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Fix emplace for types with a deleted move constructor (in the trivially destructible case)

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This commit is contained in:
Peter Dimov
2019-04-09 18:28:18 +03:00
parent 2e8ae0c796
commit 9f7e525984
2 changed files with 38 additions and 26 deletions
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49
include/boost/variant2/variant.hpp
View File

@ -651,12 +651,16 @@ template<class... T> struct variant_base_impl<true, true, T...>
template<std::size_t J, class U, bool B, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_true, mp11::mp_bool<B>, A&&... a )
{
static_assert( std::is_nothrow_constructible<U, A&&...>::value, "Logic error: U must be nothrow constructible from A&&" );
st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
template<std::size_t J, class U, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_true, A&&... a )
{
static_assert( std::is_nothrow_move_constructible<U>::value, "Logic error: U must be nothrow move constructible" );
U tmp( std::forward<A>(a)... );
st1_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
@ -665,34 +669,24 @@ template<class... T> struct variant_base_impl<true, true, T...>
template<std::size_t J, class U, class... A> void emplace_impl( mp11::mp_false, mp11::mp_false, A&&... a )
{
if( can_be_valueless<T...>::value )
static_assert( can_be_valueless<T...>::value, "Logic error: T... must have a fallback type" );
std::size_t const K = valueless_index<T...>::value;
static_assert( K < sizeof...(T), "Logic error: T... must have a fallback index" );
try
{
std::size_t const K = valueless_index<T...>::value;
assert( K < sizeof...(T) );
try
{
st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
catch( ... )
{
st1_.emplace( mp11::mp_size_t<K+1>() );
ix_ = K+1;
throw;
}
}
else
{
assert( std::is_nothrow_move_constructible<U>::value );
U tmp( std::forward<A>(a)... );
st1_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
catch( ... )
{
st1_.emplace( mp11::mp_size_t<K+1>() );
ix_ = K+1;
throw;
}
}
template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace( A&&... a )
@ -700,7 +694,10 @@ template<class... T> struct variant_base_impl<true, true, T...>
std::size_t const J = I+1;
using U = mp11::mp_at_c<variant<T...>, I>;
this->emplace_impl<J, U>( std::is_nothrow_constructible<U, A&&...>(), mp11::mp_all<detail::is_trivially_move_constructible<U>, detail::is_trivially_move_assignable<T>...>(), std::forward<A>(a)... );
constexpr bool B1 = can_be_valueless<T...>::value;
constexpr bool B2 = mp11::mp_all<detail::is_trivially_move_constructible<U>, detail::is_trivially_move_assignable<T>...>::value;
this->emplace_impl<J, U>( std::is_nothrow_constructible<U, A&&...>(), mp11::mp_bool<B2 || !B1>(), std::forward<A>(a)... );
}
};

15
test/variant_emplace_type.cpp
View File

@ -57,6 +57,16 @@ STATIC_ASSERT( !std::is_nothrow_move_constructible<X2>::value );
STATIC_ASSERT( !std::is_nothrow_copy_assignable<X2>::value );
STATIC_ASSERT( !std::is_nothrow_move_assignable<X2>::value );
struct Y1
{
};
struct Guard
{
explicit Guard(int) {}
Guard(Guard&&) = delete;
};
int main()
{
{
@ -165,5 +175,10 @@ int main()
BOOST_TEST_EQ( get<0>(v).v, 4 );
}
{
variant<Y1, Guard> v;
v.emplace<Guard>( 1 );
}
return boost::report_errors();
}