  template<typename _Tp>
+    to_chars_result
+    __to_chars(char* __first, char* __last, _Tp __val, int __base) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      to_chars_result __res;
+
+      const unsigned __len = __to_chars_len(__val, __base);
+
+      if (__builtin_expect((__last - __first) < __len, 0))
+	{
+	  __res.ptr = __last;
+	  __res.ec = errc::value_too_large;
+	  return __res;
+	}
+
+      unsigned __pos = __len - 1;
+
+      static constexpr char __digits[]
+	= "0123456789abcdefghijklmnopqrstuvwxyz";
+
+      while (__val >= __base)
+	{
+	  auto const __quo = __val / __base;
+	  auto const __rem = __val % __base;
+	  __first[__pos--] = __digits[__rem];
+	  __val = __quo;
+	}
+      *__first = __digits[__val];
+
+      __res.ptr = __first + __len;
+      __res.ec = {};
+      return __res;
+    }
+
+  template<typename _Tp>
+    __integer_to_chars_result_type<_Tp>
+    __to_chars_16(char* __first, char* __last, _Tp __val) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      to_chars_result __res;
+
+      const unsigned __len = __to_chars_len(__val, 0x10);
+
+      if (__builtin_expect((__last - __first) < __len, 0))
+	{
+	  __res.ptr = __last;
+	  __res.ec = errc::value_too_large;
+	  return __res;
+	}
+
+      static constexpr char __digits[513] =
+	"000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f"
+	"202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f"
+	"404142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f"
+	"606162636465666768696a6b6c6d6e6f707172737475767778797a7b7c7d7e7f"
+	"808182838485868788898a8b8c8d8e8f909192939495969798999a9b9c9d9e9f"
+	"a0a1a2a3a4a5a6a7a8a9aaabacadaeafb0b1b2b3b4b5b6b7b8b9babbbcbdbebf"
+	"c0c1c2c3c4c5c6c7c8c9cacbcccdcecfd0d1d2d3d4d5d6d7d8d9dadbdcdddedf"
+	"e0e1e2e3e4e5e6e7e8e9eaebecedeeeff0f1f2f3f4f5f6f7f8f9fafbfcfdfeff";
+      unsigned __pos = __len - 1;
+      while (__val >= 0x100)
+	{
+	  auto const __num = (__val % 0x100) * 2;
+	  __val /= 0x100;
+	  __first[__pos] = __digits[__num + 1];
+	  __first[__pos - 1] = __digits[__num];
+	  __pos -= 2;
+	}
+      if (__val >= 0x10)
+	{
+	  auto const __num = __val * 2;
+	  __first[__pos] = __digits[__num + 1];
+	  __first[__pos - 1] = __digits[__num];
+	}
+      else
+	__first[__pos] = "0123456789abcdef"[__val];
+      __res.ptr = __first + __len;
+      __res.ec = {};
+      return __res;
+    }
+
+  template<typename _Tp>
+    __integer_to_chars_result_type<_Tp>
+    __to_chars_10(char* __first, char* __last, _Tp __val) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      to_chars_result __res;
+
+      const unsigned __len = __to_chars_len(__val, 10);
+
+      if (__builtin_expect((__last - __first) < __len, 0))
+	{
+	  __res.ptr = __last;
+	  __res.ec = errc::value_too_large;
+	  return __res;
+	}
+
+      static constexpr char __digits[201] =
+	"0001020304050607080910111213141516171819"
+	"2021222324252627282930313233343536373839"
+	"4041424344454647484950515253545556575859"
+	"6061626364656667686970717273747576777879"
+	"8081828384858687888990919293949596979899";
+      unsigned __pos = __len - 1;
+      while (__val >= 100)
+	{
+	  auto const __num = (__val % 100) * 2;
+	  __val /= 100;
+	  __first[__pos] = __digits[__num + 1];
+	  __first[__pos - 1] = __digits[__num];
+	  __pos -= 2;
+	}
+      if (__val >= 10)
+	{
+	  auto const __num = __val * 2;
+	  __first[__pos] = __digits[__num + 1];
+	  __first[__pos - 1] = __digits[__num];
+	}
+      else
+	__first[__pos] = '0' + __val;
+      __res.ptr = __first + __len;
+      __res.ec = {};
+      return __res;
+    }
+
+  template<typename _Tp>
+    __integer_to_chars_result_type<_Tp>
+    __to_chars_8(char* __first, char* __last, _Tp __val) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      to_chars_result __res;
+
+      const unsigned __len = __to_chars_len_8(__val);
+
+      if (__builtin_expect((__last - __first) < __len, 0))
+	{
+	  __res.ptr = __last;
+	  __res.ec = errc::value_too_large;
+	  return __res;
+	}
+
+      static constexpr char __digits[129] =
+	"00010203040506071011121314151617"
+	"20212223242526273031323334353637"
+	"40414243444546475051525354555657"
+	"60616263646566677071727374757677";
+      unsigned __pos = __len - 1;
+      while (__val >= 0100)
+	{
+	  auto const __num = (__val % 0100) * 2;
+	  __val /= 0100;
+	  __first[__pos] = __digits[__num + 1];
+	  __first[__pos - 1] = __digits[__num];
+	  __pos -= 2;
+	}
+      if (__val >= 010)
+	{
+	  auto const __num = __val * 2;
+	  __first[__pos] = __digits[__num + 1];
+	  __first[__pos - 1] = __digits[__num];
+	}
+      else
+	__first[__pos] = '0' + __val;
+      __res.ptr = __first + __len;
+      __res.ec = {};
+      return __res;
+    }
+
+  template<typename _Tp>
+    __integer_to_chars_result_type<_Tp>
+    __to_chars_2(char* __first, char* __last, _Tp __val) noexcept
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      to_chars_result __res;
+
+      const unsigned __len = __to_chars_len_2(__val);
+
+      if (__builtin_expect((__last - __first) < __len, 0))
+	{
+	  __res.ptr = __last;
+	  __res.ec = errc::value_too_large;
+	  return __res;
+	}
+
+      unsigned __pos = __len - 1;
+
+      while (__pos)
+	{
+	  __first[__pos--] = '0' + (__val & 1);
+	  __val >>= 1;
+	}
+      *__first = '0' + (__val & 1);
+
+      __res.ptr = __first + __len;
+      __res.ec = {};
+      return __res;
+    }
+
+} // namespace __detail
+
+  template<typename _Tp>
+    __detail::__integer_to_chars_result_type<_Tp>
+    to_chars(char* __first, char* __last, _Tp __value, int __base = 10)
+    {
+      __glibcxx_assert(2 <= __base && __base <= 36);
+
+      using _Up = __detail::__unsigned_least_t<_Tp>;
+      _Up __unsigned_val = __value;
+
+      if (__value == 0 && __first != __last)
+	{
+	  *__first = '0';
+	  return { __first + 1, errc{} };
+	}
+
+      if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
+	if (__value < 0)
+	  {
+	    if (__builtin_expect(__first != __last, 1))
+	      *__first++ = '-';
+	    __unsigned_val = _Up(~__value) + _Up(1);
+	  }
+
+      switch (__base)
+      {
+      case 16:
+	return __detail::__to_chars_16(__first, __last, __unsigned_val);
+      case 10:
+	return __detail::__to_chars_10(__first, __last, __unsigned_val);
+      case 8:
+	return __detail::__to_chars_8(__first, __last, __unsigned_val);
+      case 2:
+	return __detail::__to_chars_2(__first, __last, __unsigned_val);
+      default:
+	return __detail::__to_chars(__first, __last, __unsigned_val, __base);
+      }
+    }
+
+namespace __detail
+{
+  template<typename _Tp>
+    bool
+    __raise_and_add(_Tp& __val, int __base, unsigned char __c)
+    {
+      if (__builtin_mul_overflow(__val, __base, &__val)
+	  || __builtin_add_overflow(__val, __c, &__val))
+	return false;
+      return true;
+    }
+
+  /// std::from_chars implementation for integers in base 2.
