On Wed, 27 May 2026 at 17:22, Patrick Palka <[email protected]> wrote:
>
> Changes in v2:
>
> - Bump FTM as per the paper
> - Fix invariant preservation of flat_meow::swap in case of exception
> - Use ranges::swap instead of ADL swap in flat_set::swap
> - Make flat_meow::swap swap the comparator last
> - Add missing flat_set::insert_range(sorted_foo_t, Rg&&) overload
> - Clean up test, check .empty() alongside .keys().empty() and
> .values.empty(), and don't bother doing .extract().
>
> -- >8 --
>
> This implements the changes in sections 5, 6 and 8 of P3567R2; the
> changes in section 4 and 7 are already effectively implemented.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/version.def (flat_map): Bump to 202511.
> (flat_set): Likewise.
> * include/bits/version.h: Regenerate.
> * include/std/flat_map (_Flat_map_impl): Remove
> is_nothrow_swappable_v assertions.
> (_Flat_map_impl::_Flat_map_impl): Explicitly default copy ctor.
> Define move ctor with corrected exception handling as per
> P3567R2.
> (_Flat_map_impl::operator=): Likewise.
> (_Flat_map_impl::insert_range): Define new __sorted_t overload
> as per P3567R2.
> (_Flat_map_impl::swap): Make conditionally noexcept as per
> P3567R2.
> * include/std/flat_set (_Flat_set_impl): Remove
> is_nothrow_swappable_v assertion.
> (_Flat_set_impl::_Flat_set_impl): Explicitly default copy ctor.
> Define move ctor with correct invariant preserving behavior as
> per P3567R2.
> (_Flat_set_impl::operator=): Likewise.
> (_Flat_set_impl::_M_insert_range): Factored out from
> insert_range. Add bool parameter __is_sorted defaulted to
> false.
> (_Flat_set_impl::insert_range): Define new __sorted_t overload
> as per P3567R2.
> (_Flat_set_impl::swap): Make conditionally noexcept as per
> P3567R2. Correct to use ranges::swap instead of ADL swap.
> * libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> (test11, test12): New tests.
> * libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> (test10, test11): New tests.
> * libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
> (test10, test11): New tests.
> * libstdc++-v3/testsuite/23_containers/flat_set/1.cc
> (test10, test11): New tests.
> ---
> libstdc++-v3/include/bits/version.def | 4 +-
> libstdc++-v3/include/bits/version.h | 8 +-
> libstdc++-v3/include/std/flat_map | 55 +++++++++-
> libstdc++-v3/include/std/flat_set | 70 ++++++++++--
> .../testsuite/23_containers/flat_map/1.cc | 103 +++++++++++++++++-
> .../23_containers/flat_multimap/1.cc | 101 +++++++++++++++++
> .../23_containers/flat_multiset/1.cc | 94 ++++++++++++++++
> .../testsuite/23_containers/flat_set/1.cc | 96 +++++++++++++++-
> 8 files changed, 508 insertions(+), 23 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/version.def
> b/libstdc++-v3/include/bits/version.def
> index 2f32a8bda98f..5d795151ec67 100644
> --- a/libstdc++-v3/include/bits/version.def
> +++ b/libstdc++-v3/include/bits/version.def
> @@ -1899,7 +1899,7 @@ ftms = {
> ftms = {
> name = flat_map;
> values = {
> - v = 202207;
> + v = 202511;
> cxxmin = 23;
> };
> };
> @@ -1907,7 +1907,7 @@ ftms = {
> ftms = {
> name = flat_set;
> values = {
> - v = 202207;
> + v = 202511;
> cxxmin = 23;
> };
> };
> diff --git a/libstdc++-v3/include/bits/version.h
> b/libstdc++-v3/include/bits/version.h
> index 517b9020ec65..c31893e34c4e 100644
> --- a/libstdc++-v3/include/bits/version.h
> +++ b/libstdc++-v3/include/bits/version.h
