std::make_any should be constrained so it can only be called if the
construction of the return value would be valid.
libstdc++-v3/ChangeLog:
PR libstdc++/102894
* include/std/any (make_any): Add SFINAE constraint.
* testsuite/20_util/any/102894.cc: New test.
libstdc++-v3/ChangeLog:
* include/std/ranges (istream_view): Replace this function
template with an alias template as per P2432R1.
(wistream_view): Define as per P2432R1.
(views::_Istream, views::istream): Likewise.
* testsuite/std/ranges/istream_view.cc (test07): New test.
This implements P1739R4 along with the resolution for LWG 3407 which
corrects the paper's wording.
libstdc++-v3/ChangeLog:
* include/bits/ranges_util.h (views::_Drop): Forward declare.
(subrange): Befriend views::_Drop.
(subrange::_S_store_size): Declare constexpr instead of just
const, remove obsolete comment.
* include/std/ranges (views::__detail::__is_empty_view): Define.
(views::__detail::__is_basic_string_view): Likewise.
(views::__detail::__is_subrange): Likewise.
(views::__detail::__is_iota_view): Likewise.
(views::__detail::__can_take_view): Rename template parm _Tp to _Dp.
(views::_Take): Rename template parm _Tp to _Dp, make it non-deducible
and fix it to range_difference_t<_Range>. Implement P1739R4 and
LWG 3407 changes.
(views::__detail::__can_drop_view): Rename template parm _Tp to _Dp.
(views::_Drop): As with views::_Take.
(views::_Counted): Implement P1739R4 changes.
* include/std/span (__detail::__is_std_span): Rename to ...
(__detail::__is_span): ... this and turn it into a variable
template.
(__detail::__is_std_array): Turn it into a variable template.
(span::span): Adjust uses of __is_std_span and __is_std_array
accordingly.
* testsuite/std/ranges/adaptors/p1739.cc: New test.
libstdc++-v3/ChangeLog:
* include/std/ranges (lazy_split_view::base): Add forward_range
constraint as per LWG 3591.
(lazy_split_view::begin, lazy_split_view::end): Also check
simpleness of _Pattern as per LWG 3592.
(split_view::base): Relax copyable constraint as per LWG 3590.
libstdc++-v3/ChangeLog:
* include/std/ranges (join_view::__iter_cat::_S_iter_cat): Adjust
criteria for returning bidirectional_iterator_tag as per LWG 3535.
(join_view::_Iterator::_S_iter_concept): Likewise.
The constraints on transform and and_then can cause errors when checking
satisfaction. The constraints that were present in R6 of the paper were
moved for he final F8 revision, and so should have been included in the
implementation.
libstdc++-v3/ChangeLog:
PR libstdc++/102863
* include/std/optional (optional::and_then, optional::transform):
Remove requires-clause.
* testsuite/20_util/optional/monadic/and_then.cc: Check
overload resolution doesn't cause errors.
* testsuite/20_util/optional/monadic/transform.cc: Likewise.
libstdc++-v3/ChangeLog:
* include/std/ranges (iota_view::_Iterator): Befriend iota_view.
(iota_view::_Sentinel): Likewise.
(iota_view::iota_view): Add three overloads, each taking an
iterator/sentinel pair as per LWG 3523.
* testsuite/std/ranges/iota/iota_view.cc (test06): New test.
This patch also reverts r11-3504 since that workaround is now obsolete
after this resolution.
libstdc++-v3/ChangeLog:
* include/bits/ranges_base.h (view_interface): Forward declare.
(__detail::__is_derived_from_view_interface_fn): Declare.
(__detail::__is_derived_from_view_interface): Define as per LWG 3549.
(enable_view): Adjust as per LWG 3549.
* include/bits/ranges_util.h (view_interface): Don't derive from
view_base.
* include/std/ranges (filter_view): Revert r11-3504 change.
(transform_view): Likewise.
(take_view): Likewise.
(take_while_view): Likewise.
(drop_view): Likewise.
