https://gcc.gnu.org/g:9840a1db02cb96011f90b8ee86ca2d23b41781db
commit r16-2242-g9840a1db02cb96011f90b8ee86ca2d23b41781db
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Sun Jul 13 15:34:15 2025 +0100
libstdc++: Add comments to deleted std::swap overloads for LWG 2766
We pre-emptively implemented part of LWG 2766, which still hasn't been
approved. Add comments to the deleted swap overloads saying why they're
there, because the standard doesn't require them.
libstdc++-v3/ChangeLog:
* include/bits/stl_pair.h (swap): Add comment to deleted
overload.
* include/bits/unique_ptr.h (swap): Likewise.
* include/std/array (swap): Likewise.
* include/std/optional (swap): Likewise.
* include/std/tuple (swap): Likewise.
* include/std/variant (swap): Likewise.
* testsuite/23_containers/array/tuple_interface/get_neg.cc:
Adjust dg-error line numbers.
Diff:
---
libstdc++-v3/include/bits/stl_pair.h | 2 ++
libstdc++-v3/include/bits/unique_ptr.h | 2 ++
libstdc++-v3/include/std/array | 2 ++
libstdc++-v3/include/std/optional | 2 ++
libstdc++-v3/include/std/tuple | 4 +++-
libstdc++-v3/include/std/variant | 2 ++
.../testsuite/23_containers/array/tuple_interface/get_neg.cc | 6 +++---
7 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_pair.h
b/libstdc++-v3/include/bits/stl_pair.h
index 8c57712b4617..393f6a016196 100644
--- a/libstdc++-v3/include/bits/stl_pair.h
+++ b/libstdc++-v3/include/bits/stl_pair.h
@@ -1132,6 +1132,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++23
#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2766. Swapping non-swappable types
template<typename _T1, typename _T2>
typename enable_if<!__and_<__is_swappable<_T1>,
__is_swappable<_T2>>::value>::type
diff --git a/libstdc++-v3/include/bits/unique_ptr.h
b/libstdc++-v3/include/bits/unique_ptr.h
index 6ae46a93800c..d76ad63ba7bf 100644
--- a/libstdc++-v3/include/bits/unique_ptr.h
+++ b/libstdc++-v3/include/bits/unique_ptr.h
@@ -832,6 +832,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ __x.swap(__y); }
#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2766. Swapping non-swappable types
template<typename _Tp, typename _Dp>
typename enable_if<!__is_swappable<_Dp>::value>::type
swap(unique_ptr<_Tp, _Dp>&,
diff --git a/libstdc++-v3/include/std/array b/libstdc++-v3/include/std/array
index fdcf0b073762..12f010921db1 100644
--- a/libstdc++-v3/include/std/array
+++ b/libstdc++-v3/include/std/array
@@ -381,6 +381,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ __one.swap(__two); }
#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2766. Swapping non-swappable types
template<typename _Tp, std::size_t _Nm>
__enable_if_t<!__array_traits<_Tp, _Nm>::_Is_swappable::value>
swap(array<_Tp, _Nm>&, array<_Tp, _Nm>&) = delete;
diff --git a/libstdc++-v3/include/std/optional
b/libstdc++-v3/include/std/optional
index cc7af5bbd7d2..e5051d72c828 100644
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -1740,6 +1740,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
noexcept(noexcept(__lhs.swap(__rhs)))
{ __lhs.swap(__rhs); }
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2766. Swapping non-swappable types
template<typename _Tp>
enable_if_t<!(is_move_constructible_v<_Tp> && is_swappable_v<_Tp>)>
swap(optional<_Tp>&, optional<_Tp>&) = delete;
diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index b39ce710984c..2e6499eab22d 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -2835,6 +2835,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ __x.swap(__y); }
#if __cpp_lib_ranges_zip // >= C++23
+ /// Exchange the values of two const tuples (if const elements can be
swapped)
template<typename... _Elements>
requires (is_swappable_v<const _Elements> && ...)
constexpr void
@@ -2844,7 +2845,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++23
#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
- /// Exchange the values of two const tuples (if const elements can be
swapped)
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2766. Swapping non-swappable types
template<typename... _Elements>
_GLIBCXX20_CONSTEXPR
typename enable_if<!__and_<__is_swappable<_Elements>...>::value>::type
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index ec46ff1dabb5..2f44f9700283 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -1387,6 +1387,8 @@ namespace __detail::__variant
noexcept(noexcept(__lhs.swap(__rhs)))
{ __lhs.swap(__rhs); }
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2766. Swapping non-swappable types
template<typename... _Types>
enable_if_t<!((is_move_constructible_v<_Types> && ...)
&& (is_swappable_v<_Types> && ...))>
diff --git
a/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
b/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
index 25511e79941d..e1e9ce9bdac1 100644
--- a/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
@@ -26,6 +26,6 @@ int n1 = std::get<1>(a);
int n2 = std::get<1>(std::move(a));
int n3 = std::get<1>(ca);
-// { dg-error "static assertion failed" "" { target *-*-* } 394 }
-// { dg-error "static assertion failed" "" { target *-*-* } 403 }
-// { dg-error "static assertion failed" "" { target *-*-* } 412 }
+// { dg-error "static assertion failed" "" { target *-*-* } 396 }
+// { dg-error "static assertion failed" "" { target *-*-* } 405 }
+// { dg-error "static assertion failed" "" { target *-*-* } 414 }
