Code size analysis

pw_async2: Cooperative async tasks for embedded

Core async2 implementation

The following table shows the code size cost of adding pw_async2 to a system. These size reports assume a baseline system with an RTOS which already uses a handful of core Pigweed components including HAL abstractions and pw_allocator.

The first row captures the core of pw_async2: the dispatcher, tasks, and wakers, using the pw::async2::BasicDispatcher. This is the minimum size cost a system must pay to adopt pw_async2. The following row demonstrates the cost of adding another task to this system. Of course, the majority of the cost of the task exists within its implementation — this simply shows that there is minimal internal overhead.

Label	Segment	Delta
Full cost of including pw_async2	FLASH +288 [section .rodata] +16 pw::containers::internal::GenericIntrusiveList<>::clear() -4 __bi_84 +228 pw::async2::size_report::Measure() -2 pw::containers::internal::IntrusiveForwardListItem::DoGetPrevious() +16 pw::containers::internal::LegacyIntrusiveList<>::push_back() +4 operator delete() NEW +228 pw::async2::Task::RunInDispatcher() NEW +80 pw::async2::Dispatcher::Post() NEW +72 pw::async2::Task::Wake() NEW +72 pw::async2::size_report::PendableValue<>::Get() NEW +56 pw::async2::Dispatcher::PopTaskToRun() NEW +56 pw::async2::Task::PostTo() NEW +56 pw::async2::Waker::operator=() NEW +56 pw::async2::internal::CloneWaker() NEW +56 pw::async2::size_report::MockTask::DoPend() NEW +50 pw::async2::Dispatcher::WakeTask() NEW +48 pw::async2::size_report::MockTask::~MockTask() NEW +42 pw::async2::Dispatcher::~Dispatcher() NEW +40 pw::async2::Dispatcher::Deregister() NEW +40 pw::async2::Dispatcher::PopTaskToRunLocked() NEW +40 pw::async2::Waker::InternalCloneIntoLocked() NEW +40 pw::async2::Waker::Wake() NEW +38 pw::async2::Task::~Task() NEW +36 __atomic_exchange_1 NEW +32 __atomic_store_1 NEW +32 pw::async2::Dispatcher::PopAndRunAllReadyTasks() NEW +32 pw::async2::Waker::InsertIntoTaskWakerList() NEW +32 pw::async2::Waker::RemoveFromTaskWakerList() NEW +28 pw::async2::BasicDispatcher NEW +28 pw::async2::Dispatcher::UnpostTaskList() NEW +28 pw::async2::RunnableDispatcher::RunToCompletion() NEW +26 pw::async2::Dispatcher::RunTask() NEW +26 pw::async2::Task::RemoveAllWakersLocked() NEW +24 pw::async2::Waker::Waker() NEW +24 pw::async2::size_report::MockTask::DoPend()::{lambda()#1}::operator()() NEW +24 pw::async2::size_report::PendableValue<>::Get()::{lambda()#1}::operator()() NEW +24 pw::containers::internal::IntrusiveListItemBase<>::unlist() NEW +22 pw::IntrusiveForwardList<>::pop_front() NEW +22 pw::async2::BasicDispatcher::~BasicDispatcher() NEW +20 pw::async2::Dispatcher NEW +20 pw::async2::PendFuncTask<> NEW +20 pw::async2::Task NEW +20 pw::async2::size_report::MockTask NEW +18 pw::async2::PendFuncTask<>::DoPend() NEW +18 pw::async2::Task::RemoveWakerLocked() NEW +18 pw::containers::internal::LegacyIntrusiveList<>::Item::~Item() NEW +16 pw::async2::Waker::InsertIntoTaskWakerListLocked() NEW +16 pw::async2::Waker::RemoveFromTaskWakerListLocked() NEW +16 pw::async2::Waker::~Waker() NEW +16 pw::containers::internal::LegacyIntrusiveList<>::~LegacyIntrusiveList() NEW +14 pw::async2::PendFuncTask<>::~PendFuncTask() NEW +14 pw::async2::Task::Unpost() NEW +12 pw::async2::BasicDispatcher::DoWaitForWake() NEW +12 pw::async2::Task::AddWakerLocked() NEW +12 pw::async2::internal::StoreWaker() NEW +10 pw::async2::BasicDispatcher::DoWake() NEW +8 pw::async2::RunnableDispatcher::DoRunUntilStalled()	+2,336
	RAM +8 [section .data] NEW +24 pw::async2::size_report::(anonymous namespace)::dispatcher NEW +8 pw::async2::internal::lock()::lock	+40
Base incremental cost of adding a task to an existing async system	FLASH +56 pw::async2::size_report::Measure() +8 vClearInterruptMaskFromISR	+64

async2 utilities

Pigweed provides several utilities to simplify writing asynchronous code. Among these are combinators which operate over several pendables, such as Join which waits for all pendables to complete, and Select which waits for the first pendable to complete.

