atomic_flag_test_and_set, atomic_flag_test_and_set_explicit

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

See also

atomic_flag_clear atomic_flag_clear_explicit (C11)	sets an atomic_flag to false (function)
C++ documentation for atomic_flag_test_and_set , atomic_flag_test_and_set_explicit