Defined in header
C atomic_fetch_or( volatile A* obj, M arg );
C atomic_fetch_or_explicit( volatile A* obj, M arg, memory_order order );
Atomically replaces the value pointed by
obj with the result of bitwise OR between the old value of
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
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 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.
|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
- C11 standard (ISO/IEC 9899:2011):
- 220.127.116.11 The atomic_fetch and modify generic functions (p: 284-285)
 See also
| atomic bitwise AND |
| atomic bitwise exclusive OR |
C++ documentation for atomic_fetch_or, atomic_fetch_or_explicit