(drop_while_view): Likewise.
(join_view): Likewise.
(lazy_split_view): Likewise.
(split_view): Likewise.
(reverse_view): Likewise.
* testsuite/std/ranges/adaptors/sizeof.cc: Update expected sizes.
* testsuite/std/ranges/view.cc (test_view::test_view): Remove
this default ctor since views no longer need to be default initable.
(test01): New test.
This more clearly expresses the intent (a completely unused, trivial
type) than using char. It's also consistent with the unions in
std::optional.
libstdc++-v3/ChangeLog:
* include/std/variant (_Uninitialized): Use an empty struct
for the unused union member, instead of char.
Another new addition to the C++23 working draft.
The new member functions of std::optional are only defined for C++23,
but the new members of _Optional_payload_base are defined for C++20 so
that they can be used in non-propagating-cache in <ranges>. The
_Optional_payload_base::_M_construct member can also be used in
non-propagating-cache now, because it's constexpr since r12-4389.
There will be an LWG issue about the feature test macro, suggesting that
we should just bump the value of __cpp_lib_optional instead. I haven't
done that here, but it can be changed once consensus is reached on the
change.
libstdc++-v3/ChangeLog:
* include/std/optional (_Optional_payload_base::_Storage): Add
constructor taking a callable function to invoke.
(_Optional_payload_base::_M_apply): New function.
(__cpp_lib_monadic_optional): Define for C++23.
(optional::and_then, optional::transform, optional::or_else):
Define for C++23.
* include/std/ranges (__detail::__cached): Remove.
(__detail::__non_propagating_cache): Remove use of __cached for
contained value. Use _Optional_payload_base::_M_construct and
_Optional_payload_base::_M_apply to set the contained value.
* include/std/version (__cpp_lib_monadic_optional): Define.
* testsuite/20_util/optional/monadic/and_then.cc: New test.
* testsuite/20_util/optional/monadic/or_else.cc: New test.
* testsuite/20_util/optional/monadic/or_else_neg.cc: New test.
* testsuite/20_util/optional/monadic/transform.cc: New test.
* testsuite/20_util/optional/monadic/version.cc: New test.
A recently approved change for the C++23 working draft.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (__cpp_lib_string_resize_and_overwrite):
Define for C++23.
(basic_string::resize_and_overwrite): Declare.
* include/bits/basic_string.tcc (basic_string::resize_and_overwrite):
Define.
* include/std/version (__cpp_lib_resize_and_overwrite): Define
for C++23.
* testsuite/21_strings/basic_string/capacity/char/resize_and_overwrite.cc:
New test.
This implements the changes in P2231R1 which make std::variant fully
constexpr in C++20.
We need to replace placement new with std::construct_at, but that isn't
defined for C++17. Use std::_Construct instead, which forwards to
std::construct_at in C++20 mode (since the related changes to make
std::optional fully constexpr, in r12-4389).
We also need to replace the untyped char buffer in _Uninitialized with a
union, which can be accessed in constexpr functions. But the union needs
to have a non-trivial destructor if its variant type is non-trivial,
which means that the _Variadic_union also needs a non-trivial
destructor. This adds a constrained partial specialization of
_Variadic_union for the C++20-only case where a non-trivial destructor
is needed.
We can't use concepts to constrain the specialization (or the primary
template's destructor) in C++17, so retain the untyped char buffer
solution for C++17 mode.
libstdc++-v3/ChangeLog:
* include/std/variant (__cpp_lib_variant): Update value for
C++20.
(__variant_cast, __variant_construct): Add constexpr for C++20.
(__variant_construct_single, __construct_by_index) Likewise. Use
std::_Construct instead of placement new.
(_Uninitialized<T, false>) [__cplusplus >= 202002]: Replace
buffer with a union and define a destructor.
(_Variadic_union) [__cplusplus >= 202002]: Add a specialization
for non-trivial destruction.
(_Variant_storage::__index_of): New helper variable template.
(_Variant_storage::~_Variant_storage()): Add constexpr.