> @@ -2108,9 +2108,9 @@
>
> #if !defined(__cpp_lib_flat_map)
> # if (__cplusplus >= 202100L)
> -# define __glibcxx_flat_map 202207L
> +# define __glibcxx_flat_map 202511L
> # if defined(__glibcxx_want_all) || defined(__glibcxx_want_flat_map)
> -# define __cpp_lib_flat_map 202207L
> +# define __cpp_lib_flat_map 202511L
> # endif
> # endif
> #endif /* !defined(__cpp_lib_flat_map) */
> @@ -2118,9 +2118,9 @@
>
> #if !defined(__cpp_lib_flat_set)
> # if (__cplusplus >= 202100L)
> -# define __glibcxx_flat_set 202207L
> +# define __glibcxx_flat_set 202511L
> # if defined(__glibcxx_want_all) || defined(__glibcxx_want_flat_set)
> -# define __cpp_lib_flat_set 202207L
> +# define __cpp_lib_flat_set 202511L
> # endif
> # endif
> #endif /* !defined(__cpp_lib_flat_set) */
> diff --git a/libstdc++-v3/include/std/flat_map
> b/libstdc++-v3/include/std/flat_map
> index a51c6625d54a..18b2d24bb1f3 100644
> --- a/libstdc++-v3/include/std/flat_map
> +++ b/libstdc++-v3/include/std/flat_map
> @@ -74,9 +74,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> static_assert(is_same_v<_Key, typename _KeyContainer::value_type>);
> static_assert(is_same_v<_Tp, typename _MappedContainer::value_type>);
>
> - static_assert(is_nothrow_swappable_v<_KeyContainer>);
> - static_assert(is_nothrow_swappable_v<_MappedContainer>);
> -
> using _Derived = __conditional_t<_Multi,
> flat_multimap<_Key, _Tp, _Compare,
> _KeyContainer,
> _MappedContainer>,
> @@ -395,6 +392,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> : _Flat_map_impl(__s, __il.begin(), __il.end(), __comp, __a)
> { }
>
> + _Flat_map_impl(const _Flat_map_impl&) = default;
> + _Flat_map_impl& operator=(const _Flat_map_impl&) = default;
> +
> + _GLIBCXX26_CONSTEXPR
> + _Flat_map_impl(_Flat_map_impl&& __other)
> + noexcept(is_nothrow_move_constructible_v<containers>
> + && is_nothrow_move_constructible_v<key_compare>)
> + try
> + : _M_cont(std::move(__other._M_cont)),
> _M_comp(std::move(__other._M_comp))
> + {
> + __other.clear();
> + }
> + catch (...)
> + {
> + __other.clear();
> + throw;
This re-throw is redundant, but if it's here for clarity (not
everybody is familiar with function-try-blocks) that's fine.
But what happens if this is compiled with -fno-exceptions? The 'try'
and 'catch' and 'throw' keywords are ill-formed in that case.
It could be made to work by delegating to a new constructor that takes
a _ClearGuard rvalue:
_GLIBCXX26_CONSTEXPR
_Flat_map_impl(_Flat_map_impl&& __other)
noexcept(is_nothrow_move_constructible_v<containers>
&& is_nothrow_move_constructible_v<key_compare>)
: _Flat_map_impl(_ClearGuard{__other._M_cont})
{ }
_GLIBCXX26_CONSTEXPR
_Flat_map_impl(_ClearGuard __g)
/* don't bother repeating noexcept? */
: _M_cont(std::move(*__g._M_cont))
{ }
This will automatically clear __other when the prvalue is destroyed,
whether that's via an exception or not.
Alternatively, you could use #if __cpp_exceptions in the move ctor.
> +
> + _GLIBCXX26_CONSTEXPR
> + _Flat_map_impl&
> + operator=(_Flat_map_impl&& __other)
> + noexcept(is_nothrow_move_assignable_v<containers>
> + && is_nothrow_move_assignable_v<key_compare>)
> + {
> + auto __guard = _M_make_clear_guard();
> + auto __guard_other = _ClearGuard{__other._M_cont};
> + _M_cont = std::move(__other._M_cont);
> + _M_comp = std::move(__other._M_comp);
> + __guard._M_disable();
> + // __guard_other._M_disable is deliberately not called.
