std::make_any should be constrained so it can only be called if the
construction of the return value would be valid.
Tested x86_64-linux, committed to trunk.
I plan to backport this too.
libstdc++-v3/ChangeLog:
PR libstdc++/102894
* include/std/any (make_any): Add SFINAE constraint.
* testsuite/20_util/any/102894.cc: New test.
---
libstdc++-v3/include/std/any | 13 +++++++++----
libstdc++-v3/testsuite/20_util/any/102894.cc | 20 ++++++++++++++++++++
2 files changed, 29 insertions(+), 4 deletions(-)
create mode 100644 libstdc++-v3/testsuite/20_util/any/102894.cc
diff --git a/libstdc++-v3/include/std/any b/libstdc++-v3/include/std/any
index 9c102a58b26..f75dddf6d92 100644
--- a/libstdc++-v3/include/std/any
+++ b/libstdc++-v3/include/std/any
@@ -428,16 +428,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// Exchange the states of two @c any objects.
inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
- /// Create an any holding a @c _Tp constructed from @c __args.
+ /// Create an `any` holding a `_Tp` constructed from `__args...`.
template <typename _Tp, typename... _Args>
- any make_any(_Args&&... __args)
+ inline
+ enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, _Args...>, any>
+ make_any(_Args&&... __args)
{
return any(in_place_type<_Tp>, std::forward<_Args>(__args)...);
}
- /// Create an any holding a @c _Tp constructed from @c __il and @c __args.
+ /// Create an `any` holding a `_Tp` constructed from `__il` and `__args...`.
template <typename _Tp, typename _Up, typename... _Args>
- any make_any(initializer_list<_Up> __il, _Args&&... __args)
+ inline
+ enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>,
+ initializer_list<_Up>&, _Args...>, any>
+ make_any(initializer_list<_Up> __il, _Args&&... __args)
{
return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...);
}
diff --git a/libstdc++-v3/testsuite/20_util/any/102894.cc
b/libstdc++-v3/testsuite/20_util/any/102894.cc
new file mode 100644
index 00000000000..66ea9a03fea
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/any/102894.cc
@@ -0,0 +1,20 @@
+// { dg-do compile { target c++17 } }
+#include <any>
+
+template<typename T, typename = void>
+struct can_make_any
+: std::false_type
+{ };
+
+template<typename T>
+struct can_make_any<T, std::void_t<decltype(std::make_any<T>())>>
+: std::true_type
+{ };
+
+struct move_only
+{
+ move_only() = default;
+ move_only(move_only&&) = default;
+};
+
+static_assert( ! can_make_any<move_only>::value ); // PR libstdc++/102894
--
2.31.1