+  template<typename _Tp>
+    bool
+    __from_chars_binary(const char*& __first, const char* __last, _Tp& __val)
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      const ptrdiff_t __len = __last - __first;
+      int __i = 0;
+      while (__i < __len)
+	{
+	  const unsigned char __c = (unsigned)__first[__i] - '0';
+	  if (__c < 2)
+	    __val = (__val << 1) | __c;
+	  else
+	    break;
+	  __i++;
+	}
+      __first += __i;
+      return __i <= (sizeof(_Tp) * __CHAR_BIT__);
+    }
+
+  /// std::from_chars implementation for integers in bases 3 to 10.
+  template<typename _Tp>
+    bool
+    __from_chars_digit(const char*& __first, const char* __last, _Tp& __val,
+		       int __base)
+    {
+      static_assert(is_integral<_Tp>::value, "implementation bug");
+      static_assert(is_unsigned<_Tp>::value, "implementation bug");
+
+      auto __matches = [__base](char __c) {
+	  return '0' <= __c && __c <= ('0' + (__base - 1));
+      };
+
+      while (__first != __last)
+	{
+	  const char __c = *__first;
+	  if (__matches(__c))
+	  {
+	    if (!__raise_and_add(__val, __base, __c - '0'))
+	      {
+		while (++__first != __last && __matches(*__first))
+		  ;
+		return false;
+	      }
+	    __first++;
+	  }
+	  else
+	    return true;
+	}
+      return true;
+    }
+
+  constexpr unsigned char
+  __from_chars_alpha_to_num(char __c)
+  {
+    switch (__c)
+    {
+    case 'a':
+    case 'A':
+      return 10;
+    case 'b':
+    case 'B':
+      return 11;
+    case 'c':
+    case 'C':
+      return 12;
+    case 'd':
+    case 'D':
+      return 13;
+    case 'e':
+    case 'E':
+      return 14;
+    case 'f':
+    case 'F':
+      return 15;
+    case 'g':
+    case 'G':
+      return 16;
+    case 'h':
+    case 'H':
+      return 17;
+    case 'i':
+    case 'I':
+      return 18;
+    case 'j':
+    case 'J':
+      return 19;
+    case 'k':
+    case 'K':
+      return 20;
+    case 'l':
+    case 'L':
+      return 21;
+    case 'm':
+    case 'M':
+      return 22;
+    case 'n':
+    case 'N':
+      return 23;
+    case 'o':
+    case 'O':
+      return 24;
+    case 'p':
+    case 'P':
+      return 25;
+    case 'q':
+    case 'Q':
+      return 26;
+    case 'r':
+    case 'R':
+      return 27;
+    case 's':
+    case 'S':
+      return 28;
+    case 't':
+    case 'T':
+      return 29;
+    case 'u':
+    case 'U':
+      return 30;
+    case 'v':
+    case 'V':
+      return 31;
+    case 'w':
+    case 'W':
+      return 32;
+    case 'x':
+    case 'X':
+      return 33;
+    case 'y':
+    case 'Y':
+      return 34;
+    case 'z':
+    case 'Z':
+      return 35;
+    }
+    return std::numeric_limits<unsigned char>::max();
+  }
+
+  /// std::from_chars implementation for integers in bases 11 to 26.
+  template<typename _Tp>
+    bool
+    __from_chars_alnum(const char*& __first, const char* __last, _Tp& __val,
+		       int __base)
+    {
+      bool __valid = true;
+      while (__first != __last)
+	{
+	  unsigned char __c = *__first;
+	  if (std::isdigit(__c))
+	    __c -= '0';
+	  else
+	    {
+	      __c = __from_chars_alpha_to_num(__c);
+	      if (__c >= __base)
+		break;
+	    }
+
+	  if (__builtin_expect(__valid, 1))
+	    __valid = __raise_and_add(__val, __base, __c);
+	  __first++;
+	}
+      return __valid;
+    }
+
+  template<typename _Tp>
+    using __integer_from_chars_result_type
+      = enable_if_t<__is_int_to_chars_type<_Tp>::value, from_chars_result>;
+
+} // namespace __detail
+
+  /// std::from_chars for integral types.
+  template<typename _Tp>
+    __detail::__integer_from_chars_result_type<_Tp>
+    from_chars(const char* __first, const char* __last, _Tp& __value,
+	       int __base = 10)
+    {
+      __glibcxx_assert(2 <= __base && __base <= 36);
+
+      from_chars_result __res{__first, {}};
+
+      int __sign = 1;
+      if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
+	if (__first != __last && *__first == '-')
+	  {
+	    __sign = -1;
+	    ++__first;
+	  }
+
+      using _Up = __detail::__unsigned_least_t<_Tp>;
+      _Up __val = 0;
+
+      const auto __start = __first;
+      bool __valid;
+      if (__base == 2)
+	__valid = __detail::__from_chars_binary(__first, __last, __val);
+      else if (__base <= 10)
+	__valid = __detail::__from_chars_digit(__first, __last, __val, __base);
+      else
+	__valid = __detail::__from_chars_alnum(__first, __last, __val, __base);
+
+      if (__builtin_expect(__first == __start, 0))
+	__res.ec = errc::invalid_argument;
+      else
+	{
+	  __res.ptr = __first;
+	  if (!__valid)
+	    __res.ec = errc::result_out_of_range;
+	  else
+	    {
+	      if _GLIBCXX17_CONSTEXPR (std::is_signed<_Tp>::value)
+		{
+		  _Tp __tmp;
+		  if (__builtin_mul_overflow(__val, __sign, &__tmp))
+		    __res.ec = errc::result_out_of_range;
+		  else
+		    __value = __tmp;
+		}
+	      else
+		{
+		  if _GLIBCXX17_CONSTEXPR
+		    (numeric_limits<_Up>::max() > numeric_limits<_Tp>::max())
+		    {
+		      if (__val > numeric_limits<_Tp>::max())
+			__res.ec = errc::result_out_of_range;
+		      else
+			__value = __val;
+		    }
+		  else
+		    __value = __val;
+		}
+	    }
+	}
+      return __res;
+    }
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+#endif // C++14
+#endif // _GLIBCXX_CHARCONV
diff --git a/libstdc++-v3/testsuite/20_util/from_chars/1.cc b/libstdc++-v3/testsuite/20_util/from_chars/1.cc
new file mode 100644
index 00000000000..b552195ae96
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/from_chars/1.cc
@@ -0,0 +1,80 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <charconv>
+#include <string_view>
+
+template<typename I>
+bool
+check_from_chars(I expected, std::string_view s, int base = 0, char term = '\0')
+{
+  I val;
+  std::from_chars_result r = base == 0
+    ? std::from_chars(s.begin(), s.end(), val)
+    : std::from_chars(s.begin(), s.end(), val, base);
+  return r.ec == std::errc{} && (r.ptr == s.end() || *r.ptr == term) && val == expected;
+}
+
+#include <climits>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  // Using base 10
+  VERIFY( check_from_chars(123, "123") );
+  VERIFY( check_from_chars(-123, "-123") );
+  VERIFY( check_from_chars(123, "123a", 10, 'a') );
+  VERIFY( check_from_chars(123, "0000000000000000000000000000123") );
+  VERIFY( check_from_chars(123, "0000000000000000000000000000123a", 10, 'a') );
+}
+
+void
+test02()
+{
+  // "0x" parsed as "0" not as hex prefix:
+  VERIFY( check_from_chars(0, "0x1", 10, 'x') );
+  VERIFY( check_from_chars(0, "0X1", 10, 'X') );
+  VERIFY( check_from_chars(0, "0x1", 16, 'x') );
+  VERIFY( check_from_chars(0, "0X1", 16, 'X') );
+
+  VERIFY( check_from_chars(1155, "xx", 34) );
+  VERIFY( check_from_chars(1155, "XX", 34) );