The table below demonstrates the code size impact of using these utilities. For both Join and Select, the report shows:

• The initial cost of using the utility with multiple pendables of the same type.

• The incremental cost of adding a second call with pendables of different types, which demonstrates the overhead of template specialization.

Additionally, the table includes a comparison showing the code size difference between using the Select helper versus manually polling each pendable.

Label	Segment	Delta
Size of calling Select() with several pendables of the same type	FLASH +164 [section .rodata] -88 pw::async2::size_report::Measure() -2 pw::async2::size_report::MockTask::~MockTask() +16 pw::async2::PendFuncTask<> +14 pw::async2::PendFuncTask<>::DoPend() +2 pw::containers::internal::LegacyIntrusiveList<>::Item::~Item() -6 operator delete() +4 __bi_84 NEW +260 pw::async2::size_report::SingleTypeSelect() NEW +192 pw::async2::Selector<>::PendFrom<>() NEW +60 pw::async2::MemberPendableWrapper<>::Pend() NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIiEEFNS2_4PollIiEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +24 pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>() NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj0EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_1NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3OZNSK_16SingleTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj1EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_1NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3OZNSK_16SingleTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj2EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_1NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3OZNSK_16SingleTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_1NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3OZNSK_16SingleTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +12 _ZNSt3__220__throw_if_valuelessB8nn220000IJRNS_7variantIJN2pw6async212SelectResultILj0EiEENS4_ILj1EiEENS4_ILj2EiEENS3_21AllPendablesCompletedEEEEEEEvDpOT_ NEW +12 _ZNSt3__226__throw_bad_variant_accessB8nn220000Ev NEW +10 pw::async2::Selector<>::Pend() NEW +6 std::__2::__libcpp_verbose_abort()	+760
Size of an additional a call to Select() with pendables of different types	FLASH +182 pw::async2::Selector<>::PendFrom<>() +8 pw::async2::size_report::Measure() +140 pw::async2::size_report::PendableValue<>::Get() +116 pw::async2::MemberPendableWrapper<>::Pend() +2 pw::async2::size_report::MockTask::~MockTask() +36 pw::async2::PendFuncTask<> +32 pw::async2::PendFuncTask<>::DoPend() +48 pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>() +48 pw::async2::size_report::PendableValue<>::Get()::{lambda()#1}::operator()() -2 pw::containers::internal::LegacyIntrusiveList<>::Item::~Item() -4 __bi_84 -2 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EiEENSD_ILj2EiEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SingleTypeSelectEjE3$_1NS_5tupleIJOZNSK_16SingleTypeSelectEjE3$_2OZNSK_16SingleTypeSelectEjE3$_3OZNSK_16SingleTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ +14 pw::async2::PendFuncTask<>::~PendFuncTask() +8 vClearInterruptMaskFromISR +10 pw::async2::Selector<>::Pend() NEW +256 pw::async2::size_report::MultiTypeSelect() NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIcEEFNS2_4PollIcEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIjEEFNS2_4PollIjEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj0EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_1NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3OZNSK_15MultiTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj1EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_1NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3OZNSK_15MultiTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj2EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_1NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3OZNSK_15MultiTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +14 