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Implement correct std::variant triviality rules from P0602R4

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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
This commit is contained in:
Jonathan Wakely 2019-04-23 13:48:28 +01:00 • committed by Jonathan Wakely
parent 06715e1cfb
commit 038bc9bfd6
3 changed files with 23 additions and 13 deletions
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9
libstdc++-v3/ChangeLog
View file

@ -1,5 +1,14 @@
2019-04-23 Jonathan Wakely <jwakely@redhat.com>
* 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.
PR libstdc++/90165
* include/std/variant (variant::__not_self): New helper for the
is_same_v<remove_cvref_t<T>, variant>==false constraints.

13
libstdc++-v3/include/std/variant
View file

@ -289,9 +289,11 @@ namespace __variant
static constexpr bool _S_trivial_move_ctor =
(is_trivially_move_constructible_v<_Types> && ...);
static constexpr bool _S_trivial_copy_assign =
_S_trivial_dtor && (is_trivially_copy_assignable_v<_Types> && ...);
_S_trivial_dtor && _S_trivial_copy_ctor
&& (is_trivially_copy_assignable_v<_Types> && ...);
static constexpr bool _S_trivial_move_assign =
_S_trivial_dtor && (is_trivially_move_assignable_v<_Types> && ...);
_S_trivial_dtor && _S_trivial_move_ctor
&& (is_trivially_move_assignable_v<_Types> && ...);
// The following nothrow traits are for non-trivial SMFs. Trivial SMFs
// are always nothrow.
@ -303,7 +305,8 @@ namespace __variant
(is_nothrow_move_constructible_v<_Types> && ...);
static constexpr bool _S_nothrow_copy_assign = false;
static constexpr bool _S_nothrow_move_assign =
_S_nothrow_move_ctor && (is_nothrow_move_assignable_v<_Types> && ...);
_S_nothrow_move_ctor
&& (is_nothrow_move_assignable_v<_Types> && ...);
};
// Defines members and ctors.
@ -654,9 +657,7 @@ namespace __variant
template<typename... _Types>
using _Copy_assign_alias =
_Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign
&& _Traits<_Types...>::_S_trivial_copy_ctor,
_Types...>;
_Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>;
template<bool, typename... _Types>
struct _Move_assign_base : _Copy_assign_alias<_Types...>

14
libstdc++-v3/testsuite/20_util/variant/compile.cc
View file

@ -522,17 +522,17 @@ void test_triviality()
TEST_TEMPLATE(=default, =default, =default, =default, , true, true, true, false)
TEST_TEMPLATE(=default, =default, =default, , =default, true, true, false, true)
TEST_TEMPLATE(=default, =default, =default, , , true, true, false, false)
TEST_TEMPLATE(=default, =default, , =default, =default, true, false, true, true)
TEST_TEMPLATE(=default, =default, , =default, =default, true, false, true, false)
TEST_TEMPLATE(=default, =default, , =default, , true, false, true, false)
TEST_TEMPLATE(=default, =default, , , =default, true, false, false, true)
TEST_TEMPLATE(=default, =default, , , =default, true, false, false, false)
TEST_TEMPLATE(=default, =default, , , , true, false, false, false)
TEST_TEMPLATE(=default, , =default, =default, =default, false, true, false, true)
TEST_TEMPLATE(=default, , =default, =default, , false, true, false, false)
TEST_TEMPLATE(=default, , =default, =default, =default, false, true, false, true)
TEST_TEMPLATE(=default, , =default, =default, , false, true, false, false)
TEST_TEMPLATE(=default, , =default, , =default, false, true, false, true)
TEST_TEMPLATE(=default, , =default, , , false, true, false, false)
TEST_TEMPLATE(=default, , , =default, =default, false, false, false, true)
TEST_TEMPLATE(=default, , , =default, , false, false, false, false)
TEST_TEMPLATE(=default, , , , =default, false, false, false, true)
TEST_TEMPLATE(=default, , , =default, =default, false, false, false, false)
TEST_TEMPLATE(=default, , , =default, , false, false, false, false)
TEST_TEMPLATE(=default, , , , =default, false, false, false, false)
TEST_TEMPLATE(=default, , , , , false, false, false, false)
TEST_TEMPLATE( , =default, =default, =default, =default, false, false, false, false)
TEST_TEMPLATE( , =default, =default, =default, , false, false, false, false)