This change ensures that std::common_type<> is a complete type (LWG
2408), and that std::common_type<T>, std::common_type<cv T1, cv T2>, and
std::common_type<T1, T2, R...> will use program-defined specializations
for std::common_type<T1, T2> (LWG 2465).
The implementation of common_type<T1, T2, R...> is changed to use
void_t, and the specializations for duration and time_point are modified
to also use void_t instead of depending on implementation details of
common_type.
PR libstdc++/89102
* doc/xml/manual/intro.xml: Document DR 2408 and 2465 changes.
* include/std/chrono (__duration_common_type_wrapper): Replace with ...
(__duration_common_type): New helper.
(common_type<chrono::duration<R1, P2>, chrono::duration<R2, P2>>): Use
__duration_common_type.
(__timepoint_common_type_wrapper): Replace with ...
(__timepoint_common_type): New helper.
(common_type<chrono::time_point<C, D2>, chrono::time_point<C, D2>>):
Use __time_point_common_type.
* include/std/type_traits (common_type<>): Define, as per LWG 2408.
(__common_type_impl): If either argument is transformed by decay,
use the common_type of the decayed types.
(__common_type_impl<_Tp, _Up, _Tp, _Up>): If the types are already
decayed, use __do_common_type_impl to get the common_type.
(common_type<_Tp>): Use common_type<_Tp, _Tp>.
(__do_member_type_wrapper, __member_type_wrapper)
(__expanded_common_type_wrapper): Remove.
(__common_type_pack, __common_type_fold): New helpers.
(common_type<_Tp, _Up, _Vp...>): Use new helpers instead of
__member_type_wrapper and __expanded_common_type_wrapper.
* testsuite/20_util/common_type/requirements/explicit_instantiation.cc:
Test zero-length template argument list.
* testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc:
Test single argument cases and argument types that should decay.
* testsuite/20_util/common_type/requirements/sfinae_friendly_2.cc:
Adjust expected error.
* testsuite/20_util/duration/literals/range_neg.cc: Use zero for
dg-error lineno.
* testsuite/20_util/duration/requirements/typedefs_neg1.cc: Likewise.
* testsuite/20_util/duration/requirements/typedefs_neg2.cc: Likewise.
* testsuite/20_util/duration/requirements/typedefs_neg3.cc: Likewise.
Tested powerpc64le-linux, committed to trunk.
commit 3f6b849095f82205598cd5b6ce223a7a2a26bd98
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Feb 6 11:51:37 2019 +0000
PR libstdc++/89102 implement new common_type rules (P0435R1, P0548R1)
This change ensures that std::common_type<> is a complete type (LWG
2408), and that std::common_type<T>, std::common_type<cv T1, cv T2>, and
std::common_type<T1, T2, R...> will use program-defined specializations
for std::common_type<T1, T2> (LWG 2465).
The implementation of common_type<T1, T2, R...> is changed to use
void_t, and the specializations for duration and time_point are modified
to also use void_t instead of depending on implementation details of
common_type.
PR libstdc++/89102
* doc/xml/manual/intro.xml: Document DR 2408 and 2465 changes.
* include/std/chrono (__duration_common_type_wrapper): Replace with
...
(__duration_common_type): New helper.
(common_type<chrono::duration<R1, P2>, chrono::duration<R2, P2>>):
Use
__duration_common_type.
(__timepoint_common_type_wrapper): Replace with ...
(__timepoint_common_type): New helper.
(common_type<chrono::time_point<C, D2>, chrono::time_point<C, D2>>):
Use __time_point_common_type.
* include/std/type_traits (common_type<>): Define, as per LWG 2408.
(__common_type_impl): If either argument is transformed by decay,
use the common_type of the decayed types.
(__common_type_impl<_Tp, _Up, _Tp, _Up>): If the types are already
decayed, use __do_common_type_impl to get the common_type.
(common_type<_Tp>): Use common_type<_Tp, _Tp>.
(__do_member_type_wrapper, __member_type_wrapper)
(__expanded_common_type_wrapper): Remove.
(__common_type_pack, __common_type_fold): New helpers.