+  VERIFY( check_from_chars(1155, "Xx", 34) );
+  VERIFY( check_from_chars(1224, "yy", 35) );
+  VERIFY( check_from_chars(1224, "YY", 35) );
+  VERIFY( check_from_chars(1224, "yY", 35) );
+  VERIFY( check_from_chars(1295, "zz", 36) );
+  VERIFY( check_from_chars(1295, "ZZ", 36) );
+  VERIFY( check_from_chars(1295, "Zz", 36) );
+
+  // Parsing stops at first invalid digit for the given base:
+  VERIFY( check_from_chars(1, "01234", 2, '2') );
+  VERIFY( check_from_chars(27, "1234", 4, '4') );
+  VERIFY( check_from_chars(1155, "xxy", 34, 'y') );
+  VERIFY( check_from_chars(1224, "yyz", 35, 'z') );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}
diff --git a/libstdc++-v3/testsuite/20_util/from_chars/1_neg.cc b/libstdc++-v3/testsuite/20_util/from_chars/1_neg.cc
new file mode 100644
index 00000000000..d826ba9712b
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/from_chars/1_neg.cc
@@ -0,0 +1,38 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <charconv>
+
+void
+test01(const char* first, const char* last)
+{
+#if _GLIBCXX_USE_WCHAR_T
+  wchar_t wc;
+  std::from_chars(first, last, wc); // { dg-error "no matching" }
+  std::from_chars(first, last, wc, 10); // { dg-error "no matching" }
+#endif
+
+  char16_t c16;
+  std::from_chars(first, last, c16); // { dg-error "no matching" }
+  std::from_chars(first, last, c16, 10); // { dg-error "no matching" }
+  char32_t c32;
+  std::from_chars(first, last, c32); // { dg-error "no matching" }
+  std::from_chars(first, last, c32, 10); // { dg-error "no matching" }
+}
diff --git a/libstdc++-v3/testsuite/20_util/from_chars/2.cc b/libstdc++-v3/testsuite/20_util/from_chars/2.cc
new file mode 100644
index 00000000000..117cf74662a
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/from_chars/2.cc
@@ -0,0 +1,205 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <charconv>
+#include <string_view>
+#include <testsuite_hooks.h>
+
+// Test std::from_chars error handling.
+
+void
+test01()
+{
+  std::from_chars_result r;
+  int i = 999;
+  std::string_view s;
+
+  s = "";
+  r = std::from_chars(s.begin(), s.end(), i);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  VERIFY( i == 999 );
+
+  s = "*";
+  r = std::from_chars(s.begin(), s.end(), i);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  VERIFY( i == 999 );
+
+  s = "-";
+  r = std::from_chars(s.begin(), s.end(), i);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  VERIFY( i == 999 );
+
+  s = "-*";
+  r = std::from_chars(s.begin(), s.end(), i);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  VERIFY( i == 999 );
+
+  unsigned u = 888;
+  s = "-1";
+  r = std::from_chars(s.begin(), s.end(), u);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  s = "-a";
+  r = std::from_chars(s.begin(), s.end(), u);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  s = "-";
+  r = std::from_chars(s.begin(), s.end(), u);
+  VERIFY( r.ec == std::errc::invalid_argument );
+  VERIFY( r.ptr == s.begin() );
+  VERIFY( u == 888 );
+
+  for (int base = 2; base <= 36; ++base)
+  {
+    const char digits[] = "0123456789abcdefghijklmnopqrstuvwxyz*";
+    const char buf[2] = { '-', digits[base] };
+    r = std::from_chars(buf, buf + 1, i, base);
+    VERIFY( r.ec == std::errc::invalid_argument );
+    VERIFY( r.ptr == buf );
+    VERIFY( i == 999 );
+    r = std::from_chars(buf + 1, buf + 2, i, base);
+    VERIFY( r.ec == std::errc::invalid_argument );
+    VERIFY( r.ptr == buf + 1 );
+    VERIFY( i == 999 );
+    r = std::from_chars(buf, buf + 2, i, base);
+    VERIFY( r.ec == std::errc::invalid_argument );
+    VERIFY( r.ptr == buf );
+    VERIFY( i == 999 );
+  }
+}
+
+void
+test02()
+{
+  std::from_chars_result r;
+  std::string_view s;
+
+  signed char c = -5;
+  s = "-10000001";
+  r = std::from_chars(s.begin(), s.end(), c, 2);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "-10000001*";
+  r = std::from_chars(s.begin(), s.end(), c, 2);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 9 );
+  s = "-10000001000*";
+  r = std::from_chars(s.begin(), s.end(), c, 2);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 12 );
+  s = "-129";
+  r = std::from_chars(s.begin(), s.end(), c, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "-129*";
+  r = std::from_chars(s.begin(), s.end(), c, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 4 );
+  s = "-100";
+  r = std::from_chars(s.begin(), s.end(), c, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "-100*";
+  r = std::from_chars(s.begin(), s.end(), c, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 4 );
+  s = "-81";
+  r = std::from_chars(s.begin(), s.end(), c, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "-81*";
+  r = std::from_chars(s.begin(), s.end(), c, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 3 );
+  s = "128";
+  r = std::from_chars(s.begin(), s.end(), c, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "128*";
+  r = std::from_chars(s.begin(), s.end(), c, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 3 );
+  s = "80";
+  r = std::from_chars(s.begin(), s.end(), c, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "80*";
+  r = std::from_chars(s.begin(), s.end(), c, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 2 );
+  VERIFY( c == -5 );
+
+  unsigned char uc = 9;
+  s = "100000000";
+  r = std::from_chars(s.begin(), s.end(), uc, 2);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "100000000*";
+  r = std::from_chars(s.begin(), s.end(), uc, 2);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 9 );
+  s = "100000000000*";
+  r = std::from_chars(s.begin(), s.end(), uc, 2);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 12 );
+  s = "256";
+  r = std::from_chars(s.begin(), s.end(), uc, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "256**";
+  r = std::from_chars(s.begin(), s.end(), uc, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 3 );
+  s = "256000**";
+  r = std::from_chars(s.begin(), s.end(), uc, 10);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 6 );
+  s = "100";
+  r = std::from_chars(s.begin(), s.end(), uc, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.end() );
+  s = "100**";
+  r = std::from_chars(s.begin(), s.end(), uc, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 3 );
+  s = "100000**";
+  r = std::from_chars(s.begin(), s.end(), uc, 16);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 6 );
+  VERIFY( uc == 9 );
+
+  unsigned long long ull = 123;
+  s = "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz****";
+  r = std::from_chars(s.begin(), s.end(), ull, 36);
+  VERIFY( r.ec == std::errc::result_out_of_range );
+  VERIFY( r.ptr == s.begin() + 42 );
