int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock)
{
# if defined(__GNUC__) && defined(__ATOMIC_ACQ_REL)
    if (__atomic_is_lock_free(sizeof(*val), val)) {
        *ret = __atomic_add_fetch(val, amount, __ATOMIC_ACQ_REL);
        return 1;
    }
# endif
    if (!CRYPTO_THREAD_write_lock(lock))
        return 0;

    *val += amount;
    *ret  = *val;

    if (!CRYPTO_THREAD_unlock(lock))
        return 0;

    return 1;
}