(_Variant_storage::_M_reset()): Likewise.
(_Copy_ctor_base, _Move_ctor_base): Likewise.
(_Copy_assign_base, _Move_assign_base): Likewise.
(variant, swap): Likewise.
* include/std/version (__cpp_lib_variant): Update value for
C++20.
* testsuite/20_util/optional/version.cc: Check for exact value
in C++17.
* testsuite/20_util/variant/87619.cc: Increase timeout for
C++20 mode.
* testsuite/20_util/variant/constexpr.cc: New test.
* testsuite/20_util/variant/version.cc: New test.
The __variant_construct_by_index helper function sets the new index
before constructing the new object. This means that if the construction
throws then the exception needs to be caught, so the index can be reset
to variant_npos, and then the exception rethrown. This means callers are
responsible for restoring the variant's invariants and they need the
overhead of a catch handler and a rethrow.
If we don't set the index until after construction completes then the
invariant is never broken, and callers can ignore the exception and let
it propagate. The callers all call _M_reset() first, which sets index to
variant_npos as required while the variant is valueless.
We need to be slightly careful here, because changing the order of
operations in __variant_construct_by_index and removing the try-block
from variant::emplace<I> changes an implicit ABI contract between those
two functions. If the linker were to create an executable containing an
instantiation of the old __variant_construct_by_index and an
instantiation of the new variant::emplace<I> code then we would have a
combination that breaks the invariant and doesn't have the exception
handling to restore it. To avoid this problem, we can rename the
__variant_construct_by_index function so that the new emplace<I> code
calls a new symbol, and is unaffected by the behaviour of the old
symbol.
libstdc++-v3/ChangeLog:
* include/std/variant (__detail::__variant::__get_storage):
Remove unused function.
(__variant_construct_by_index): Set index after construction is
complete. Rename to ...
(__detail::__variant::__construct_by_index): ... this.
(variant): Use new name for __variant_construct_by_index friend
declaration. Remove __get_storage friend declaration.
(variant::emplace): Use new name and remove try-blocks.
These functions aren't used, and accessing the storage as a void* isn't
compatible with C++20 constexpr requirements anyway, so we're unlikely
to ever start using them in future.
libstdc++-v3/ChangeLog:
* include/std/variant (_Variant_storage::_M_storage()): Remove.
(__detail::__variant::__get_storage): Remove.
(variant): Remove friend declaration of __get_storage.
libstdc++-v3/ChangeLog:
* include/std/variant (__variant::__get(in_place_index_t<N>, U&&)):
Rename to __get_n and remove first argument. Replace pair of
overloads with a single function using 'if constexpr'.
(__variant::__get(Variant&&)): Adjust to use __get_n.
This implements the changes in P2231R1 which make std::optional fully
constexpr in C++20.
libstdc++-v3/ChangeLog:
* include/bits/stl_construct.h (_Construct): Use
std::construct_at when constant evaluated.
* include/std/optional (_Storage, _Optional_payload, optional):
Add constexpr as specified by P2231R1.
* include/std/version (__cpp_lib_optional): Update value for
C++20.
* testsuite/20_util/optional/requirements.cc: Check feature test
macro.
* testsuite/20_util/optional/constexpr/assign.cc: New test.
* testsuite/20_util/optional/constexpr/cons/conv.cc: New test.
* testsuite/20_util/optional/constexpr/modifiers.cc: New test.
* testsuite/20_util/optional/constexpr/swap.cc: New test.
* testsuite/20_util/optional/version.cc: New test.
The r12-3022 commit only fixed the case where an array is the last
element of the tuple. This fixes the other cases too. We can just define
the move constructor as defaulted, which does the right thing. Changing
the move constructor to be trivial would be an ABI break, but since the
last base class still has a non-trivial move constructor, defining the
derived ones as defaulted doesn't change anything.
libstdc++-v3/ChangeLog:
PR libstdc++/101960
* include/std/tuple (_Tuple_impl(_Tuple_impl&&)): Define as
defauled.
