_, err = f.Write(out)
		check(err)
		check(f.Close())

		cert, err := plistExtract(fname, "DeveloperCertificates:0")
		check(err)
		pcert, err := x509.ParseCertificate(cert)
		check(err)
		fmt.Printf("export GOIOS_DEV_ID=\"%s\"\n", pcert.Subject.CommonName)

		appID, err := plistExtract(fname, "Entitlements:application-identifier")
		check(err)
		fmt.Printf("export GOIOS_APP_ID=%s\n", appID)

			major := uint32((dev >> 8) & 0xff)
			minor := uint32(dev & 0xffff00ff)
			h.Devmajor, h.Devminor = int64(major), int64(minor)
		case "freebsd":
			// Copied from golang.org/x/sys/unix/dev_freebsd.go.
			major := uint32((dev >> 8) & 0xff)
			minor := uint32(dev & 0xffff00ff)
			h.Devmajor, h.Devminor = int64(major), int64(minor)
		case "netbsd":
			// Copied from golang.org/x/sys/unix/dev_netbsd.go.

		// by the same feature being implemented on all ports. That is, it shouldn't
		// say "pkg syscall (darwin-amd64), type RawSockaddrInet6 struct" is missing.
		// See https://go.dev/issue/4303.
		{
			name: "contexts reconverging after api/next/* update",
			features: []string{
				"A",
				"pkg syscall, type RawSockaddrInet6 struct",
			},
			required: []string{
				"A",

		t.Skip("skipping root only test on a non-root builder")
	}
	if runtime.GOOS == "linux" {
		if _, err := os.Stat("/etc/alpine-release"); err == nil {
			t.Skip("skipping failing test on alpine - go.dev/issue/19938")
		}
	}

	// Launch some threads in C.
	const cts = 5
	C.trial(cts)
	defer C.cleanup()

	vs := []struct {
		call           string
		fn             func() error

		fm: 0777 | fs.ModeSymlink,
	}, {
		// character device node.
		h: &Header{
			Name:     "dev/null",
			Mode:     0666,
			Size:     0,
			ModTime:  time.Unix(1360578951, 0),
			Typeflag: TypeChar,
		},
		fm: 0666 | fs.ModeDevice | fs.ModeCharDevice,
	}, {
		// block device node.
		h: &Header{
			Name:     "dev/sda",
			Mode:     0660,
			Size:     0,
			ModTime:  time.Unix(1360578954, 0),

				ModTime:  time.Unix(1314603082, 0),
			}, nil},
			testWrite{"", 0, nil},

			testClose{nil},
		},
	}, {
		// The truncated test file was produced using these commands:
		//   dd if=/dev/zero bs=1048576 count=16384 > /tmp/16gig.txt
		//   tar -b 1 -c -f- /tmp/16gig.txt | dd bs=512 count=8 > writer-big.tar
		file: "testdata/writer-big.tar",
		tests: []testFnc{
			testHeader{Header{
				Typeflag: TypeReg,