+  VERIFY( ull == 123 );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}
diff --git a/libstdc++-v3/testsuite/20_util/from_chars/requirements.cc b/libstdc++-v3/testsuite/20_util/from_chars/requirements.cc
new file mode 100644
index 00000000000..00b7d875664
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/from_chars/requirements.cc
@@ -0,0 +1,61 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <charconv>
+
+namespace std
+{
+  struct from_chars_result;
+
+  const char* from_chars_result::*pm2 = &from_chars_result::ptr;
+  errc from_chars_result::*pm1 = &from_chars_result::ec;
+
+  from_chars_result (*f1)(const char*, const char*, char&, int)
+    = &from_chars;
+  from_chars_result (*f2)(const char*, const char*, signed char&, int)
+    = &from_chars;
+  from_chars_result (*f3)(const char*, const char*, unsigned char&, int)
+    = &from_chars;
+  from_chars_result (*f4)(const char*, const char*, signed short&, int)
+    = &from_chars;
+  from_chars_result (*f5)(const char*, const char*, unsigned short&, int)
+    = &from_chars;
+  from_chars_result (*f6)(const char*, const char*, signed int&, int)
+    = &from_chars;
+  from_chars_result (*f7)(const char*, const char*, unsigned int&, int)
+    = &from_chars;
+  from_chars_result (*f8)(const char*, const char*, signed long&, int)
+    = &from_chars;
+  from_chars_result (*f9)(const char*, const char*, unsigned long&, int)
+    = &from_chars;
+  from_chars_result (*f10)(const char*, const char*, signed long long&, int)
+    = &from_chars;
+  from_chars_result (*f11)(const char*, const char*, unsigned long long&, int)
+    = &from_chars;
+}
+
+void bind()
+{
+  const char buf[1] = "";
+  int i;
+  auto [p, e] = std::from_chars(buf, buf + 1, i, 10);
+  const char** pa = &p;
+  std::errc* ea = &e;
+}
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/1.cc b/libstdc++-v3/testsuite/20_util/to_chars/1.cc
new file mode 100644
index 00000000000..bdd961104a2
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/to_chars/1.cc
@@ -0,0 +1,661 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <charconv>
+#include <string_view>
+
+template<typename I>
+bool
+check_to_chars(I val, std::string_view expected, int base = 0)
+{
+  // Space for minus sign, 64 binary digits, final '*', and null terminator:
+  char buf[67] = "******************************************************************";
+  std::to_chars_result r = base == 0
+    ? std::to_chars(buf, buf+sizeof(buf), val)
+    : std::to_chars(buf, buf+sizeof(buf), val, base);
+  return r.ec == std::errc{} && *r.ptr == '*' && std::string_view(buf, r.ptr - buf) == expected;
+}
+
+#include <string>
+#include <climits>
+#include <testsuite_hooks.h>
+
+// Using default base 10
+void
+test01()
+{
+  VERIFY( check_to_chars<char>(0, "0") );
+  VERIFY( check_to_chars<signed char>(0, "0") );
+  VERIFY( check_to_chars<unsigned char>(0, "0") );
+  VERIFY( check_to_chars<signed short>(0, "0") );
+  VERIFY( check_to_chars<unsigned short>(0, "0") );
+  VERIFY( check_to_chars<signed int>(0, "0") );
+  VERIFY( check_to_chars<unsigned int>(0, "0") );
+  VERIFY( check_to_chars<signed long>(0, "0") );
+  VERIFY( check_to_chars<unsigned long>(0, "0") );
+  VERIFY( check_to_chars<signed long long>(0, "0") );
+  VERIFY( check_to_chars<unsigned long long>(0, "0") );
+
+  VERIFY( check_to_chars<char>(1, "1") );
+  VERIFY( check_to_chars<signed char>(1, "1") );
+  VERIFY( check_to_chars<unsigned char>(1, "1") );
+  VERIFY( check_to_chars<signed short>(1, "1") );
+  VERIFY( check_to_chars<unsigned short>(1, "1") );
+  VERIFY( check_to_chars<signed int>(1, "1") );
+  VERIFY( check_to_chars<unsigned int>(1, "1") );
+  VERIFY( check_to_chars<signed long>(1, "1") );
+  VERIFY( check_to_chars<unsigned long>(1, "1") );
+  VERIFY( check_to_chars<signed long long>(1, "1") );
+  VERIFY( check_to_chars<unsigned long long>(1, "1") );
+
+  VERIFY( check_to_chars<char>(123, "123") );
+  VERIFY( check_to_chars<signed char>(123, "123") );
+  VERIFY( check_to_chars<unsigned char>(123, "123") );
+  VERIFY( check_to_chars<signed short>(123, "123") );
+  VERIFY( check_to_chars<unsigned short>(123, "123") );
+  VERIFY( check_to_chars<signed int>(123, "123") );
+  VERIFY( check_to_chars<unsigned int>(123, "123") );
+  VERIFY( check_to_chars<signed long>(123, "123") );
+  VERIFY( check_to_chars<unsigned long>(123, "123") );
+  VERIFY( check_to_chars<signed long long>(123, "123") );
+  VERIFY( check_to_chars<unsigned long long>(123, "123") );
+
+  if constexpr (std::is_signed_v<char>)
+    VERIFY( check_to_chars<char>(-79, "-79") );
+  VERIFY( check_to_chars<signed char>(-79, "-79") );
+  VERIFY( check_to_chars<signed short>(-79, "-79") );
+  VERIFY( check_to_chars<signed int>(-79, "-79") );
+  VERIFY( check_to_chars<signed long>(-79, "-79") );
+  VERIFY( check_to_chars<signed long long>(-79, "-79") );
+
+  using std::to_string;
+
+  VERIFY( check_to_chars<char>(CHAR_MAX, to_string(CHAR_MAX)) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX, to_string(SCHAR_MAX)) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX, to_string(UCHAR_MAX)) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX, to_string(SHRT_MAX)) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX, to_string(USHRT_MAX)) );
+  VERIFY( check_to_chars<signed int>(INT_MAX, to_string(INT_MAX)) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX, to_string(UINT_MAX)) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX, to_string(LONG_MAX)) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX, to_string(ULONG_MAX)) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX, to_string(LLONG_MAX)) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX, to_string(ULLONG_MAX)) );
+
+  VERIFY( check_to_chars<char>(CHAR_MIN, to_string(CHAR_MIN)) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MIN, to_string(SCHAR_MIN)) );
+  VERIFY( check_to_chars<signed short>(SHRT_MIN, to_string(SHRT_MIN)) );
+  VERIFY( check_to_chars<signed int>(INT_MIN, to_string(INT_MIN)) );
+  VERIFY( check_to_chars<signed long>(LONG_MIN, to_string(LONG_MIN)) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MIN, to_string(LLONG_MIN)) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX/2, to_string(CHAR_MAX/2)) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX/2, to_string(SCHAR_MAX/2)) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX/2, to_string(UCHAR_MAX/2)) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX/2, to_string(SHRT_MAX/2)) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX/2, to_string(USHRT_MAX/2)) );
