pub rec Timespec;
来自时钟源的秒和纳秒
sec：整秒数 nsec：秒内的纳秒数 [0, 999999999]
pub val SEEK_SET: i32 = 0
文件定位基准（seek whence）
pub val SEEK_CUR: i32 = 1
pub val SEEK_END: i32 = 2
pub val PROT_NONE: u32 = 0b000
内存保护标志
pub val PROT_READ: u32 = 0b001
pub val PROT_WRITE: u32 = 0b010
pub val PROT_EXEC: u32 = 0b100
pub val ADVISE_NORMAL: u32 = 0
内存访问建议提示（memory advisory hints）
pub val ADVISE_RANDOM: u32 = 1
pub val ADVISE_SEQUENTIAL: u32 = 2
pub val ADVISE_WILL_NEED: u32 = 3
pub val ADVISE_DONT_NEED: u32 = 4
pub val HUGE_2MB: usize = 2097152
标准巨型页大小（huge page sizes）
pub val HUGE_1GB: usize = 1073741824
pub val HEAP_RESERVE: usize = 268435456
堆区域保留大小（256MB）
pub val NOT_FOUND: i64 = -1
平台无关的哨兵值
pub fun has_exited(status: i32) bool;
pub fun exit_code(status: i32) i32;
pub fun was_signaled(status: i32) bool;
pub fun term_signal(status: i32) i32;
pub fun was_stopped(status: i32) bool;
pub fun stop_signal(status: i32) i32;
pub fun was_continued(status: i32) bool;