The use of std::optional in _Node_handle makes the node handle types for
associative and unordered containers larger than necessary. It also
greatly increases the amount of code included, as <optional> is quite
large.
The boolean flag that records whether the std::optional contains a value
is redundant, because the _Node_handle::_M_ptr member provides the same
information. If the node handle has a non-null pointer it also has an
allocator, and not otherwise. By replacing std::optional with a custom
union type (and using _M_ptr to tell which union member is active) all
node handle sizes can be reduced by sizeof(allocator_type::pointer).
This makes the node handle types incompatible with previous releases, so
must be done before the C++17 ABI is fixed for GCC 11.
libstdc++-v3/ChangeLog:
* include/bits/node_handle.h (_Node_handle_common): Replace
std::optional with custom type.
* testsuite/20_util/variant/exception_safety.cc: Add missing
header include.
The <new> and <exception> headers each include each other, which makes
building them as header-units "exciting". The <new> header only needs
the definition of std::exception (in order to derive from it) which is
already in its own header, so just include that.
libstdc++-v3/ChangeLog:
* include/bits/stl_iterator.h: Include <bits/exception_defines.h>
for definitions of __try, __catch and __throw_exception_again.
(counted_iterator::operator++(int)): Use __throw_exception_again
instead of throw.
* libsupc++/new: Include <bits/exception.h> not <exception>.
* libsupc++/new_opvnt.cc: Include <bits/exception_defines.h>.
* testsuite/18_support/destroying_delete.cc: Include
<type_traits> for std::is_same_v definition.
* testsuite/20_util/variant/index_type.cc: Qualify size_t.
PR libstdc++/91807
* include/std/variant
(_Copy_assign_base::operator=(const _Copy_assign_base&):
Do the move-assignment from a temporary so that the temporary
is constructed with an explicit index.
* testsuite/20_util/variant/91807.cc: New.
G++ implements P1972R2 since r11-1597-0ca22d027ecc and so we no longer
need the P0608R3 special case to prevent narrowing conversions to bool.
Since non-GNU compilers don't necessarily implment P1972R2 yet, this
may cause a regression for those compilers. There is no feature-test
macro we can use to detect it though, so we'll have to live with it.
libstdc++-v3/ChangeLog:
PR libstdc++/95832
* include/std/variant (__detail::__variant::_Build_FUN): Remove
partial specialization to prevent narrowing conversions to bool.
* testsuite/20_util/variant/compile.cc: Test non-narrowing
conversions to bool.
* testsuite/20_util/variant/run.cc: Likewise.
* testsuite/20_util/variant/compile.cc: Fix narrowing test for ILP32
targets. Add more cases from P0608R3.
* testsuite/20_util/variant/run.cc: Add more cases from P0608R3.
From-SVN: r271325
* include/std/variant (__overload_set): Remove.
(_Arr): New helper.
(_Build_FUN): New class template to define a single FUN overload,
with specializations to prevent unwanted conversions, as per P0608R3.
(_Build_FUNs): New class template to build an overload set of FUN.
(_FUN_type): New alias template to perform overload resolution.
(__accepted_type): Use integer_constant base for failure case. Use
_FUN_type for successful case.
(variant::__accepted_index): Use _Tp instead of _Tp&&.
(variant::variant(_Tp&&)): Likewise.
(variant::operator=(_Tp&&)): Likewise.
From-SVN: r271296
The pmr::string typedef isn't available for the old COW string, so some
tests that use it were failing.
* testsuite/20_util/variant/run.cc: Use a new Hashable type to test
hashing, because pmr::string depends on _GLIBCXX_USE_CXX11_ABI==1.
* testsuite/21_strings/basic_string/hash/hash.cc
[!_GLIBCXX_USE_CXX11_ABI]: Don't test pmr strings.
* testsuite/21_strings/basic_string/hash/hash_char8_t.cc
[!_GLIBCXX_USE_CXX11_ABI]: Likewise.
From-SVN: r270604
* include/std/variant (__variant_construct): Use template parameter
type instead of equivalent decltype-specifier.