+  VERIFY( check_to_chars<signed int>(INT_MAX/2, to_string(INT_MAX/2)) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX/2, to_string(UINT_MAX/2)) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX/2, to_string(LONG_MAX/2)) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX/2, to_string(ULONG_MAX/2)) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX/2, to_string(LLONG_MAX/2)) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX/2, to_string(ULLONG_MAX/2)) );
+}
+
+// Using explicit base 10
+void
+test02()
+{
+  VERIFY( check_to_chars<char>(0, "0", 10) );
+  VERIFY( check_to_chars<signed char>(0, "0", 10) );
+  VERIFY( check_to_chars<unsigned char>(0, "0", 10) );
+  VERIFY( check_to_chars<signed short>(0, "0", 10) );
+  VERIFY( check_to_chars<unsigned short>(0, "0", 10) );
+  VERIFY( check_to_chars<signed int>(0, "0", 10) );
+  VERIFY( check_to_chars<unsigned int>(0, "0", 10) );
+  VERIFY( check_to_chars<signed long>(0, "0", 10) );
+  VERIFY( check_to_chars<unsigned long>(0, "0", 10) );
+  VERIFY( check_to_chars<signed long long>(0, "0", 10) );
+  VERIFY( check_to_chars<unsigned long long>(0, "0", 10) );
+
+  VERIFY( check_to_chars<char>(1, "1", 10) );
+  VERIFY( check_to_chars<signed char>(1, "1", 10) );
+  VERIFY( check_to_chars<unsigned char>(1, "1", 10) );
+  VERIFY( check_to_chars<signed short>(1, "1", 10) );
+  VERIFY( check_to_chars<unsigned short>(1, "1", 10) );
+  VERIFY( check_to_chars<signed int>(1, "1", 10) );
+  VERIFY( check_to_chars<unsigned int>(1, "1", 10) );
+  VERIFY( check_to_chars<signed long>(1, "1", 10) );
+  VERIFY( check_to_chars<unsigned long>(1, "1", 10) );
+  VERIFY( check_to_chars<signed long long>(1, "1", 10) );
+  VERIFY( check_to_chars<unsigned long long>(1, "1", 10) );
+
+  VERIFY( check_to_chars<char>(123, "123", 10) );
+  VERIFY( check_to_chars<signed char>(123, "123", 10) );
+  VERIFY( check_to_chars<unsigned char>(123, "123", 10) );
+  VERIFY( check_to_chars<signed short>(123, "123", 10) );
+  VERIFY( check_to_chars<unsigned short>(123, "123", 10) );
+  VERIFY( check_to_chars<signed int>(123, "123", 10) );
+  VERIFY( check_to_chars<unsigned int>(123, "123", 10) );
+  VERIFY( check_to_chars<signed long>(123, "123", 10) );
+  VERIFY( check_to_chars<unsigned long>(123, "123", 10) );
+  VERIFY( check_to_chars<signed long long>(123, "123", 10) );
+  VERIFY( check_to_chars<unsigned long long>(123, "123", 10) );
+
+  if constexpr (std::is_signed_v<char>)
+    VERIFY( check_to_chars<char>(-79, "-79", 10) );
+  VERIFY( check_to_chars<signed char>(-79, "-79", 10) );
+  VERIFY( check_to_chars<signed short>(-79, "-79", 10) );
+  VERIFY( check_to_chars<signed int>(-79, "-79", 10) );
+  VERIFY( check_to_chars<signed long>(-79, "-79", 10) );
+  VERIFY( check_to_chars<signed long long>(-79, "-79", 10) );
+
+  using std::to_string;
+
+  VERIFY( check_to_chars<char>(CHAR_MAX, to_string(CHAR_MAX), 10) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX, to_string(SCHAR_MAX), 10) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX, to_string(UCHAR_MAX), 10) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX, to_string(SHRT_MAX), 10) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX, to_string(USHRT_MAX), 10) );
+  VERIFY( check_to_chars<signed int>(INT_MAX, to_string(INT_MAX), 10) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX, to_string(UINT_MAX), 10) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX, to_string(LONG_MAX), 10) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX, to_string(ULONG_MAX), 10) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX, to_string(LLONG_MAX), 10) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX, to_string(ULLONG_MAX), 10) );
+
+  VERIFY( check_to_chars<char>(CHAR_MIN, to_string(CHAR_MIN), 10) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MIN, to_string(SCHAR_MIN), 10) );
+  VERIFY( check_to_chars<signed short>(SHRT_MIN, to_string(SHRT_MIN), 10) );
+  VERIFY( check_to_chars<signed int>(INT_MIN, to_string(INT_MIN), 10) );
+  VERIFY( check_to_chars<signed long>(LONG_MIN, to_string(LONG_MIN), 10) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MIN, to_string(LLONG_MIN), 10) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX/2, to_string(CHAR_MAX/2), 10) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX/2, to_string(SCHAR_MAX/2), 10) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX/2, to_string(UCHAR_MAX/2), 10) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX/2, to_string(SHRT_MAX/2), 10) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX/2, to_string(USHRT_MAX/2), 10) );
+  VERIFY( check_to_chars<signed int>(INT_MAX/2, to_string(INT_MAX/2), 10) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX/2, to_string(UINT_MAX/2), 10) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX/2, to_string(LONG_MAX/2), 10) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX/2, to_string(ULONG_MAX/2), 10) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX/2, to_string(LLONG_MAX/2), 10) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX/2, to_string(ULLONG_MAX/2), 10) );
+}
+
+// Using all bases
+void
+test03()
+{
+  // -2017 in all bases from [2,36]
+  const char* str2017[37] = { nullptr, nullptr,
+    "-11111100001",
+    "-2202201",
+    "-133201",
+    "-31032",
+    "-13201",
+    "-5611",
+    "-3741",
+    "-2681",
+    "-2017",
+    "-1574",
+    "-1201",
+    "-bc2",
+    "-a41",
+    "-8e7",
+    "-7e1",
+    "-6gb",
+    "-641",
+    "-5b3",
+    "-50h",
+    "-4c1",
+    "-43f",
+    "-3ig",
+    "-3c1",
+    "-35h",
+    "-2pf",
+    "-2kj",
+    "-2g1",
+    "-2bg",
+    "-277",
+    "-232",
+    "-1v1",
+    "-1s4",
+    "-1pb",
+    "-1mm",
+    "-1k1"
+  };
+  // -12345 in all bases from [2,36]
+  const char* str12345[37] = { nullptr, nullptr,
+    "-11000000111001",
+    "-121221020",
+    "-3000321",
+    "-343340",
+    "-133053",
+    "-50664",
+    "-30071",
+    "-17836",
+    "-12345",
+    "-9303",
+    "-7189",
+    "-5808",
+    "-46db",
+    "-39d0",
+    "-3039",
+    "-28c3",
+    "-221f",
+    "-1f3e",
+    "-1ah5",
+    "-16ki",
+    "-13b3",
+    "-107h",
+    "-la9",
+    "-jik",
+    "-i6l",
+    "-gp6",
+    "-fkp",
+    "-ejk",
+    "-dlf",
+    "-cq7",
+    "-c1p",
+    "-bb3",
+    "-an3",
+    "-a2p",
+    "-9ix"
+  };
+  // -23456 in all bases from [2,36]
+  const char* str23456[37] = { nullptr, nullptr,
+    "-101101110100000",
+    "-1012011202",
+    "-11232200",
+    "-1222311",
+    "-300332",
+    "-125246",
+    "-55640",
+    "-35152",
+    "-23456",
+    "-16694",
+    "-116a8",
+    "-a8a4",
+    "-8796",
+    "-6e3b",
+    "-5ba0",
+    "-4d2d",
+    "-4072",
+    "-37ia",
+    "-2icg",
+    "-2b3k",
+    "-24a4",
+    "-1l7j",
+    "-1gh8",
+    "-1cd6",
+    "-18i4",
+    "-154k",
+    "-11pk",
+    "-rpo",
+    "-q1q",
+    "-ock",
+    "-mt0",
+    "-lhq",
+    "-k9u",
+    "-j56",
+    "-i3k"
+  };
