atomic_compare_exchange_strong_explicit
is a function that compares memory contents pointed to by two different objects. In addition, it also allows you to specify the memory order in the case of success and failure. memory_order is used as an argument to functions that involve atomic operations for synchronization of operations on other threads.
bool atomic_compare_exchange_strong_explicit( volatile A* obj, C* expected, C desired, memory_order success, memory_order failure );
The function compares the value of obj
with expected
. If they are bitwise equal, it replaces the value contained in obj
with the desired
value. Otherwise, it replaces the value pointed by expected
with the one contained in obj
by performing a load operation.
The operation of the function described above, where it reads and replaces data is atomic. This means that other threads cannot change the value between the time it is read and replaced.
As the name suggests, this function makes strong comparisons which means that the actual contents on the disk are compared. This comparison may fail for some values that compare using the ==
operator.
Unlike its counterpart, atomic_compare_exchange_weak
, this function only returns true when both the values pointed by obj
and expected
are indeed equal to each other. Hence, it does not allow any spurious failures. But, in some scenarios where loops are used, atomic_compare_exchange_weak
is a better option performance-wise.
obj
is a pointer to an atomic object to be compared.expected
is a pointer to the value that is to be compared with the one contained in obj
.desired
is the value to store in obj
if the comparison is successful.success
is the synchronization mode when the comparison is successful. All memory_order
values are accepted in this argument.failure
is the synchronization mode when the comparison is unsuccessful. All memory_order
values except memory_order_release
, memory_order_acq_rel
and the ones stronger than success
are accepted in this argument.The function returns true
if the values pointed by obj
and expected
are equal and false
if otherwise.
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