Defined in header <atomic>  

(1)  (since C++11)  
template< class T > T atomic_fetch_xor( std::atomic<T>* obj, typename std::atomic<T>::value_type arg ) noexcept;  
template< class T > T atomic_fetch_xor( volatile std::atomic<T>* obj, typename std::atomic<T>::value_type arg ) noexcept;  
(2)  (since C++11)  
template< class T > T atomic_fetch_xor_explicit( std::atomic<T>* obj, typename std::atomic<T>::value_type arg, std::memory_order order) noexcept;  
template< class T > T atomic_fetch_xor_explicit( volatile std::atomic<T>* obj, typename std::atomic<T>::value_type arg, std::memory_order order) noexcept; 
Atomically replaces the value pointed by obj
with the result of bitwise XOR between the old value of obj
and arg
. Returns the value obj
held previously.
The operation is performed as if the following is executed:
obj>fetch_xor(arg)
obj>fetch_xor(arg, order)
If std::atomic<T>
has no fetch_xor
member (this member is only provided for integral types), the program is illformed.
obj    pointer to the atomic object to modify 
arg    the value to bitwise XOR to the value stored in the atomic object 
order    the memory synchronization ordering for this operation: all values are permitted. 
The value immediately preceding the effects of this function in the modification order of *obj
.
template< class T > T atomic_fetch_xor( std::atomic<T>* obj, typename std::atomic<T>::value_type arg ) { return obj>fetch_xor(arg); } 
The following behaviorchanging defect reports were applied retroactively to previously published C++ standards.
DR  Applied to  Behavior as published  Correct behavior 

P0558R1  C++11  exact type match required because T is deduced from multiple arguments  T is deduced from the atomic argument only 
atomically performs bitwise XOR between the argument and the value of the atomic object and obtains the value held previously (public member function of std::atomic<T> ) 

(C++11)(C++11)  replaces the atomic object with the result of bitwise OR with a nonatomic argument and obtains the previous value of the atomic (function template) 
(C++11)(C++11)  replaces the atomic object with the result of bitwise AND with a nonatomic argument and obtains the previous value of the atomic (function template) 
C documentation for atomic_fetch_xor, atomic_fetch_xor_explicit 
© cppreference.com
Licensed under the Creative Commons AttributionShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/atomic/atomic_fetch_xor