+  // INT_MIN in all bases from [2,36]
+  const char* strINT_MIN[37] = { nullptr, nullptr,
+    "-10000000000000000000000000000000",
+    "-12112122212110202102",
+    "-2000000000000000",
+    "-13344223434043",
+    "-553032005532",
+    "-104134211162",
+    "-20000000000",
+    "-5478773672",
+    "-2147483648",
+    "-a02220282",
+    "-4bb2308a8",
+    "-282ba4aab",
+    "-1652ca932",
+    "-c87e66b8",
+    "-80000000",
+    "-53g7f549",
+    "-3928g3h2",
+    "-27c57h33",
+    "-1db1f928",
+    "-140h2d92",
+    "-ikf5bf2",
+    "-ebelf96",
+    "-b5gge58",
+    "-8jmdnkn",
+    "-6oj8ioo",
+    "-5ehnckb",
+    "-4clm98g",
+    "-3hk7988",
+    "-2sb6cs8",
+    "-2d09uc2",
+    "-2000000",
+    "-1lsqtl2",
+    "-1d8xqrq",
+    "-15v22un",
+    "-zik0zk"
+  };
+
+  for (int base = 2; base <= 36; ++base)
+  {
+    VERIFY( check_to_chars<char>(0, "0", base) );
+    VERIFY( check_to_chars<signed char>(0, "0", base) );
+    VERIFY( check_to_chars<unsigned char>(0, "0", base) );
+    VERIFY( check_to_chars<signed short>(0, "0", base) );
+    VERIFY( check_to_chars<unsigned short>(0, "0", base) );
+    VERIFY( check_to_chars<signed int>(0, "0", base) );
+    VERIFY( check_to_chars<unsigned int>(0, "0", base) );
+    VERIFY( check_to_chars<signed long>(0, "0", base) );
+    VERIFY( check_to_chars<unsigned long>(0, "0", base) );
+    VERIFY( check_to_chars<signed long long>(0, "0", base) );
+    VERIFY( check_to_chars<unsigned long long>(0, "0", base) );
+
+    VERIFY( check_to_chars<char>(1, "1", base) );
+    VERIFY( check_to_chars<signed char>(1, "1", base) );
+    VERIFY( check_to_chars<unsigned char>(1, "1", base) );
+    VERIFY( check_to_chars<signed short>(1, "1", base) );
+    VERIFY( check_to_chars<unsigned short>(1, "1", base) );
+    VERIFY( check_to_chars<signed int>(1, "1", base) );
+    VERIFY( check_to_chars<unsigned int>(1, "1", base) );
+    VERIFY( check_to_chars<signed long>(1, "1", base) );
+    VERIFY( check_to_chars<unsigned long>(1, "1", base) );
+    VERIFY( check_to_chars<signed long long>(1, "1", base) );
+    VERIFY( check_to_chars<unsigned long long>(1, "1", base) );
+
+    if constexpr (std::is_signed_v<char>)
+      VERIFY( check_to_chars<char>(-1, "-1", base) );
+    VERIFY( check_to_chars<signed char>(-1, "-1", base) );
+    VERIFY( check_to_chars<signed short>(-1, "-1", base) );
+    VERIFY( check_to_chars<signed int>(-1, "-1", base) );
+    VERIFY( check_to_chars<signed long>(-1, "-1", base) );
+    VERIFY( check_to_chars<signed long long>(-1, "-1", base) );
+
+    if (base > 2)
+    {
+      VERIFY( check_to_chars<char>(2, "2", base) );
+      VERIFY( check_to_chars<signed char>(2, "2", base) );
+      VERIFY( check_to_chars<unsigned char>(2, "2", base) );
+      VERIFY( check_to_chars<signed short>(2, "2", base) );
+      VERIFY( check_to_chars<unsigned short>(2, "2", base) );
+      VERIFY( check_to_chars<signed int>(2, "2", base) );
+      VERIFY( check_to_chars<unsigned int>(2, "2", base) );
+      VERIFY( check_to_chars<signed long>(2, "2", base) );
+      VERIFY( check_to_chars<unsigned long>(2, "2", base) );
+      VERIFY( check_to_chars<signed long long>(2, "2", base) );
+      VERIFY( check_to_chars<unsigned long long>(2, "2", base) );
+
+      if constexpr (std::is_signed_v<char>)
+	VERIFY( check_to_chars<char>(-2, "-2", base) );
+      VERIFY( check_to_chars<signed char>(-2, "-2", base) );
+      VERIFY( check_to_chars<signed short>(-2, "-2", base) );
+      VERIFY( check_to_chars<signed int>(-2, "-2", base) );
+      VERIFY( check_to_chars<signed long>(-2, "-2", base) );
+      VERIFY( check_to_chars<signed long long>(-2, "-2", base) );
+    }
+
+    VERIFY( check_to_chars(2017u, str2017[base]+1, base) );
+    VERIFY( check_to_chars(2017, str2017[base]+1, base) );
+    VERIFY( check_to_chars(-2017, str2017[base], base) );
+    VERIFY( check_to_chars(12345u, str12345[base]+1, base) );
+    VERIFY( check_to_chars(12345, str12345[base]+1, base) );
+    VERIFY( check_to_chars(-12345, str12345[base], base) );
+    VERIFY( check_to_chars(23456u, str23456[base]+1, base) );
+    VERIFY( check_to_chars(23456, str23456[base]+1, base) );
+    VERIFY( check_to_chars(-23456, str23456[base], base) );
+    VERIFY( check_to_chars(INT_MAX + 1ull, strINT_MIN[base]+1, base) );
+    VERIFY( check_to_chars(INT_MAX + 1ll, strINT_MIN[base]+1, base) );
+    VERIFY( check_to_chars(INT_MIN, strINT_MIN[base], base) );
+  }
+
+  VERIFY( check_to_chars(1155, "xx", 34) );
+  VERIFY( check_to_chars(1224, "yy", 35) );
+  VERIFY( check_to_chars(1295, "zz", 36) );
+}
+
+#include <sstream>
+#include <ios>
+
+// base 8
+void
+test04()
+{
+  auto to_string = [](auto val) {
+    std::ostringstream ss;
+    ss << std::oct;
+    if (val < 0)
+      ss << '-' << (~val + 1ull);
+    else if (sizeof(val) == 1)
+      ss << (int)val;
+    else
+      ss << val;
+    return ss.str();
+  };
+
+  VERIFY( check_to_chars<char>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<signed char>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<unsigned char>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<signed short>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<unsigned short>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<signed int>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<unsigned int>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<signed long>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<unsigned long>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<signed long long>(123, to_string(123), 8) );
+  VERIFY( check_to_chars<unsigned long long>(123, to_string(123), 8) );
+
+  if constexpr (std::is_signed_v<char>)
+    VERIFY( check_to_chars<char>(-79, to_string(-79), 8) );
+  VERIFY( check_to_chars<signed char>(-79, to_string(-79), 8) );
+  VERIFY( check_to_chars<signed short>(-79, to_string(-79), 8) );
+  VERIFY( check_to_chars<signed int>(-79, to_string(-79), 8) );
+  VERIFY( check_to_chars<signed long>(-79, to_string(-79), 8) );
+  VERIFY( check_to_chars<signed long long>(-79, to_string(-79), 8) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX, to_string(CHAR_MAX), 8) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX, to_string(SCHAR_MAX), 8) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX, to_string(UCHAR_MAX), 8) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX, to_string(SHRT_MAX), 8) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX, to_string(USHRT_MAX), 8) );
+  VERIFY( check_to_chars<signed int>(INT_MAX, to_string(INT_MAX), 8) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX, to_string(UINT_MAX), 8) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX, to_string(LONG_MAX), 8) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX, to_string(ULONG_MAX), 8) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX, to_string(LLONG_MAX), 8) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX, to_string(ULLONG_MAX), 8) );
