Merge pull request #978 from cppalliance/977

Fix duplicate symbols on some PPC64 platforms

Author: mborland

include/boost/decimal/detail/config.hpp

@@ -382,4 +382,20 @@ typedef unsigned __int128 builtin_uint128_t;
 
 #endif // Exceptions
 
+#ifndef BOOST_DECIMAL_BULID_MODULE
+#  include <cfloat>
+#  include <type_traits>
+#endif
+
+// Check for PPC64LE with IEEE long double (which is an alias to __float128) or x64 with "-mlong-double-128"
+//
+// IBM128 has 106 Mantissa Digits whereas IEEE128 has 113
+// https://developers.redhat.com/articles/2023/05/16/benefits-fedora-38-long-double-transition-ppc64le#
+#if ((defined(__ppc64__) || defined(__PPC64__) || defined(__ppc64le__) || defined(__PPC64LE__)) && (defined(__LONG_DOUBLE_IEEE128__) || LDBL_MANT_DIG == 113))
+
+#define BOOST_DECIMAL_LDBL_IS_FLOAT128
+static_assert(std::is_same<long double, __float128>::value, "__float128 should be an alias to long double. Please open an issue at: https://github.com/cppalliance/decimal");
+
+#endif
+
 #endif // BOOST_DECIMAL_DETAIL_CONFIG_HPP

include/boost/decimal/detail/ryu/ryu_generic_128.hpp

@@ -348,7 +348,7 @@ BOOST_DECIMAL_CXX20_CONSTEXPR auto floating_point_to_fd128<long double>(long dou
 
 #endif
 
-#if defined(BOOST_DECIMAL_HAS_FLOAT128)
+#if defined(BOOST_DECIMAL_HAS_FLOAT128) && !defined(BOOST_DECIMAL_LDBL_IS_FLOAT128)
 
 template <>
 BOOST_DECIMAL_CXX20_CONSTEXPR auto floating_point_to_fd128<__float128>(__float128 val) noexcept -> floating_decimal_128

include/boost/decimal/detail/type_traits.hpp

@@ -121,7 +121,7 @@ constexpr bool is_integral_v = is_integral<T>::value;
 template <typename T>
 struct is_floating_point { static constexpr bool value = std::is_floating_point<T>::value; };
 
-#ifdef BOOST_DECIMAL_HAS_FLOAT128
+#if defined(BOOST_DECIMAL_HAS_FLOAT128) && !defined(BOOST_DECIMAL_LDBL_IS_FLOAT128)
 template <>
 struct is_floating_point<__float128> { static constexpr bool value = true; };
 #endif