pkg syscall (darwin-arm64), const IPPROTO_TTP = 84
pkg syscall (darwin-arm64), const IPPROTO_TTP ideal-int
pkg syscall (darwin-arm64), const IPPROTO_VINES = 83
pkg syscall (darwin-arm64), const IPPROTO_VINES ideal-int
pkg syscall (darwin-arm64), const IPPROTO_VISA = 70
pkg syscall (darwin-arm64), const IPPROTO_VISA ideal-int
pkg syscall (darwin-arm64), const IPPROTO_VMTP = 81

	if err != nil {
		t.Fatalf("go tool addr2line %v: %v\n%s", os.Args[0], err, string(out))
	}
	f := strings.Split(string(out), "\n")
	if len(f) < 3 && f[2] == "" {
		t.Fatal("addr2line output must have 2 lines")
	}
	funcname = f[0]
	pathAndLineNo := f[1]
	f = strings.Split(pathAndLineNo, ":")
	if runtime.GOOS == "windows" && len(f) == 3 {
		// Reattach drive letter.
		f = []string{f[0] + ":" + f[1], f[2]}
	}

pkg syscall (freebsd-arm64), const IPPROTO_TTP = 84
pkg syscall (freebsd-arm64), const IPPROTO_TTP ideal-int
pkg syscall (freebsd-arm64), const IPPROTO_VINES = 83
pkg syscall (freebsd-arm64), const IPPROTO_VINES ideal-int
pkg syscall (freebsd-arm64), const IPPROTO_VISA = 70
pkg syscall (freebsd-arm64), const IPPROTO_VISA ideal-int
pkg syscall (freebsd-arm64), const IPPROTO_VMTP = 81

pkg syscall (darwin-386), const IPPROTO_TRUNK1 ideal-int
pkg syscall (darwin-386), const IPPROTO_TRUNK2 ideal-int
pkg syscall (darwin-386), const IPPROTO_TTP ideal-int
pkg syscall (darwin-386), const IPPROTO_VINES ideal-int
pkg syscall (darwin-386), const IPPROTO_VISA ideal-int
pkg syscall (darwin-386), const IPPROTO_VMTP ideal-int
pkg syscall (darwin-386), const IPPROTO_WBEXPAK ideal-int

pkg syscall (freebsd-riscv64), const IPPROTO_TTP = 84 #53466
pkg syscall (freebsd-riscv64), const IPPROTO_TTP ideal-int #53466
pkg syscall (freebsd-riscv64), const IPPROTO_VINES = 83 #53466
pkg syscall (freebsd-riscv64), const IPPROTO_VINES ideal-int #53466
pkg syscall (freebsd-riscv64), const IPPROTO_VISA = 70 #53466
pkg syscall (freebsd-riscv64), const IPPROTO_VISA ideal-int #53466

		return nil, err
	}
	return bytes.TrimSpace(out), nil
}

func getLines(cmd *exec.Cmd) [][]byte {
	out := output(cmd)
	lines := bytes.Split(out, []byte("\n"))
	// Skip the empty line at the end.
	if len(lines[len(lines)-1]) == 0 {
		lines = lines[:len(lines)-1]
	}
	return lines
}

func output(cmd *exec.Cmd) []byte {
	out, err := cmd.Output()
	if err != nil {
		fmt.Println(strings.Join(cmd.Args, "\n"))

Each file is a list of API features, one per line.

go1.txt (and similarly named files) are frozen once a version has been
shipped. Each file adds new lines but does not remove any.

except.txt lists features that may disappear without breaking true
compatibility.

Starting with go1.19.txt, each API feature line must end in "#nnnnn"

	lineNum       int   // Line number in source file.
	errorLine     int   // Line number of last error.
	errorCount    int   // Number of errors.
	sawCode       bool  // saw code in this file (as opposed to comments and blank lines)
	pc            int64 // virtual PC; count of Progs; doesn't advance for GLOBL or DATA.
	input         []lex.Token
	inputPos      int
	pendingLabels []string // Labels to attach to next instruction.

pkg syscall (darwin-386), const IPPROTO_TRUNK1 = 23
pkg syscall (darwin-386), const IPPROTO_TRUNK2 = 24
pkg syscall (darwin-386), const IPPROTO_TTP = 84
pkg syscall (darwin-386), const IPPROTO_VINES = 83
pkg syscall (darwin-386), const IPPROTO_VISA = 70
pkg syscall (darwin-386), const IPPROTO_VMTP = 81
pkg syscall (darwin-386), const IPPROTO_WBEXPAK = 79
pkg syscall (darwin-386), const IPPROTO_WBMON = 78

	const text = "abcdefghijklmn\nopqrstuvwxyz"
	lines := []string{
		"abcdefghijklmn",
		"opqrstuvwxyz",
	}
	testNoNewline(text, lines, t)
}

// Test that the line splitter handles a final line with a carriage return but no newline.
func TestScanLineReturnButNoNewline(t *testing.T) {
	const text = "abcdefghijklmn\nopqrstuvwxyz\r"
	lines := []string{
		"abcdefghijklmn",
		"opqrstuvwxyz",
	}