(common_type<_Tp, _Up, _Vp...>): Use new helpers instead of
__member_type_wrapper and __expanded_common_type_wrapper.
*
testsuite/20_util/common_type/requirements/explicit_instantiation.cc:
Test zero-length template argument list.
* testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc:
Test single argument cases and argument types that should decay.
* testsuite/20_util/common_type/requirements/sfinae_friendly_2.cc:
Adjust expected error.
* testsuite/20_util/duration/literals/range_neg.cc: Use zero for
dg-error lineno.
* testsuite/20_util/duration/requirements/typedefs_neg1.cc:
Likewise.
* testsuite/20_util/duration/requirements/typedefs_neg2.cc:
Likewise.
* testsuite/20_util/duration/requirements/typedefs_neg3.cc:
Likewise.
diff --git a/libstdc++-v3/doc/xml/manual/intro.xml
b/libstdc++-v3/doc/xml/manual/intro.xml
index 518981559a0..35a2016f5c3 100644
--- a/libstdc++-v3/doc/xml/manual/intro.xml
+++ b/libstdc++-v3/doc/xml/manual/intro.xml
@@ -1045,6 +1045,17 @@ requirements of the license of GCC.
<listitem><para>Remove <code>explicit</code> from the constructor.
</para></listitem></varlistentry>
+ <varlistentry xml:id="manual.bugs.dr2408"><term><link
xmlns:xlink="http://www.w3.org/1999/xlink"; xlink:href="&DR;#2408">2408</link>:
+ <emphasis>SFINAE-friendly
+ <code>common_type</code>/<code>iterator_traits</code>
+ is missing in C++14
+ </emphasis>
+ </term>
+ <listitem><para>Make <code>iterator_traits</code> empty if any of the
+ types is not present in the iterator.
+ Make <code>common_type<></code> empty.
+ </para></listitem></varlistentry>
+
<varlistentry xml:id="manual.bugs.dr2415"><term><link
xmlns:xlink="http://www.w3.org/1999/xlink"; xlink:href="&DR;#2415">2415</link>:
<emphasis>Inconsistency between <code>unique_ptr</code> and
<code>shared_ptr</code></emphasis>
</term>
@@ -1105,6 +1116,15 @@ requirements of the license of GCC.
<listitem><para>Add debug mode assertion.
</para></listitem></varlistentry>
+ <varlistentry xml:id="manual.bugs.dr2465"><term><link
xmlns:xlink="http://www.w3.org/1999/xlink"; xlink:href="&DR;#2465">2465</link>:
+ <emphasis>SFINAE-friendly <code>common_type</code> is nearly impossible
+ to specialize correctly and regresses key functionality
+ </emphasis>
+ </term>
+ <listitem><para>Detect whether <code>decay_t</code> changes either type
+ and use the decayed types if so.
+ </para></listitem></varlistentry>
+
<varlistentry xml:id="manual.bugs.dr2466"><term><link
xmlns:xlink="http://www.w3.org/1999/xlink"; xlink:href="&DR;#2466">2466</link>:
<emphasis><code>allocator_traits::max_size()</code> default behavior is
incorrect
</emphasis>
diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono
index 1d6326cdd55..b7c1d750067 100644
--- a/libstdc++-v3/include/std/chrono
+++ b/libstdc++-v3/include/std/chrono
@@ -67,48 +67,51 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// 20.11.4.3 specialization of common_type (for duration, sfinae-friendly)
+ template<typename _CT, typename _Period1, typename _Period2, typename = void>
+ struct __duration_common_type
+ { };
+
template<typename _CT, typename _Period1, typename _Period2>
- struct __duration_common_type_wrapper
+ struct __duration_common_type<_CT, _Period1, _Period2,
+ __void_t<typename _CT::type>>
{
private:
- typedef __static_gcd<_Period1::num, _Period2::num> __gcd_num;
- typedef __static_gcd<_Period1::den, _Period2::den> __gcd_den;
- typedef typename _CT::type __cr;
- typedef ratio<__gcd_num::value,
- (_Period1::den / __gcd_den::value) * _Period2::den> __r;
+ using __gcd_num = __static_gcd<_Period1::num, _Period2::num>;
+ using __gcd_den = __static_gcd<_Period1::den, _Period2::den>;
+ using __cr = typename _CT::type;
+ using __r = ratio<__gcd_num::value,
+ (_Period1::den / __gcd_den::value) * _Period2::den>;