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report15MultiTypeSelectEjE3$_1NS_5tupleIJOZNSK_15MultiTypeSelectEjE3$_2OZNSK_15MultiTypeSelectEjE3$_3OZNSK_15MultiTypeSelectEjE3$_4EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSV_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSU_DpT0_ NEW +12 _ZNSt3__220__throw_if_valuelessB8nn220000IJRNS_7variantIJN2pw6async212SelectResultILj0EiEENS4_ILj1EjEENS4_ILj2EcEENS3_21AllPendablesCompletedEEEEEEEvDpOT_	+1,008
Cost of using Select() versus manually polling each pendable	FLASH +164 [section .rodata] -62 pw::async2::size_report::SelectComparison::Pend() +16 pw::async2::PendFuncTask<> -2 pw::async2::PendFuncTask<>::DoPend() -4 __bi_84 -6 operator delete() -4 vClearInterruptMaskFromISR NEW +180 pw::async2::Selector<>::PendFrom<>() NEW +176 pw::async2::MemberPendableWrapper<>::Pend() NEW +72 pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>() NEW +72 pw::async2::size_report::SelectComparison::Pend()::{lambda()#1}::operator()() NEW +36 pw::async2::internal::VisitSelectResult<>()::{lambda()#1}::operator()<>() NEW +32 _ZNSt3__216__variant_detail12__visitation9__variant13__visit_valueB8nn220000IZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_JSF_EEEDcSU_DpOT0_ NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIcEEFNS2_4PollIcEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIiEEFNS2_4PollIiEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIjEEFNS2_4PollIjEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +22 _ZNSt3__25visitB8nn220000IZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS2_12SelectResultILj0EiEENS6_ILj1EjEENS6_ILj2EcEENS2_21AllPendablesCompletedEEEEZNS2_11size_report16SelectComparison4PendERNS2_7ContextEEUlSA_E_NS_5tupleIJOZNSE_4PendESG_EUliE_OZNSE_4PendESG_EUljE_OZNSE_4PendESG_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSR_E_JSC_EvEEDcSR_DpOT0_ NEW +18 pw::async2::VisitSelectResult<>() NEW +18 pw::async2::internal::VisitSelectResult<>() NEW +12 _ZNSt3__220__throw_if_valuelessB8nn220000IJRNS_7variantIJN2pw6async212SelectResultILj0EiEENS4_ILj1EjEENS4_ILj2EcEENS3_21AllPendablesCompletedEEEEEEEvDpOT_ NEW +12 _ZNSt3__226__throw_bad_variant_accessB8nn220000Ev NEW +12 _ZNSt3__28__invokeB8nn220000IJZN2pw6async211size_report16SelectComparison4PendERNS2_7ContextEEUliE_iEEENS_20__invoke_result_implIvJDpT_EE4typeEDpOS9_ NEW +10 _ZNKSt3__216__variant_detail12__visitation9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_EclB8nn220000IJRNS0_5__altILj0ESA_EEEEEDcDpOT_ NEW +10 _ZNKSt3__216__variant_detail12__visitation9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_EclB8nn220000IJRNS0_5__altILj1ESB_EEEEEDcDpOT_ NEW +10 _ZNKSt3__216__variant_detail12__visitation9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS5_12SelectResultILj0EiEENS9_ILj1EjEENS9_ILj2EcEENS5_21AllPendablesCompletedEEEEZNS5_11size_report16SelectComparison4PendERNS5_7ContextEEUlSD_E_NS_5tupleIJOZNSH_4PendESJ_EUliE_OZNSH_4PendESJ_EUljE_OZNSH_4PendESJ_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSU_E_EclB8nn220000IJRNS0_5__altILj2ESC_EEEEEDcDpOT_ NEW +10 _ZNSt3__28__invokeB8nn220000IJZN2pw6async211size_report16SelectComparison4PendERNS2_7ContextEEUlcE_cEEENS_20__invoke_result_implIvJDpT_EE4typeEDpOS9_ NEW +10 _ZNSt3__28__invokeB8nn220000IJZN2pw6async211size_report16SelectComparison4PendERNS2_7ContextEEUljE_jEEENS_20__invoke_result_implIvJDpT_EE4typeEDpOS9_ NEW +10 pw::async2::Selector<>::Pend() NEW +8 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj0EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_ NEW +8 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj1EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_ NEW +8 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj2EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_ NEW +6 std::__2::__libcpp_verbose_abort() NEW +2 _ZNSt3__216__variant_detail12__visitation6__base12__dispatcherIJLj3EEE10__dispatchB8nn220000IONS1_9__variant15__value_visitorIZN2pw6async28internal17VisitSelectResultIRNS_7variantIJNS9_12SelectResultILj0EiEENSD_ILj1EjEENSD_ILj2EcEENS9_21AllPendablesCompletedEEEEZNS9_11size_report16SelectComparison4PendERNS9_7ContextEEUlSH_E_NS_5tupleIJOZNSL_4PendESN_EUliE_OZNSL_4PendESN_EUljE_OZNSL_4PendESN_EUlcE_EEEJLj0ELj1ELj2EEEEvOT_OT0_OT1_NS_16integer_sequenceIjJXspT2_EEEEEUlSY_E_EEJRNS0_6__baseILNS0_6_TraitE0EJSE_SF_SG_SH_EEEEEEDcSX_DpT0_	+928
Size of calling Join() with several pendables of the same type	FLASH +112 [section .rodata] -88 pw::async2::size_report::Measure() -2 pw::async2::size_report::MockTask::~MockTask() +16 pw::async2::PendFuncTask<>::DoPend() +2 pw::containers::internal::LegacyIntrusiveList<>::Item::~Item() +4 vClearInterruptMaskFromISR NEW +212 pw::async2::size_report::SingleTypeJoin() NEW +124 pw::async2::Joiner<>::PendElement<>() NEW +60 pw::async2::MemberPendableWrapper<>::Pend() NEW +46 pw::async2::Joiner<>::Pend() NEW +42 pw::async2::Joiner<>::PendElements<>() NEW +40 _ZNSt3__223__optional_storage_baseINS_5tupleIJOiS2_S2_EEELb0EE13__assign_fromB8nn220000INS_27__optional_move_assign_baseIS3_Lb0EEEEEvOT_ NEW +28 _ZNSt3__227__memberwise_forward_assignB8nn220000INS_5tupleIJOiS2_S2_EEES3_JS2_S2_S2_EJLj0ELj1ELj2EEEEvRT_OT0_NS_13__tuple_typesIJDpT1_EEENS_18__integer_sequenceIjJXspT2_EEEE NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIiEEFNS2_4PollIiEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +24 pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>() NEW +12 _ZNSt3__25tupleIJOiS1_S1_EEaSB8nn220000EOS2_	+656
Size of an additional a call to Join() with pendables of different types	FLASH +8 pw::async2::size_report::Measure() +118 pw::async2::Joiner<>::PendElement<>() +140 pw::async2::size_report::PendableValue<>::Get() +116 pw::async2::MemberPendableWrapper<>::Pend() +46 pw::async2::Joiner<>::Pend() +2 pw::async2::size_report::MockTask::~MockTask() +42 pw::async2::Joiner<>::PendElements<>() +34 pw::async2::PendFuncTask<>::DoPend() -2 _ZNSt3__227__memberwise_forward_assignB8nn220000INS_5tupleIJOiS2_S2_EEES3_JS2_S2_S2_EJLj0ELj1ELj2EEEEvRT_OT0_NS_13__tuple_typesIJDpT1_EEENS_18__integer_sequenceIjJXspT2_EEEE +48 pw::async2::MemberPendableWrapper<>::Pend()::{lambda()#1}::operator()<>() +48 pw::async2::size_report::PendableValue<>::Get()::{lambda()#1}::operator()() +20 pw::async2::PendFuncTask<> -2 pw::containers::internal::LegacyIntrusiveList<>::Item::~Item() -8 vClearInterruptMaskFromISR +14 pw::async2::PendFuncTask<>::~PendFuncTask() +4 __bi_84 NEW +164 pw::async2::size_report::MultiTypeJoin() NEW +40 _ZNSt3__223__optional_storage_baseINS_5tupleIJOiOjOcEEELb0EE13__assign_fromB8nn220000INS_27__optional_move_assign_baseIS5_Lb0EEEEEvOT_ NEW +28 _ZNSt3__227__memberwise_forward_assignB8nn220000INS_5tupleIJOiOjOcEEES5_JS2_S3_S4_EJLj0ELj1ELj2EEEEvRT_OT0_NS_13__tuple_typesIJDpT1_EEENS_18__integer_sequenceIjJXspT2_EEEE NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIcEEFNS2_4PollIcEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +24 _ZNSt3__28__invokeB8nn220000IJMN2pw6async211size_report13PendableValueIjEEFNS2_4PollIjEERNS2_7ContextEERPS5_S9_EEENS_20__invoke_result_implIvJDpT_EE4typeEDpOSF_ NEW +12 _ZNSt3__25tupleIJOiOjOcEEaSB8nn220000EOS4_	+920

