diff --git a/include/boost/charconv/from_chars.hpp b/include/boost/charconv/from_chars.hpp
index b640791..ae1d6cb 100644
--- a/include/boost/charconv/from_chars.hpp
+++ b/include/boost/charconv/from_chars.hpp
@@ -12,7 +12,6 @@
 #include <boost/config.hpp>
 #include <type_traits>
 #include <limits>
-#include <array>
 #include <cstdlib>
 #include <cerrno>
 #include <cstddef>
@@ -45,8 +44,8 @@ struct from_chars_result
 
 namespace detail {
 
-static constexpr std::array<unsigned char, 256> uchar_values =
-    {{255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+static constexpr unsigned char uchar_values[] =
+     {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
       255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
       255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
         0,   1,   2,   3,   4,   5,   6,   7,   8,   9, 255, 255, 255, 255, 255, 255,
@@ -61,7 +60,9 @@ static constexpr std::array<unsigned char, 256> uchar_values =
       255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
       255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
       255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-      255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255}};
+      255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255};
+
+static_assert(sizeof(uchar_values) == 256, "uchar_values should represent all 256 values of unsigned char");
 
 // Convert characters for 0-9, A-Z, a-z to 0-35. Anything else is 255
 constexpr unsigned char digit_from_char(char val) noexcept
@@ -74,6 +75,10 @@ constexpr unsigned char digit_from_char(char val) noexcept
 # pragma warning(disable: 4146) // unary minus operator applied to unsigned type, result still unsigned
 # pragma warning(disable: 4189) // 'is_negative': local variable is initialized but not referenced
 
+#elif defined(__clang__) && defined(__APPLE__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wconstant-conversion"
+
 #elif defined(__GNUC__) && (__GNUC__ < 7)
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Woverflow"
@@ -234,6 +239,8 @@ BOOST_CXX14_CONSTEXPR from_chars_result from_chars_integer_impl(const char* firs
 
 #ifdef BOOST_MSVC
 # pragma warning(pop)
+#elif defined(__clang__) && defined(__APPLE__)
+# pragma clang diagnostic pop
 #elif defined(__GNUC__) && (__GNUC__ < 7)
 # pragma GCC diagnostic pop
 #endif
diff --git a/test/limits.cpp b/test/limits.cpp
index 52f3ce5..0b1a76b 100644
--- a/test/limits.cpp
+++ b/test/limits.cpp
@@ -172,16 +172,16 @@ int main()
     test_integral<long long>();
     test_integral<unsigned long long>();
 
-#if !defined(__CYGWIN__)
+#if !defined(__CYGWIN__) && !defined(__s390x__) && !((defined(__arm__) || defined(__aarch64__))  && !defined(__APPLE__)) && !(defined(__APPLE__) && (__clang_major__ == 12))
 
-    // the stub implementations fail under Cygwin;
+    // the stub implementations fail under Cygwin, s390x, linux ARM, and Apple Clang w/Xcode 12.2;
     // re-enable these when we have real ones
 
     test_floating_point<float>();
     test_floating_point<double>();
     test_floating_point<long double>();
 
-#endif // !defined(__CYGWIN__)
+#endif // Broken Platforms
 
 #ifdef BOOST_CHARCONV_HAS_INT128
 
diff --git a/test/roundtrip.cpp b/test/roundtrip.cpp
index 5a48d4d..0f7523e 100644
--- a/test/roundtrip.cpp
+++ b/test/roundtrip.cpp
@@ -296,9 +296,9 @@ int main()
 #endif
     }
 
-#if !defined(__CYGWIN__)
+#if !defined(__CYGWIN__) && !defined(__s390x__) && !((defined(__arm__) || defined(__aarch64__))  && !defined(__APPLE__)) && !(defined(__APPLE__) && (__clang_major__ == 12))
 
-    // the stub implementations fail under Cygwin;
+    // the stub implementations fail under Cygwin, s390x, linux ARM, and Apple Clang w/Xcode 12.2;
     // re-enable these when we have real ones
 
     // float
@@ -368,7 +368,7 @@ int main()
         test_roundtrip_bv<long double>();
     }
 
-#endif // !defined(__CYGWIN__)
+#endif // Broken platforms
 
     return boost::report_errors();
 }