> + return *this;
> + }
> +
> _GLIBCXX26_CONSTEXPR
> _Derived&
> operator=(initializer_list<value_type> __il)
> @@ -644,6 +674,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> insert_range(_Rg&& __rg)
> { _M_insert(ranges::begin(__rg), ranges::end(__rg)); }
>
> + template<__detail::__container_compatible_range<value_type> _Rg>
> + _GLIBCXX26_CONSTEXPR
> + void
> + insert_range(__sorted_t, _Rg&& __rg)
> + { _M_insert(ranges::begin(__rg), ranges::end(__rg), true); }
> +
> _GLIBCXX26_CONSTEXPR
> void
> insert(initializer_list<value_type> __il)
> @@ -728,11 +764,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
> _GLIBCXX26_CONSTEXPR
> void
> - swap(_Derived& __y) noexcept
> + swap(_Derived& __y)
> + noexcept(is_nothrow_swappable_v<key_container_type>
> + && is_nothrow_swappable_v<mapped_container_type>
> + && is_nothrow_swappable_v<key_compare>)
> {
> - ranges::swap(_M_comp, __y._M_comp);
> + auto __guard = _M_make_clear_guard();
> + auto __guard_y = _ClearGuard{__y._M_cont};
> ranges::swap(_M_cont.keys, __y._M_cont.keys);
> ranges::swap(_M_cont.values, __y._M_cont.values);
> + ranges::swap(_M_comp, __y._M_comp);
> + __guard._M_disable();
> + __guard_y._M_disable();
> }
>
> _GLIBCXX26_CONSTEXPR
> @@ -974,7 +1017,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> }
>
> friend _GLIBCXX26_CONSTEXPR void
> - swap(_Derived& __x, _Derived& __y) noexcept
> + swap(_Derived& __x, _Derived& __y) noexcept(noexcept(__x.swap(__y)))
> { return __x.swap(__y); }
>
> template<typename _Predicate>
> diff --git a/libstdc++-v3/include/std/flat_set
> b/libstdc++-v3/include/std/flat_set
> index 286290896ae0..f583d352875e 100644
> --- a/libstdc++-v3/include/std/flat_set
> +++ b/libstdc++-v3/include/std/flat_set
> @@ -71,7 +71,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> class _Flat_set_impl
> {
> static_assert(is_same_v<_Key, typename _KeyContainer::value_type>);
> - static_assert(is_nothrow_swappable_v<_KeyContainer>);
>
> using _Derived = __conditional_t<_Multi,
> flat_multiset<_Key, _Compare,
> _KeyContainer>,
> @@ -324,6 +323,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> : _Flat_set_impl(__s, __il.begin(), __il.end(), __comp, __a)
> { }
>
> + _Flat_set_impl(const _Flat_set_impl&) = default;
> + _Flat_set_impl& operator=(const _Flat_set_impl&) = default;
> +
> + _GLIBCXX26_CONSTEXPR
> + _Flat_set_impl(_Flat_set_impl&& __other)
> + noexcept(is_nothrow_move_constructible_v<container_type>
> + && is_nothrow_move_constructible_v<key_compare>)
> + try
> + : _M_cont(std::move(__other._M_cont)),
> _M_comp(std::move(__other._M_comp))
> + {
> + __other.clear();
> + }
> + catch (...)
> + {
> + __other.clear();
> + throw;
> + }
> +
> + _GLIBCXX26_CONSTEXPR
> + _Flat_set_impl&
> + operator=(_Flat_set_impl&& __other)
> + noexcept(is_nothrow_move_assignable_v<container_type>
> + && is_nothrow_move_assignable_v<key_compare>)
> + {
> + auto __guard = _M_make_clear_guard();
> + auto __guard_other = _ClearGuard{__other._M_cont};
> + _M_cont = std::move(__other._M_cont);
> + _M_comp = std::move(__other._M_comp);
> + __guard._M_disable();
> + // __guard_other._M_disable is deliberately not called.