* testsuite/20_util/tuple/cons/101960.cc: Check tuples with
array elements before the last element.
We don't need to have <wchar.h> support in order to delete overloads
for inserting wide characters into narrow streams.
libstdc++-v3/ChangeLog:
PR libstdc++/98725
* include/std/ostream (operator<<(basic_ostream<char, Tr>&, wchar_t))
(operator<<(basic_ostream<char, Tr>&, const wchar_t*)): Always
define as deleted. Do not check _GLIBCXX_USE_WCHAR_T.
None of these traits depend on libc support for wchar_t, so they should
be defined unconditionally. The wchar_t type is always defined in C++.
libstdc++-v3/ChangeLog:
PR libstdc++/98725
* include/c_global/cstddef [!_GLIBCXX_USE_WCHAR_T]
(__byte_operand<wchar_t>): Define specialization.
* include/std/type_traits (__make_signed<wchar_t>)
(__make_unsigned<wchar_t>): Remove redundant check for
__WCHAR_TYPE__ being defined.
* include/tr1/type_traits [!_GLIBCXX_USE_WCHAR_T]
(__is_integral_helper<wchar_t>): Likewise.
The wstring and wstring_view typedefs should be enabled even if
<wchar.h> isn't supported, because char_traits<wchar_t> works
unconditionally. Similarly, the std::hash specializations for wide
strings do not depend on <wchar.h> support.
Although the primary template works OK for std::char_traits<wchar_t> in
the absence of <wchar.h> support, this patch still defines it as an
explicit specialization for compatibility with declarations that expect
it to be specialized. The explicit specialization just uses the same
__gnu_cxx::char_traits base class as the primary template.
libstdc++-v3/ChangeLog:
PR libstdc++/98725
* include/bits/char_traits.h (char_traits<wchar_t>): Define
explicit specialization unconditionally.
* include/bits/basic_string.h (hash<wstring>): Define
unconditionally. Do not check _GLIBCXX_USE_WCHAR_T.
* include/bits/stringfwd.h (wstring): Likewise.
* include/debug/string (wstring): Likewise.
* include/experimental/string_view (experimental::wstring_view)
(hash<experimental::wstring_view>): Likewise.
* include/std/string (pmr::wstring, hash<pmr::wstring>):
Likewise.
* include/std/string_view (wstring_view, hash<wstring_view>):
Likewise.
This is a missing piece of the C++20 <chrono> header.
It would be good to move the code into the compiled library, so that we
don't need <sstream> in <chrono>. It could also use spanstream in C++20,
to avoid memory allocations. That can be changed at a later date.
libstdc++-v3/ChangeLog:
* include/std/chrono (__detail::__units_suffix_misc): New
helper function.
(__detail::__units_suffix): Likewise.
(chrono::operator<<(basic_ostream&, const duration&)): Define.
* testsuite/20_util/duration/io.cc: New test.
This moves the "classic" contents of <chrono> to a new header, so that
<future>, <thread> etc. can get use durations and clocks without
calendar types, time zones, and chrono I/O.
libstdc++-v3/ChangeLog:
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/std/chrono (duration, time_point, system_clock)
(steady_clock, high_resolution_clock, chrono_literals, sys_time)
(file_clock, file_time): Move to ...
* include/bits/chrono.h: New file.
* include/bits/atomic_futex.h: Include new header instead of
<chrono>.
* include/bits/atomic_timed_wait.h: Likewise.
* include/bits/fs_fwd.h: Likewise.
* include/bits/semaphore_base.h: Likewise.
* include/bits/this_thread_sleep.h: Likewise.
* include/bits/unique_lock.h: Likewise.
* include/experimental/bits/fs_fwd.h: Likewise.
* include/experimental/chrono: Likewise.
* include/experimental/io_context: Likewise.
* include/experimental/netfwd: Likewise.
* include/experimental/timer: Likewise.
* include/std/condition_variable: Likewise.
* include/std/mutex: Likewise.
* include/std/shared_mutex: Likewise.
