I've just created LWG 4295 proposing this change, and am implementing it
via this patch.
libstdc++-v3/ChangeLog:
* include/experimental/memory (swap, make_observer_ptr): Add
constexpr.
(operator==, operator!=, operator<, operator>, operator<=)
(operator>=): Likewise.
* testsuite/experimental/memory/observer_ptr/make_observer.cc:
Checks for constant evaluation.
* testsuite/experimental/memory/observer_ptr/relops/relops.cc:
Likewise.
* testsuite/experimental/memory/observer_ptr/swap/swap.cc:
Likewise.
---
Tested x86_64-linux.
libstdc++-v3/include/experimental/memory | 22 +++++++--------
.../memory/observer_ptr/make_observer.cc | 11 ++++++--
.../memory/observer_ptr/relops/relops.cc | 28 +++++++++++--------
.../memory/observer_ptr/swap/swap.cc | 20 ++++++++-----
4 files changed, 50 insertions(+), 31 deletions(-)
diff --git a/libstdc++-v3/include/experimental/memory
b/libstdc++-v3/include/experimental/memory
index 131e5acc03d9..1b01462e1b26 100644
--- a/libstdc++-v3/include/experimental/memory
+++ b/libstdc++-v3/include/experimental/memory
@@ -148,42 +148,42 @@ inline namespace fundamentals_v2
}; // observer_ptr<>
template<typename _Tp>
- void
+ constexpr void
swap(observer_ptr<_Tp>& __p1, observer_ptr<_Tp>& __p2) noexcept
{
__p1.swap(__p2);
}
template<typename _Tp>
- observer_ptr<_Tp>
+ constexpr observer_ptr<_Tp>
make_observer(_Tp* __p) noexcept
{
return observer_ptr<_Tp>(__p);
}
template<typename _Tp, typename _Up>
- bool
+ constexpr bool
operator==(observer_ptr<_Tp> __p1, observer_ptr<_Up> __p2)
{
return __p1.get() == __p2.get();
}
template<typename _Tp, typename _Up>
- bool
+ constexpr bool
operator!=(observer_ptr<_Tp> __p1, observer_ptr<_Up> __p2)
{
return !(__p1 == __p2);
}
template<typename _Tp>
- bool
+ constexpr bool
operator==(observer_ptr<_Tp> __p, nullptr_t) noexcept
{
return !__p;
}
template<typename _Tp>
- bool
+ constexpr bool
operator==(nullptr_t, observer_ptr<_Tp> __p) noexcept
{
return !__p;
@@ -197,14 +197,14 @@ inline namespace fundamentals_v2
}
template<typename _Tp>
- bool
+ constexpr bool
operator!=(nullptr_t, observer_ptr<_Tp> __p) noexcept
{
return bool(__p);
}
template<typename _Tp, typename _Up>
- bool
+ constexpr bool
operator<(observer_ptr<_Tp> __p1, observer_ptr<_Up> __p2)
{
return std::less<typename common_type<typename add_pointer<_Tp>::type,
@@ -214,21 +214,21 @@ inline namespace fundamentals_v2
}
template<typename _Tp, typename _Up>
- bool
+ constexpr bool
operator>(observer_ptr<_Tp> __p1, observer_ptr<_Up> __p2)
{
return __p2 < __p1;
}
template<typename _Tp, typename _Up>
- bool
+ constexpr bool
operator<=(observer_ptr<_Tp> __p1, observer_ptr<_Up> __p2)
{
return !(__p2 < __p1);
}
template<typename _Tp, typename _Up>
- bool
+ constexpr bool
operator>=(observer_ptr<_Tp> __p1, observer_ptr<_Up> __p2)
{
return !(__p1 < __p2);
diff --git
a/libstdc++-v3/testsuite/experimental/memory/observer_ptr/make_observer.cc
b/libstdc++-v3/testsuite/experimental/memory/observer_ptr/make_observer.cc
index 048735ff63ae..1de9cf095092 100644
--- a/libstdc++-v3/testsuite/experimental/memory/observer_ptr/make_observer.cc
+++ b/libstdc++-v3/testsuite/experimental/memory/observer_ptr/make_observer.cc