> + return *this;
> + }
> +
> _GLIBCXX26_CONSTEXPR
> _Derived&
> operator=(initializer_list<value_type> __il)
> @@ -540,10 +572,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> __guard._M_disable();
> }
>
> - template<__detail::__container_compatible_range<value_type> _Rg>
> + template<typename _Rg>
> _GLIBCXX26_CONSTEXPR
> void
> - insert_range(_Rg&& __rg)
> + _M_insert_range(_Rg&& __rg, bool __is_sorted = false)
> {
> auto __guard = _M_make_clear_guard();
> typename container_type::iterator __it;
> @@ -561,13 +593,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> _M_cont.emplace_back(*__first);
> __it = _M_cont.begin() + __n;
> }
> - std::sort(__it, _M_cont.end(), _M_comp);
> + if (__is_sorted)
> + _GLIBCXX_DEBUG_ASSERT(ranges::is_sorted(_M_cont, _M_comp));
> + else
> + std::sort(__it, _M_cont.end(), _M_comp);
> std::inplace_merge(_M_cont.begin(), __it, _M_cont.end(), _M_comp);
> if constexpr (!_Multi)
> _M_unique();
> __guard._M_disable();
> }
>
> + template<__detail::__container_compatible_range<value_type> _Rg>
> + _GLIBCXX26_CONSTEXPR
> + void
> + insert_range(_Rg&& __rg)
> + { _M_insert_range(std::forward<_Rg>(__rg)); }
> +
> + template<__detail::__container_compatible_range<value_type> _Rg>
> + _GLIBCXX26_CONSTEXPR
> + void
> + insert_range(__sorted_t, _Rg&& __rg)
> + { _M_insert_range(std::forward<_Rg>(__rg), true); }
> +
> _GLIBCXX26_CONSTEXPR
> void
> insert(initializer_list<value_type> __il)
> @@ -628,11 +675,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
> _GLIBCXX26_CONSTEXPR
> void
> - swap(_Derived& __x) noexcept
> + swap(_Derived& __y)
> + noexcept(is_nothrow_swappable_v<container_type>
> + && is_nothrow_swappable_v<key_compare>)
> {
> - using std::swap;
> - swap(_M_cont, __x._M_cont);
> - swap(_M_comp, __x._M_comp);
> + auto __guard = _M_make_clear_guard();
> + auto __guard_y = _ClearGuard{__y._M_cont};
> + ranges::swap(_M_comp, __y._M_comp);
> + ranges::swap(_M_cont, __y._M_cont);
> + __guard._M_disable();
> + __guard_y._M_disable();
> }
>
> _GLIBCXX26_CONSTEXPR
> @@ -830,7 +882,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> }
>
> friend _GLIBCXX26_CONSTEXPR void
> - swap(_Derived& __x, _Derived& __y) noexcept
> + swap(_Derived& __x, _Derived& __y) noexcept(noexcept(__x.swap(__y)))
> { return __x.swap(__y); }
>
> template<typename _Predicate>
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> index 1cb088f511eb..b4d84d30a1ed 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_map/1.cc
> @@ -3,7 +3,7 @@
>
> #include <flat_map>
>
> -#if __cpp_lib_flat_map != 202207L
> +#if __cpp_lib_flat_map != 202511L
> # error "Feature-test macro __cpp_lib_flat_map has wrong value in <flat_map>"
> #endif
>
> @@ -299,6 +299,102 @@ test10()
> VERIFY (k == "world");
> }
>
> +template<typename T>
> +struct throwing_vector : std::vector<T>
> +{
> + static inline bool throw_on_move = false;
> +
> + throwing_vector() = default;
> + throwing_vector(const throwing_vector&) = default;
> + throwing_vector& operator=(const throwing_vector&) = default;
> +
> + throwing_vector(throwing_vector&& other)
> + : std::vector<T>(std::move(other))
> + {
> + if (throw_on_move)
> + throw std::runtime_error("move ctor");
> + }
> +
> + throwing_vector&
> + operator=(throwing_vector&& other)
> + {
> + static_cast<std::vector<T>&>(*this) = std::move(other);
> + if (throw_on_move)
> + throw std::runtime_error("move assign");
> + return *this;
> + }
> +};
> +
> +template<template<typename> class KC, template<typename> class MC>
> +void
> +test11()
> +{
> +#if __cpp_exceptions
> + using flat_map = std::flat_map<int, int, std::less<int>, KC<int>, MC<int>>;
> +
> + auto is_really_empty = [](const flat_map& m) {
> + return m.empty() && m.keys().empty() && m.values().empty();
> + };
> + throwing_vector<int>::throw_on_move = true;
> +
> + // Verify invariant preservation upon throwing move construction.
