std::promise

 

C++

Compiler support

Freestanding and hosted

Language

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Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

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Technical specifications

Symbols index

External libraries

 

Concurrency support library

Threads thread (C++11) jthread (C++20) hardware_destructive_interference_sizehardware_constructive_interference_size (C++17)(C++17) this_thread namespace get_id (C++11) yield (C++11) sleep_for (C++11) sleep_until (C++11) Cooperative cancellation stop_token (C++20) inplace_stop_token (C++26) never_stop_token (C++26) stop_source (C++20) inplace_stop_source (C++26)   stop_callback (C++20) inplace_stop_callback (C++26) stop_callback_for_t (C++26) stoppable_token (C++26) unstoppable_token (C++26) stoppable-source (C++26) stoppable-callback-for (C++26)   Mutual exclusion mutex (C++11) recursive_mutex (C++11) shared_mutex (C++17) timed_mutex (C++11) recursive_timed_mutex (C++11) shared_timed_mutex (C++14) Generic lock management lock (C++11) lock_guard (C++11) scoped_lock (C++17) unique_lock (C++11) shared_lock (C++14) once_flag (C++11) call_once (C++11) try_lock (C++11) defer_locktry_to_lockadopt_lockdefer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11)(C++11)(C++11)(C++11) Condition variables condition_variable (C++11) condition_variable_any (C++11) notify_all_at_thread_exit (C++11) cv_status (C++11) Semaphores counting_semaphorebinary_semaphore (C++20)(C++20) Latches and Barriers latch (C++20) barrier (C++20) Futures promise (C++11) future (C++11) shared_future (C++11) packaged_task (C++11) async (C++11) launch (C++11) future_status (C++11) future_error (C++11) future_category (C++11) future_errc (C++11) Safe Reclamation rcu_obj_base (C++26) rcu_domain (C++26) rcu_default_domain (C++26) rcu_synchronize (C++26) rcu_barrier (C++26) rcu_retire (C++26) Hazard Pointers hazard_pointer_obj_base (C++26) hazard_pointer (C++26) make_hazard_pointer (C++26)

Atomic types atomic (C++11) atomic_ref (C++20) atomic_flag (C++11) Initialization of atomic types atomic_init (C++11)(deprecated in C++20) ATOMIC_VAR_INIT (C++11)(deprecated in C++20) ATOMIC_FLAG_INIT (C++11) Memory ordering memory_order (C++11) kill_dependency (C++11) atomic_thread_fence (C++11) atomic_signal_fence (C++11) Free functions for atomic operations atomic_storeatomic_store_explicit (C++11)(C++11) atomic_loadatomic_load_explicit (C++11)(C++11) atomic_exchangeatomic_exchange_explicit (C++11)(C++11) atomic_compare_exchange_weakatomic_compare_exchange_weak_explicitatomic_compare_exchange_strongatomic_compare_exchange_strong_explicit (C++11)(C++11)(C++11)(C++11) atomic_fetch_addatomic_fetch_add_explicit (C++11)(C++11) atomic_fetch_subatomic_fetch_sub_explicit (C++11)(C++11) atomic_fetch_andatomic_fetch_and_explicit (C++11)(C++11) atomic_fetch_oratomic_fetch_or_explicit (C++11)(C++11) atomic_fetch_xoratomic_fetch_xor_explicit (C++11)(C++11) atomic_fetch_maxatomic_fetch_max_explicit (C++26)(C++26) atomic_fetch_minatomic_fetch_min_explicit (C++26)(C++26) atomic_is_lock_free (C++11) atomic_waitatomic_wait_explicit (C++20)(C++20) atomic_notify_one (C++20) atomic_notify_all (C++20) Free functions for atomic flags atomic_flag_test_and_setatomic_flag_test_and_set_explicit (C++11)(C++11) atomic_flag_clearatomic_flag_clear_explicit (C++11)(C++11) atomic_flag_testatomic_flag_test_explicit (C++20)(C++20) atomic_flag_waitatomic_flag_wait_explicit (C++20)(C++20) atomic_flag_notify_one (C++20) atomic_flag_notify_all (C++20)

 

std::promise

Member functions

promise::promise

promise::~promise

promise::operator=

promise::swap

Getting the result

promise::get_future

Setting the result

promise::set_value

promise::set_value_at_thread_exit

promise::set_exception

promise::set_exception_at_thread_exit

Non-member Functions

swap(std::promise)

Helper Classes

uses_allocator<std::promise>

 

Template:ddcl list begin <tr class="t-dsc-header">

<td>

Defined in header <future>

</td>

<td></td> <td></td> </tr> <tr class="t-dcl ">

<td >

template< class T > class promise;

</td>

<td > (1) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

template< class T > class promise<T&>;

</td>

<td > (2) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

template<>          class promise<void>;

</td>

<td > (3) </td> <td > (since C++11) </td> </tr> Template:ddcl list end

The class template std::promise provides a facility to store a value that is later acquired asynchronously via a std::future object, that the std::promise can supply.

Member functions

Template:cpp/thread/promise/dcl list constructorTemplate:cpp/thread/promise/dcl list destructorTemplate:cpp/thread/promise/dcl list operator=Template:cpp/thread/promise/dcl list swapTemplate:cpp/thread/promise/dcl list get futureTemplate:cpp/thread/promise/dcl list set valueTemplate:cpp/thread/promise/dcl list set value at thread exitTemplate:cpp/thread/promise/dcl list set exceptionTemplate:cpp/thread/promise/dcl list set exception at thread exit

Getting the result

Setting the result

Non-member functions

Template:cpp/thread/promise/dcl list swap2

Helper classes

Template:cpp/thread/promise/dcl list uses allocator