Tested on Linux-x64.
2017-03-16 Ville Voutilainen <ville.voutilai...@gmail.com>
Implement LWG 2857, {variant,optional,any}::emplace should
return the constructed value.
* include/std/any (any_cast(any*)): Forward-declare.
(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.
diff --git a/libstdc++-v3/include/std/any b/libstdc++-v3/include/std/any
index e807617..fff13d9 100644
--- a/libstdc++-v3/include/std/any
+++ b/libstdc++-v3/include/std/any
@@ -74,6 +74,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* An @c any object's state is either empty or it stores a contained object
* of CopyConstructible type.
*/
+ class any;
+ template<typename _ValueType>
+ inline _ValueType* any_cast(any* __any) noexcept;
+
class any
{
// Holds either pointer to a heap object or the contained object itself.
@@ -268,18 +272,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// Emplace with an object created from @p __args as the contained object.
template <typename _ValueType, typename... _Args>
- typename __any_constructible<void,
+ typename __any_constructible<_Decay<_ValueType>&,
_Decay<_ValueType>, _Args&&...>::type
emplace(_Args&&... __args)
{
__do_emplace<_Decay<_ValueType>>
(std::forward<_Args>(__args)...);
+ return *(std::any_cast<_Decay<_ValueType>>(this));
}
/// Emplace with an object created from @p __il and @p __args as
/// the contained object.
template <typename _ValueType, typename _Up, typename... _Args>
- typename __any_constructible<void,
+ typename __any_constructible<_Decay<_ValueType>&,
_Decay<_ValueType>,
initializer_list<_Up>,
_Args&&...>::type
@@ -287,6 +292,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
__do_emplace<_Decay<_ValueType>, _Up>
(__il, std::forward<_Args>(__args)...);
+ return *(std::any_cast<_Decay<_ValueType>>(this));
}
// modifiers
diff --git a/libstdc++-v3/include/std/optional
b/libstdc++-v3/include/std/optional
index 5e796ac..3f540ec 100644
--- a/libstdc++-v3/include/std/optional
+++ b/libstdc++-v3/include/std/optional
@@ -592,20 +592,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
template<typename... _Args>
- enable_if_t<is_constructible<_Tp, _Args&&...>::value>
+ enable_if_t<is_constructible<_Tp, _Args&&...>::value, _Tp&>
emplace(_Args&&... __args)
{
this->_M_reset();
this->_M_construct(std::forward<_Args>(__args)...);
+ return this->_M_get();
}
template<typename _Up, typename... _Args>
enable_if_t<is_constructible<_Tp, initializer_list<_Up>&,
- _Args&&...>::value>
+ _Args&&...>::value, _Tp&>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
this->_M_reset();
this->_M_construct(__il, std::forward<_Args>(__args)...);
+ return this->_M_get();
}
// Destructor is implicit, implemented in _Optional_base.
