Added C++20 <bit>, added to <type_traits>, fixed __NOEXCEPT in C++98 (#536)

Author: ZERICO2005

src/libc/include/cdefs.h

@@ -12,15 +12,19 @@
 #ifndef __cplusplus
 # define __BEGIN_DECLS
 # define __END_DECLS
-# define __NOEXCEPT     __attribute__((__nothrow__, __leaf__))
 # define __IGNORE(expr) ((void)(expr))
 #else /* __cplusplus */
 # define __BEGIN_DECLS  extern "C" {
 # define __END_DECLS    }
-# define __NOEXCEPT     noexcept
 # define __IGNORE(expr) (static_cast<void>(expr))
 #endif /* __cplusplus */
 
+#if defined(__cplusplus) && __cplusplus >= 201103L
+# define __NOEXCEPT noexcept
+#else /* __cplusplus */
+# define __NOEXCEPT __attribute__((__nothrow__, __leaf__))
+#endif /* __cplusplus */
+
 #ifndef NULL
 # ifndef __cplusplus
 #  define NULL ((void *)0)

src/libcxx/include/bit

@@ -0,0 +1,33 @@
+// -*- C++ -*-
+#ifndef _EZCXX_BIT
+#define _EZCXX_BIT
+
+#include <cstring> // for memcpy
+#include <type_traits>
+
+#pragma clang system_header
+
+namespace std {
+
+enum class endian {
+    little = __ORDER_LITTLE_ENDIAN__,
+    big    = __ORDER_BIG_ENDIAN__,
+    native = __BYTE_ORDER__
+}; // endian
+
+template<class _To, class _From>
+std::enable_if_t<
+    sizeof(_To) == sizeof(_From) &&
+    std::is_trivially_copyable_v<_From> &&
+    std::is_trivially_copyable_v<_To>, _To>
+constexpr bit_cast(const _From& src) noexcept {
+    static_assert(std::is_trivially_constructible_v<_To>,
+        "destination type is required to be trivially constructible");
+    _To dst;
+    std::memcpy(&dst, &src, sizeof(_To));
+    return dst;
+}
+
+} // namespace std
+
+#endif // _EZCXX_BIT

src/libcxx/include/type_traits

@@ -120,6 +120,9 @@ template<class _Tp> inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::
 template<class _Tp> using is_fundamental = disjunction<is_void<_Tp>, is_null_pointer<_Tp>, is_arithmetic<_Tp>>;
 template<class _Tp> inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
 
+template<class _Tp> struct is_compound : std::integral_constant<bool, !std::is_fundamental<_Tp>::value> {};
+template<class _Tp> inline constexpr bool is_compound_v = is_compound<_Tp>::value;
+
 template<class _Tp, bool = is_arithmetic<_Tp>::value> struct __is_signed : integral_constant<bool, _Tp(-1) < _Tp(0)> {};
 template<class _Tp>                                   struct __is_signed<_Tp, false> : false_type {};
 template<class _Tp> struct is_signed : __is_signed<_Tp>::type {};
@@ -150,6 +153,41 @@ template<class _Tp> inline constexpr bool is_class_v = __is_class(_Tp);
 template<class _Tp> using is_class = bool_constant<is_class_v<_Tp>>;
 #endif
 
