* [v3 PATCH] Implement LWG 2451
@ 2016-07-05 21:45 Ville Voutilainen
2016-07-06 12:51 ` Jonathan Wakely
0 siblings, 1 reply; 2+ messages in thread
From: Ville Voutilainen @ 2016-07-05 21:45 UTC (permalink / raw)
To: gcc-patches, libstdc++
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Tested on Linux-x64.
2016-07-05 Ville Voutilainen <ville.voutilainen@gmail.com>
Implement LWG 2451, optional<T> should 'forward' T's
implicit conversions.
* include/experimental/optional (__is_optional_impl, __is_optional):
New.
(optional()): Make constexpr and default.
(optional(_Up&&), optional(const optional<_Up>&),
optional(optional<_Up>&& __t): New.
(operator=(_Up&&)): Constrain.
(operator=(const optional<_Up>&), operator=(optional<_Up>&&)): New.
* testsuite/experimental/optional/cons/value.cc:
Add tests for the functionality added by LWG 2451.
* testsuite/experimental/optional/cons/value_neg.cc: New.
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diff --git a/libstdc++-v3/include/experimental/optional b/libstdc++-v3/include/experimental/optional
index 7524a7e..5657524 100644
--- a/libstdc++-v3/include/experimental/optional
+++ b/libstdc++-v3/include/experimental/optional
@@ -470,6 +470,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
bool _M_engaged = false;
};
+ template<typename _Tp>
+ class optional;
+
+ template<typename>
+ struct __is_optional_impl : false_type
+ { };
+
+ template<typename _Tp>
+ struct __is_optional_impl<optional<_Tp>> : true_type
+ { };
+
+ template<typename _Tp>
+ struct __is_optional
+ : public __is_optional_impl<typename std::remove_cv
+ <typename std::remove_reference<_Tp>::type>::type>::type
+ { };
+
+
/**
* @brief Class template for optional values.
*/
@@ -502,6 +520,78 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// _Optional_base has the responsibility for construction.
using _Base::_Base;
+ constexpr optional() = default;
+ // Converting constructors for engaged optionals.
+ template <typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>,
+ is_constructible<_Tp, _Up&&>,
+ is_convertible<_Up&&, _Tp>
+ >::value, bool>::type = true>
+ constexpr optional(_Up&& __t)
+ : _Base(_Tp(std::forward<_Up>(__t))) { }
+
+ template <typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>,
+ is_constructible<_Tp, _Up&&>,
+ __not_<is_convertible<_Up&&, _Tp>>
+ >::value, bool>::type = false>
+ explicit constexpr optional(_Up&& __t)
+ : _Base(_Tp(std::forward<_Up>(__t))) { }
+
+ template <typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>,
+ __not_<is_constructible<
+ _Tp, const optional<_Up>&>>,
+ __not_<is_convertible<
+ const optional<_Up>&, _Tp>>,
+ is_constructible<_Tp, const _Up&>,
+ is_convertible<const _Up&, _Tp>
+ >::value, bool>::type = true>
+ constexpr optional(const optional<_Up>& __t)
+ : _Base(__t ? optional<_Tp>(*__t) : optional<_Tp>()) { }
+
+ template <typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>,
+ __not_<is_constructible<
+ _Tp, const optional<_Up>&>>,
+ __not_<is_convertible<
+ const optional<_Up>&, _Tp>>,
+ is_constructible<_Tp, const _Up&>,
+ __not_<is_convertible<const _Up&, _Tp>>
+ >::value, bool>::type = false>
+ explicit constexpr optional(const optional<_Up>& __t)
+ : _Base(__t ? optional<_Tp>(*__t) : optional<_Tp>()) { }
+
+ template <typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>,
+ __not_<is_constructible<
+ _Tp, optional<_Up>&&>>,
+ __not_<is_convertible<
+ optional<_Up>&&, _Tp>>,
+ is_constructible<_Tp, _Up&&>,
+ is_convertible<_Up&&, _Tp>
+ >::value, bool>::type = true>
+ constexpr optional(optional<_Up>&& __t)
+ : _Base(__t ? optional<_Tp>(std::move(*__t)) : optional<_Tp>()) { }
+
+ template <typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>,
+ __not_<is_constructible<
+ _Tp, optional<_Up>&&>>,
+ __not_<is_convertible<
+ optional<_Up>&&, _Tp>>,
+ is_constructible<_Tp, _Up&&>,
+ __not_<is_convertible<_Up&&, _Tp>>
+ >::value, bool>::type = false>
+ explicit constexpr optional(optional<_Up>&& __t)
+ : _Base(__t ? optional<_Tp>(std::move(*__t)) : optional<_Tp>()) { }
+
// [X.Y.4.3] (partly) Assignment.