OnceSender and OnceReceiver

The next table shows sizes of the pair of OnceSender and OnceReceiver types, which allow for returning a delayed result from an async function, similar to a Future type in other languages. This type is templated on its stored value, causing specialization overhead for each type sent through the sender/receiver pair. The first row showcases the base cost of using a OnceSender and OnceReceiver; the second row adds another template specialization on top of this to demonstrate the incremental cost.

Label	Segment	Delta
Size of OnceSender / OnceReceiver	FLASH +172 [section .rodata] +52 pw::async2::size_report::Measure() -6 operator delete() NEW +112 pw::async2::OnceReceiver<>::Pend() NEW +96 pw::async2::OnceReceiver<>::OnceReceiver() NEW +60 pw::async2::size_report::SenderAdd() NEW +52 pw::async2::OnceSender<>::emplace<>() NEW +52 pw::async2::size_report::ReceiverTask<>::ReceiverTask() NEW +46 pw::async2::size_report::ReceiverTask<>::~ReceiverTask() NEW +44 pw::async2::OnceReceiver<>::~OnceReceiver() NEW +44 pw::async2::OnceSender<>::~OnceSender() NEW +40 _ZN2pw15internal_result12StatusOrDataIjLb1EEC2INS_6StatusETnNSt3__29enable_ifIXsr3std16is_constructibleIS4_OT_EE5valueEiE4typeELi0EEES8_ NEW +24 pw::async2::OnceReceiver<>::Pend()::{lambda()#1}::operator()() NEW +22 pw::async2::size_report::ReceiverTask<>::DoPend() NEW +20 _ZNSt3__28optionalIN2pw6ResultIjEEEC2B8nn220000INS1_6StatusETnNS_9enable_ifIXclsr22_CheckOptionalLikeCtorIT_OS8_EE17__enable_implicitIS8_EEEiE4typeELi0EEEONS0_IS8_EE NEW +20 pw::async2::size_report::ReceiverTask<> NEW +20 std::__2::pair<>::~pair() NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIjEELb0EE11__constructB8nn220000IJNS1_6StatusEEEEvDpOT_ NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIjEELb0EE16__construct_fromB8nn220000INS_8optionalINS1_6StatusEEEEEvOT_ NEW +12 _ZNRSt3__28optionalIjE5valueB8nn220000Ev NEW +12 _ZNSt3__227__throw_bad_optional_accessB8nn220000Ev NEW +6 std::__2::__libcpp_verbose_abort()	+928
	RAM NEW +8 pw::async2::sender_receiver_lock()::lock	+8
Cost of additional OnceSender / OnceReceiver template specialization	FLASH +56 pw::async2::size_report::Measure() +112 pw::async2::OnceReceiver<>::Pend() +96 pw::async2::OnceReceiver<>::OnceReceiver() +52 pw::async2::OnceSender<>::emplace<>() +52 pw::async2::size_report::ReceiverTask<>::ReceiverTask() +46 pw::async2::size_report::ReceiverTask<>::~ReceiverTask() +44 pw::async2::OnceReceiver<>::~OnceReceiver() +44 pw::async2::OnceSender<>::~OnceSender() +24 pw::async2::OnceReceiver<>::Pend()::{lambda()#1}::operator()() +22 pw::async2::size_report::ReceiverTask<>::DoPend() +20 pw::async2::size_report::ReceiverTask<> +18 std::__2::pair<>::~pair() +4 __bi_84 +8 vClearInterruptMaskFromISR NEW +62 pw::async2::size_report::SenderSub() NEW +40 _ZN2pw15internal_result12StatusOrDataIiLb1EEC2INS_6StatusETnNSt3__29enable_ifIXsr3std16is_constructibleIS4_OT_EE5valueEiE4typeELi0EEES8_ NEW +20 _ZNSt3__28optionalIN2pw6ResultIiEEEC2B8nn220000INS1_6StatusETnNS_9enable_ifIXclsr22_CheckOptionalLikeCtorIT_OS8_EE17__enable_implicitIS8_EEEiE4typeELi0EEEONS0_IS8_EE NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIiEELb0EE11__constructB8nn220000IJNS1_6StatusEEEEvDpOT_ NEW +14 _ZNSt3__223__optional_storage_baseIN2pw6ResultIiEELb0EE16__construct_fromB8nn220000INS_8optionalINS1_6StatusEEEEEvOT_ NEW +12 _ZNRSt3__28optionalIiE5valueB8nn220000Ev	+760