and of course there is nothing stopping the C code from doing anything
it likes. However, programs that break these rules are likely to fail
in unexpected and unpredictable ways.

The runtime/cgo.Handle type can be used to safely pass Go values
between Go and C. See the runtime/cgo package documentation for details.

Note: the current implementation has a bug. While Go code is permitted

// ending offset is aligned down to the nearest block edge.
//
// Even though the Go tar Reader and the BSD tar utility can handle entries
// with arbitrary offsets and lengths, the GNU tar utility can only handle
// offsets and lengths that are multiples of blockSize.
func alignSparseEntries(src []sparseEntry, size int64) []sparseEntry {
	dst := src[:0]
	for _, s := range src {

			case TypeGNULongLink:
				gnuLongLink = p.parseString(realname)
			}
			continue // This is a meta header affecting the next header
		default:
			// The old GNU sparse format is handled here since it is technically
			// just a regular file with additional attributes.

			if err := mergePAX(hdr, paxHdrs); err != nil {
				return nil, err
			}
			if gnuLongName != "" {

	// flags.
	if h.raw && !h.hasDataDescriptor() {
		b.uint32(h.CRC32)
		b.uint32(uint32(min(h.CompressedSize64, uint32max)))
		b.uint32(uint32(min(h.UncompressedSize64, uint32max)))
	} else {
		// When this package handle the compression, these values are
		// always written to the trailing data descriptor.
		b.uint32(0) // crc32
		b.uint32(0) // compressed size
		b.uint32(0) // uncompressed size
	}
	b.uint16(uint16(len(h.Name)))

		name = buf.String()
	}
	switch typ := typ.Underlying().(type) {
	case *types.Struct:
		w.emitStructType(name, typ)
	case *types.Interface:
		w.emitIfaceType(name, typ)
		return // methods are handled by emitIfaceType
	default:
		w.emitf("type %s %s", name, w.typeString(typ.Underlying()))
	}

	// emit methods with value receiver
	var methodNames map[string]bool
	vset := types.NewMethodSet(typ)