> + flat_map source;
> + source.insert({{1, 100}, {2, 200}});
> + try
> + {
> + flat_map target(std::move(source));
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( is_really_empty(source) );
> + }
> +
> + // Verify invariant preservation upon throwing move assignment.
> + source.clear();
> + source.insert({{1, 100}, {2, 200}});
> + flat_map target;
> + target.insert({{3, 300}, {4, 400}});
> + try
> + {
> + target = std::move(source);
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( is_really_empty(source) );
> + VERIFY( is_really_empty(target) );
> + }
> +
> + // Verify invariant preservation upon throwing swap.
> + source.clear();
> + source.insert({{1, 100}, {2, 200}});
> + target.clear();
> + target.insert({{3, 300}, {4, 400}});
> + try
> + {
> + source.swap(target);
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( is_really_empty(source) );
> + VERIFY( is_really_empty(target) );
> + }
> +#endif
> +}
> +
> +constexpr
> +void
> +test12()
> +{
> + // Verify usability of flat_map::insert_range(sorted_unique_t, Rg&&).
> + std::flat_map<int, int> m;
> + std::pair<int, int> s[] = {{1, 100}, {2, 200}};
> + m.insert_range(std::sorted_unique, s);
> + VERIFY( std::ranges::equal(m.keys(), (int[]){1, 2}) );
> + VERIFY( std::ranges::equal(m.values(), (int[]){100, 200}) );
> +}
> +
> void
> test()
> {
> @@ -315,6 +411,9 @@ test()
> test08();
> test09();
> test10();
> + test11<std::vector, throwing_vector>();
> + test11<throwing_vector, std::vector>();
> + test12();
> }
>
> constexpr
> @@ -333,6 +432,8 @@ test_constexpr()
> #if __cpp_lib_constexpr_string >= 201907L
> test10();
> #endif
> + // test11() is non-constexpr
> + test12();
> return true;
> }
>
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> index 00644c14061a..0e81ef8b11e9 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_multimap/1.cc
> @@ -252,6 +252,102 @@ test09()
> using value_type = std::pair<int, int>;
> }
>
> +template<typename T>
> +struct throwing_vector : std::vector<T>
> +{
> + static inline bool throw_on_move = false;
> +
> + throwing_vector() = default;
> + throwing_vector(const throwing_vector&) = default;
> + throwing_vector& operator=(const throwing_vector&) = default;
> +
> + throwing_vector(throwing_vector&& other)
> + : std::vector<T>(std::move(other))
> + {
> + if (throw_on_move)
> + throw std::runtime_error("move ctor");
> + }
> +
> + throwing_vector&
> + operator=(throwing_vector&& other)
> + {
> + static_cast<std::vector<T>&>(*this) = std::move(other);
> + if (throw_on_move)
> + throw std::runtime_error("move assign");
> + return *this;
> + }
> +};
> +
> +template<template<typename> class KC, template<typename> class MC>
> +void
> +test10()
> +{
> +#if __cpp_exceptions
> + using flat_multimap = std::flat_multimap<int, int, std::less<int>,
> KC<int>, MC<int>>;
> +
> + auto is_really_empty = [](const flat_multimap& m) {
> + return m.empty() && m.keys().empty() && m.values().empty();
> + };
> + throwing_vector<int>::throw_on_move = true;
> +
> + // Verify invariant preservation upon throwing move construction.