(_Move_ctor_base<false, Types...>::_Move_ctor_base(_Move_ctor_base&&)):
Replace forward with move.
(_Move_ctor_base<false, Types...>::_M_destructive_move)
(_Move_ctor_base<false, Types...>::_M_destructive_copy)
(_Move_ctor_base<true, Types...>::_M_destructive_move)
(_Move_ctor_base<true, Types...>::_M_destructive_copy): Only set the
index after construction succeeds.
(_Copy_assign_base<false, Types...>::operator=): Remove redundant
if-constexpr checks that are always true. Use __remove_cvref_t instead
of remove_reference so that is_nothrow_move_constructible check
doesn't use a const rvalue parameter. In the potentially-throwing case
construct a temporary and move assign it, as per LWG 2904.
(_Move_assign_base<false, Types...>::operator=): Remove redundant
if-constexpr checks that are always true. Use emplace as per LWG 2904.
(variant::operator=(T&&)): Only use emplace conditionally, otherwise
construct a temporary and move assign from it, as per LWG 2904.
* testsuite/20_util/variant/exception_safety.cc: Check that
assignment operators have strong exception safety guarantee.
From-SVN: r270525
The std::variant move assignment operator should not be trivial if the
variant is not trivially move constructible.
* include/std/variant (__detail::__variant::_Traits): Make
_S_trivial_copy_assign depend on _S_trivial_copy_ctor and make
_S_trivial_move_assign depend on _S_trivial_move_ctor, as per
P0602R4.
(__detail::__variant::_Copy_assign_alias): Only depend on
_S_trivial_copy_assign, which subsumes _S_trivial_copy_ctor now.
* testsuite/20_util/variant/compile.cc: Correct checks for trivial
move assignment operators.
From-SVN: r270510
Also refactor some constraints slightly to be more readable.
PR libstdc++/90165
* include/std/variant (variant::__not_self): New helper for the
is_same_v<remove_cvref_t<T>, variant>==false constraints.
(variant::__to_type_impl): Remove.
(variant::__to_type): Add default argument to check pack size, instead
of using __to_type_impl.
(variant::__accepted_type): Add default argument using __not_self.
(variant::__is_in_place_tag, variant::__not_in_place_tag): New helpers
for variant(T&&) constructor constraint.
(variant::variant(T&&)): Use __not_in_place_tag in constraints.
Extract __accepted_type into a named template parameter for reuse in
other constraints and in the exception specification.
(variant::variant(in_place_type_t<T>, Args&&...))
(variant::variant(in_place_type_t<T>, initializer_list<U>, Args&&...))
(variant::variant(in_place_index_t<T>, Args&&...))
(variant::variant(in_place_index_t<T>, initializer_list<U>, Args&&...))
(variant::operator=T&&)): Remove redundant && from trait arguments.
* testsuite/20_util/variant/compile.cc: Check variant(T&&) constructor
isn't used for in_place_type or in_place_index arguments.
From-SVN: r270509
A regression was introduced by the recent changes to provide the strong
exception safety guarantee for "never valueless" types that have O(1),
non-throwing move assignment. The problematic code is:
else if constexpr (__detail::__variant::_Never_valueless_alt<type>())
{
// This construction might throw:
variant __tmp(in_place_index<_Np>, __il,
std::forward<_Args>(__args)...);
// But _Never_valueless_alt<type> means this won't:
*this = std::move(__tmp);
}
When the variant is not assignable, the assignment is ill-formed, so
should not be attempted. When the variant has a copy assignment operator
but not a move assignment operator, the assignment performs a copy
assignment and that could throw, so should not be attempted.
The solution is to only take that branch when the variant has a move
assignment operator, which is determined by the _Traits::_S_move_assign
constant. When that is false the strong exception safety guarantee is
not possible, and so the __never_valueless function should also depend
on _S_move_assign.
While testing the fixes for this I noticed that the partial
specialization _Never_valueless_alt<basic_string<C,T,A>> incorrectly
assumed that is_nothrow_move_constructible<basic_string<C,T,A>> is
always true, but that's wrong for fully-dynamic COW strings. Fix the
partial specialization, and improve the comment describing
_Never_valueless_alt to be clear it depends on move construction as well
as move assignment.