+
public:
- typedef __success_type<chrono::duration<__cr, __r>> type;
+ using type = chrono::duration<__cr, __r>;
};
template<typename _Period1, typename _Period2>
- struct __duration_common_type_wrapper<__failure_type, _Period1, _Period2>
+ struct __duration_common_type<__failure_type, _Period1, _Period2>
{ typedef __failure_type type; };
template<typename _Rep1, typename _Period1, typename _Rep2, typename
_Period2>
struct common_type<chrono::duration<_Rep1, _Period1>,
- chrono::duration<_Rep2, _Period2>>
- : public __duration_common_type_wrapper<typename __member_type_wrapper<
- common_type<_Rep1, _Rep2>>::type, _Period1, _Period2>::type
+ chrono::duration<_Rep2, _Period2>>
+ : __duration_common_type<common_type<_Rep1, _Rep2>, _Period1, _Period2>
{ };
// 20.11.4.3 specialization of common_type (for time_point, sfinae-friendly)
- template<typename _CT, typename _Clock>
- struct __timepoint_common_type_wrapper
- {
- typedef __success_type<chrono::time_point<_Clock, typename _CT::type>>
- type;
- };
+ template<typename _CT, typename _Clock, typename = void>
+ struct __timepoint_common_type
+ { };
- template<typename _Clock>
- struct __timepoint_common_type_wrapper<__failure_type, _Clock>
- { typedef __failure_type type; };
+ template<typename _CT, typename _Clock>
+ struct __timepoint_common_type<_CT, _Clock, __void_t<typename _CT::type>>
+ {
+ using type = chrono::time_point<_Clock, typename _CT::type>;
+ };
template<typename _Clock, typename _Duration1, typename _Duration2>
struct common_type<chrono::time_point<_Clock, _Duration1>,
- chrono::time_point<_Clock, _Duration2>>
- : public __timepoint_common_type_wrapper<typename __member_type_wrapper<
- common_type<_Duration1, _Duration2>>::type, _Clock>::type
+ chrono::time_point<_Clock, _Duration2>>
+ : __timepoint_common_type<common_type<_Duration1, _Duration2>, _Clock>
{ };
namespace chrono
diff --git a/libstdc++-v3/include/std/type_traits
b/libstdc++-v3/include/std/type_traits
index 1d14c751cfa..ea733e7b7b2 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -2106,6 +2106,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct conditional<false, _Iftrue, _Iffalse>
{ typedef _Iffalse type; };
+ // __void_t (std::void_t for C++11)
+ template<typename...> using __void_t = void;
+
/// common_type
template<typename... _Tp>
struct common_type;
@@ -2115,65 +2118,81 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct __do_common_type_impl
{
template<typename _Tp, typename _Up>
- static __success_type<typename decay<decltype
- (true ? std::declval<_Tp>()
- : std::declval<_Up>())>::type> _S_test(int);
+ using __cond_t
+ = decltype(true ? std::declval<_Tp>() : std::declval<_Up>());
+
+ template<typename _Tp, typename _Up>
+ static __success_type<typename decay<__cond_t<_Tp, _Up>>::type>
+ _S_test(int);
template<typename, typename>
- static __failure_type _S_test(...);
+ static __failure_type
+ _S_test(...);
};
- template<typename _Tp, typename _Up>
- struct __common_type_impl
- : private __do_common_type_impl
- {
- typedef decltype(_S_test<_Tp, _Up>(0)) type;
- };
-
- struct __do_member_type_wrapper
- {
- template<typename _Tp>
- static __success_type<typename _Tp::type> _S_test(int);
-
- template<typename>
- static __failure_type _S_test(...);
- };
-
- template<typename _Tp>
- struct __member_type_wrapper
- : private __do_member_type_wrapper
- {
- typedef decltype(_S_test<_Tp>(0)) type;
- };
-
- template<typename _CTp, typename... _Args>
- struct __expanded_common_type_wrapper
- {
- typedef common_type<typename _CTp::type, _Args...> type;
- };
-
- template<typename... _Args>
- struct __expanded_common_type_wrapper<__failure_type, _Args...>
- { typedef __failure_type type; };
-
+ // If sizeof...(T) is zero, there shall be no member type.