> + flat_multimap source;
> + source.insert({{1, 100}, {2, 200}});
> + try
> + {
> + flat_multimap target(std::move(source));
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( is_really_empty(source) );
> + }
> +
> + // Verify invariant preservation upon throwing move assignment.
> + source.clear();
> + source.insert({{1, 100}, {2, 200}});
> + flat_multimap target;
> + target.insert({{3, 300}, {4, 400}});
> + try
> + {
> + target = std::move(source);
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( is_really_empty(source) );
> + VERIFY( is_really_empty(target) );
> + }
> +
> + // Verify invariant preservation upon throwing swap.
> + source.clear();
> + source.insert({{1, 100}, {2, 200}});
> + target.clear();
> + target.insert({{3, 300}, {4, 400}});
> + try
> + {
> + source.swap(target);
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( is_really_empty(source) );
> + VERIFY( is_really_empty(target) );
> + }
> +#endif
> +}
> +
> +constexpr
> +void
> +test11()
> +{
> + // Verify usability of flat_multimap::insert_range(sorted_equivalent_t,
> Rg&&).
> + std::flat_multimap<int, int> m;
> + std::pair<int, int> s[] = {{1, 100}, {2, 200}};
> + m.insert_range(std::sorted_equivalent, s);
> + VERIFY( std::ranges::equal(m.keys(), (int[]){1, 2}) );
> + VERIFY( std::ranges::equal(m.values(), (int[]){100, 200}) );
> +}
> +
> void
> test()
> {
> @@ -266,6 +362,9 @@ test()
> test06();
> test07();
> test09();
> + test10<std::vector, throwing_vector>();
> + test10<throwing_vector, std::vector>();
> + test11();
> }
>
> constexpr
> @@ -280,6 +379,8 @@ test_constexpr()
> test06();
> test07();
> test09();
> + // test11() is non-constexpr
> + test11();
> return true;
> }
>
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
> index be330fefdd05..a60c74069633 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_multiset/1.cc
> @@ -265,6 +265,96 @@ test09()
> VERIFY( std::ranges::equal(s, (int[]){2,2,4}) );
> }
>
> +template<typename T>
> +struct throwing_vector : std::vector<T>
> +{
> + static inline bool throw_on_move = false;
> +
> + throwing_vector() = default;
> + throwing_vector(const throwing_vector&) = default;
> + throwing_vector& operator=(const throwing_vector&) = default;
> +
> + throwing_vector(throwing_vector&& other)
> + : std::vector<T>(std::move(other))
> + {
> + if (throw_on_move)
> + throw std::runtime_error("move ctor");
> + }
> +
> + throwing_vector&
> + operator=(throwing_vector&& other)
> + {
> + static_cast<std::vector<T>&>(*this) = std::move(other);
> + if (throw_on_move)
> + throw std::runtime_error("move assign");
> + return *this;
> + }
> +};
> +
> +void
> +test10()
> +{
> +#if __cpp_exceptions
> + using flat_multiset = std::flat_multiset<int, std::less<int>,
> throwing_vector<int>>;
> +
> + throwing_vector<int>::throw_on_move = true;
> +
> + // Verify invariant preservation upon throwing move construction.
> + flat_multiset source = {1, 2};
> + try
> + {
> + flat_multiset target(std::move(source));
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( source.empty() );
> + }
> +
> + // Verify invariant preservation upon throwing move assignment.
> + source.clear();
> + source.insert({1, 2});
> + flat_multiset target = {3, 4};
> + try
> + {
> + target = std::move(source);
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( source.empty() );
> + VERIFY( target.empty() );
> + }
> +
> + // Verify invariant preservation upon throwing swap.
> + source.clear();
> + source.insert({1, 2});
> + target.clear();
> + target.insert({3, 4});
> + try
> + {
> + source.swap(target);
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( source.empty() );
> + VERIFY( target.empty() );
> + }
> +#endif
> +}
> +
> +constexpr
> +void
> +test11()
> +{
> + // Verify usability of flat_multiset::insert_range(sorted_equivalent_t,
> Rg&&).
