Index: libcxx/include/charconv
===================================================================
--- libcxx/include/charconv
+++ libcxx/include/charconv
@@ -96,7 +96,7 @@
 _LIBCPP_FUNC_VIS char* __u32toa(uint32_t __value, char* __buffer);
 }
 
-#if _LIBCPP_STD_VER > 11
+#ifndef _LIBCPP_CXX03_LANG
 
 enum class _LIBCPP_ENUM_VIS chars_format
 {
@@ -124,7 +124,7 @@
 namespace __itoa
 {
 
-static constexpr uint64_t __pow10_64[] = {
+static _LIBCPP_CONSTEXPR uint64_t __pow10_64[] = {
     UINT64_C(0),
     UINT64_C(10),
     UINT64_C(100),
@@ -147,7 +147,7 @@
     UINT64_C(10000000000000000000),
 };
 
-static constexpr uint32_t __pow10_32[] = {
+static _LIBCPP_CONSTEXPR uint32_t __pow10_32[] = {
     UINT32_C(0),          UINT32_C(10),       UINT32_C(100),
     UINT32_C(1000),       UINT32_C(10000),    UINT32_C(100000),
     UINT32_C(1000000),    UINT32_C(10000000), UINT32_C(100000000),
@@ -172,7 +172,7 @@
         return __u64toa(__v, __p);
     }
 
-    static _LIBCPP_INLINE_VISIBILITY auto& __pow() { return __pow10_64; }
+    static _LIBCPP_INLINE_VISIBILITY decltype(__pow10_64)& __pow() { return __pow10_64; }
 };
 
 template <typename _Tp>
@@ -194,7 +194,7 @@
         return __u32toa(__v, __p);
     }
 
-    static _LIBCPP_INLINE_VISIBILITY auto& __pow() { return __pow10_32; }
+    static _LIBCPP_INLINE_VISIBILITY decltype(__pow10_32)& __pow() { return __pow10_32; }
 };
 
 template <typename _Tp>
@@ -239,7 +239,7 @@
 template <typename _Tp>
 struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp>
 {
-    static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
+    static _LIBCPP_CONSTEXPR int digits = numeric_limits<_Tp>::digits10 + 1;
     using __traits_base<_Tp>::__pow;
     using typename __traits_base<_Tp>::type;
 
@@ -285,10 +285,10 @@
 }
 
 template <typename _Tp>
-inline _LIBCPP_INLINE_VISIBILITY auto
+inline _LIBCPP_INLINE_VISIBILITY typename make_unsigned<_Tp>::type
 __to_unsigned(_Tp __x)
 {
-    return static_cast<make_unsigned_t<_Tp>>(__x);
+    return static_cast<typename make_unsigned<_Tp>::type>(__x);
 }
 
 template <typename _Tp>
@@ -379,14 +379,14 @@
     }
 }
 
-template <typename _Tp, enable_if_t<is_integral<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY to_chars_result
 to_chars(char* __first, char* __last, _Tp __value)
 {
     return __to_chars_itoa(__first, __last, __value, is_signed<_Tp>());
 }
 
-template <typename _Tp, enable_if_t<is_integral<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY to_chars_result
 to_chars(char* __first, char* __last, _Tp __value, int __base)
 {
@@ -501,7 +501,7 @@
     return __r;
 }
 
-template <typename _Tp, enable_if_t<is_unsigned<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 __from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
 {
@@ -527,7 +527,7 @@
         });
 }
 
-template <typename _Tp, enable_if_t<is_signed<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 __from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
 {
@@ -535,7 +535,7 @@
     return __sign_combinator(__first, __last, __value, __from_chars_atoi<__t>);
 }
 
-template <typename _Tp, enable_if_t<is_unsigned<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 __from_chars_integral(const char* __first, const char* __last, _Tp& __value,
                       int __base)
@@ -582,7 +582,7 @@
         __base);
 }
 
-template <typename _Tp, enable_if_t<is_signed<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 __from_chars_integral(const char* __first, const char* __last, _Tp& __value,
                       int __base)
@@ -592,14 +592,14 @@
                              __from_chars_integral<__t>, __base);
 }
 
-template <typename _Tp, enable_if_t<is_integral<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 from_chars(const char* __first, const char* __last, _Tp& __value)
 {
     return __from_chars_atoi(__first, __last, __value);
 }
 