In commit r12-4083 I tried to make the std::erase and std::erase_if
function avoid the unnecessary overhead of safe iterators. It didn't
work, for two reasons. Firstly, for the RB tree containers the
__niter_base function is a no-op (because the iterators aren't
random access) so the safe iterators were still used. Secondly, for the
cases where __niter_base did remove the safe iterator layer, there was
still unnecessary overhead to create a new safe iterator and link it to
the container.
This solves the problem by simply binding a reference to the non-debug
version of the conainer. For normal mode this is a no-op, and for debug
mode it binds a reference to the debug container's base class. That
means the rest of the function operates directly on the non-debug
container, and avoids all checking.
For std::basic_string there's no need to unwrap anything, because we use
std::basic_string directly in debug mode anyway.
libstdc++-v3/ChangeLog:
* include/bits/erase_if.h (__erase_nodes_if): Remove redundant
__niter_base calls.
* include/std/string (erase, erase_if): Likewise.
* include/std/deque (erase, erase_if): Access non-debug
container directly.
* include/std/map (erase, erase_if): Likewise.
* include/std/set (erase, erase_if): Likewise.
* include/std/unordered_map (erase, erase_if): Likewise.
* include/std/unordered_set (erase, erase_if): Likewise.
* include/std/vector (erase, erase_if): Likewise.
* include/experimental/deque (erase, erase_if): Likewise.
* include/experimental/map (erase, erase_if): Likewise.
* include/experimental/set (erase, erase_if): Likewise.
* include/experimental/unordered_map (erase, erase_if):
Likewise.
* include/experimental/unordered_set (erase, erase_if):
Likewise.
* include/experimental/vector (erase, erase_if): Likewise.
libstdc++-v3/ChangeLog:
* include/bits/utility.h (__is_in_place_type_v): Define
variable template to detect in_place_type_t specializations.
(__is_in_place_type): Replace class template with alias
template using __is_in_place_type_v.
* include/std/any (any(T&&)): Check __is_in_place_type first and
avoid instantiating is_copy_constructible unnecessarily.
To avoid needing to export a new symbol from the library (for now) the
new member function uses __attribute__((always_inline)).
libstdc++-v3/ChangeLog:
* include/std/ostream (operator<<(const volatile void*)):
Add new overload, as per P1147R1.
* testsuite/27_io/basic_ostream/inserters_other/char/volatile_ptr.cc:
New test.
I started implementing this feature before it was voted into the C++ WP,
and forgot to update the feature test macro after it was approved.
This defines it to the correct value, as specified in the C++23 draft.
libstdc++-v3/ChangeLog:
* include/bits/stl_queue.h
(__cpp_lib_adaptor_iterator_pair_constructor): Set to correct
value.
* include/bits/stl_stack.h
(__cpp_lib_adaptor_iterator_pair_constructor): Likewise.
* include/std/version
(__cpp_lib_adaptor_iterator_pair_constructor): Likewise.
* testsuite/23_containers/queue/cons_from_iters.cc: Update
expected value.
* testsuite/23_containers/stack/cons_from_iters.cc: Likewise.
Implement this C++23 feature. Because construction from a null pointer
is undefined, we can implement it for C++11 and up, turning undefined
behaviour into a compilation error.
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string(nullptr_t)): Define
as deleted.
(operator=(nullptr_t)): Likewise.
* include/bits/cow_string.h (basic_string(nullptr_t)): Likewise.
(operator=(nullptr_t)): Likewise.
* include/std/string_view (basic_string_view(nullptr_t)):
Likewise.
* testsuite/21_strings/basic_string/cons/char/nullptr.cc: New test.
* testsuite/21_strings/basic_string_view/cons/char/nonnull.cc:
Change dg-warning to dg-error.
* testsuite/21_strings/basic_string_view/cons/wchar_t/nonnull.cc:
Likewise.
This reduces the preprocessed size of <deque>, <string> and <vector> by
not including <bits/stl_algo.h> for std::remove and std::remove_if.
