atomic_fetch_or, atomic_fetch_or_explicit

Defined in header <stdatomic.h>
C atomic_fetch_or ( volatile A * obj, M arg ) ;	(1)	(since C11)
C atomic_fetch_or_explicit ( volatile A * obj, M arg, memory_order order ) ;	(2)	(since C11)

Atomically replaces the value pointed by obj with the result of bitwise OR between the old value of obj and arg , and returns the value obj held previously. The operation is read-modify-write operation. The first version orders memory accesses according to memory_order_seq_cst , the second version orders memory accesses according to order .

This is a generic function defined for all atomic object types A . The argument is pointer to a volatile atomic type to accept addresses of both non-volatile and volatile (e.g. memory-mapped I/O) atomic objects, and volatile semantic is preserved when applying this operation to volatile atomic objects. M is either the non-atomic type corresponding to A if A is atomic integer type, or ptrdiff_t if A is atomic pointer type.

It is unspecified whether the name of a generic function is a macro or an identifier declared with external linkage. If a macro definition is suppressed in order to access an actual function (e.g. parenthesized like ( atomic_fetch_or ) ( ... ) ), or a program defines an external identifier with the name of a generic function, the behavior is undefined.

Parameters

obj	-	pointer to the atomic object to modify
arg	-	the value to bitwise OR to the value stored in the atomic object
order	-	the memory synchronization ordering for this operation: all values are permitted

Return value

The value held previously be the atomic object pointed to by obj .

References

See also

atomic_fetch_and atomic_fetch_and_explicit (C11)	atomic bitwise AND (function)
atomic_fetch_xor atomic_fetch_xor_explicit (C11)	atomic bitwise exclusive OR (function)
C++ documentation for atomic_fetch_or , atomic_fetch_or_explicit