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put the receiver at a stable address so the env pulled from it stays valid #2014

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Merged
ericniebler merged 1 commit into from
Apr 11, 2026
Merged

put the receiver at a stable address so the env pulled from it stays valid #2014

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44 changes: 23 additions & 21 deletions include/stdexec/__detail/__task.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -472,12 +472,10 @@ namespace STDEXEC
return __parent_.unhandled_stopped();
}

// STDEXEC_IMMOVABLE_NO_UNIQUE_ADDRESS
__own_env_t<_ParentPromise> __own_env_;
// STDEXEC_IMMOVABLE_NO_UNIQUE_ADDRESS
_Env __env_;
__std::coroutine_handle<> __continuation_;
_ParentPromise& __parent_;
_Env __env_;
__std::coroutine_handle<> __continuation_;
_ParentPromise& __parent_;
};

struct __attrs
Expand Down Expand Up @@ -507,30 +505,37 @@ namespace STDEXEC
__std::coroutine_handle<promise_type> __coro_;
};

template <class _Rcvr>
struct __rcvr_box
{
_Rcvr __rcvr_;
};

////////////////////////////////////////////////////////////////////////////////////////
// task<T,E>::__opstate
template <class _Ty, class _Env>
template <class _Rcvr>
struct STDEXEC_ATTRIBUTE(empty_bases) task<_Ty, _Env>::__opstate final
: __opstate_base
: __rcvr_box<_Rcvr> // holds the receiver so that we can pass __opstate_base a reference to it
, __opstate_base
, __stop_callback_box_t<_Rcvr>
{
public:
using operation_state_concept = operation_state_tag;

explicit __opstate(task&& __task, _Rcvr&& __rcvr) noexcept
: __opstate_base(static_cast<task&&>(__task), __rcvr)
, __own_env_(__mk_own_env(__rcvr))
, __env_(__mk_env(__rcvr, __own_env_))
, __rcvr_(static_cast<_Rcvr&&>(__rcvr))
: __rcvr_box<_Rcvr>{static_cast<_Rcvr&&>(__rcvr)}
, __opstate_base(static_cast<task&&>(__task), this->__rcvr_)
, __own_env_(__mk_own_env(this->__rcvr_))
, __env_(__mk_env(this->__rcvr_, __own_env_))
{}

void start() & noexcept
{
STDEXEC_TRY
{
// Register a stop callback if needed
this->__register_callback(__rcvr_, this->__handle().promise().__stop_);
this->__register_callback(this->__rcvr_, this->__handle().promise().__stop_);
this->__handle().resume();
}
STDEXEC_CATCH_ALL
Expand All @@ -542,7 +547,7 @@ namespace STDEXEC
else if constexpr (__mapply<__mcontains<set_error_t(std::exception_ptr)>,
error_types>::value)
{
STDEXEC::set_error(static_cast<_Rcvr&&>(__rcvr_), std::current_exception());
STDEXEC::set_error(static_cast<_Rcvr&&>(this->__rcvr_), std::current_exception());
}
else
{
Expand All @@ -565,19 +570,19 @@ namespace STDEXEC
// Move the errors out of the promise before destroying the coroutine.
auto __errors = std::move(this->__errors_);
__sink(static_cast<task&&>(this->__task_));
__visit(STDEXEC::set_error, std::move(__errors), static_cast<_Rcvr&&>(__rcvr_));
__visit(STDEXEC::set_error, std::move(__errors), static_cast<_Rcvr&&>(this->__rcvr_));
}
else if constexpr (__same_as<_Ty, void>)
{
__sink(static_cast<task&&>(this->__task_));
STDEXEC::set_value(static_cast<_Rcvr&&>(__rcvr_));
STDEXEC::set_value(static_cast<_Rcvr&&>(this->__rcvr_));
}
else
{
// Move the result out of the promise before destroying the coroutine.
_Ty __result = static_cast<_Ty&&>(*this->__handle().promise().__result_);
__sink(static_cast<task&&>(this->__task_));
STDEXEC::set_value(static_cast<_Rcvr&&>(__rcvr_), static_cast<_Ty&&>(__result));
STDEXEC::set_value(static_cast<_Rcvr&&>(this->__rcvr_), static_cast<_Ty&&>(__result));
}
}
STDEXEC_CATCH_ALL
Expand All @@ -586,7 +591,7 @@ namespace STDEXEC
|| !__nothrow_move_constructible<__error_variant_t>)
{
__sink(static_cast<task&&>(this->__task_));
STDEXEC::set_error(static_cast<_Rcvr&&>(__rcvr_), std::current_exception());
STDEXEC::set_error(static_cast<_Rcvr&&>(this->__rcvr_), std::current_exception());
}
}
return std::noop_coroutine();
Expand All @@ -596,15 +601,12 @@ namespace STDEXEC
{
this->__reset_callback();
__sink(static_cast<task&&>(this->__task_));
STDEXEC::set_stopped(static_cast<_Rcvr&&>(__rcvr_));
STDEXEC::set_stopped(static_cast<_Rcvr&&>(this->__rcvr_));
return std::noop_coroutine();
}

// STDEXEC_IMMOVABLE_NO_UNIQUE_ADDRESS
__own_env_t<_Rcvr> __own_env_;
// STDEXEC_IMMOVABLE_NO_UNIQUE_ADDRESS
_Env __env_;
_Rcvr __rcvr_;
_Env __env_;
};

////////////////////////////////////////////////////////////////////////////////////////
Expand Down
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