Finally, I also observed that _Variant_storage<false, T...>::_M_valid()
was not taking advantage of the __never_valueless<T...>() function to
avoid a runtime check. Only the _Variant_storage<true, T...>::_M_valid()
function was using __never_valueless. That is also fixed.
PR libstdc++/87431
* include/bits/basic_string.h (_Never_valueless_alt): Make partial
specialization also depend on is_nothrow_move_constructible.
* include/std/variant (__detail::__variant::__never_valueless()):
Only true if the variant would have a move assignment operator.
(__detail::__variant::_Variant_storage<false, T...>::_M_valid()):
Check __never_valueless<T...>().
(variant::emplace): Only perform non-throwing move assignments
for never-valueless alternatives if the variant has a move assignment
operator.
* testsuite/20_util/variant/compile.cc: Check that never-valueless
types can be emplaced into non-assignable variants.
* testsuite/20_util/variant/run.cc: Check that never-valueless types
don't get copied when emplaced into non-assignable variants.
From-SVN: r270502
The standard says the std::variant copy constructor is defined as
deleted unless all alternative types are copy constructible, but we were
making it also depend on move constructible. Fix the condition and
enhance the tests to check the semantics with pathological copy-only
types (i.e. supporting copying but having deleted moves).
The enhanced tests revealed a regression in copy assignment for
non-trivial alternative types, where the assignment would not be
performed because the condition in the _Copy_assign_base visitor is
false: is_same_v<remove_reference_t<T&>, remove_reference_t<const T&>>.
* include/std/variant (__detail::__variant::_Traits::_S_copy_assign):
Do not depend on whether all alternative types are move constructible.
(__detail::__variant::_Copy_assign_base::operator=): Remove cv-quals
from the operand when deciding whether to perform the assignment.
* testsuite/20_util/variant/compile.cc (DeletedMoves): Define type
with deleted move constructor and deleted move assignment operator.
(default_ctor, copy_ctor, move_ctor, copy_assign, move_assign): Check
behaviour of variants with DeletedMoves as an alternative.
* testsuite/20_util/variant/run.cc (DeletedMoves): Define same type.
(move_ctor, move_assign): Check that moving a variant with a
DeletedMoves alternative falls back to copying instead of moving.
From-SVN: r270425
The string literal is optional in C++17 and all these are empty so add
no value.
* testsuite/20_util/variant/compile.cc: Remove empty string literals
from static_assert declarations.
From-SVN: r270424
* testsuite/20_util/variant/compile.cc (MoveCtorOnly): Fix type to
actually match its name.
(MoveCtorAndSwapOnly): Define new type that adds swap to MoveCtorOnly.
(test_swap()): Fix result for MoveCtorOnly and check
MoveCtorAndSwapOnly.
From-SVN: r270423
Add a test for the regression introduced with r269422 and fixed with
r270056.
PR libstdc++/89851
* testsuite/20_util/variant/89851.cc: New test.
From-SVN: r270249
* include/std/variant: Adjust whitespace. Add comments.
(_Multi_array): Leave primary template undefined.
(_Multi_array<_Tp>): Define partial specialization for base case of
recursion.
(__gen_vtable_impl, __gen_vtable): Remove redundant && from type
which is always a reference.
(__gen_vtable::_S_apply()): Remove function, inline body into
default member initializer.
* testsuite/20_util/variant/visit.cc: Test with noncopyable types.
From-SVN: r270238
The __visitor_result_type helper didn't use std::invoke and so didn't
compile when the visitor was a pointer-to-member rather than a function
object. Use std::invoke_result instead.
* include/std/variant (__variant_idx_cookie): Add member type.
(__visitor_result_type): Remove.
(__do_visit): Use invoke_result instead of __visitor_result_type.
* testsuite/20_util/variant/visit.cc: New test.
From-SVN: r270237
* include/std/variant (__do_visit): Add a template parameter
for enforcing same return types for visit.
(__gen_vtable_impl): Likewise.
(_S_apply_single_alt): Adjust.
