| 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
- C11 standard (ISO/IEC 9899:2011):
- 7.17.8.1 The atomic_flag_test_and_set functions (p: 285-286)
See also
| sets an atomic_flag to false (function) | |
C++ documentation for atomic_flag_test_and_set, atomic_flag_test_and_set_explicit | |
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