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make task construct its scheduler with its allocator if possible #1953

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Merged
ericniebler merged 1 commit into from
Mar 23, 2026
Merged

make task construct its scheduler with its allocator if possible #1953

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23 changes: 16 additions & 7 deletions include/stdexec/__detail/__task.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -132,9 +132,10 @@ namespace STDEXEC
_Alloc(STDEXEC::get_allocator(STDEXEC::get_env(__has_env)));
};

template <class _EnvProvider, class _Scheduler>
concept __has_scheduler_compatible_with = requires(_EnvProvider const & __has_env) {
_Scheduler(STDEXEC::get_scheduler(STDEXEC::get_env(__has_env)));
template <class _EnvProvider, class _Scheduler, class... _Alloc>
concept __has_scheduler_compatible_with = requires(_EnvProvider const & __has_env,
_Alloc const &... __alloc) {
_Scheduler(STDEXEC::get_scheduler(STDEXEC::get_env(__has_env)), __alloc...);
};

template <class _StopSource>
Expand Down Expand Up @@ -299,9 +300,17 @@ namespace STDEXEC

template <class _EnvProvider>
[[nodiscard]]
static auto __mk_sched(_EnvProvider const & __has_env) noexcept -> scheduler_type
static auto __mk_sched(_EnvProvider const & __has_env, allocator_type const & __alloc) noexcept
-> scheduler_type
{
if constexpr (__task::__has_scheduler_compatible_with<_EnvProvider, scheduler_type>)
// NOT TO SPEC: try constructing the scheduler with the allocator if possible.
if constexpr (__task::__has_scheduler_compatible_with<_EnvProvider,
scheduler_type,
allocator_type>)
{
return scheduler_type(get_scheduler(STDEXEC::get_env(__has_env)), __alloc);
}
else if constexpr (__task::__has_scheduler_compatible_with<_EnvProvider, scheduler_type>)
{
return scheduler_type(get_scheduler(STDEXEC::get_env(__has_env)));
}
Expand Down Expand Up @@ -350,7 +359,7 @@ namespace STDEXEC
template <class _EnvProvider>
constexpr explicit __opstate_base(task&& __task, _EnvProvider const & __has_env) noexcept
: allocator_type(__mk_alloc(__has_env))
, __sch_(__mk_sched(__has_env))
, __sch_(__mk_sched(__has_env, __get_allocator()))
, __task_(static_cast<task&&>(__task))
{
auto& __promise = __task_.__coro_.promise();
Expand All @@ -376,7 +385,7 @@ namespace STDEXEC
virtual auto __canceled() noexcept -> __std::coroutine_handle<> = 0;

[[nodiscard]]
constexpr auto __get_allocator() const noexcept -> allocator_type
constexpr auto __get_allocator() const noexcept -> allocator_type const &
{
return static_cast<allocator_type const &>(*this);
}
Expand Down
7 changes: 3 additions & 4 deletions include/stdexec/__detail/__task_scheduler.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -598,13 +598,12 @@ namespace STDEXEC
class __opstate : _Alloc
{
public:
using allocator_type = _Alloc;
using receiver_proxy = system_context_replaceability::receiver_proxy;
using __receiver_t = __detail::__proxy_receiver<receiver_proxy, _Env>;
using __rcvr_proxy_t = system_context_replaceability::receiver_proxy;
using __receiver_t = __detail::__proxy_receiver<__rcvr_proxy_t, _Env>;

constexpr explicit __opstate(_Alloc __alloc,
_Sndr __sndr,
receiver_proxy& __rcvr,
__rcvr_proxy_t& __rcvr,
bool __in_situ)
: _Alloc(std::move(__alloc))
, __opstate_(STDEXEC::connect(std::move(__sndr),
Expand Down
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