(__visit_invoke_impl): New. Handle casting to void.
(__do_visit_invoke): New. Enforces same return types.
(__do_visit_invoke_r): New. Converts return types.
(__visit_invoke): Adjust.
(__gen_vtable): Add a template parameter for enforcing
same return types for visit.
* testsuite/20_util/variant/visit_r.cc: Add a test for a visitor with
different return types.
* testsuite/20_util/variant/visit_neg.cc: New. Ensures that
visitors with different return types don't accidentally
compile with regular visitation.
From-SVN: r270216
Avoid creating arbitrarily large objects on the stack when emplacing
trivially copyable objects into a variant. Currently we provide the
strong exception-safety guarantee for all trivially copyable types, by
constructing a second variant and then doing a non-throwing move
assignment from the temporary. This patch restricts that behaviour to
trivially copyable types that are no larger than 256 bytes. For larger
types the object will be emplaced directly into the variant, and if its
initialization throws then the variant becomes valueless.
Also implement Antony Polukhin's suggestion to whitelist specific types
that are not trivially copyable but can be efficiently move-assigned.
Emplacing those types will never cause a variant to become valueless.
The whitelisted types are: std::shared_ptr, std::weak_ptr,
std::unique_ptr, std::function, and std::any. Additionally,
std::basic_string, std::vector, and __gnu_debug::vector are whitelisted
if their allocator traits give them a non-throwing move assignment
operator. Specifically, this means std::string is whitelisted, but
std::pmr::string is not.
As part of this patch, additional if-constexpr branches are added for
the cases where the initialization is known to be non-throwing (so the
overhead of the try-catch block can be avoided) and where a scalar is
being produced by a potentially-throwing conversion operator (so that
the overhead of constructing and move-assigning a variant is avoided).
These changes should have no semantic effect, just better codegen.
PR libstdc++/87431 (again)
* include/bits/basic_string.h (__variant::_Never_valueless_alt):
Define partial specialization for basic_string.
* include/bits/shared_ptr.h (_Never_valueless_alt): Likewise for
shared_ptr and weak_ptr.
* include/bits/std_function.h (_Never_valueless_alt): Likewise for
function.
* include/bits/stl_vector.h (_Never_valueless_alt): Likewise for
vector.
* include/bits/unique_ptr.h (_Never_valueless_alt): Likewise for
unique_ptr.
* include/debug/vector (_Never_valueless_alt): Likewise for debug
vector.
* include/std/any (_Never_valueless_alt): Define explicit
specialization for any.
* include/std/variant (_Never_valueless_alt): Define primary template.
(__never_valueless): Use _Never_valueless_alt instead of
is_trivially_copyable.
(variant::emplace<N>(Args&&...)): Add special case for non-throwing
initializations to avoid try-catch overhead. Add special case for
scalars produced by potentially-throwing conversions. Use
_Never_valueless_alt instead of is_trivially_copyable for the
remaining strong exception-safety cases.
(variant::emplace<N>(initializer_list<U>, Args&&...)): Likewise.
* testsuite/20_util/variant/87431.cc: Run both test functions.
* testsuite/20_util/variant/exception_safety.cc: New test.
* testsuite/20_util/variant/run.cc: Use pmr::string instead of string,
so the variant becomes valueless.
From-SVN: r270170
* include/std/variant (__do_visit): New.
(__variant_cast): Likewise.
(__variant_cookie): Likewise.
(__erased_*): Remove.
(_Variant_storage::_S_vtable): Likewise.
(_Variant_storage::__M_reset_impl): Adjust to use __do_visit.
(_Variant_storage::__M_reset): Adjust.
(__variant_construct): New.
(_Copy_ctor_base(const _Copy_ctor_base&)): Adjust to use
__variant_construct.
(_Move_ctor_base(_Move_ctor_base&&)): Likewise.
(_Move_ctor_base::__M_destructive_copy): New.
(_Move_ctor_base::__M_destructive_move): Adjust to use
__variant_construct.
(_Copy_assign_base::operator=): Adjust to use __do_visit.
(_Copy_assign_alias): Adjust to check both copy assignment
and copy construction for triviality.