template<>
struct common_type<>
{ };
- template<typename _Tp>
- struct common_type<_Tp>
- : common_type<_Tp, _Tp>
+ // If sizeof...(T) is one, the same type, if any, as common_type_t<T0, T0>.
+ template<typename _Tp0>
+ struct common_type<_Tp0>
+ : public common_type<_Tp0, _Tp0>
{ };
- template<typename _Tp, typename _Up>
- struct common_type<_Tp, _Up>
- : public __common_type_impl<_Tp, _Up>::type
+ // If sizeof...(T) is two, ...
+ template<typename _Tp1, typename _Tp2,
+ typename _Dp1 = typename decay<_Tp1>::type,
+ typename _Dp2 = typename decay<_Tp2>::type>
+ struct __common_type_impl
+ {
+ // If is_same_v<T1, D1> is false or is_same_v<T2, D2> is false,
+ // let C denote the same type, if any, as common_type_t<D1, D2>.
+ using type = common_type<_Dp1, _Dp2>;
+ };
+
+ template<typename _Tp1, typename _Tp2>
+ struct __common_type_impl<_Tp1, _Tp2, _Tp1, _Tp2>
+ : private __do_common_type_impl
+ {
+ // Otherwise, if decay_t<decltype(false ? declval<D1>() : declval<D2>())>
+ // denotes a valid type, let C denote that type.
+ using type = decltype(_S_test<_Tp1, _Tp2>(0));
+ };
+
+ // If sizeof...(T) is two, ...
+ template<typename _Tp1, typename _Tp2>
+ struct common_type<_Tp1, _Tp2>
+ : public __common_type_impl<_Tp1, _Tp2>::type
{ };
- template<typename _Tp, typename _Up, typename... _Vp>
- struct common_type<_Tp, _Up, _Vp...>
- : public __expanded_common_type_wrapper<typename __member_type_wrapper<
- common_type<_Tp, _Up>>::type, _Vp...>::type
+ template<typename...>
+ struct __common_type_pack
+ { };
+
+ template<typename, typename, typename = void>
+ struct __common_type_fold;
+
+ // If sizeof...(T) is greater than two, ...
+ template<typename _Tp1, typename _Tp2, typename... _Rp>
+ struct common_type<_Tp1, _Tp2, _Rp...>
+ : public __common_type_fold<common_type<_Tp1, _Tp2>,
+ __common_type_pack<_Rp...>>
+ { };
+
+ // Let C denote the same type, if any, as common_type_t<T1, T2>.
+ // If there is such a type C, type shall denote the same type, if any,
+ // as common_type_t<C, R...>.
+ template<typename _CTp, typename... _Rp>
+ struct __common_type_fold<_CTp, __common_type_pack<_Rp...>,
+ __void_t<typename _CTp::type>>
+ : public common_type<typename _CTp::type, _Rp...>
+ { };
+
+ // Otherwise, there shall be no member type.
+ template<typename _CTp, typename _Rp>
+ struct __common_type_fold<_CTp, _Rp, void>
{ };
template<typename _Tp, bool = is_enum<_Tp>::value>
@@ -2446,9 +2465,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<bool _Cond, typename _Tp = void>
using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
- // __void_t (std::void_t for C++11)
- template<typename...> using __void_t = void;
-
#if __cplusplus >= 201703L || !defined(__STRICT_ANSI__) // c++17 or gnu++11
#define __cpp_lib_void_t 201411
/// A metafunction that always yields void, used for detecting valid types.
