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LWG-3460 Unimplementable noop_coroutine_handle guarantees #1452

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merged 8 commits into from
Dec 2, 2020
Merged

LWG-3460 Unimplementable noop_coroutine_handle guarantees #1452

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601461a
Implement LWG-3460
CaseyCarter Aug 21, 2020
d744965
Derp
CaseyCarter Nov 12, 2020
dbf617a
no plan survives first contact with the enemy
CaseyCarter Nov 12, 2020
1be493b
Bah - missed noop_coroutine_handle::address
CaseyCarter Dec 1, 2020
5958b30
Add a bit more test coverage for noop_coroutine_handle
CaseyCarter Dec 1, 2020
250bf06
Oops - finish noexcept coverage
CaseyCarter Dec 1, 2020
1f60458
Verify that `explicit operator bool` is noexcept.
StephanTLavavej Dec 1, 2020
37721ce
Consistently validate that coroutine_handle<>'s conversion to bool is…
CaseyCarter Dec 2, 2020
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26 changes: 20 additions & 6 deletions stl/inc/coroutine
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Original file line number Diff line number Diff line change
Expand Up @@ -93,7 +93,7 @@ protected:
};

template <class _Promise>
struct coroutine_handle : coroutine_handle<> {
struct coroutine_handle : private coroutine_handle<> {
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using coroutine_handle<>::coroutine_handle;

_NODISCARD static coroutine_handle from_promise(_Promise& _Prom) noexcept { // strengthened
Expand All @@ -109,12 +109,24 @@ struct coroutine_handle : coroutine_handle<> {
return *this;
}

using coroutine_handle<>::address;
_NODISCARD static constexpr coroutine_handle from_address(void* const _Addr) noexcept { // strengthened
coroutine_handle _Result;
_Result._Ptr = _Addr;
return _Result;
}

constexpr operator coroutine_handle<>() const noexcept {
return static_cast<const coroutine_handle<>&>(*this);
}

using coroutine_handle<>::operator bool;
using coroutine_handle<>::done;

using coroutine_handle<>::operator();
using coroutine_handle<>::resume;
using coroutine_handle<>::destroy;

_NODISCARD _Promise& promise() const noexcept { // strengthened
return *reinterpret_cast<_Promise*>(__builtin_coro_promise(_Ptr, 0, false));
}
Expand Down Expand Up @@ -145,9 +157,13 @@ struct noop_coroutine_promise {};

// STRUCT coroutine_handle<noop_coroutine_promise>
template <>
struct coroutine_handle<noop_coroutine_promise> : coroutine_handle<> {
struct coroutine_handle<noop_coroutine_promise> : private coroutine_handle<> {
friend coroutine_handle noop_coroutine() noexcept;

constexpr operator coroutine_handle<>() const noexcept {
return static_cast<const coroutine_handle<>&>(*this);
}

constexpr explicit operator bool() const noexcept {
return true;
}
Expand All @@ -159,11 +175,9 @@ struct coroutine_handle<noop_coroutine_promise> : coroutine_handle<> {
constexpr void resume() const noexcept {}
constexpr void destroy() const noexcept {}

using _Promise = noop_coroutine_promise;

_NODISCARD _Promise& promise() const noexcept {
_NODISCARD noop_coroutine_promise& promise() const noexcept {
// Returns a reference to the associated promise
return *reinterpret_cast<_Promise*>(__builtin_coro_promise(_Ptr, 0, false));
return *reinterpret_cast<noop_coroutine_promise*>(__builtin_coro_promise(_Ptr, 0, false));
}

private:
Expand Down