atomic_exchange, atomic_exchange_explicit

Defined in header <stdatomic.h>
C atomic_exchange ( volatile A * obj, C desired ) ;	(1)	(since C11)
C atomic_exchange_explicit ( volatile A * obj, C desired, memory_order order ) ;	(2)	(since C11)

Atomically replaces the value pointed by obj with desired 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. C is the non-atomic type corresponding to A .

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_exchange ) ( ... ) ), 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
desired	-	the value to replace the atomic object with
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_compare_exchange_strong atomic_compare_exchange_strong_explicit atomic_compare_exchange_weak atomic_compare_exchange_weak_explicit (C11)	swaps a value with an atomic object if the old value is what is expected, otherwise reads the old value (function)
C++ documentation for atomic_exchange , atomic_exchange_explicit