Implement signature changes for char_traits in WG21-N2349 (#3739)

Co-authored-by: Stephan T. Lavavej <[email protected]>
microsoft · Jun 15, 2023 · 15aea98 · 15aea98
1 parent 3e00fa3
commit 15aea98
Show file tree

Hide file tree

Showing 4 changed files with 69 additions and 18 deletions.
diff --git a/stl/inc/xstring b/stl/inc/xstring
@@ -190,27 +190,27 @@ struct _Char_traits { // properties of a string or stream element
         }
     }
 
-    _NODISCARD static constexpr bool eq(const _Elem& _Left, const _Elem& _Right) noexcept {
+    _NODISCARD static constexpr bool eq(const _Elem _Left, const _Elem _Right) noexcept {
         return _Left == _Right;
     }
 
-    _NODISCARD static constexpr bool lt(const _Elem& _Left, const _Elem& _Right) noexcept {
+    _NODISCARD static constexpr bool lt(const _Elem _Left, const _Elem _Right) noexcept {
         return _Left < _Right;
     }
 
-    _NODISCARD static constexpr _Elem to_char_type(const int_type& _Meta) noexcept {
+    _NODISCARD static constexpr _Elem to_char_type(const int_type _Meta) noexcept {
         return static_cast<_Elem>(_Meta);
     }
 
-    _NODISCARD static constexpr int_type to_int_type(const _Elem& _Ch) noexcept {
+    _NODISCARD static constexpr int_type to_int_type(const _Elem _Ch) noexcept {
         return static_cast<int_type>(_Ch);
     }
 
-    _NODISCARD static constexpr bool eq_int_type(const int_type& _Left, const int_type& _Right) noexcept {
+    _NODISCARD static constexpr bool eq_int_type(const int_type _Left, const int_type _Right) noexcept {
         return _Left == _Right;
     }
 
-    _NODISCARD static constexpr int_type not_eof(const int_type& _Meta) noexcept {
+    _NODISCARD static constexpr int_type not_eof(const int_type _Meta) noexcept {
         return _Meta != eof() ? _Meta : !eof();
     }
 
@@ -302,27 +302,27 @@ public:
         _Left = _Right;
     }
 
-    _NODISCARD static constexpr bool eq(const _Elem& _Left, const _Elem& _Right) noexcept {
+    _NODISCARD static constexpr bool eq(const _Elem _Left, const _Elem _Right) noexcept {
         return _Left == _Right;
     }
 
-    _NODISCARD static constexpr bool lt(const _Elem& _Left, const _Elem& _Right) noexcept {
+    _NODISCARD static constexpr bool lt(const _Elem _Left, const _Elem _Right) noexcept {
         return _Left < _Right;
     }
 
-    _NODISCARD static constexpr _Elem to_char_type(const int_type& _Meta) noexcept {
+    _NODISCARD static constexpr _Elem to_char_type(const int_type _Meta) noexcept {
         return _Meta;
     }
 
-    _NODISCARD static constexpr int_type to_int_type(const _Elem& _Ch) noexcept {
+    _NODISCARD static constexpr int_type to_int_type(const _Elem _Ch) noexcept {
         return _Ch;
     }
 
-    _NODISCARD static constexpr bool eq_int_type(const int_type& _Left, const int_type& _Right) noexcept {
+    _NODISCARD static constexpr bool eq_int_type(const int_type _Left, const int_type _Right) noexcept {
         return _Left == _Right;
     }
 
-    _NODISCARD static constexpr int_type not_eof(const int_type& _Meta) noexcept {
+    _NODISCARD static constexpr int_type not_eof(const int_type _Meta) noexcept {
         return _Meta != eof() ? _Meta : static_cast<int_type>(!eof());
     }
 
@@ -446,27 +446,27 @@ public:
         _Left = _Right;
     }
 
-    _NODISCARD static constexpr bool eq(const _Elem& _Left, const _Elem& _Right) noexcept {
+    _NODISCARD static constexpr bool eq(const _Elem _Left, const _Elem _Right) noexcept {
         return _Left == _Right;
     }
 
