On 29/01/20 13:47 +0000, Jonathan Wakely wrote:
--- a/libstdc++-v3/libsupc++/compare
+++ b/libstdc++-v3/libsupc++/compare
@@ -525,7 +525,9 @@ namespace std
// BUILTIN-PTR-THREE-WAY(T, U)
template<typename _Tp, typename _Up>
concept __3way_builtin_ptr_cmp
- = convertible_to<_Tp, const volatile void*>
+ = requires(_Tp&& __t, _Up&& __u)
+ { static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u); }
Doh. This should just use std::threeway_comparable_with, and then
subsumption makes it redundant to use this concept to constrain the
compare_threeway::operator() because we have (A || (A && B)) which is
just (A).
Tested powerpc64le-linux, committed to master.
commit f214ffb336d582a66149068a2a96b7fcf395b5de
Author: Jonathan Wakely <jwak...@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 --git a/libstdc++-v3/libsupc++/compare b/libstdc++-v3/libsupc++/compare
index aabd0c56530..a7a29ef0440 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 7da1df15848..f4f0a36685b 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" }
