feedc0de/boost_variant2
1
0
Fork 0
forked from boostorg/variant2
Code Pull Requests Activity

Fix emplace for types with a deleted move constructor (in the not trivially destructible case)

Browse Source
This commit is contained in:
Peter Dimov
2019-04-09 19:22:04 +03:00
parent 9f7e525984
commit 2d6385031e
2 changed files with 59 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

88
include/boost/variant2/variant.hpp
View File

@ -651,7 +651,7 @@ 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&&" );
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;
@ -836,51 +836,61 @@ template<class... T> struct variant_base_impl<false, true, T...>
return st1_.get( mp11::mp_size_t<I+1>() );
}
template<std::size_t J, class U, class... A> void emplace_impl( mp11::mp_int<0>, A&&... a )
{
static_assert( std::is_nothrow_constructible<U, A&&...>::value, "Logic error: U must be nothrow constructible from A&&..." );
_destroy();
st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
template<std::size_t J, class U, class... A> void emplace_impl( mp11::mp_int<1>, A&&... a )
{
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" );
_destroy();
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;
}
}
template<std::size_t J, class U, class... A> void emplace_impl( mp11::mp_int<2>, 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)... );
_destroy();
st1_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
ix_ = J;
}
template<std::size_t I, class... A> void emplace( A&&... a )
{
size_t const J = I+1;
using U = mp11::mp_at_c<variant<T...>, I>;
if( std::is_nothrow_constructible<U, A...>::value )
{
_destroy();
int const D = std::is_nothrow_constructible<U, A&&...>::value? 0: ( can_be_valueless<T...>::value? 1: 2 );
st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
ix_ = J;
}
else if( can_be_valueless<T...>::value )
{
std::size_t const K = valueless_index<T...>::value;
assert( K < sizeof...(T) );
_destroy();
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)... );
_destroy();
st1_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
ix_ = J;
}
this->emplace_impl<J, U>( mp11::mp_int<D>(), std::forward<A>(a)... );
}
};

10
test/variant_emplace_type.cpp
View File

@ -61,6 +61,11 @@ struct Y1
{
};
struct Y2
{
~Y2() {}
};
struct Guard
{
explicit Guard(int) {}
@ -180,5 +185,10 @@ int main()
v.emplace<Guard>( 1 );
}
{
variant<Y2, Guard> v;
v.emplace<Guard>( 1 );
}
return boost::report_errors();
}