Tested x86_64-linux.
Since this only affects C++20 and later it seems OK for trunk now.
-- >8 --
I'm only treating this as a DR for C++20 for now, because it's less work
and only requires changes to operator== and operator<=>. To do this for
older standards would require changes to the six relational operators
used pre-C++20.
libstdc++-v3/ChangeLog:
PR libstdc++/113386
* include/bits/stl_pair.h (operator==, operator<=>): Support
heterogeneous comparisons, as per LWG 3865.
* testsuite/20_util/pair/comparison_operators/lwg3865.cc: New
test.
---
libstdc++-v3/include/bits/stl_pair.h | 32 ++++++++++++++-----
.../pair/comparison_operators/lwg3865.cc | 15 +++++++++
2 files changed, 39 insertions(+), 8 deletions(-)
create mode 100644
libstdc++-v3/testsuite/20_util/pair/comparison_operators/lwg3865.cc
diff --git a/libstdc++-v3/include/bits/stl_pair.h
b/libstdc++-v3/include/bits/stl_pair.h
index 4f5c8389fa6..45317417c9c 100644
--- a/libstdc++-v3/include/bits/stl_pair.h
+++ b/libstdc++-v3/include/bits/stl_pair.h
@@ -1000,23 +1000,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _T1, typename _T2> pair(_T1, _T2) -> pair<_T1, _T2>;
#endif
- /// Two pairs of the same type are equal iff their members are equal.
- template<typename _T1, typename _T2>
+#if __cpp_lib_three_way_comparison && __cpp_lib_concepts
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 3865. Sorting a range of pairs
+
+ /// Two pairs are equal iff their members are equal.
+ template<typename _T1, typename _T2, typename _U1, typename _U2>
inline _GLIBCXX_CONSTEXPR bool
- operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
+ operator==(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y)
{ return __x.first == __y.first && __x.second == __y.second; }
-#if __cpp_lib_three_way_comparison && __cpp_lib_concepts
- template<typename _T1, typename _T2>
- constexpr common_comparison_category_t<__detail::__synth3way_t<_T1>,
- __detail::__synth3way_t<_T2>>
- operator<=>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
+ /** Defines a lexicographical order for pairs.
+ *
+ * For two pairs of comparable types, `P` is ordered before `Q` if
+ * `P.first` is less than `Q.first`, or if `P.first` and `Q.first`
+ * are equivalent (neither is less than the other) and `P.second` is
+ * less than `Q.second`.
+ */
+ template<typename _T1, typename _T2, typename _U1, typename _U2>
+ constexpr common_comparison_category_t<__detail::__synth3way_t<_T1, _U1>,
+ __detail::__synth3way_t<_T2, _U2>>
+ operator<=>(const pair<_T1, _T2>& __x, const pair<_U1, _U2>& __y)
{
if (auto __c = __detail::__synth3way(__x.first, __y.first); __c != 0)
return __c;
return __detail::__synth3way(__x.second, __y.second);
}
#else
+ /// Two pairs of the same type are equal iff their members are equal.
+ template<typename _T1, typename _T2>
+ inline _GLIBCXX_CONSTEXPR bool
+ operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
+ { return __x.first == __y.first && __x.second == __y.second; }
+
/** Defines a lexicographical order for pairs.
*
* For two pairs of the same type, `P` is ordered before `Q` if
diff --git
a/libstdc++-v3/testsuite/20_util/pair/comparison_operators/lwg3865.cc
b/libstdc++-v3/testsuite/20_util/pair/comparison_operators/lwg3865.cc
new file mode 100644
index 00000000000..2bbd54af192
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/pair/comparison_operators/lwg3865.cc
@@ -0,0 +1,15 @@
+// { dg-do run { target c++20 } }
+
+// LWG 3865. Sorting a range of pairs
+
+#include <utility>
+#include <testsuite_hooks.h>
+
+int main()
+{
+ std::pair<int, int> p(1, 2);
+ std::pair<int&, int&> p2(p.first, p.second);
+ VERIFY( p == p2 );
+ VERIFY( p <= p2 );
+ VERIFY( p >= p2 );
+}
--
2.44.0
