The atomic_compare_exchange_weak
function compares memory contents that are pointed to by two different objects.
bool atomic_compare_exchange_weak( volatile A* obj, C* expected, C desired );
The function compares the value of obj
with expected
, and if they are bitwise equal, it replaces the value contained in obj
with 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.
This function reads and compares the actual contents on the disk of the value contained in
obj
and the value pointed byexpected
. The comparison may fail for some values that compare using the==
operator.
Unlike its counterpart, atomic_compare_exchange_strong
, this function is allowed to fail spuriously. This means that it can act as if *obj != *expected
even if they are the same and return false. Such behavior might be acceptable for certain algorithms that involve loops, which will to better performance on some platforms.
obj
is a pointer to an atomic object to be compared.expected
is a pointer to the value which is to be compared with the one contained in obj
.desired
is the value to store in obj
if the comparison is successful.The function returns true
if the values pointed by obj
and expected
are equal; otherwise, it returns false
.
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