Ensure that hash<basic_string> uses char_traits (41876)

[zoecarver]

Summary

This patch ensures that std::hash<basic_string> uses char_traits<_CharT> and not a template parameter _Trait. Resolves 41876.

[mclow.lists]

Other than the skimpy traits implementation, this looks good to me.

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

21

You should put a full traits implementation in here; just to be sure that some other failure isn't masking the one that you want. Just copy the default one from <__string>.

30

You can use expected-error-re to avoid having to spell out the entire error message.
Something like this:
// expected-error-re {{call to implicitly-deleted default constructor of 'std::hash<evil_char_string>' aka {{*}}}}

[zoecarver]

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

21

Will do.

30

Good to know! That would also allow my first implementation to work where I created a function to hide all this in.

[zoecarver]

• copy trait from __string
• update expected-error-re

[mclow.lists]

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

25

these may need std:: qualifications

29

You should get rid of the _LIBCPP_CONSTEXPR_AFTER_CXX14 and _LIBCPP_CONSTEXPR and _LIBCPP_INLINE_VISIBILITY and _NOEXCEPT bits.

[zoecarver]

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

25

See line 17.

29

Will do. I was a bit lazy with copying this in :P

[mclow.lists]

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

25

We don't usually do using namespace std; in our tests.

[zoecarver]

• remove libc++ macros
• stlying

[zoecarver]

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

25

Good to know. I will remove it.

[zoecarver]

• remove using namespace std;

[mclow.lists]

LGTM.

[mclow.lists]

Committed as revision 361201

include/string

 template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator_impl : public true_type {};
 #elif defined(_LIBCPP_HAS_NO_NOEXCEPT)
 template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator_impl : public false_type {};
 #else
 template <class _Iter, bool = __is_forward_iterator<_Iter>::value>
 struct __libcpp_string_gets_noexcept_iterator_impl : public _LIBCPP_BOOL_CONSTANT((
-    noexcept(++(declval<_Iter&>())) && 
-    is_nothrow_assignable<_Iter&, _Iter>::value && 
-    noexcept(declval<_Iter>() == declval<_Iter>()) && 
+    noexcept(++(declval<_Iter&>())) &&
+    is_nothrow_assignable<_Iter&, _Iter>::value &&
+    noexcept(declval<_Iter>() == declval<_Iter>()) &&
     noexcept(*declval<_Iter>())
 )) {};
 
-template <class _Iter> 
+template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator_impl<_Iter, false> : public false_type {};
 #endif
 
 
 template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator
     : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value || __libcpp_string_gets_noexcept_iterator_impl<_Iter>::value) {};
 
#if _LIBCPP_STD_VER > 17
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool ends_with(const value_type* __s) const _NOEXCEPT
     { return ends_with(__self_view(__s)); }
 #endif
 
     _LIBCPP_INLINE_VISIBILITY bool __invariants() const;
 
     _LIBCPP_INLINE_VISIBILITY void __clear_and_shrink() _NOEXCEPT;
-    
     _LIBCPP_INLINE_VISIBILITY
     bool __is_long() const _NOEXCEPT
         {return bool(__r_.first().__s.__size_ & __short_mask);}
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
 
     bool __dereferenceable(const const_iterator* __i) const;
     bool __decrementable(const const_iterator* __i) const;
template<class _CharT,
          class _Allocator = allocator<_CharT>,
          class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
          class _Sz = typename allocator_traits<_Allocator>::size_type
          >
 basic_string(basic_string_view<_CharT, _Traits>, _Sz, _Sz, const _Allocator& = _Allocator())
   -> basic_string<_CharT, _Traits, _Allocator>;
 #endif
 
-                  
 template <class _CharT, class _Traits, class _Allocator>
 inline
 void
 basic_string<_CharT, _Traits, _Allocator>::__invalidate_all_iterators()
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__invalidate_all(this);
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
basic_string<_CharT, _Traits, _Allocator>::__append_forward_unsafe(
     {
         typedef typename iterator_traits<_ForwardIterator>::reference _CharRef;
         _CharRef __tmp_ref = *__first;
         if (__ptr_in_range(_VSTD::addressof(__tmp_ref), data(), data() + size()))
         {
             const basic_string __temp (__first, __last, __alloc());
             append(__temp.data(), __temp.size());
         }
-        else 
+        else
         {
             if (__cap - __sz < __n)
                 __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
             pointer __p = __get_pointer() + __sz;
             for (; __first != __last; ++__p, ++__first)
                 traits_type::assign(*__p, *__first);
             traits_type::assign(*__p, value_type());
             __set_size(__sz + __n);
if (data()[size()] != value_type(0))
         return false;
     return true;
 }
 