diff --git
a/libstdc++-v3/testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc
b/libstdc++-v3/testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc
index 9b94eb13434..a54da7c24b2 100644
---
a/libstdc++-v3/testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc
+++
b/libstdc++-v3/testsuite/20_util/common_type/requirements/sfinae_friendly_1.cc
@@ -214,6 +214,7 @@ static_assert(is_type<std::common_type<void(&&)(),
void(&)()>,
static_assert(is_type<std::common_type<void(&&)(), void(&&)()>,
void(*)()>(), "");
static_assert(is_type<std::common_type<ImplicitTo<int>, int>, int>(), "");
+static_assert(is_type<std::common_type<const ImplicitTo<int>, int>, int>(),
"");
static_assert(is_type<std::common_type<ImplicitTo<int>, ImplicitTo<int>>,
ImplicitTo<int>>(), "");
static_assert(is_type<std::common_type<ImplicitTo<int>, int,
@@ -260,19 +261,22 @@ static_assert(is_type<std::common_type<volatile Ukn&&,
volatile Ukn&&>,
Ukn>(), "");
static_assert(is_type<std::common_type<X1, X2>, RX12>(), "");
+static_assert(is_type<std::common_type<const X1, X2>, RX12>(), "");
+static_assert(is_type<std::common_type<X1&, const X2>, RX12>(), "");
+static_assert(is_type<std::common_type<const X1&, const X2&>, RX12>(), "");
static_assert(is_type<std::common_type<X2, X1>, RX21>(), "");
static_assert(is_type<std::common_type<X1, X2, X1>, Y1>(), "");
static_assert(is_type<std::common_type<X2, X1, X1>, Y3>(), "");
static_assert(is_type<std::common_type<X1, X1, X2>, RX12>(), "");
+static_assert(is_type<std::common_type<X1&, const X1, const X2&&>, RX12>(),
"");
static_assert(is_type<std::common_type<X1, X1, X2, X1>, Y1>(), "");
static_assert(!has_type<std::common_type<>>(), "");
static_assert(!has_type<std::common_type<int, S>>(), "");
static_assert(!has_type<std::common_type<U, S>>(), "");
static_assert(!has_type<std::common_type<U, U2>>(), "");
-static_assert(!has_type<std::common_type<const ImplicitTo<int>, int>>(), "");
static_assert(!has_type<std::common_type<PrivateImplicitTo<int>, int>>(), "");
static_assert(!has_type<std::common_type<const PrivateImplicitTo<int>,
int>>(), "");
diff --git a/libstdc++-v3/testsuite/20_util/duration/literals/range_neg.cc
b/libstdc++-v3/testsuite/20_util/duration/literals/range_neg.cc
index 1c3ee90c4a6..8be1be5423f 100644
--- a/libstdc++-v3/testsuite/20_util/duration/literals/range_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/literals/range_neg.cc
@@ -26,6 +26,6 @@ test01()
// std::numeric_limits<int64_t>::max() == 9223372036854775807;
auto h = 9223372036854775808h;
- // { dg-error "cannot be represented" "" { target *-*-* } 908 }
+ // { dg-error "cannot be represented by duration" "" { target *-*-* } 0 }
}
// { dg-prune-output "in .constexpr. expansion" } // needed for -O0
diff --git
a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
index 9181488a612..9c25552892d 100644
--- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg1.cc
@@ -29,4 +29,4 @@ void test01()
test_type d; // { dg-error "required from here" }
}
-// { dg-error "rep cannot be a duration" "" { target *-*-* } 316 }
+// { dg-error "rep cannot be a duration" "" { target *-*-* } 0 }
diff --git
a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
index e3e450ebf6b..e6029fc782a 100644
--- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc
@@ -30,5 +30,5 @@ void test01()
test_type d; // { dg-error "required from here" }
}
-// { dg-error "must be a specialization of ratio" "" { target *-*-* } 317 }
+// { dg-error "must be a specialization of ratio" "" { target *-*-* } 0 }
// { dg-prune-output "not a member" }
diff --git
a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
index de0c6659b24..ed8baa195c7 100644
--- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
+++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg3.cc
@@ -31,4 +31,4 @@ void test01()
test_type d; // { dg-error "required from here" }
}
-// { dg-error "period must be positive" "" { target *-*-* } 319 }
+// { dg-error "period must be positive" "" { target *-*-* } 0 }