-template <typename _Tp, enable_if_t<is_integral<_Tp>::value, int> = 0>
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
 {
@@ -607,7 +607,7 @@
     return __from_chars_integral(__first, __last, __value, __base);
 }
 
-#endif  // _LIBCPP_STD_VER > 11
+#endif  // _LIBCPP_CXX03_LANG
 
 _LIBCPP_END_NAMESPACE_STD
 
Index: libcxx/test/std/utilities/charconv/charconv.from.chars/integral.bool.fail.cpp
===================================================================
--- libcxx/test/std/utilities/charconv/charconv.from.chars/integral.bool.fail.cpp
+++ libcxx/test/std/utilities/charconv/charconv.from.chars/integral.bool.fail.cpp
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++98, c++03, c++11
+// UNSUPPORTED: c++98, c++03
 // <charconv>
 
 // In
Index: libcxx/test/std/utilities/charconv/charconv.from.chars/integral.pass.cpp
===================================================================
--- libcxx/test/std/utilities/charconv/charconv.from.chars/integral.pass.cpp
+++ libcxx/test/std/utilities/charconv/charconv.from.chars/integral.pass.cpp
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++98, c++03, c++11
+// UNSUPPORTED: c++98, c++03
 
 // XFAIL: with_system_cxx_lib=macosx10.14
 // XFAIL: with_system_cxx_lib=macosx10.13
Index: libcxx/test/std/utilities/charconv/charconv.to.chars/integral.bool.fail.cpp
===================================================================
--- libcxx/test/std/utilities/charconv/charconv.to.chars/integral.bool.fail.cpp
+++ libcxx/test/std/utilities/charconv/charconv.to.chars/integral.bool.fail.cpp
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++98, c++03, c++11
+// UNSUPPORTED: c++98, c++03
 // <charconv>
 
 // In
Index: libcxx/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp
===================================================================
--- libcxx/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp
+++ libcxx/test/std/utilities/charconv/charconv.to.chars/integral.pass.cpp
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++98, c++03, c++11
+// UNSUPPORTED: c++98, c++03
 
 // XFAIL: with_system_cxx_lib=macosx10.14
 // XFAIL: with_system_cxx_lib=macosx10.13
Index: libcxx/test/support/charconv_test_helpers.h
===================================================================
--- libcxx/test/support/charconv_test_helpers.h
+++ libcxx/test/support/charconv_test_helpers.h
@@ -17,8 +17,8 @@
 
 #include "test_macros.h"
 
-#if TEST_STD_VER <= 11
-#error This file requires C++14
+#if TEST_STD_VER < 11
+#error This file requires C++11
 #endif
 
 using std::false_type;
@@ -56,14 +56,14 @@
 constexpr bool
 _fits_in(T v, false_type, true_type /* T signed */, false_type /* X unsigned*/)
 {
-    return 0 <= v && std::make_unsigned_t<T>(v) <= (xl::max)();
+    return 0 <= v && typename std::make_unsigned<T>::type(v) <= (xl::max)();
 }
 
 template <typename X, typename T, typename xl = std::numeric_limits<X>>
 constexpr bool
 _fits_in(T v, false_type, false_type /* T unsigned */, ...)
 {
-    return v <= std::make_unsigned_t<X>((xl::max)());
+    return v <= typename std::make_unsigned<X>::type((xl::max)());
 }
 
 template <typename X, typename T>
@@ -119,25 +119,26 @@
     }
 
 private:
-    static auto fromchars(char const* p, char const* ep, int base, true_type)
+    static long long fromchars(char const* p, char const* ep, int base, true_type)
     {
         char* last;
-        auto r = strtoll(p, &last, base);
+        long long r = strtoll(p, &last, base);
         assert(last == ep);
 
         return r;
     }
 
-    static auto fromchars(char const* p, char const* ep, int base, false_type)
+    static unsigned long long fromchars(char const* p, char const* ep, int base, false_type)
     {
         char* last;
-        auto r = strtoull(p, &last, base);
+        unsigned long long r = strtoull(p, &last, base);
         assert(last == ep);
 
         return r;
     }
 
     static auto fromchars(char const* p, char const* ep, int base = 10)
+    -> decltype(fromchars(p, ep, base, std::is_signed<X>()))
     {
         return fromchars(p, ep, base, std::is_signed<X>());
     }