+#if __has_feature(is_trivial)
+template<class _Tp> inline constexpr bool is_trivial_v = __is_trivial(_Tp);
+template<class _Tp> using is_trivial = bool_constant<is_trivial_v<_Tp>>;
+#endif
+
+#if __has_feature(is_trivially_copyable)
+template<class _Tp> inline constexpr bool is_trivially_copyable_v = __is_trivially_copyable(_Tp);
+template<class _Tp> using is_trivially_copyable = bool_constant<is_trivially_copyable_v<_Tp>>;
+#endif
+
+#if __has_feature(is_standard_layout)
+template<class _Tp> inline constexpr bool is_standard_layout_v = __is_standard_layout(_Tp);
+template<class _Tp> using is_standard_layout = bool_constant<is_standard_layout_v<_Tp>>;
+#endif
+
+#if __has_feature(is_pod)
+template<class _Tp> inline constexpr bool is_pod_v = __is_pod(_Tp);
+template<class _Tp> using is_pod = bool_constant<is_pod_v<_Tp>>;
+#endif
+
+#if __has_feature(is_empty)
+template<class _Tp> inline constexpr bool is_empty_v = __is_empty(_Tp);
+template<class _Tp> using is_empty = bool_constant<is_empty_v<_Tp>>;
+#endif
+
+#if __has_feature(is_polymorphic)
+template<class _Tp> inline constexpr bool is_polymorphic_v = __is_polymorphic(_Tp);
+template<class _Tp> using is_polymorphic = bool_constant<is_polymorphic_v<_Tp>>;
+#endif
+
+#if __has_feature(is_abstract)
+template<class _Tp> inline constexpr bool is_abstract_v = __is_abstract(_Tp);
+template<class _Tp> using is_abstract = bool_constant<is_abstract_v<_Tp>>;
+#endif
+
 template<class>     struct is_pointer       : false_type {};
 template<class _Tp> struct is_pointer<_Tp*> : true_type  {};
 template<class _Tp> inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
@@ -183,6 +221,23 @@ template<class _Tp, class _Cp> struct __member_object_pointer<_Tp _Cp::*> : nega
 template<class _Tp> using is_member_object_pointer = __member_object_pointer<remove_cv_t<_Tp>>;
 template<class _Tp> inline constexpr bool is_member_object_pointer_v = is_member_object_pointer<_Tp>::value;
 
+template <class _Tp> struct is_scalar : public integral_constant<bool,
+    is_arithmetic<_Tp>::value ||
+    is_member_pointer<_Tp>::value ||
+    is_pointer<_Tp>::value ||
+    is_null_pointer<_Tp>::value ||
+    is_enum<_Tp>::value
+> {};
+template <class _Tp> inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
+
+template <class _Tp> struct is_object : integral_constant<bool,
+    is_scalar<_Tp>::value ||
+    is_array<_Tp>::value ||
+    is_union<_Tp>::value ||
+    is_class<_Tp>::value
+> {};
+template <class _Tp> inline constexpr bool is_object_v = is_object<_Tp>::value;
+
 // const/volatile addition traits:
 template<class _Tp> using add_const = conditional<disjunction_v<is_reference<_Tp>, is_function<_Tp>, is_const<_Tp>>,
                                                   _Tp, _Tp const>;

src/libcxx/type_traits.cpp

@@ -481,6 +481,32 @@ C((is_nothrow_move_constructible<test_class>::value));
 C((is_nothrow_move_constructible_v<test_union>));
 C((!is_nothrow_move_constructible<int()>::value));
 
+// test is_signed
+C((std::is_signed_v<void> == false));
+C((std::is_signed_v<void*> == false));
+C((std::is_signed_v<int> == true));
+C((std::is_signed_v<int*> == false));
+C((std::is_signed_v<unsigned int> == false));
+C((std::is_signed_v<unsigned int*> == false));
+C((std::is_signed_v<float> == true));
+C((std::is_signed_v<double> == true));
+C((std::is_signed_v<  signed __int48> == true));
+C((std::is_signed_v<unsigned __int48> == false));
+C((std::is_signed_v<bool> == false));
+
+// test is_unsigned
+C((std::is_unsigned_v<void> == false));
+C((std::is_unsigned_v<void*> == false));
+C((std::is_unsigned_v<int> == false));
+C((std::is_unsigned_v<int*> == false));
+C((std::is_unsigned_v<unsigned int> == true));
+C((std::is_unsigned_v<unsigned int*> == false));
+C((std::is_unsigned_v<float> == false));
+C((std::is_unsigned_v<double> == false));
+C((std::is_unsigned_v<  signed __int48> == false));
+C((std::is_unsigned_v<unsigned __int48> == true));
+C((std::is_unsigned_v<bool> == true));
+
 #undef C
 
 } // namespace