}
			if h.Typeflag == TypeGNUSparse {
				whyOnlyGNU = "only GNU supports TypeGNUSparse"
				format.mayOnlyBe(FormatGNU)
			} else {
				whyNoGNU = "GNU supports sparse files only with TypeGNUSparse"
				format.mustNotBe(FormatGNU)
			}
			whyNoUSTAR = "USTAR does not support sparse files"
			format.mustNotBe(FormatUSTAR)
		}
	*/

	// Check desired format.

must support both internal and external linking, depending on the
circumstances: if net is the only cgo-using package, then internal
linking is probably fine, but if other packages are involved, so that there
are dependencies on libraries beyond libc, external linking is likely
to work better. The compilation of a package records the relevant
information to support both linking modes, leaving the decision

	// flag bit is set. However, there are several problems:
	//
	//	* Many ZIP readers still do not support UTF-8.
	//	* If the UTF-8 flag is cleared, several readers simply interpret the
	//	name and comment fields as whatever the local system encoding is.
	//
	// In order to avoid breaking readers without UTF-8 support,
	// we avoid setting the UTF-8 flag if the strings are CP-437 compatible.

		// io.Seeker, but calling Seek always returns an error and performs
		// no action. Thus, we try an innocent seek to the current position
		// to see if Seek is really supported.
		pos1, err := sr.Seek(0, io.SeekCurrent)
		if pos1 >= 0 && err == nil {
			// Seek seems supported, so perform the real Seek.
			pos2, err := sr.Seek(n-1, io.SeekCurrent)
			if pos2 < 0 || err != nil {
				return err
			}
			seekSkipped = pos2 - pos1
		}

				Uname:    "rawr",
				Gname:    "dsnet",
				ModTime:  time.Unix(0, 0),
				Format:   FormatGNU,
			}, nil},
			testClose{nil},
		},
		// TODO(dsnet): Re-enable this test when adding sparse support.
		// See https://golang.org/issue/22735
		/*
			}, {
				file: "testdata/gnu-nil-sparse-data.tar",
				tests: []testFnc{
					testHeader{Header{
						Typeflag:    TypeGNUSparse,