(_Move_assign_base::operator=): Adjust to use __do_visit.
(_Multi_array): Add support for visitors that accept and return
a __variant_cookie.
(__gen_vtable_impl::_S_apply_all_alts): Likewise.
(__gen_vtable_impl::_S_apply_single_alt): Likewise.
(__gen_vtable_impl::__element_by_index_or_cookie): New. Generate
a __variant_cookie temporary for a variant that is valueless and..
(__gen_vtable_impl::__visit_invoke): ..adjust here.
(__gen_vtable::_Array_type): Conditionally make space for
the __variant_cookie visitor case.
(__variant_construct_by_index): New.
(get_if): Adjust to use std::addressof.
(relops): Adjust to use __do_visit.
(variant): Add __variant_cast and __variant_construct_by_index
as friends.
(variant::emplace): Use _M_reset() and __variant_construct_by_index
instead of self-destruction.
(variant::swap): Adjust to use __do_visit.
(visit): Reimplement in terms of __do_visit.
(__variant_hash_call_base_impl::operator()): Adjust to use __do_visit.
* testsuite/20_util/variant/compile.cc: Adjust.
* testsuite/20_util/variant/run.cc: Likewise.
From-SVN: r269422
The previous patch for PR 87431 assumed that initialing a scalar type
could not throw, but it can obtain its value via a conversion operator,
which could throw. This meant the variant could get into a valueless
state, but the valueless_by_exception() member function would always
return false.
This patch fixes it by changing the emplace members to have strong
exception safety when initializing a contained value of trivially
copyable type. The _M_valid() member gets a corresponding change to
always return true for trivially copyable types, not just scalar types.
Strong exception safety (i.e. never becoming valueless) is achieved by
only replacing the current contained value once any potentially throwing
operations have completed. If constructing the new contained value can
throw then a new std::variant object is constructed to hold it, and then
move-assigned to *this (which won't throw).
PR libstdc++/87431
* include/std/variant (_Variant_storage<true, _Types...>::_M_valid):
Check is_trivially_copyable instead of is_scalar.
(variant::emplace<N, Args>(Args&&...)): If construction of the new
contained value can throw and its type is trivially copyable then
construct into a temporary variant and move from it, to provide the
strong exception safety guarantee.
(variant::emplace<N, U, Args>(initializer_list<U>, Args&&...)):
Likewise.
* testsuite/20_util/variant/87431.cc: New test.
* testsuite/20_util/variant/run.cc: Adjust test so that throwing
conversion causes valueless state.
From-SVN: r267614
PR libstdc++/86874
* include/std/variant (_Copy_ctor_base::_M_destructive_move): Define
here instead of in _Move_assign_base.
(_Copy_ctor_base<true, _Types...>::_M_destructive_move): Define.
(_Copy_assign_base::operator=): Use _M_destructive_move when changing
the contained value to another alternative.
(_Move_assign_base::operator=): Likewise.
(_Move_assign_base::_M_destructive_move): Remove.
* testsuite/20_util/variant/86874.cc: New test.
From-SVN: r263365
2017-07-14 Jason Merrill <jason@redhat.com>
Jonathan Wakely <jwakely@redhat.com>
* include/std/variant (variant::variant(_Tp&&)): Constrain to remove
the constructor for empty variants from the candidate functions
during class template argument deduction.
* testsuite/20_util/variant/deduction.cc: New.
Co-Authored-By: Jonathan Wakely <jwakely@redhat.com>
From-SVN: r250213
PR libstdc++/80187
* include/std/variant (variant::variant, variant::~variant,
variant::operator=): Implement triviality forwarding for four
special member functions.
* testsuite/20_util/variant/compile.cc: Tests.
From-SVN: r249706
Implement LWG 2857, {variant,optional,any}::emplace should
return the constructed value.
* include/std/any (emplace(_Args&&...)): Change the return type and
return a reference to the constructed value.
(emplace(initializer_list<_Up>, _Args&&...)): Likewise.
* include/std/optional (emplace(_Args&&...)): Likewise.
(emplace(initializer_list<_Up>, _Args&&...)): Likewise.
