https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115222
Bug ID: 115222
Summary: clang does not think libstdc++'s std::optional is
nothrow destructible
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: pobrn at protonmail dot com
Target Milestone: ---
clang and gcc disagree whether libstdc++'s std::optional<T> is nothrow
destructible when T is not. My reading of https://eel.is/c++draft/optional.dtor
suggests that the destructor should be `noexcept(true)` (by omission).
Consider the following piece of C++ code:
```
#include <optional>
#include <type_traits>
struct A { ~A() noexcept(false); };
static_assert(std::is_nothrow_destructible_v<std::optional<A>>);
```
the assertion passes on gcc, while it fails on clang:
https://gcc.godbolt.org/z/1ndxK1avM
Now I have tried to reduce the input, and arrived at something like this (
https://gcc.godbolt.org/z/orx5j1Eaf ):
```
template <typename _Tp> _Tp declval() noexcept;
template <typename _Tp>
inline constexpr bool is_nothrow_destructible_v = noexcept(declval<_Tp>());
template <typename _Tp>
struct _Optional_payload_base {
union _Storage {
_Tp _M_value;
} _M_payload;
};
template <typename _Tp>
struct _Optional_payload : _Optional_payload_base<_Tp> {
~_Optional_payload();
};
struct A {
~A() noexcept(false);
};
static_assert(is_nothrow_destructible_v<_Optional_payload<A>>);
```
The assertion passes on gcc, but fails on clang (and edg).