+
+  VERIFY( check_to_chars<char>(CHAR_MIN, to_string(CHAR_MIN), 8) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MIN, to_string(SCHAR_MIN), 8) );
+  VERIFY( check_to_chars<signed short>(SHRT_MIN, to_string(SHRT_MIN), 8) );
+  VERIFY( check_to_chars<signed int>(INT_MIN, to_string(INT_MIN), 8) );
+  VERIFY( check_to_chars<signed long>(LONG_MIN, to_string(LONG_MIN), 8) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MIN, to_string(LLONG_MIN), 8) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX/2, to_string(CHAR_MAX/2), 8) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX/2, to_string(SCHAR_MAX/2), 8) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX/2, to_string(UCHAR_MAX/2), 8) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX/2, to_string(SHRT_MAX/2), 8) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX/2, to_string(USHRT_MAX/2), 8) );
+  VERIFY( check_to_chars<signed int>(INT_MAX/2, to_string(INT_MAX/2), 8) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX/2, to_string(UINT_MAX/2), 8) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX/2, to_string(LONG_MAX/2), 8) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX/2, to_string(ULONG_MAX/2), 8) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX/2, to_string(LLONG_MAX/2), 8) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX/2, to_string(ULLONG_MAX/2), 8) );
+}
+
+// base 16
+void
+test05()
+{
+  auto to_string = [](auto val) {
+    std::ostringstream ss;
+    ss << std::hex;
+    if (val < 0)
+      ss << '-' << (~val + 1ull);
+    else if (sizeof(val) == 1)
+      ss << (int)val;
+    else
+      ss << val;
+    return ss.str();
+  };
+
+  VERIFY( check_to_chars<char>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<signed char>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<unsigned char>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<signed short>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<unsigned short>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<signed int>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<unsigned int>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<signed long>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<unsigned long>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<signed long long>(123, to_string(123), 16) );
+  VERIFY( check_to_chars<unsigned long long>(123, to_string(123), 16) );
+
+  if constexpr (std::is_signed_v<char>)
+    VERIFY( check_to_chars<char>(-79, to_string(-79), 16) );
+  VERIFY( check_to_chars<signed char>(-79, to_string(-79), 16) );
+  VERIFY( check_to_chars<signed short>(-79, to_string(-79), 16) );
+  VERIFY( check_to_chars<signed int>(-79, to_string(-79), 16) );
+  VERIFY( check_to_chars<signed long>(-79, to_string(-79), 16) );
+  VERIFY( check_to_chars<signed long long>(-79, to_string(-79), 16) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX, to_string(CHAR_MAX), 16) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX, to_string(SCHAR_MAX), 16) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX, to_string(UCHAR_MAX), 16) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX, to_string(SHRT_MAX), 16) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX, to_string(USHRT_MAX), 16) );
+  VERIFY( check_to_chars<signed int>(INT_MAX, to_string(INT_MAX), 16) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX, to_string(UINT_MAX), 16) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX, to_string(LONG_MAX), 16) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX, to_string(ULONG_MAX), 16) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX, to_string(LLONG_MAX), 16) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX, to_string(ULLONG_MAX), 16) );
+
+  VERIFY( check_to_chars<char>(CHAR_MIN, to_string(CHAR_MIN), 16) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MIN, to_string(SCHAR_MIN), 16) );
+  VERIFY( check_to_chars<signed short>(SHRT_MIN, to_string(SHRT_MIN), 16) );
+  VERIFY( check_to_chars<signed int>(INT_MIN, to_string(INT_MIN), 16) );
+  VERIFY( check_to_chars<signed long>(LONG_MIN, to_string(LONG_MIN), 16) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MIN, to_string(LLONG_MIN), 16) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX/2, to_string(CHAR_MAX/2), 16) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX/2, to_string(SCHAR_MAX/2), 16) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX/2, to_string(UCHAR_MAX/2), 16) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX/2, to_string(SHRT_MAX/2), 16) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX/2, to_string(USHRT_MAX/2), 16) );
+  VERIFY( check_to_chars<signed int>(INT_MAX/2, to_string(INT_MAX/2), 16) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX/2, to_string(UINT_MAX/2), 16) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX/2, to_string(LONG_MAX/2), 16) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX/2, to_string(ULONG_MAX/2), 16) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX/2, to_string(LLONG_MAX/2), 16) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX/2, to_string(ULLONG_MAX/2), 16) );
+}
+
+#include <bitset>
+
+// base 2
+void
+test06()
+{
+  auto to_string = [](auto val) {
+    std::string s, sign;
+    if (val < 0)
+    {
+      auto absval = ~val + 1ull;
+      s = std::bitset<sizeof(absval) * CHAR_BIT>(absval).to_string();
+      sign = '-';
+    }
+    else
+      s = std::bitset<sizeof(val) * CHAR_BIT>(val).to_string();
+    auto pos = s.find_first_not_of("0");
+    if (pos == std::string::npos)
+      s.resize(1);
+    else
+      s.erase(0, pos);
+    return sign + s;
+  };
+
+  VERIFY( check_to_chars<char>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<signed char>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<unsigned char>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<signed short>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<unsigned short>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<signed int>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<unsigned int>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<signed long>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<unsigned long>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<signed long long>(123, to_string(123), 2) );
+  VERIFY( check_to_chars<unsigned long long>(123, to_string(123), 2) );
+
+  if constexpr (std::is_signed_v<char>)
+    VERIFY( check_to_chars<char>(-79, to_string(-79), 2) );