* include/std/variant (emplace<_Tp>(_Args&&...)): Likewise.
(emplace<_Tp>(initializer_list<_Up>, _Args&&...)): Likewise.
(emplace<_Np>(_Args&&...)): Likewise.
(emplace<_Np>(initializer_list<_Up>, _Args&&...)): Likewise.
* testsuite/20_util/any/assign/emplace.cc: Add tests for
checking the return value of emplace.
* testsuite/20_util/any/misc/any_cast_neg.cc: Adjust.
* testsuite/20_util/optional/assignment/6.cc: Add tests for
checking the return value of emplace.
* testsuite/20_util/variant/run.cc: Likewise.
From-SVN: r246182
* include/bits/invoke.h (__invoke): Use __invoke_result instead of
result_of, and __is_nothrow_invocable instead of
__is_nothrow_callable.
* include/bits/shared_ptr_base.h (__shared_ptr): Use __is_invocable
instead of __is_callable.
* include/std/functional (invoke): use invoke_result_t instead of
result_of_t and is_nothrow_invocable instead of is_nothrow_callable.
(_Not_fn): Use __invoke_result instead of result_of.
* include/std/type_traits (__result_of_memobj, __result_of_memfun):
Remove partial specializations for reference_wrapper types.
(__result_of_impl): Use __inv_unwrap to strip reference_wrapper.
(__invoke_result): Define replacement for result_of and then use it to
define result_of.
(__is_callable_impl, __is_callable, __is_nothrow_callable): Replace
with __is_invocable_impl, __is_invocable, and __is_nothrow_invocable
respectively.
(invoke_result, invoke_result_t): Define for C++17.
(is_callable, is_nothrow_callable): Replace with is_invocable,
is_invocable_r, is_nothrow_invocable, and is_nothrow_invocable_r.
(is_callable_v, is_nothrow_callable_v): Replace with is_invocable_v,
is_invocable_r_v, is_nothrow_invocable_v, and is_nothrow_invocable_r_v.
* include/std/variant (hash<variant<T...>>): Use is_nothrow_invocable_v
instead of is_nothrow_callable_v.
* testsuite/20_util/function_objects/invoke/59768.cc: Remove unused
main function.
* testsuite/20_util/function_objects/not_fn/1.cc: Use is_invocable
instead of is_callable.
* testsuite/20_util/is_callable/*: Rename directory and adjust tests
to use new traits.
* testsuite/20_util/is_notjrow_callable/*: Likewise.
* testsuite/20_util/optional/hash.cc: Use is_invocable_v instead of
is_callable.
* testsuite/20_util/variant/hash.cc: Likewise.
From-SVN: r246036
* include/bits/functional_hash.h
(__poison_hash::__enable_hash_call): New.
* include/std/optional (__optional_hash_call_base): New.
(hash<optional<_Tp>>): Derive from the new base,
move the hash function into that base.
* include/std/variant (__variant_hash_call_base_impl): New.
(__variant_hash_call_base): Likewise.
(hash<variant<_Types...>>): Derive from the new base,
move the hash function into that base.
* testsuite/20_util/optional/hash.cc: Add tests for is_callable.
* testsuite/20_util/variant/hash.cc: Likewise.
From-SVN: r244748
Reduce the size of variant, it doesn't need an index of
type size_t internally.
* include/std/variant (parse_numbers.h): New include.
(__select_index): New.
(_Variant_storage<false, _Types...>::_M_reset_impl): Use
_index_type for comparison with variant_npos.
(_Variant_storage<false, _Types...>::__index_type): New.
(_Variant_storage<false, _Types...>::_M_index): Change the
type from size_t to __index_type.
(_Variant_storage<true, _Types...>::__index_type): New.
(_Variant_storage<true, _Types...>::_M_index): Change the
type from size_t to __index_type.
(_Variant_base::_M_valid): Use _Storage::__index_type
for comparison with variant_npos.
(variant::index): Use _Base::_Storage::__index_type
for comparison with variant_npos.
* testsuite/20_util/variant/index_type.cc: New.
From-SVN: r244309