Also unwrap iterators using __niter_base, to avoid redundant debug mode
checks.
PR libstdc++/92546
* include/bits/erase_if.h (__erase_nodes_if): Use __niter_base to
unwrap debug iterators.
* include/bits/refwrap.h: Do not error if included in C++03.
* include/bits/stl_algo.h (__remove_if): Move to ...
* include/bits/stl_algobase.h (__remove_if): ... here.
* include/std/deque (erase, erase_if): Use __remove_if instead of
remove and remove_if.
* include/std/string (erase, erase_if): Likewise.
* include/std/vector (erase, erase_if): Likewise.
This adds a non-standard extension to support initializing a
std::jthread with a pointer to a member function that expects a
stop_token to be added to the arguments. That use case is not supported
by C++20, because the stop_token would get added as the first argument,
which is where the object argument needs to be to invoke a pointer to
member function.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/100612
* include/std/thread (__pmf_expects_stop_token): New variable
template to detect a pointer to member function that needs a
stop_token to be added to the arguments.
(jthread::__S_create): Use __pmf_expects_stop_token.
(jthread::__S_create_pmf): New function.
* testsuite/30_threads/jthread/100612.cc: New test.
This adds a feature that was recently added to the C++23 working draft.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/stl_queue.h
(__cpp_lib_adaptor_iterator_pair_constructor): Define for C++23, as
per P1425R4.
(queue(InputIterator, InputIterator)): Likewise.
(queue(InputIterator, InputIterator, const Alloc&)): Likewise.
* include/bits/stl_stack.h
(__cpp_lib_adaptor_iterator_pair_constructor): Likewise.
(stack(InputIterator, InputIterator)): Likewise.
(stack(InputIterator, InputIterator, const Alloc&)): Likewise.
* include/std/version (__cpp_lib_adaptor_iterator_pair_constructor):
Define.
* testsuite/23_containers/queue/cons_from_iters.cc: New test.
* testsuite/23_containers/stack/cons_from_iters.cc: New test.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/variant (__do_visit): Use variant_npos instead of
literal -1 that requires a narrowing conversion.
This change is inspired by the suggestion in
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1715r0.html
The new std::__conditional_t alias template is functionally equivalent
to std::conditional_t but should be more efficient to compile, due to
only ever instantiating two specializations (std::__conditional<true>
and std::__conditional<false>) rather than a new specialization for
every use of std::conditional.
The new alias template is also available in C++11, unlike the C++14
std::conditional_t alias.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/std/type_traits (__conditional): New class template
for internal uses of std::conditional.
(__conditional_t): New alias template to replace conditional_t.
(__and_, __or_, __result_of_memfun, __result_of_memobj): Use
__conditional_t instead of conditional::type.
* include/bits/atomic_base.h (__atomic_impl::_Diff): Likewise.
* include/bits/hashtable.h (_Hashtable): Likewise.
* include/bits/hashtable_policy.h (_Node_iterator, _Insert_base)
(_Local_iterator): Likewise. Replace typedefs with
using-declarations.
* include/bits/move.h (move_if_noexcept): Use __conditional_t.
* include/bits/parse_numbers.h (_Select_int_base): Likewise.
* include/bits/ptr_traits.h (__make_not_void): Likewise.
* include/bits/ranges_algobase.h (__copy_or_move_backward)
(__copy_or_move): Likewise.
* include/bits/ranges_base.h (borrowed_iterator_t): Likewise.
* include/bits/ranges_util.h (borrowed_subrange_t): Likewise.
* include/bits/regex_compiler.h (_BracketMatcher): Use
__conditional_t. Replace typedefs with using-declarations.
* include/bits/shared_ptr_base.h (__shared_count): Use
__conditional_t.
* include/bits/stl_algobase.h (__copy_move, __copy_move_backward):
Likewise.
* include/bits/stl_iterator.h (__detail::__clamp_iter_cat)
(reverse_iterator::iterator_concept)
(__make_move_if_noexcept_iterator)
(iterator_traits<common_iterator<_It, _Sent>>)
(iterator_traits<counted_iterator<_It>>): Likewise.