+  VERIFY( check_to_chars<signed char>(-79, to_string(-79), 2) );
+  VERIFY( check_to_chars<signed short>(-79, to_string(-79), 2) );
+  VERIFY( check_to_chars<signed int>(-79, to_string(-79), 2) );
+  VERIFY( check_to_chars<signed long>(-79, to_string(-79), 2) );
+  VERIFY( check_to_chars<signed long long>(-79, to_string(-79), 2) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX, to_string(CHAR_MAX), 2) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX, to_string(SCHAR_MAX), 2) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX, to_string(UCHAR_MAX), 2) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX, to_string(SHRT_MAX), 2) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX, to_string(USHRT_MAX), 2) );
+  VERIFY( check_to_chars<signed int>(INT_MAX, to_string(INT_MAX), 2) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX, to_string(UINT_MAX), 2) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX, to_string(LONG_MAX), 2) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX, to_string(ULONG_MAX), 2) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX, to_string(LLONG_MAX), 2) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX, to_string(ULLONG_MAX), 2) );
+
+  VERIFY( check_to_chars<char>(CHAR_MIN, to_string(CHAR_MIN), 2) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MIN, to_string(SCHAR_MIN), 2) );
+  VERIFY( check_to_chars<signed short>(SHRT_MIN, to_string(SHRT_MIN), 2) );
+  VERIFY( check_to_chars<signed int>(INT_MIN, to_string(INT_MIN), 2) );
+  VERIFY( check_to_chars<signed long>(LONG_MIN, to_string(LONG_MIN), 2) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MIN, to_string(LLONG_MIN), 2) );
+
+  VERIFY( check_to_chars<char>(CHAR_MAX/2, to_string(CHAR_MAX/2), 2) );
+  VERIFY( check_to_chars<signed char>(SCHAR_MAX/2, to_string(SCHAR_MAX/2), 2) );
+  VERIFY( check_to_chars<unsigned char>(UCHAR_MAX/2, to_string(UCHAR_MAX/2), 2) );
+  VERIFY( check_to_chars<signed short>(SHRT_MAX/2, to_string(SHRT_MAX/2), 2) );
+  VERIFY( check_to_chars<unsigned short>(USHRT_MAX/2, to_string(USHRT_MAX/2), 2) );
+  VERIFY( check_to_chars<signed int>(INT_MAX/2, to_string(INT_MAX/2), 2) );
+  VERIFY( check_to_chars<unsigned int>(UINT_MAX/2, to_string(UINT_MAX/2), 2) );
+  VERIFY( check_to_chars<signed long>(LONG_MAX/2, to_string(LONG_MAX/2), 2) );
+  VERIFY( check_to_chars<unsigned long>(ULONG_MAX/2, to_string(ULONG_MAX/2), 2) );
+  VERIFY( check_to_chars<signed long long>(LLONG_MAX/2, to_string(LLONG_MAX/2), 2) );
+  VERIFY( check_to_chars<unsigned long long>(ULLONG_MAX/2, to_string(ULLONG_MAX/2), 2) );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+  test05();
+  test06();
+}
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/1_neg.cc b/libstdc++-v3/testsuite/20_util/to_chars/1_neg.cc
new file mode 100644
index 00000000000..8302b250cd0
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/to_chars/1_neg.cc
@@ -0,0 +1,35 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <charconv>
+
+void
+test01(char* first, char* last)
+{
+#if _GLIBCXX_USE_WCHAR_T
+  std::to_chars(first, last, L'\x1'); // { dg-error "no matching" }
+  std::to_chars(first, last, L'\x1', 10); // { dg-error "no matching" }
+#endif
+
+  std::to_chars(first, last, u'\x1'); // { dg-error "no matching" }
+  std::to_chars(first, last, u'\x1', 10); // { dg-error "no matching" }
+  std::to_chars(first, last, U'\x1'); // { dg-error "no matching" }
+  std::to_chars(first, last, U'\x1', 10); // { dg-error "no matching" }
+}
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/2.cc b/libstdc++-v3/testsuite/20_util/to_chars/2.cc
new file mode 100644
index 00000000000..b28320cc7b8
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/to_chars/2.cc
@@ -0,0 +1,78 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <charconv>
+#include <testsuite_hooks.h>
+
+// Test std::to_chars error handling.
+
+void
+test01()
+{
+  char buf[9] = "********";
+  std::to_chars_result r;
+
+  r = std::to_chars(buf, buf, 1);
+  VERIFY( r.ec == std::errc::value_too_large );
+  VERIFY( r.ptr == buf );
+  VERIFY( *r.ptr == '*' );
+
+  r = std::to_chars(buf, buf + 3, 0b1000, 2);
+  VERIFY( r.ec == std::errc::value_too_large );
+  VERIFY( r.ptr == buf + 3 );
+  VERIFY( *r.ptr == '*' );
+  r = std::to_chars(buf, buf + 4, 0b1000, 2);
+  VERIFY( r.ec == std::errc{} );
+  VERIFY( r.ptr == buf + 4 );
+  VERIFY( *r.ptr == '*' );
+
+  r = std::to_chars(buf, buf + 4, 010000, 8);
+  VERIFY( r.ec == std::errc::value_too_large );
+  VERIFY( r.ptr == buf + 4 );
+  VERIFY( *r.ptr == '*' );
+  r = std::to_chars(buf, buf + 5, 010000, 8);
+  VERIFY( r.ec == std::errc{} );
+  VERIFY( r.ptr == buf + 5 );
+  VERIFY( *r.ptr == '*' );
+
+  r = std::to_chars(buf, buf + 5, 100000, 10);
+  VERIFY( r.ec == std::errc::value_too_large );
+  VERIFY( r.ptr == buf + 5 );
+  VERIFY( *r.ptr == '*' );
+  r = std::to_chars(buf, buf + 6, 100000, 10);
+  VERIFY( r.ec == std::errc{} );
+  VERIFY( r.ptr == buf + 6 );
+  VERIFY( *r.ptr == '*' );
+
+  r = std::to_chars(buf, buf + 6, 0x1000000, 16);
+  VERIFY( r.ec == std::errc::value_too_large );
+  VERIFY( r.ptr == buf + 6 );
+  VERIFY( *r.ptr == '*' );
+  r = std::to_chars(buf, buf + 7, 0x1000000, 16);
+  VERIFY( r.ec == std::errc{} );
+  VERIFY( r.ptr == buf + 7 );
+  VERIFY( *r.ptr == '*' );
+}
+
+int
+main()
+{
+  test01();
+}
diff --git a/libstdc++-v3/testsuite/20_util/to_chars/requirements.cc b/libstdc++-v3/testsuite/20_util/to_chars/requirements.cc
new file mode 100644
index 00000000000..d50588bd902
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/to_chars/requirements.cc
@@ -0,0 +1,49 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <charconv>
+
+namespace std
+{
+  struct to_chars_result;
+
+  char* to_chars_result::*pm2 = &to_chars_result::ptr;
+  errc to_chars_result::*pm1 = &to_chars_result::ec;
+
+  to_chars_result (*f1)(char*, char*, char, int) = &to_chars;
+  to_chars_result (*f2)(char*, char*, signed char, int) = &to_chars;
+  to_chars_result (*f3)(char*, char*, unsigned char, int) = &to_chars;
+  to_chars_result (*f4)(char*, char*, signed short, int) = &to_chars;
+  to_chars_result (*f5)(char*, char*, unsigned short, int) = &to_chars;
+  to_chars_result (*f6)(char*, char*, signed int, int) = &to_chars;
+  to_chars_result (*f7)(char*, char*, unsigned int, int) = &to_chars;
+  to_chars_result (*f8)(char*, char*, signed long, int) = &to_chars;
+  to_chars_result (*f9)(char*, char*, unsigned long, int) = &to_chars;
+  to_chars_result (*f10)(char*, char*, signed long long, int) = &to_chars;
+  to_chars_result (*f11)(char*, char*, unsigned long long, int) = &to_chars;
+}
+
+void bind()
+{
+  char buf[1];
+  auto [p, e] = std::to_chars(buf, buf + 1, 1, 10);
+  char** pa = &p;
+  std::errc* ea = &e;
+}