// Get a pidfd of the current process (opening of "/proc/self" won't
	// work for waitid).
	fd, err := unix.PidFDOpen(syscall.Getpid(), 0)
	if err != nil {
		return NewSyscallError("pidfd_open", err)
	}
	defer syscall.Close(int(fd))

	// Check waitid(P_PIDFD) works.
	for {
		_, _, err = syscall.Syscall6(syscall.SYS_WAITID, _P_PIDFD, fd, 0, syscall.WEXITED, 0, 0)
		if err != syscall.EINTR {
			break
		}
	}

	os.Setenv("GODEBUG", godebug)

	if os.Getenv("GO_EXEC_TEST_PID") != "" {
		return
	}
	if runtime.GOOS == "windows" {
		return
	}
	for fd := uintptr(3); fd <= 100; fd++ {
		if poll.IsPollDescriptor(fd) {
			continue
		}

		if fdtest.Exists(fd) {
			haveUnexpectedFDs = true
			return
		}
	}
}

// TestMain allows the test binary to impersonate many other binaries,

			fdMu.Lock()
			defer fdMu.Unlock()
			if len(fds) == 0 {
				return nil
			}
			fdsCopy := fds
			for _, fd := range fdsCopy {
				// Grab a fallback disk
				fds = fds[1:]
				if fd != nil && fd.IsOnline() {
					return fd
				}
			}
		}
		// Either no more disks for fallback or
		// not a storage error.
		return nil
	}

	sysattr := &syscall.ProcAttr{
		Dir: attr.Dir,
		Env: attr.Env,
		Sys: attr.Sys,
	}

	sysattr.Files = make([]uintptr, 0, len(attr.Files))
	for _, f := range attr.Files {
		sysattr.Files = append(sysattr.Files, f.Fd())
	}

	pid, _, e := syscall.StartProcess(name, argv, sysattr)
	if e != nil {
		return nil, &PathError{Op: "fork/exec", Path: name, Err: e}
	}

	return newPIDProcess(pid), nil
}

		sysattr.Env, err = execenv.Default(sysattr.Sys)
		if err != nil {
			return nil, err
		}
	}
	sysattr.Files = make([]uintptr, 0, len(attr.Files))
	for _, f := range attr.Files {
		sysattr.Files = append(sysattr.Files, f.Fd())
	}

	pid, h, e := syscall.StartProcess(name, argv, sysattr)

	// Make sure we don't run the finalizers of attr.Files.
	runtime.KeepAlive(attr)

	if e != nil {

			pathErr.Path = parentDir + string(PathSeparator) + pathErr.Path
			err = pathErr
		}
		return err
	}
	return nil
}

func removeAllFrom(parent *File, base string) error {
	parentFd := int(parent.Fd())
	// Simple case: if Unlink (aka remove) works, we're done.
	err := ignoringEINTR(func() error {
		return unix.Unlinkat(parentFd, base, 0)
	})
	if err == nil || IsNotExist(err) {
		return nil
	}

		_, err := io.Copy(w, pr)
		pr.Close() // in case io.Copy stopped due to write error
		return err
	})
	return pw, nil
}

func closeDescriptors(closers []io.Closer) {
	for _, fd := range closers {
		fd.Close()
	}
}

// Run starts the specified command and waits for it to complete.
//
// The returned error is nil if the command runs, has no problems