* include/bits/stl_pair.h (_PCC, pair::operator=): Likewise.
* include/bits/stl_tree.h (_Rb_tree::insert_return_type)
(_Rb_tree::_M_clone_node): Likewise.
* include/bits/unique_ptr.h (unique_ptr(unique_ptr<U,E>&&)):
Likewise.
* include/bits/uses_allocator.h (__uses_alloc): Likewise.
(__is_uses_allocator_predicate): Likewise.
* include/debug/functions.h (__foreign_iterator_aux2): Likewise.
* include/experimental/any (any::_Manager, __any_caster):
Likewise.
* include/experimental/executor (async_completion): Likewise.
* include/experimental/functional (__boyer_moore_base_t):
Likewise.
* include/std/any (any::_Manager): Likewise.
* include/std/functional (__boyer_moore_base_t): Likewise.
* include/std/ranges (borrowed_iterator_t)
(borrowed_subrange_t, __detail::__maybe_present_t)
(__detail::__maybe_const_t, split_view): Likewise.
* include/std/tuple (__empty_not_final, tuple::operator=):
Likewise.
* include/std/variant (__detail::__variant::__get_t): Likewise.
GCC does not do a good job of optimizing the table of function pointers
used for variant visitation. This avoids using the table for the common
case of visiting a single variant with a small number of alternative
types. Instead we use:
switch(v.index())
{
case 0: return visitor(get<0>(v));
case 1: return visitor(get<1>(v));
...
}
It's not quite that simple, because get<1>(v) is ill-formed if the
variant only has one alternative, and similarly for each get<N>. We
need to ensure each case only applies the visitor if the index is in
range for the actual type we're dealing with, and tell the compiler that
the case is unreachable otherwise. We also need to invoke the visitor
via the __gen_vtable_impl::__visit_invoke function, to handle the raw
visitation cases used to implement std::variant assignments and
comparisons.
Because that gets quite verbose and repetitive, a macro is used to stamp
out the cases.
We also need to handle the valueless_by_exception case, but only for raw
visitation, because std::visit already checks for it before calling
__do_visit.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/78113
* include/std/variant (__do_visit): Use a switch when we have a
single variant with a small number of alternatives.
Implement the changes from P2162R2 (as a DR for C++17).
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/90943
* include/std/variant (__cpp_lib_variant): Update value.
(__detail::__variant::__as): New helpers implementing the
as-variant exposition-only function templates.
(visit, visit<R>): Use __as to upcast the variant parameters.
* include/std/version (__cpp_lib_variant): Update value.
* testsuite/20_util/variant/visit_inherited.cc: New test.
Also rename the test so it actually runs.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/102270
* include/std/tuple (_Tuple_impl): Add constexpr to constructor
missed in previous patch.
* testsuite/20_util/tuple/cons/102270.C: Moved to...
* testsuite/20_util/tuple/cons/102270.cc: ...here.
* testsuite/util/testsuite_allocator.h (SimpleAllocator): Add
constexpr to constructor so it can be used for C++20 tests.
The last missing piece of the C++17 standard library is the hardware
intereference size constants. Much of the delay in implementing these has
been due to uncertainty about what the right values are, and even whether
there is a single constant value that is suitable; the destructive
interference size is intended to be used in structure layout, so program
ABIs will depend on it.
In principle, both of these values should be the same as the target's L1
cache line size. When compiling for a generic target that is intended to
support a range of target CPUs with different cache line sizes, the
constructive size should probably be the minimum size, and the destructive
size the maximum, unless you are constrained by ABI compatibility with
previous code.
From discussion on gcc-patches, I've come to the conclusion that the
solution to the difficulty of choosing stable values is to give up on it,
and instead encourage only uses where ABI stability is unimportant: in
particular, uses where the ABI is shared at most between translation units
built at the same time with the same flags.
To that end, I've added a warning for any use of the constant value of
std::hardware_destructive_interference_size in a header or module export.