> + std::flat_multiset<int> m;
> + int s[] = {1, 2};
> + m.insert_range(std::sorted_equivalent, s);
> + VERIFY( std::ranges::equal(m, s) );
> +}
> +
> void
> test()
> {
> @@ -278,6 +368,8 @@ test()
> test07();
> test08();
> test09();
> + test10();
> + test11();
> }
>
> constexpr
> @@ -292,6 +384,8 @@ test_constexpr()
> test07();
> test08();
> test09();
> + // test10() is non-constexpr
> + test11();
> return true;
> }
>
> diff --git a/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
> b/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
> index a14d03476e18..16b21f9181ea 100644
> --- a/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
> +++ b/libstdc++-v3/testsuite/23_containers/flat_set/1.cc
> @@ -2,7 +2,7 @@
>
> #include <flat_set>
>
> -#if __cpp_lib_flat_set != 202207L
> +#if __cpp_lib_flat_set != 202511L
> # error "Feature-test macro __cpp_lib_flat_set has wrong value in <flat_set>"
> #endif
>
> @@ -277,6 +277,96 @@ test09()
> VERIFY( std::ranges::equal(s, (int[]){2,4}) );
> }
>
> +template<typename T>
> +struct throwing_vector : std::vector<T>
> +{
> + static inline bool throw_on_move = false;
> +
> + throwing_vector() = default;
> + throwing_vector(const throwing_vector&) = default;
> + throwing_vector& operator=(const throwing_vector&) = default;
> +
> + throwing_vector(throwing_vector&& other)
> + : std::vector<T>(std::move(other))
> + {
> + if (throw_on_move)
> + throw std::runtime_error("move ctor");
> + }
> +
> + throwing_vector&
> + operator=(throwing_vector&& other)
> + {
> + static_cast<std::vector<T>&>(*this) = std::move(other);
> + if (throw_on_move)
> + throw std::runtime_error("move assign");
> + return *this;
> + }
> +};
> +
> +void
> +test10()
> +{
> +#if __cpp_exceptions
> + using flat_set = std::flat_set<int, std::less<int>, throwing_vector<int>>;
> +
> + throwing_vector<int>::throw_on_move = true;
> +
> + // Verify invariant preservation upon throwing move construction.
> + flat_set source = {1, 2};
> + try
> + {
> + flat_set target(std::move(source));
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( source.empty() );
> + }
> +
> + // Verify invariant preservation upon throwing move assignment.
> + source.clear();
> + source.insert({1, 2});
> + flat_set target = {3, 4};
> + try
> + {
> + target = std::move(source);
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( source.empty() );
> + VERIFY( target.empty() );
> + }
> +
> + // Verify invariant preservation upon throwing swap.
> + source.clear();
> + source.insert({1, 2});
> + target.clear();
> + target.insert({3, 4});
> + try
> + {
> + source.swap(target);
> + VERIFY( false );
> + }
> + catch (const std::runtime_error&)
> + {
> + VERIFY( source.empty() );
> + VERIFY( target.empty() );
> + }
> +#endif
> +}
> +
> +constexpr
> +void
> +test11()
> +{
> + // Verify usability of flat_set::insert_range(sorted_unique_t, Rg&&).
> + std::flat_set<int> m;
> + int s[] = {1, 2};
> + m.insert_range(std::sorted_unique, s);
> + VERIFY( std::ranges::equal(m, s) );
> +}
> +
> void
> test()
> {
> @@ -290,6 +380,8 @@ test()
> test07();
> test08();
> test09();
> + test10();
> + test11();
> }
>
> constexpr
> @@ -304,6 +396,8 @@ test_constexpr()
> test07();
> test08();
> test09();
> + // test10() is non-constexpr
> + test11();
> return true;
> }
>
> --
> 2.54.0.rc1.54.g60f07c4f5c
>