 // __clear_and_shrink
 
 template<class _CharT, class _Traits, class _Allocator>
 inline
-void 
+void
 basic_string<_CharT, _Traits, _Allocator>::__clear_and_shrink() _NOEXCEPT
 {
     clear();
     if(__is_long())
     {
         __alloc_traits::deallocate(__alloc(), __get_long_pointer(), capacity() + 1);
         __set_long_cap(0);
         __set_short_size(0);
     }
-} 
+}
 
 // operator==
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
 operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
            const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT

 _LIBCPP_FUNC_VIS wstring to_wstring(float __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(double __val);
 _LIBCPP_FUNC_VIS wstring to_wstring(long double __val);
 
 template<class _CharT, class _Traits, class _Allocator>
     const typename basic_string<_CharT, _Traits, _Allocator>::size_type
                    basic_string<_CharT, _Traits, _Allocator>::npos;
 
-template<class _CharT, class _Traits, class _Allocator>
-struct _LIBCPP_TEMPLATE_VIS hash<basic_string<_CharT, _Traits, _Allocator> >
-    : public unary_function<basic_string<_CharT, _Traits, _Allocator>, size_t>
+template <class _CharT, class _Allocator>
+struct _LIBCPP_TEMPLATE_VIS
+    hash<basic_string<_CharT, char_traits<_CharT>, _Allocator> >
+    : public unary_function<
+          basic_string<_CharT, char_traits<_CharT>, _Allocator>, size_t>
 {
     size_t
-        operator()(const basic_string<_CharT, _Traits, _Allocator>& __val) const _NOEXCEPT;
+    operator()(const basic_string<_CharT, char_traits<_CharT>, _Allocator>& __val) const _NOEXCEPT;
 };
 
-template<class _CharT, class _Traits, class _Allocator>
+
+template<class _CharT, class _Allocator>
 size_t
-hash<basic_string<_CharT, _Traits, _Allocator> >::operator()(
-        const basic_string<_CharT, _Traits, _Allocator>& __val) const _NOEXCEPT
+hash<basic_string<_CharT, char_traits<_CharT>, _Allocator> >::operator()(
+        const basic_string<_CharT, char_traits<_CharT>, _Allocator>& __val) const _NOEXCEPT
 {
     return __do_string_hash(__val.data(), __val.data() + __val.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
            const basic_string<_CharT, _Traits, _Allocator>& __str);
basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const
     return this->data() <= __p && __p < this->data() + this->size();
 }
 
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<wchar_t>)
 
-#if _LIBCPP_STD_VER > 11 
+#if _LIBCPP_STD_VER > 11
 // Literal suffixes for basic_string [basic.string.literals]
 inline namespace literals
 {
   inline namespace string_literals
   {
     inline _LIBCPP_INLINE_VISIBILITY
     basic_string<char> operator "" s( const char *__str, size_t __len )
     {

test/std/strings/basic.string.hash/char_type_hash.fail.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <string>
+
+// Test that hash specializations for <string> require "char_traits<_CharT>" not just any "_Trait".
+
+#include <string>
+
+template <class _CharT>
+struct trait // copied from <__string>
+{
+    typedef _CharT         char_type;
+    typedef int            int_type;
+    typedef std::streamoff off_type;
+    typedef std::streampos pos_type;
+    typedef std::mbstate_t state_type;
+
+    static inline void assign(char_type& __c1, const char_type& __c2) {
+        __c1 = __c2;
+    }
+    static inline bool eq(char_type __c1, char_type __c2) { return __c1 == __c2; }
+    static inline bool lt(char_type __c1, char_type __c2) { return __c1 < __c2; }
+
+    static int compare(const char_type* __s1, const char_type* __s2, size_t __n);
+    static size_t length(const char_type* __s);
+    static const char_type* find(const char_type* __s, size_t __n,
+                                 const char_type& __a);
+
+    static char_type* move(char_type* __s1, const char_type* __s2, size_t __n);
+    static char_type* copy(char_type* __s1, const char_type* __s2, size_t __n);
+    static char_type* assign(char_type* __s, size_t __n, char_type __a);
+
+    static inline int_type not_eof(int_type __c) {
+        return eq_int_type(__c, eof()) ? ~eof() : __c;
+    }
+    static inline char_type to_char_type(int_type __c) { return char_type(__c); }
+    static inline int_type to_int_type(char_type __c) { return int_type(__c); }
+    static inline bool eq_int_type(int_type __c1, int_type __c2) {
+        return __c1 == __c2;
+    }
+    static inline int_type eof() { return int_type(EOF); }
+};
+
+template <class CharT>
+void test() {
+    typedef std::basic_string<CharT, trait<CharT> > str_t;
+    std::hash<str_t>
+        h; // call to implicitly-deleted default constructor of 'std::hash<str_t>' {{*}}}}
+}
+
+int main(int, char**) {
+    test<char>();
+    test<wchar_t>();
+    test<char16_t>();
+    test<char32_t>();
+
+    return 0;
+}