Appropriate uses within a project can disable the warning.
A previous iteration of this patch included an -finterference-tune flag to
make the value vary with -mtune; this iteration makes that the default
behavior, which should be appropriate for all reasonable uses of the
variable. The previous default of "stable-ish" seems to me likely to have
been more of an attractive nuisance; since we can't promise actual
stability, we should instead make proper uses more convenient.
JF Bastien's implementation proposal is summarized at
https://github.com/itanium-cxx-abi/cxx-abi/issues/74
I implement this by adding new --params for the two sizes. Targets can
override these values in targetm.target_option.override() to support a range
of values for the generic target; otherwise, both will default to the L1
cache line size.
64 bytes still seems correct for all x86.
I'm not sure why he proposed 64/64 for generic 32-bit ARM, since the Cortex
A9 has a 32-byte cache line, so I'd think 32/64 would make more sense.
He proposed 64/128 for generic AArch64, but since the A64FX now has a 256B
cache line, I've changed that to 64/256.
Other arch maintainers are invited to set ranges for their generic targets
if that seems better than using the default cache line size for both values.
With the above choice to reject stability as a goal, getting these values
"right" is now just a matter of what we want the default optimization to be,
and we can feel free to adjust them as CPUs with different cache lines
become more and less common.
gcc/ChangeLog:
* params.opt: Add destructive-interference-size and
constructive-interference-size.
* doc/invoke.texi: Document them.
* config/aarch64/aarch64.c (aarch64_override_options_internal):
Set them.
* config/arm/arm.c (arm_option_override): Set them.
* config/i386/i386-options.c (ix86_option_override_internal):
Set them.
gcc/c-family/ChangeLog:
* c.opt: Add -Winterference-size.
* c-cppbuiltin.c (cpp_atomic_builtins): Add __GCC_DESTRUCTIVE_SIZE
and __GCC_CONSTRUCTIVE_SIZE.
gcc/cp/ChangeLog:
* constexpr.c (maybe_warn_about_constant_value):
Complain about std::hardware_destructive_interference_size.
(cxx_eval_constant_expression): Call it.
* decl.c (cxx_init_decl_processing): Check
--param *-interference-size values.
libstdc++-v3/ChangeLog:
* include/std/version: Define __cpp_lib_hardware_interference_size.
* libsupc++/new: Define hardware interference size variables.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Winterference.H: New file.
* g++.dg/warn/Winterference.C: New test.
* g++.target/aarch64/interference.C: New test.
* g++.target/arm/interference.C: New test.
* g++.target/i386/interference.C: New test.
For some reason r170217 didn't add compare_exchange_weak to the
__atomic_base<T*> partial specialization, and so weak compare exchange
operations on pointers use compare_exchange_strong instead.
This adds __atomic_base<T*>::compare_exchange_weak and then uses it in
std::atomic<T*>::compare_exchange_weak.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/atomic_base.h (__atomic_base<P*>::compare_exchange_weak):
Add new functions.
* include/std/atomic (atomic<T*>::compare_exchange_weak): Use
it.
P0418R2 removed some preconditions from std::atomic::compare_exchange_*
but we still enforce them via __glibcxx_assert. This removes those
assertions.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR c++/102177
* include/bits/atomic_base.h (__is_valid_cmpexch_failure_order):
New function to check if a memory order is valid for the failure
case of compare exchange operations.
(__atomic_base<I>::compare_exchange_weak): Simplify assertions
by using __is_valid_cmpexch_failure_order.
(__atomic_base<I>::compare_exchange_strong): Likewise.
(__atomic_base<P*>::compare_exchange_weak): Likewise.
(__atomic_base<P*>::compare_exchange_strong): Likewise.
(__atomic_impl::compare_exchange_weak): Add assertion.
(__atomic_impl::compare_exchange_strong): Likewise.
* include/std/atomic (atomic::compare_exchange_weak): Likewise.
(atomic::compare_exchange_strong): Likewise.
