ATOMIC_*_LOCK_FREE

定义于头文件 `<stdatomic.h>`
#define ATOMIC_BOOL_LOCK_FREE /* implementation-defined / #define ATOMIC_CHAR_LOCK_FREE / implementation-defined / #define ATOMIC_CHAR16_T_LOCK_FREE / implementation-defined / #define ATOMIC_CHAR32_T_LOCK_FREE / implementation-defined / #define ATOMIC_WCHAR_T_LOCK_FREE / implementation-defined / #define ATOMIC_SHORT_LOCK_FREE / implementation-defined / #define ATOMIC_INT_LOCK_FREE / implementation-defined / #define ATOMIC_LONG_LOCK_FREE / implementation-defined / #define ATOMIC_LLONG_LOCK_FREE / implementation-defined / #define ATOMIC_POINTER_LOCK_FREE / implementation-defined */		(C11 起)

展开成求值为 0 或 1 或 2 的预处理器常量表达式，它指示对应原子类型（有符号及无符号一同）的免锁属性。