atomic_flag_test_and_set, atomic_flag_test_and_set_explicit

 

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Atomic flags atomic_flag ATOMIC_FLAG_INIT atomic_flag_test_and_set atomic_flag_clear Memory ordering memory_order kill_dependency atomic_thread_fence atomic_signal_fence Mutual exclusion mtx_init mtx_lock mtx_timedlock mtx_trylock call_once mtx_unlock mtx_destroy mtx_plainmtx_recursivemtx_timed Condition variables cnd_init cnd_signal cnd_broadcast cnd_wait cnd_timedwait cnd_destroy Thread-local storage thread_local TSS_DTOR_ITERATIONS    tss_create tss_get tss_set tss_delete

 

Defined in header <stdatomic.h>
_Bool atomic_flag_test_and_set( volatile atomic_flag* obj );	(1)	(since C11)
_Bool atomic_flag_test_and_set_explicit( volatile atomic_flag* obj, memory_order order );	(2)	(since C11)

Atomically changes the state of a atomic_flag pointed to by obj to set (true) and returns the previous value. The first version orders memory accesses according to memory_order_seq_cst, the second version orders memory accesses according to order.

The argument is pointer to a volatile atomic flag to accept addresses of both non-volatile and volatile (e.g. memory-mapped I/O) atomic flags.

Parameters

obj	-	pointer to the atomic flag object to modify
order	-	the memory synchronization ordering for this operation: all values are permitted

Return value

The previous value held by the atomic flag pointed to by obj.

References

• C17 standard (ISO/IEC 9899:2018):

• 7.17.8.1 The atomic_flag_test_and_set functions (p: 209)

• C11 standard (ISO/IEC 9899:2011):

• 7.17.8.1 The atomic_flag_test_and_set functions (p: 285-286)

See also

atomic_flag_clearatomic_flag_clear_explicit (C11)

sets an atomic_flag to false (function)