optional&
operator=(nullopt_t) noexcept
@@ -510,8 +600,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return *this;
}
- template<typename _Up>
- enable_if_t<is_same<_Tp, decay_t<_Up>>::value, optional&>
+ template<typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Up, nullopt_t>>,
+ __not_<__is_optional<_Up>>>::value,
+ bool>::type = true>
+ optional&
operator=(_Up&& __u)
{
static_assert(__and_<is_constructible<_Tp, _Up>,
@@ -526,6 +620,57 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return *this;
}
+ template<typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>>::value,
+ bool>::type = true>
+ optional&
+ operator=(const optional<_Up>& __u)
+ {
+ static_assert(__and_<is_constructible<_Tp, _Up>,
+ is_assignable<_Tp&, _Up>>(),
+ "Cannot assign to value type from argument");
+
+ if (__u)
+ {
+ if (this->_M_is_engaged())
+ this->_M_get() = *__u;
+ else
+ this->_M_construct(*__u);
+ }
+ else
+ {
+ this->_M_reset();
+ }
+ return *this;
+ }
+
+ template<typename _Up,
+ typename enable_if<__and_<
+ __not_<is_same<_Tp, _Up>>>::value,
+ bool>::type = true>
+ optional&
+ operator=(optional<_Up>&& __u)
+ {
+ static_assert(__and_<is_constructible<_Tp, _Up>,
+ is_assignable<_Tp&, _Up>>(),
+ "Cannot assign to value type from argument");
+
+ if (__u)
+ {
+ if (this->_M_is_engaged())
+ this->_M_get() = std::move(*__u);
+ else
+ this->_M_construct(std::move(*__u));
+ }
+ else
+ {
+ this->_M_reset();
+ }
+
+ return *this;
+ }
+
template<typename... _Args>
void
emplace(_Args&&... __args)
diff --git a/libstdc++-v3/testsuite/experimental/optional/cons/value.cc b/libstdc++-v3/testsuite/experimental/optional/cons/value.cc
index a916951..123a89e 100644
--- a/libstdc++-v3/testsuite/experimental/optional/cons/value.cc
+++ b/libstdc++-v3/testsuite/experimental/optional/cons/value.cc
@@ -22,6 +22,7 @@
#include <testsuite_hooks.h>
#include <vector>
+#include <string>
struct tracker
{
@@ -236,4 +237,22 @@ int main()
VERIFY( result == caught );
}
+
+ {
+ std::experimental::optional<std::string> os = "foo";
+ struct X
+ {
+ explicit X(int) {}
+ X& operator=(int) {return *this;}
+ };
+ std::experimental::optional<X> ox{42};
+ std::experimental::optional<int> oi{42};
+ std::experimental::optional<X> ox2{oi};
+ std::experimental::optional<std::string> os2;
+ os2 = "foo";
+ std::experimental::optional<X> ox3;
+ ox3 = 42;
+ std::experimental::optional<X> ox4;
+ ox4 = oi;
+ }
}
diff --git a/libstdc++-v3/testsuite/experimental/optional/cons/value_neg.cc b/libstdc++-v3/testsuite/experimental/optional/cons/value_neg.cc
new file mode 100644
index 0000000..c862a04
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/optional/cons/value_neg.cc
@@ -0,0 +1,39 @@
+// { dg-options "-std=gnu++14" }
+// { dg-do compile }
+
+// Copyright (C) 2013-2016 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a moved_to of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <experimental/optional>
+#include <testsuite_hooks.h>
+
+#include <string>
+#include <memory>
+
+int main()
+{
+ {
+ struct X
+ {
+ explicit X(int) {}
+ };
+ std::experimental::optional<X> ox{42};
+ std::experimental::optional<X> ox2 = 42; // { dg-error "conversion" }
+ std::experimental::optional<std::unique_ptr<int>> oup{new int};
+ std::experimental::optional<std::unique_ptr<int>> oup2 = new int; // { dg-error "conversion" }
+ }
+}
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [v3 PATCH] Implement LWG 2451
2016-07-05 21:45 [v3 PATCH] Implement LWG 2451 Ville Voutilainen
@ 2016-07-06 12:51 ` Jonathan Wakely
0 siblings, 0 replies; 2+ messages in thread
From: Jonathan Wakely @ 2016-07-06 12:51 UTC (permalink / raw)
To: Ville Voutilainen; +Cc: gcc-patches, libstdc++
On 06/07/16 00:44 +0300, Ville Voutilainen wrote:
> Implement LWG 2451, optional<T> should 'forward' T's
> implicit conversions.
> * include/experimental/optional (__is_optional_impl, __is_optional):
> New.
> (optional()): Make constexpr and default.
> (optional(_Up&&), optional(const optional<_Up>&),
> optional(optional<_Up>&& __t): New.
> (operator=(_Up&&)): Constrain.
> (operator=(const optional<_Up>&), operator=(optional<_Up>&&)): New.
> * testsuite/experimental/optional/cons/value.cc:
> Add tests for the functionality added by LWG 2451.
> * testsuite/experimental/optional/cons/value_neg.cc: New.
As I mentioned on IRC, experimental::optional is C++14-only so you can
use remove_cv_t and enable_if_t to get rid of some of the typename
X::type clutter.
OK for trunk and gcc-6 with or without that change, your choice.
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