[gcc/devel/c++-coroutines] libstdc++: Simplify constraints on std::compare_three_way

Iain D Sandoe iains@gcc.gnu.org
Wed Jan 29 20:42:00 GMT 2020


https://gcc.gnu.org/g:f214ffb336d582a66149068a2a96b7fcf395b5de

commit f214ffb336d582a66149068a2a96b7fcf395b5de
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jan 29 13:56:49 2020 +0000

    libstdc++: Simplify constraints on std::compare_three_way
    
    The __3way_builtin_ptr_cmp concept can use three_way_comparable_with to
    check whether <=> is valid. Doing that makes it obvious that the
    disjunction on compare_three_way::operator() is redundant, because
    the second constraint subsumes the first.
    
    The workaround for PR c++/91073 can also be removed as that bug is fixed
    now.
    
    	* libsupc++/compare (__detail::__3way_builtin_ptr_cmp): Use
    	three_way_comparable_with.
    	(__detail::__3way_cmp_with): Remove workaround for fixed bug.
    	(compare_three_way::operator()): Remove redundant constraint from
    	requires-clause.
    	(__detail::_Synth3way::operator()): Use three_way_comparable_with
    	instead of workaround.
    	* testsuite/18_support/comparisons/object/93479.cc: Prune extra
    	output due to simplified constraints on compare_three_way::operator().

Diff:
---
 libstdc++-v3/ChangeLog                                       | 10 ++++++++++
 libstdc++-v3/libsupc++/compare                               | 12 +++---------
 .../testsuite/18_support/comparisons/object/93479.cc         |  2 ++
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 2c3d33e..e9a8a67 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,15 @@
 2020-01-29  Jonathan Wakely  <jwakely@redhat.com>
 
+	* libsupc++/compare (__detail::__3way_builtin_ptr_cmp): Use
+	three_way_comparable_with.
+	(__detail::__3way_cmp_with): Remove workaround for fixed bug.
+	(compare_three_way::operator()): Remove redundant constraint from
+	requires-clause.
+	(__detail::_Synth3way::operator()): Use three_way_comparable_with
+	instead of workaround.
+	* testsuite/18_support/comparisons/object/93479.cc: Prune extra
+	output due to simplified constraints on compare_three_way::operator().
+
 	PR libstdc++/93479
 	* libsupc++/compare (__3way_builtin_ptr_cmp): Require <=> to be valid.
 	* testsuite/18_support/comparisons/object/93479.cc: New test.
diff --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index aabd0c5..a7a29ef 100644
--- a/libstdc++-v3/libsupc++/compare
+++ b/libstdc++-v3/libsupc++/compare
@@ -525,26 +525,20 @@ namespace std
     // BUILTIN-PTR-THREE-WAY(T, U)
     template<typename _Tp, typename _Up>
       concept __3way_builtin_ptr_cmp
-	= requires(_Tp&& __t, _Up&& __u)
-	    { static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u); }
+	= three_way_comparable_with<_Tp, _Up>
 	  && convertible_to<_Tp, const volatile void*>
 	  && convertible_to<_Up, const volatile void*>
 	  && ! requires(_Tp&& __t, _Up&& __u)
 	     { operator<=>(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); }
 	  && ! requires(_Tp&& __t, _Up&& __u)
 	     { static_cast<_Tp&&>(__t).operator<=>(static_cast<_Up&&>(__u)); };
-
-    // FIXME: workaround for PR c++/91073
-    template<typename _Tp, typename _Up>
-      concept __3way_cmp_with = three_way_comparable_with<_Tp, _Up>;
   } // namespace __detail
 
   // [cmp.object], typename compare_three_way
   struct compare_three_way
   {
     template<typename _Tp, typename _Up>
-      requires (__detail::__3way_cmp_with<_Tp, _Up>
-	  || __detail::__3way_builtin_ptr_cmp<_Tp, _Up>)
+      requires three_way_comparable_with<_Tp, _Up>
       constexpr auto
       operator()(_Tp&& __t, _Up&& __u) const noexcept
       {
@@ -919,7 +913,7 @@ namespace std
 	  { __u < __t } -> convertible_to<bool>;
 	}
 	{
-	  if constexpr (__3way_cmp_with<_Tp, _Up>)
+	  if constexpr (three_way_comparable_with<_Tp, _Up>)
 	    return __t <=> __u;
 	  else
 	    {
diff --git a/libstdc++-v3/testsuite/18_support/comparisons/object/93479.cc b/libstdc++-v3/testsuite/18_support/comparisons/object/93479.cc
index 7da1df1..f4f0a36 100644
--- a/libstdc++-v3/testsuite/18_support/comparisons/object/93479.cc
+++ b/libstdc++-v3/testsuite/18_support/comparisons/object/93479.cc
@@ -42,3 +42,5 @@ test02()
   std::compare_three_way{}(x, ""); // { dg-error "no match" }
   std::compare_three_way{}("", x); // { dg-error "no match" }
 }
+
+// { dg-prune-output "in requirements with" }



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