EFAULT    = C.EFAULT
	EBUSY     = C.EBUSY
	EAGAIN    = C.EAGAIN
	ETIMEDOUT = C.ETIMEDOUT

	O_WRONLY   = C.O_WRONLY
	O_NONBLOCK = C.O_NONBLOCK
	O_CREAT    = C.O_CREAT
	O_TRUNC    = C.O_TRUNC
	O_CLOEXEC  = C.O_CLOEXEC

	PROT_NONE  = C.PROT_NONE
	PROT_READ  = C.PROT_READ
	PROT_WRITE = C.PROT_WRITE
	PROT_EXEC  = C.PROT_EXEC

	MAP_ANON    = C.MAP_ANON
	MAP_PRIVATE = C.MAP_PRIVATE
	MAP_FIXED   = C.MAP_FIXED

// Pipe returns a connected pair of Files; reads from r return bytes written to w.
// It returns the files and an error, if any.
func Pipe() (r *File, w *File, err error) {
	var p [2]int

	e := syscall.Pipe2(p[0:], syscall.O_CLOEXEC)
	if e != nil {
		return nil, nil, NewSyscallError("pipe2", e)
	}

	return newFile(p[0], "|0", kindPipe, false), newFile(p[1], "|1", kindPipe, false), nil

*/
import "C"

const (
	EINTR  = C.EINTR
	EFAULT = C.EFAULT
	EAGAIN = C.EAGAIN

	O_WRONLY   = C.O_WRONLY
	O_NONBLOCK = C.O_NONBLOCK
	O_CREAT    = C.O_CREAT
	O_TRUNC    = C.O_TRUNC
	O_CLOEXEC  = C.O_CLOEXEC

	PROT_NONE  = C.PROT_NONE
	PROT_READ  = C.PROT_READ
	PROT_WRITE = C.PROT_WRITE
	PROT_EXEC  = C.PROT_EXEC

	MAP_ANON    = C.MAP_ANON
	MAP_PRIVATE = C.MAP_PRIVATE
	MAP_FIXED   = C.MAP_FIXED

const (
	EINTR     = C.EINTR
	EFAULT    = C.EFAULT
	EAGAIN    = C.EAGAIN
	ETIMEDOUT = C.ETIMEDOUT

	O_WRONLY   = C.O_WRONLY
	O_NONBLOCK = C.O_NONBLOCK
	O_CREAT    = C.O_CREAT
	O_TRUNC    = C.O_TRUNC
	O_CLOEXEC  = C.O_CLOEXEC

	PROT_NONE  = C.PROT_NONE
	PROT_READ  = C.PROT_READ
	PROT_WRITE = C.PROT_WRITE
	PROT_EXEC  = C.PROT_EXEC

	MAP_ANON    = C.MAP_ANON
	MAP_SHARED  = C.MAP_SHARED
	MAP_PRIVATE = C.MAP_PRIVATE

// The contents of this file are not relevant for test caching.
func openDirAt(dirfd int, name string) (*File, error) {
	var r int
	for {
		var e error
		r, e = unix.Openat(dirfd, name, O_RDONLY|syscall.O_CLOEXEC|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
		if e == nil {
			break
		}

		// See comment in openFileNolog.
		if e == syscall.EINTR {
			continue
		}

		return nil, e
	}

)

const (
	O_RDONLY = 0
	O_WRONLY = 1
	O_RDWR   = 2

	O_CREAT  = 0100
	O_CREATE = O_CREAT
	O_TRUNC  = 01000
	O_APPEND = 02000
	O_EXCL   = 0200
	O_SYNC   = 010000

	O_CLOEXEC = 0
)

const (
	F_DUPFD   = 0
	F_GETFD   = 1
	F_SETFD   = 2
	F_GETFL   = 3
	F_SETFL   = 4
	F_GETOWN  = 5
	F_SETOWN  = 6
	F_GETLK   = 7
	F_SETLK   = 8
	F_SETLKW  = 9

		}
	}

	var (
		r int
		s poll.SysFile
		e error
	)
	// We have to check EINTR here, per issues 11180 and 39237.
	ignoringEINTR(func() error {
		r, s, e = open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
		return e
	})
	if e != nil {
		return nil, &PathError{Op: "open", Path: name, Err: e}
	}

	// open(2) itself won't handle the sticky bit on *BSD and Solaris
	if setSticky {

}

func PtraceSingleStep(pid int) (err error) {
	return ptrace(PT_STEP, pid, 1, 0)
}

func Dup3(oldfd, newfd, flags int) error {
	if oldfd == newfd || flags&^O_CLOEXEC != 0 {
		return EINVAL
	}
	how := F_DUP2FD
	if flags&O_CLOEXEC != 0 {
		how = F_DUP2FD_CLOEXEC
	}
	_, err := fcntl(oldfd, how, newfd)
	return err
}

/*
 * Exposed directly
 */

		_, _, err1 = RawSyscall(SYS_DUP3, uintptr(pipe), uintptr(nextfd), O_CLOEXEC)
		if err1 != 0 {
			goto childerror
		}
		pipe = nextfd
		nextfd++
	}
	for i = 0; i < len(fd); i++ {
		if fd[i] >= 0 && fd[i] < i {
			if nextfd == pipe { // don't stomp on pipe
				nextfd++
			}
			_, _, err1 = RawSyscall(SYS_DUP3, uintptr(fd[i]), uintptr(nextfd), O_CLOEXEC)
			if err1 != 0 {
				goto childerror
			}

//
//   - [Pipe]. Use pipe2 if available. Otherwise, does not block,
//     so use ForkLock.
//   - [Socket]. Use SOCK_CLOEXEC if available. Otherwise, does not
//     block, so use ForkLock.
//   - [Open]. Use [O_CLOEXEC] if available. Otherwise, may block,
//     so live with the race.
//   - [Dup]. Use [F_DUPFD_CLOEXEC] or dup3 if available. Otherwise,
//     does not block, so use ForkLock.
var ForkLock sync.RWMutex