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
Calling std::get will check some static assertions and also do a runtime
check for a valid index before calling __detail::__variant::__get. The
std::visit function already handles the case where any variant has an
invalid index, so __get can be used directly in __visit_invoke.
* include/std/variant (__gen_vtable_impl::__visit_invoke): Call __get
directly instead of get, as caller ensures correct index is used.
(holds_alternative, get, get_if): Remove redundant inline specifiers.
(_VARIANT_RELATION_FUNCTION_TEMPLATE): Likewise.
From-SVN: r264786
If a std::variant can never get into valueless state then we don't need
to do a runtime check for a valid alternative.
PR libstdc++/87431
* include/std/variant (_Variant_storage<true, _Types...>::_M_valid):
Avoid runtime test when all alternatives are scalars and so cannot
throw during initialization.
From-SVN: r264574
The bug https://bugs.llvm.org/show_bug.cgi?id=33222 is now fixed on
Clang trunk, so the workaround won't be needed for Clang 8.0 and later.
* include/std/variant (variant) [__clang__]: Limit workaround to
Clang 7 and older.
From-SVN: r264271
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
PR libstdc++/79433
* doc/xml/manual/status_cxx2017.xml: Update feature-test macros.
* doc/html/*: Regenerate.
* include/Makefile.am: Remove <bits/c++17_warning.h>.
* include/Makefile.in: Regenerate.
* include/bits/c++17_warning.h: Remove.
* include/bits/string_view.tcc: Do not include <bits/c++17_warning.h>
for pre-C++17 modes.
* include/std/any: Likewise.
(__cpp_lib_any): Define.
* include/std/mutex (__cpp_lib_scoped_lock): Adjust value as per new
SD-6 draft.
* include/std/numeric (__cpp_lib_gcd_lcm): Define as per new SD-6
draft.
* include/std/optional: Do not include <bits/c++17_warning.h>.
(__cpp_lib_optional): Define.
* include/std/shared_mutex: Do not include <bits/c++14_warning.h>.
* include/std/string_view: Do not include <bits/c++17_warning.h>.
(__cpp_lib_string_view): Define.
* include/std/variant: Do not include <bits/c++17_warning.h>.
(__cpp_lib_variant): Define.
* testsuite/20_util/optional/cons/value_neg.cc: Adjust dg-error line
numbers.
* testsuite/26_numerics/gcd/1.cc: Test for __cpp_lib_gcd_lcm.
* testsuite/26_numerics/gcd/gcd_neg.cc: Adjust dg-error line
numbers.
* testsuite/26_numerics/lcm/1.cc: Test for __cpp_lib_gcd_lcm.
* testsuite/26_numerics/lcm/lcm_neg.cc: Adjust dg-error line
numbers.
* testsuite/30_threads/scoped_lock/requirements/typedefs.cc: Adjust
expected value of __cpp_lib_scoped_lock.
From-SVN: r252018
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
* include/std/variant (visit): Make visit constexpr. Also cleanup
__get_alternative and __storage, since we don't support reference/void
alternatives any more.
* testsuite/20_util/variant/compile.cc: Add tests.
From-SVN: r243295
* include/std/variant: Remove variant<T&>, variant<void>, variant<> support
to rebase on the post-Issaquah design.
* testsuite/20_util/variant/compile.cc: Likewise.
From-SVN: r242437
Implement P0504R0 (Revisiting in-place tag types for
any/optional/variant).
* include/std/any (any(_ValueType&& __value)): Constrain
the __is_in_place_type with the decayed type.
(make_any): Adjust to use the new tag type.
* include/std/utility (in_place_tag): Remove.
(in_place_t): Turn into a non-reference tag type.
(__in_place, __in_place_type, __in_place_index): Remove.
(in_place): Turn into an inline variable of non-reference
tag type.
(in_place<_Tp>): Remove.
(in_place_index<_Idx>): Remove.
(in_place_type_t): New.
(in_place_type): Turn into a variable template of non-reference
type.
(in_place_index_t): New.
(in_place_index): Turn into a variable template of non-reference
type.
* include/std/variant
(_Variant_storage(in_place_index_t<_Np>, _Args&&...)): Adjust to
use the new tag type.
(_Union(in_place_index_t<0>, _Args&&...)): Likewise.
(_Union(in_place_index_t<_Np>, _Args&&...)): Likewise.
(_Variant_base()): Likewise.
(variant(_Tp&&)): Likewise.
(variant(in_place_type_t<_Tp>, _Args&&...)): Likewise.
(variant(in_place_type_t<_Tp>, initializer_list<_Up>,
_Args&&...)): Likewise.
(variant(in_place_index_t<_Np>, _Args&&...)): Likewise.
(variant(in_place_index_t<_Np>, initializer_list<_Up>,
_Args&&...)): Likewise
(variant(allocator_arg_t, const _Alloc&)): Likewise.
(variant(allocator_arg_t, const _Alloc&, _Tp&&)): Likewise.
(variant(allocator_arg_t, const _Alloc&, in_place_type_t<_Tp>,
_Args&&...)): Likewise.
(variant(allocator_arg_t, const _Alloc&, in_place_type_t<_Tp>,
initializer_list<_Up>, _Args&&...)): Likewise.
(variant(allocator_arg_t, const _Alloc&, in_place_index_t<_Np>,
_Args&&...)): Likewise.
(variant(allocator_arg_t, const _Alloc&, in_place_index_t<_Np>,
initializer_list<_Up>, _Args&&...)): Likewise.
(emplace(_Args&&...)): Likewise.
(emplace(initializer_list<_Up>, _Args&&...)): Likewise.
* testsuite/20_util/any/cons/explicit.cc: Likewise.
* testsuite/20_util/any/cons/in_place.cc: Likewise.
* testsuite/20_util/any/requirements.cc: Add tests to
check that any is not constructible from the new in_place_type_t
of any value category.
* testsuite/20_util/in_place/requirements.cc: Adjust to
use the new tag type.
* testsuite/20_util/variant/compile.cc: Likewise.
* testsuite/20_util/variant/run.cc: Likewise.
From-SVN: r242401
Jonathan Wakely