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#ifndef __has_builtin
#define __has_builtin(x) 0
#endif
#ifndef __has_feature
#define __has_feature(x) 0
#endif
/**
* Swap macro that enforces a happens-before relationship with a corresponding
* ATOMIC_LOAD.
*/
#if __has_feature(cxx_atomic)
#define ATOMIC_SWAP(addr, val)\
__atomic_exchange(addr, val, __ATOMIC_ACQ_REL)
#elif __has_builtin(__sync_swap)
#define ATOMIC_SWAP(addr, val)\
__sync_swap(addr, val)
#else
#define ATOMIC_SWAP(addr, val)\
__sync_lock_test_and_set(addr, val)
#endif
#if __has_feature(cxx_atomic)
#define ATOMIC_LOAD(addr)\
__atomic_load(addr, __ATOMIC_ACQUIRE)
#else
#define ATOMIC_LOAD(addr)\
(__sync_synchronize(), *addr)
#endif