[libc++] Remove generic char_traits implementation

This has been deprecated and should be removed now.

Reviewed By: #libc, Mordante

Spies: Mordante, libcxx-commits

Differential Revision: https://reviews.llvm.org/D157058

Author: philnik777

libcxx/docs/ReleaseNotes/18.rst

@@ -47,22 +47,20 @@ Improvements and New Features
 Deprecations and Removals
 -------------------------
 
+- The base template for ``std::char_traits`` has been removed. If you are using
+  ``std::char_traits`` with types other than ``char``, ``wchar_t``, ``char8_t``,
+  ``char16_t``, ``char32_t`` or a custom character type for which you
+  specialized ``std::char_traits``, your code will no longer work. The Standard
+  does not mandate that a base template is provided, and such a base template is
+  bound to be incorrect for some types, which could previously cause unexpected
+  behavior while going undetected.
 
 Upcoming Deprecations and Removals
 ----------------------------------
 
 LLVM 18
 ~~~~~~~
 
-- The base template for ``std::char_traits`` has been marked as deprecated and
-  will be removed in LLVM 18. If you are using ``std::char_traits`` with types
-  other than ``char``, ``wchar_t``, ``char8_t``, ``char16_t``, ``char32_t`` or
-  a custom character type for which you specialized ``std::char_traits``, your code
-  will stop working when we remove the base template. The Standard does not
-  mandate that a base template is provided, and such a base template is bound
-  to be incorrect for some types, which could currently cause unexpected
-  behavior while going undetected.
-
 - The ``_LIBCPP_AVAILABILITY_CUSTOM_VERBOSE_ABORT_PROVIDED`` macro will not be honored anymore in LLVM 18.
   Please see the updated documentation about the safe libc++ mode and in particular the ``_LIBCPP_VERBOSE_ABORT``
   macro for details.
@@ -79,4 +77,3 @@ ABI Affecting Changes
 
 Build System Changes
 --------------------
-

libcxx/include/__string/char_traits.h

@@ -71,106 +71,6 @@ exposition-only to document what members a char_traits specialization should pro
 };
 */
 
-//
-// Temporary extension to provide a base template for std::char_traits.
-// TODO(LLVM-18): Remove this class.
-//
-template <class _CharT>
-struct _LIBCPP_DEPRECATED_("char_traits<T> for T not equal to char, wchar_t, char8_t, char16_t or char32_t is non-standard and is provided for a temporary period. It will be removed in LLVM 18, so please migrate off of it.")
-    char_traits
-{
-    using char_type  = _CharT;
-    using int_type   = int;
-    using off_type   = streamoff;
-    using pos_type   = streampos;
-    using state_type = mbstate_t;
-
-    static inline void _LIBCPP_CONSTEXPR_SINCE_CXX17 _LIBCPP_HIDE_FROM_ABI
-        assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 < __c2;}
-
-    static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17
-    int compare(const char_type* __s1, const char_type* __s2, size_t __n) {
-        for (; __n; --__n, ++__s1, ++__s2)
-        {
-            if (lt(*__s1, *__s2))
-                return -1;
-            if (lt(*__s2, *__s1))
-                return 1;
-        }
-        return 0;
-    }
-    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
-    size_t length(const char_type* __s) {
-        size_t __len = 0;
-        for (; !eq(*__s, char_type(0)); ++__s)
-            ++__len;
-        return __len;
-    }
-    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_SINCE_CXX17
-    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) {
-        for (; __n; --__n)
-        {
-            if (eq(*__s, __a))
-                return __s;
-            ++__s;
-        }
-        return nullptr;
-    }
-    static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20
-    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) {
-        if (__n == 0) return __s1;
-        char_type* __r = __s1;
-        if (__s1 < __s2)
-        {
-            for (; __n; --__n, ++__s1, ++__s2)
-                assign(*__s1, *__s2);
-        }
-        else if (__s2 < __s1)
-        {
-            __s1 += __n;
-            __s2 += __n;
-            for (; __n; --__n)
-                assign(*--__s1, *--__s2);
-        }
-        return __r;
-    }
-    _LIBCPP_INLINE_VISIBILITY
-    static _LIBCPP_CONSTEXPR_SINCE_CXX20
-    char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) {
-        if (!__libcpp_is_constant_evaluated()) {
-            _LIBCPP_ASSERT_NON_OVERLAPPING_RANGES(
-                __s2 < __s1 || __s2 >= __s1 + __n, "char_traits::copy overlapped range");
-        }
-        char_type* __r = __s1;
-        for (; __n; --__n, ++__s1, ++__s2)
-            assign(*__s1, *__s2);
-        return __r;
-    }
-    _LIBCPP_INLINE_VISIBILITY
-    static _LIBCPP_CONSTEXPR_SINCE_CXX20
-    char_type*       assign(char_type* __s, size_t __n, char_type __a) {
-        char_type* __r = __s;
-        for (; __n; --__n, ++__s)
-            assign(*__s, __a);
-        return __r;
-    }
-
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
-        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
-        {return char_type(__c);}
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int_type  to_int_type(char_type __c) _NOEXCEPT
-        {return int_type(__c);}
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR bool      eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
-        {return int_type(EOF);}
-};
-
 // char_traits<char>
 
 template <>

libcxx/test/libcxx/strings/char.traits/char.traits.specializations/arbitrary_char_type.deprecated.verify.cpp

@@ -412,6 +412,4 @@ void test() {
   test<char8_t>();
   test<char16_t>();
   test<char32_t>();
-
-  test<int>();
 }