-    _NODISCARD static constexpr bool lt(const _Elem& _Left, const _Elem& _Right) noexcept {
+    _NODISCARD static constexpr bool lt(const _Elem _Left, const _Elem _Right) noexcept {
         return static_cast<unsigned char>(_Left) < static_cast<unsigned char>(_Right);
     }
 
-    _NODISCARD static constexpr _Elem to_char_type(const int_type& _Meta) noexcept {
+    _NODISCARD static constexpr _Elem to_char_type(const int_type _Meta) noexcept {
         return static_cast<_Elem>(_Meta);
     }
 
-    _NODISCARD static constexpr int_type to_int_type(const _Elem& _Ch) noexcept {
+    _NODISCARD static constexpr int_type to_int_type(const _Elem _Ch) noexcept {
         return static_cast<unsigned char>(_Ch);
     }
 
-    _NODISCARD static constexpr bool eq_int_type(const int_type& _Left, const int_type& _Right) noexcept {
+    _NODISCARD static constexpr bool eq_int_type(const int_type _Left, const int_type _Right) noexcept {
         return _Left == _Right;
     }
 
-    _NODISCARD static constexpr int_type not_eof(const int_type& _Meta) noexcept {
+    _NODISCARD static constexpr int_type not_eof(const int_type _Meta) noexcept {
         return _Meta != eof() ? _Meta : !eof();
     }
 

diff --git a/tests/std/test.lst b/tests/std/test.lst
@@ -225,6 +225,7 @@ tests\GH_003246_cmath_narrowing
 tests\GH_003570_allocate_at_least
 tests\GH_003617_vectorized_meow_element
 tests\GH_003676_format_large_hh_mm_ss_values
+tests\GH_003735_char_traits_signatures
 tests\LWG2381_num_get_floating_point
 tests\LWG2597_complex_branch_cut
 tests\LWG3018_shared_ptr_function

diff --git a/tests/std/tests/GH_003735_char_traits_signatures/env.lst b/tests/std/tests/GH_003735_char_traits_signatures/env.lst
@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_matrix.lst
diff --git a/tests/std/tests/GH_003735_char_traits_signatures/test.compile.pass.cpp b/tests/std/tests/GH_003735_char_traits_signatures/test.compile.pass.cpp
@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <cstdint>
+#include <cstdio>
+#include <cwchar>
+#include <string>
+#include <type_traits>
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+using namespace std;
+
+// Also ensure that the member type int_type is correct for standard specializations.
+STATIC_ASSERT(is_same_v<char_traits<char>::int_type, int>);
+#ifdef __cpp_char8_t
+STATIC_ASSERT(is_same_v<char_traits<char8_t>::int_type, unsigned int>);
+#endif // __cpp_char8_t
+STATIC_ASSERT(is_same_v<char_traits<char16_t>::int_type, uint_least16_t>);
+STATIC_ASSERT(is_same_v<char_traits<char32_t>::int_type, uint_least32_t>);
+STATIC_ASSERT(is_same_v<char_traits<wchar_t>::int_type, wint_t>);
+
+template <class CharT>
+void test_n2349_char_traits_signatures() {
+    using IntT = typename char_traits<CharT>::int_type;
+
+    volatile CharT c{};
+    volatile IntT i{};
+
+    (void) char_traits<CharT>::eq(c, c);
+    (void) char_traits<CharT>::lt(c, c);
+    (void) char_traits<CharT>::not_eof(i);
+    (void) char_traits<CharT>::to_char_type(i);
+    (void) char_traits<CharT>::to_int_type(c);
+    (void) char_traits<CharT>::eq_int_type(i, i);
+}
+
+void test_n2349_char_traits_signatures_all() {
+    test_n2349_char_traits_signatures<char>();
+#ifdef __cpp_char8_t
+    test_n2349_char_traits_signatures<char8_t>();
+#endif // __cpp_char8_t
+    test_n2349_char_traits_signatures<char16_t>();
+    test_n2349_char_traits_signatures<char32_t>();
+    test_n2349_char_traits_signatures<wchar_t>();
+}