https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116455
Bug ID: 116455
Summary: Should std::noop_coroutine() be constexpr?
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: daidodo at gmail dot com
Target Milestone: ---
Currently, the signature of std::noop_coroutine() is without `constexpr`:
```
inline std::noop_coroutine_handle noop_coroutine() noexcept {
return noop_coroutine_handle();
}
```
(https://github.com/daidodo/gcc/blob/master/libstdc%2B%2B-v3/include/std/coroutine#L317)
There is no way to define a `constexpr noop_coroutine_handle`:
```
constexpr std::noop_coroutine_handle noop = std::noop_coroutine(); // error
```
Is that intentional or something missing?
Actually, `std::noop_coroutine_handle` has a default (constexpr) ctor.
And both `std::coroutine_handle<void>` and `std::coroutine_handle<Promise>`
have `constexpr` ctors and `from_address` (except that `from_promise` is
non-constexpr).
It seems unreasonable that we can define constexpr coroutine_handle's for
`void` and all promises but not noop_coroutine_handle.
I tested locally and it's just a keyword away for the following to work:
```
inline constexpr std::noop_coroutine_handle noop_coroutine() noexcept {
return noop_coroutine_handle();
}
// Now users can define constexpr noop_coroutine_handle.
constexpr std::noop_coroutine_handle noop = std::noop_coroutine();
```
Regards,
Zhao