@@ -20,12 +20,19 @@
#include <experimental/memory>
#include <testsuite_hooks.h>
-int main()
+constexpr bool test()
{
const int i = 42;
auto o = std::experimental::make_observer(&i);
static_assert( std::is_same<decltype(o),
- std::experimental::observer_ptr<const int>>(), "" );
+ std::experimental::observer_ptr<const int>>(), "" );
VERIFY( o && *o == 42 );
VERIFY( o.get() == &i );
+ return true;
+}
+
+int main()
+{
+ test();
+ static_assert( test(), "LWG 4295 - make_observer should be constexpr" );
}
diff --git
a/libstdc++-v3/testsuite/experimental/memory/observer_ptr/relops/relops.cc
b/libstdc++-v3/testsuite/experimental/memory/observer_ptr/relops/relops.cc
index 3e23e0b452be..d03dd5dcbd80 100644
--- a/libstdc++-v3/testsuite/experimental/memory/observer_ptr/relops/relops.cc
+++ b/libstdc++-v3/testsuite/experimental/memory/observer_ptr/relops/relops.cc
@@ -22,13 +22,13 @@
using std::experimental::observer_ptr;
-void test01()
+constexpr void test01()
{
observer_ptr<int> a, b;
VERIFY(a == b);
}
-void test02()
+constexpr void test02()
{
int x[2]{};
observer_ptr<int> a{&x[0]};
@@ -40,7 +40,7 @@ void test02()
VERIFY(b > a);
}
-void test03()
+constexpr void test03()
{
int x{};
observer_ptr<int> a{&x};
@@ -48,9 +48,10 @@ void test03()
VERIFY(a == b);
}
-void test04()
+int x[2]{};
+
+constexpr void test04()
{
- static constexpr int x[2]{};
constexpr observer_ptr<const int> a{&x[0]};
constexpr observer_ptr<const int> b{&x[1]};
VERIFY(a != b);
@@ -60,20 +61,25 @@ void test04()
VERIFY(b > a);
}
-void test05()
+constexpr void test05()
{
- static constexpr int x{};
- constexpr observer_ptr<const int> a{&x};
- constexpr observer_ptr<const int> b{&x};
+ constexpr observer_ptr<const int> a{&x[0]};
+ constexpr observer_ptr<const int> b{&x[0]};
VERIFY(a == b);
}
-
-int main()
+constexpr bool all_tests()
{
test01();
test02();
test03();
test04();
test05();
+ return true;
+}
+
+int main()
+{
+ all_tests();
+ static_assert( all_tests(), "LWG 4295 - relops should be constexpr" );
}
diff --git
a/libstdc++-v3/testsuite/experimental/memory/observer_ptr/swap/swap.cc
b/libstdc++-v3/testsuite/experimental/memory/observer_ptr/swap/swap.cc
index 9e7678863512..84b8844af34d 100644
--- a/libstdc++-v3/testsuite/experimental/memory/observer_ptr/swap/swap.cc
+++ b/libstdc++-v3/testsuite/experimental/memory/observer_ptr/swap/swap.cc
@@ -25,7 +25,7 @@ using std::experimental::observer_ptr;
struct B {};
struct D : B {};
-void test01()
+constexpr void test01()
{
observer_ptr<int> a, b;
VERIFY(a == b);
@@ -33,7 +33,7 @@ void test01()
VERIFY(a == b);
}
-void test02()
+constexpr void test02()
{
int x{};
observer_ptr<int> a;
@@ -45,7 +45,7 @@ void test02()
VERIFY(!b);
}
-void test03()
+constexpr void test03()
{
int x[2]{1,2};
observer_ptr<int> a{&x[0]};
@@ -57,10 +57,16 @@ void test03()
VERIFY(*b == 1);
}
-
int main()
{
- test01();
- test02();
- test03();
+ auto tests = [] {
+ test01();
+ test02();
+ test03();
+ return true;
+ };
+ tests();
+#if __cpp_lib_constexpr_algorithms >= 201806L // >= C++20
+ static_assert( tests(), "LWG 4295 - swap should be constexpr" );
+#endif
}
--
2.50.1
