// Have to give it a name to simulate C "struct foo" references.
		tag := dt.StructName
		if dt.ByteSize < 0 && tag == "" { // opaque unnamed struct - should not be possible
			break
		}
		if tag == "" {
			tag = anonymousStructTag[dt]
			if tag == "" {
				tag = "__" + strconv.Itoa(tagGen)
				tagGen++
				anonymousStructTag[dt] = tag
			}
		} else if t.C.Empty() {
			t.C.Set(dt.Kind + " " + tag)

			context = ctxType
		} else {
			context = ctxExpr
		}
		f.walk(n.List, context, visit)
		f.walk(n.Body, ctxStmt, visit)
	case *ast.SwitchStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(&n.Tag, ctxExpr, visit)
		f.walk(n.Body, ctxSwitch, visit)
	case *ast.TypeSwitchStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(n.Assign, ctxStmt, visit)
		f.walk(n.Body, ctxTypeSwitch, visit)
	case *ast.CommClause:

		Method: Deflate,
		Extra:  []byte(ts.Format(time.RFC3339Nano)), // missing tag and len, but Extra is best-effort parsing
	}
	h.SetModTime(ts)

	testValidHeader(&h, t)
}

func TestHeaderTooShort(t *testing.T) {
	h := FileHeader{
		Name:   "foo.txt",
		Method: Deflate,
		Extra:  []byte{zip64ExtraID}, // missing size and second half of tag, but Extra is best-effort parsing
	}
	testValidHeader(&h, t)
}

but are otherwise ignored.
</p>

<pre>
struct {
	x, y float64 ""  // an empty tag string is like an absent tag
	name string  "any string is permitted as a tag"
	_    [4]byte "ceci n'est pas un champ de structure"
}

// A struct corresponding to a TimeStamp protocol buffer.
// The tag strings define the protocol buffer field numbers;
// they follow the convention outlined by the reflect package.
struct {

The [Stat] function now sets the [ModeSocket] bit for
files that are Unix sockets on Windows. These files are identified

	// Most notably, it cannot support sparse files, files larger than 8GiB,
	// filenames larger than 256 characters, and non-ASCII filenames.
	//
	// Reference:
	//	http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_06
	FormatUSTAR

	// FormatPAX represents the PAX header format defined in POSIX.1-2001.
	//
	// PAX extends USTAR by writing a special file with Typeflag TypeXHeader

	// Other zip authors might not even follow the basic format,
	// and we'll just ignore the Extra content in that case.
	var modified time.Time
parseExtras:
	for extra := readBuf(f.Extra); len(extra) >= 4; { // need at least tag and size
		fieldTag := extra.uint16()
		fieldSize := int(extra.uint16())
		if len(extra) < fieldSize {
			break
		}
		fieldBuf := extra.sub(fieldSize)

		switch fieldTag {
		case zip64ExtraID:

	// for more detail.
	tags = append(tags, context.GOOS, context.GOARCH)
	sort.Strings(tags)

	for _, tag := range tags {
		if ctags[tag] {
			key += "," + tag
			ctags[tag] = false
		}
	}
	return key
}

type listImports struct {
	stdPackages []string                     // names, omitting "unsafe", internal, and vendored packages

var sysStat func(fi fs.FileInfo, h *Header, doNameLookups bool) error

const (
	// Mode constants from the USTAR spec:
	// See http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_06
	c_ISUID = 04000 // Set uid
	c_ISGID = 02000 // Set gid
	c_ISVTX = 01000 // Save text (sticky bit)

	// Common Unix mode constants; these are not defined in any common tar standard.

	{"TrimRight", "abba", "ab", ""},
	{"TrimLeft", "abba", "a", "bba"},
	{"TrimLeft", "abba", "b", "abba"},
	{"TrimRight", "abba", "a", "abb"},
	{"TrimRight", "abba", "b", "abba"},
	{"Trim", "<tag>", "<>", "tag"},
	{"Trim", "* listitem", " *", "listitem"},
	{"Trim", `"quote"`, `"`, "quote"},
	{"Trim", "\u2C6F\u2C6F\u0250\u0250\u2C6F\u2C6F", "\u2C6F", "\u0250\u0250"},
	{"Trim", "\x80test\xff", "\xff", "test"},