if err != nil {
		t.Errorf("read error: %v", err)
	}
	if n != 0 {
		t.Errorf("wrong count; got %d want 0", n)
	}
}

func TestUnreadByte(t *testing.T) {
	b := new(Buffer)

	// check at EOF
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte at EOF: got no error")
	}
	if _, err := b.ReadByte(); err == nil {
		t.Fatal("ReadByte at EOF: got no error")
	}

			p.errorf("register list: expected ']', found EOF")
		} else {
			p.errorf("register list: bad low register in `[%s`", loName)
		}
		return
	}
	if tok := p.next().ScanToken; tok != '-' {
		p.errorf("register list: expected '-' after `[%s`, found %s", loName, tok)
		return
	}
	hiName := p.next().String()
	hi, ok := p.arch.Register[hiName]
	if !ok {

		t.Errorf("UncompressedSize: got %d, want %d\n", got, want)
	}
	if got, want := fh2.UncompressedSize64, wantUncompressedSize64; got != want {
		t.Errorf("UncompressedSize64: got %d, want %d\n", got, want)
	}
	if got, want := fh2.ModifiedTime, fh.ModifiedTime; got != want {
		t.Errorf("ModifiedTime: got %d, want %d\n", got, want)
	}

						if err := tw.WriteHeader(file.hdr); err != nil {
							b.Errorf("unexpected WriteHeader error: %v", err)
						}
						if _, err := tw.Write(file.body); err != nil {
							b.Errorf("unexpected Write error: %v", err)
						}
					}
					if err := tw.Close(); err != nil {
						b.Errorf("unexpected Close error: %v", err)
					}
				}
			})
		}
	})

var (
	ErrHeader          = errors.New("archive/tar: invalid tar header")
	ErrWriteTooLong    = errors.New("archive/tar: write too long")
	ErrFieldTooLong    = errors.New("archive/tar: header field too long")
	ErrWriteAfterClose = errors.New("archive/tar: write after close")
	ErrInsecurePath    = errors.New("archive/tar: insecure file path")
	errMissData        = errors.New("archive/tar: sparse file references non-existent data")

				t.Errorf("%s: missing error, want %s", fileline, all)
			} else if !strings.Contains(err, mm[0][1]) {
				t.Errorf("%s: wrong error for %s:\n%s", fileline, all, err)
			}
		} else {
			if errors[fileline] != "" {
				t.Errorf("unexpected error on %s: %v", fileline, errors[fileline])
			}
		}
		delete(errors, fileline)
	}
	var extra []string
	for key := range errors {
		extra = append(extra, key)

			t.Errorf("WriteHeader() = got %v, want non-nil error", err)
		}
		if _, err := tw.Write(nil); err == nil {
			t.Errorf("Write() = %v, want non-nil error", err)
		}
		if err := tw.Flush(); err == nil {
			t.Errorf("Flush() = %v, want non-nil error", err)
		}
		if err := tw.Close(); err == nil {
			t.Errorf("Close() = %v, want non-nil error", err)
		}
	})
}

		case sys.ARM:
			if !arch.ARMConditionCodes(prog, cond) {
				p.errorf("unrecognized condition code .%q", cond)
				return
			}

		case sys.ARM64:
			if !arch.ARM64Suffix(prog, cond) {
				p.errorf("unrecognized suffix .%q", cond)
				return
			}

		case sys.AMD64, sys.I386:
			if err := x86.ParseSuffix(prog, cond); err != nil {
				p.errorf("%v", err)
				return
			}
		case sys.RISCV64:

This program will not compile, but cgo can use the presence or absence
of an error message on a given line to deduce the information it
needs. The program is syntactically valid regardless of whether each
name is a type or an ordinary identifier, so there will be no syntax
errors that might stop parsing early.

An error on not-declared:1 indicates that foo is undeclared.

	}
	exception := fileFeatures(filepath.Join(testenv.GOROOT(t), "api/except.txt"), false)

	if exitCode == 1 {
		t.Errorf("API database problems found")
	}
	if !compareAPI(bw, features, required, exception) {
		t.Errorf("API differences found")
	}
}

// export emits the exported package features.
func (w *Walker) export(pkg *apiPackage) {
	if verbose {
		log.Println(pkg)