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 46d7b92..58bf8c7 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -1007,25 +1007,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
template<typename _Tp, typename... _Args>
- enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>>
+ enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
+ _Tp&>
emplace(_Args&&... __args)
{
- this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
+ auto& ret =
+ this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
__glibcxx_assert(holds_alternative<_Tp>(*this));
+ return ret;
}
template<typename _Tp, typename _Up, typename... _Args>
enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
- && __exactly_once<_Tp>>
+ && __exactly_once<_Tp>,
+ _Tp&>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
- this->emplace<__index_of<_Tp>>(__il, std::forward<_Args>(__args)...);
+ auto& ret =
+ this->emplace<__index_of<_Tp>>(__il,
+ std::forward<_Args>(__args)...);
__glibcxx_assert(holds_alternative<_Tp>(*this));
+ return ret;
}
template<size_t _Np, typename... _Args>
enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
- _Args...>>
+ _Args...>,
+ variant_alternative_t<_Np, variant>&>
emplace(_Args&&... __args)
{
static_assert(_Np < sizeof...(_Types),
@@ -1042,11 +1050,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__throw_exception_again;
}
__glibcxx_assert(index() == _Np);
+ return std::get<_Np>(*this);
}
template<size_t _Np, typename _Up, typename... _Args>
enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
- initializer_list<_Up>&, _Args...>>
+ initializer_list<_Up>&, _Args...>,
+ variant_alternative_t<_Np, variant>&>
emplace(initializer_list<_Up> __il, _Args&&... __args)
{
static_assert(_Np < sizeof...(_Types),
@@ -1063,6 +1073,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__throw_exception_again;
}
__glibcxx_assert(index() == _Np);
+ return std::get<_Np>(*this);
}
constexpr bool valueless_by_exception() const noexcept
diff --git a/libstdc++-v3/testsuite/20_util/any/assign/emplace.cc
b/libstdc++-v3/testsuite/20_util/any/assign/emplace.cc
index 07cbdde..119104b 100644
--- a/libstdc++-v3/testsuite/20_util/any/assign/emplace.cc
+++ b/libstdc++-v3/testsuite/20_util/any/assign/emplace.cc
@@ -72,4 +72,8 @@ int main()
std::any o10;
o10.emplace<char*>(nullptr);
VERIFY(o9.type() == o10.type());
+ std::any o11;
+ VERIFY(&o11.emplace<int>(42) == &std::any_cast<int&>(o11));
+ VERIFY(&o11.emplace<std::vector<int>>({1,2,3}) ==
+ &std::any_cast<std::vector<int>&>(o11));
}
diff --git a/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
b/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
index 61f0bc4..2d2b3d3 100644
--- a/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/any/misc/any_cast_neg.cc
@@ -26,5 +26,5 @@ void test01()
using std::any_cast;
const any y(1);
- any_cast<int&>(y); // { dg-error "invalid static_cast" "" { target { *-*-* }
} 455 }
+ any_cast<int&>(y); // { dg-error "invalid static_cast" "" { target { *-*-* }
} 461 }
}
diff --git a/libstdc++-v3/testsuite/20_util/optional/assignment/6.cc
b/libstdc++-v3/testsuite/20_util/optional/assignment/6.cc
index 4d754c1..40a537a 100644
--- a/libstdc++-v3/testsuite/20_util/optional/assignment/6.cc
+++ b/libstdc++-v3/testsuite/20_util/optional/assignment/6.cc
@@ -76,6 +76,11 @@ int main()
o.emplace({ 'a' }, "");
VERIFY( o && o->state == 2 );
}
+ {
+ O o;
+ VERIFY(&o.emplace(0) == &*o);
+ VERIFY(&o.emplace({ 'a' }, "") == &*o);
+ }
static_assert( !std::is_constructible<O, std::initializer_list<int>, int>(),
"" );
diff --git a/libstdc++-v3/testsuite/20_util/variant/run.cc
b/libstdc++-v3/testsuite/20_util/variant/run.cc
index db4529e..c6c2bc9 100644
--- a/libstdc++-v3/testsuite/20_util/variant/run.cc
+++ b/libstdc++-v3/testsuite/20_util/variant/run.cc
@@ -189,6 +189,15 @@ void emplace()
try { v.emplace<1>(AlwaysThrow{}); } catch (nullptr_t) { }
VERIFY(v.valueless_by_exception());
}
+ VERIFY(&v.emplace<0>(1) == &std::get<0>(v));
+ VERIFY(&v.emplace<int>(1) == &std::get<int>(v));
+ VERIFY(&v.emplace<1>("a") == &std::get<1>(v));
+ VERIFY(&v.emplace<string>("a") == &std::get<string>(v));
+ {
+ variant<vector<int>> v;
+ VERIFY(&v.emplace<0>({1,2,3}) == &std::get<0>(v));
+ VERIFY(&v.emplace<vector<int>>({1,2,3}) == &std::get<vector<int>>(v));
+ }
}
void test_get()
