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atomic_compare_exchange_weak, atomic_compare_exchange_strong, atomic_compare_exchange_weak_explicit, atomic_compare_exchange_strong_explicit

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< c‎ | atomic

 
 
Biblioteca operações atômica
Tipos
Original:
Types
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memory_order
atomic_flag
Macros
Original:
Macros
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ATOMIC_***_LOCK_FREE
ATOMIC_FLAG_INIT
ATOMIC_VAR_INIT
kill_dependency
Funções
Original:
Functions
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atomic_flag_test_and_set
atomic_flag_clear
atomic_init
atomic_is_lock_free
atomic_store
atomic_load
atomic_exchange
atomic_compare_exchange
atomic_fetch_add
atomic_fetch_sub
atomic_fetch_or
atomic_fetch_xor
atomic_fetch_and
atomic_thread_fence
atomic_signal_fence
 
Defined in header <stdatomic.h>
_Bool atomic_compare_exchange_strong( volatile A* obj,
                                      C* expected, C desired );
(1)
_Bool atomic_compare_exchange_weak( volatile A *obj,
                                    C* expected, C desired );
(2)
_Bool atomic_compare_exchange_strong_explicit( volatile A* obj,

                                               C* expected, C desired,
                                               memory_order succ,

                                               memory_order fail );
(3)
_Bool atomic_compare_exchange_weak_explicit( volatile A *obj,

                                             C* expected, C desired,
                                             memory_order succ,

                                             memory_order fail );
(4)
Atomicamente compara o valor apontado por obj com o valor apontado por expected, e se estas forem iguais, substitui o ex-desired (executa ler-modificar-escrever a operação). Caso contrário, carrega o valor real apontado por obj em *expected (executa a operação de carga).
Original:
Atomically compares the value pointed to by obj with the value pointed to by expected, and if those are equal, replaces the former with desired (performs read-modify-write operation). Otherwise, loads the actual value pointed to by obj into *expected (performs load operation).
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Os modelos de memória para a leitura-modificação-gravação e operações de carga são succ e fail respectivamente. As versões (1-2) usar memory_order_seq_cst por padrão.
Original:
The memory models for the read-modify-write and load operations are succ and fail respectively. The (1-2) versions use memory_order_seq_cst by default.
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As formas fracas ((1) e (3)) das funções podem falhar spuriously, isto é, actuar como se *obj != *expected mesmo se eles forem iguais. Quando uma comparação e troca-se em um loop, a versão fraca trará melhor desempenho em algumas plataformas. Quando um fraco comparar-e-troca exigiria um laço e um forte não, o forte é preferível.
Original:
The weak forms ((1) and (3)) of the functions are allowed to fail spuriously, that is, act as if *obj != *expected even if they are equal. When a compare-and-exchange is in a loop, the weak version will yield better performance on some platforms. When a weak compare-and-exchange would require a loop and a strong one would not, the strong one is preferable.
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Esta é uma função genérica definida para todos os tipos de objectos atómicos. A é o tipo de um objeto atômico, C é do tipo não-atômica correspondente a A.
Original:
This is a função genérica defined for all atomic object types. A is the type of an atomic object, C is the non-atomic type corresponding to A.
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[editar] Parâmetros

obj -
ponteiro para o objeto atômico para testar e modificar
Original:
pointer to the atomic object to test and modify
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expected -
ponteiro para o valor esperado para ser encontrado no objeto atómica
Original:
pointer to the value expected to be found in the atomic object
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desired -
o valor para armazenar no objeto atômico se for como o esperado
Original:
the value to store in the atomic object if it is as expected
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succ -
a sincronização de memória de ordenação para a leitura-modificação-gravação operação, se a comparação for bem-sucedido. Todos os valores são permitidos .
Original:
the memory synchronization ordering for the read-modify-write operation if the comparison succeeds. All values are permitted.
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fail -
a sincronização da memória de ordenação para a operação de carregamento se a comparação falhar. Não pode ser memory_order_release ou memory_order_ack_rel e não pode especificar mais forte do que succ ordenação
Original:
the memory synchronization ordering for the load operation if the comparison fails. Cannot be memory_order_release or memory_order_ack_rel and cannot specify stronger ordering than succ
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[editar] Valor de retorno

O resultado da comparação: true se *obj foi igual a *exp, false contrário.
Original:
The result of the comparison: true if *obj was equal to *exp, false otherwise.
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[editar] Veja também

swaps um valor com o valor de um objeto atómico
Original:
swaps a value with the value of an atomic object
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(função) [edit]
C++ documentation for atomic_compare_exchange_weak, atomic_compare_exchange_strong, atomic_compare_exchange_weak_explicit, atomic_compare_exchange_strong_explicit