std::atomic::fetch_or
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                    |  (since C++11)  (member only of atomic<Integral> template specialization)  | 
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|   T fetch_or( T arg,  
std::memory_order order = std::memory_order_seq_cst );  | 
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|   T fetch_or( T arg,  
std::memory_order order = std::memory_order_seq_cst ) volatile;  | 
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Atomically replaces the current value with the result of bitwise OR of the value and arg. The operation is read-modify-write operation. Memory is affected according to the value of order.
Contents | 
[edit] Parameters
| arg | - | the other argument of bitwise OR | 
| order | - | memory order constraints to enforce | 
[edit] Return value
The value immediately preceding the effects of this function in the modification order of *this.
[edit] Exceptions
noexcept specification:  
noexcept
  [edit] See also
|    (C++11)(C++11) 
 | 
   replaces the atomic object with the result of logical OR with a non-atomic argument and obtains the previous value of the atomic   (function template)  |