[gcc r13-1138] libstdc++: Apply r13-1096-g6abe341558abec change to vstring too [PR101482]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:51309d1158b85560a975819260776c0ca68fd142

commit r13-1138-g51309d1158b85560a975819260776c0ca68fd142
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jun 16 11:02:11 2022 +0100

    libstdc++: Apply r13-1096-g6abe341558abec change to vstring too [PR101482]
    
    As recently done for std::basic_string, __gnu_cxx::__versa_string
    equality comparisons can check lengths first for any character type and
    traits type, not only for std::char_traits<char>.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/101482
            * include/ext/vstring.h (operator==): Always check lengths
            before comparing.

Diff:
---
 libstdc++-v3/include/ext/vstring.h | 45 +++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 25 deletions(-)

diff --git a/libstdc++-v3/include/ext/vstring.h b/libstdc++-v3/include/ext/vstring.h
index 4406695919d..47cbabf24f1 100644
--- a/libstdc++-v3/include/ext/vstring.h
+++ b/libstdc++-v3/include/ext/vstring.h
@@ -2338,18 +2338,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     operator==(const __versa_string<_CharT, _Traits, _Alloc, _Base>& __lhs,
 	       const __versa_string<_CharT, _Traits, _Alloc, _Base>& __rhs)
-    { return __lhs.compare(__rhs) == 0; }
+    {
+      return __lhs.size() == __rhs.size()
+	       && !_Traits::compare(__lhs.data(), __rhs.data(), __lhs.size());
+    }
 
-  template<typename _CharT,
+  /**
+   *  @brief  Test equivalence of string and C string.
+   *  @param __lhs  String.
+   *  @param __rhs  C string.
+   *  @return  True if @a __lhs.compare(@a __rhs) == 0.  False otherwise.
+   */
+  template<typename _CharT, typename _Traits, typename _Alloc,
 	   template <typename, typename, typename> class _Base>
-    inline typename __enable_if<std::__is_char<_CharT>::__value, bool>::__type
-    operator==(const __versa_string<_CharT, std::char_traits<_CharT>,
-	       std::allocator<_CharT>, _Base>& __lhs,
-	       const __versa_string<_CharT, std::char_traits<_CharT>,
-	       std::allocator<_CharT>, _Base>& __rhs)
-    { return (__lhs.size() == __rhs.size()
-	      && !std::char_traits<_CharT>::compare(__lhs.data(), __rhs.data(),
-						    __lhs.size())); }
+    inline bool
+    operator==(const __versa_string<_CharT, _Traits, _Alloc, _Base>& __lhs,
+	       const _CharT* __rhs)
+    {
+      return __lhs.size() == _Traits::length(__rhs)
+	       && !_Traits::compare(__lhs.data(), __rhs, __lhs.size());
+    }
 
   /**
    *  @brief  Test equivalence of C string and string.
@@ -2362,20 +2370,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     operator==(const _CharT* __lhs,
 	       const __versa_string<_CharT, _Traits, _Alloc, _Base>& __rhs)
-    { return __rhs.compare(__lhs) == 0; }
-
-  /**
-   *  @brief  Test equivalence of string and C string.
-   *  @param __lhs  String.
-   *  @param __rhs  C string.
-   *  @return  True if @a __lhs.compare(@a __rhs) == 0.  False otherwise.
-   */
-  template<typename _CharT, typename _Traits, typename _Alloc,
-	   template <typename, typename, typename> class _Base>
-    inline bool
-    operator==(const __versa_string<_CharT, _Traits, _Alloc, _Base>& __lhs,
-	       const _CharT* __rhs)
-    { return __lhs.compare(__rhs) == 0; }
+    { return __rhs == __lhs; }
 
   // operator !=
   /**
@@ -2402,7 +2397,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     operator!=(const _CharT* __lhs,
 	       const __versa_string<_CharT, _Traits, _Alloc, _Base>& __rhs)
-    { return !(__lhs == __rhs); }
+    { return !(__rhs == __lhs); }
 
   /**
    *  @brief  Test difference of string and C string.