go/src/cmd/compile/internal/gc/lex.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:generate go run mkbuiltin.go

package gc

import (
	"cmd/compile/internal/ssa"
	"cmd/internal/obj"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"path"
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"
)

var imported_unsafe bool

var (
	goos    string
	goarch  string
	goroot  string
	buildid string
)

var (
	Debug_append int
	Debug_panic  int
	Debug_slice  int
	Debug_wb     int
)

const BOM = 0xFEFF

// Debug arguments.
// These can be specified with the -d flag, as in "-d nil"
// to set the debug_checknil variable. In general the list passed
// to -d can be comma-separated.
var debugtab = []struct {
	name string
	val  *int
}{
	{"append", &Debug_append},         // print information about append compilation
	{"disablenil", &Disable_checknil}, // disable nil checks
	{"gcprog", &Debug_gcprog},         // print dump of GC programs
	{"nil", &Debug_checknil},          // print information about nil checks
	{"panic", &Debug_panic},           // do not hide any compiler panic
	{"slice", &Debug_slice},           // print information about slice compilation
	{"typeassert", &Debug_typeassert}, // print information about type assertion inlining
	{"wb", &Debug_wb},                 // print information about write barriers
	{"export", &Debug_export},         // print export data
}

const (
	EOF = -1
)

func usage() {
	fmt.Printf("usage: compile [options] file.go...\n")
	obj.Flagprint(1)
	Exit(2)
}

func hidePanic() {
	if Debug_panic == 0 && nsavederrors+nerrors > 0 {
		// If we've already complained about things
		// in the program, don't bother complaining
		// about a panic too; let the user clean up
		// the code and try again.
		if err := recover(); err != nil {
			errorexit()
		}
	}
}

func doversion() {
	p := obj.Expstring()
	if p == "X:none" {
		p = ""
	}
	sep := ""
	if p != "" {
		sep = " "
	}
	fmt.Printf("compile version %s%s%s\n", obj.Getgoversion(), sep, p)
	os.Exit(0)
}

func Main() {
	defer hidePanic()

	// Allow GOARCH=thearch.thestring or GOARCH=thearch.thestringsuffix,
	// but not other values.
	p := obj.Getgoarch()

	if !strings.HasPrefix(p, Thearch.Thestring) {
		log.Fatalf("cannot use %cg with GOARCH=%s", Thearch.Thechar, p)
	}
	goarch = p

	Thearch.Linkarchinit()
	Ctxt = obj.Linknew(Thearch.Thelinkarch)
	Ctxt.DiagFunc = Yyerror
	Ctxt.Bso = &bstdout
	bstdout = *obj.Binitw(os.Stdout)

	localpkg = mkpkg("")
	localpkg.Prefix = "\"\""

	// pseudo-package, for scoping
	builtinpkg = mkpkg("go.builtin")

	builtinpkg.Prefix = "go.builtin" // not go%2ebuiltin

	// pseudo-package, accessed by import "unsafe"
	unsafepkg = mkpkg("unsafe")

	unsafepkg.Name = "unsafe"

	// real package, referred to by generated runtime calls
	Runtimepkg = mkpkg("runtime")

	Runtimepkg.Name = "runtime"

	// pseudo-packages used in symbol tables
	gostringpkg = mkpkg("go.string")

	gostringpkg.Name = "go.string"
	gostringpkg.Prefix = "go.string" // not go%2estring

	itabpkg = mkpkg("go.itab")

	itabpkg.Name = "go.itab"
	itabpkg.Prefix = "go.itab" // not go%2eitab

	weaktypepkg = mkpkg("go.weak.type")

	weaktypepkg.Name = "go.weak.type"
	weaktypepkg.Prefix = "go.weak.type" // not go%2eweak%2etype

	typelinkpkg = mkpkg("go.typelink")
	typelinkpkg.Name = "go.typelink"
	typelinkpkg.Prefix = "go.typelink" // not go%2etypelink

	trackpkg = mkpkg("go.track")

	trackpkg.Name = "go.track"
	trackpkg.Prefix = "go.track" // not go%2etrack

	typepkg = mkpkg("type")

	typepkg.Name = "type"

	goroot = obj.Getgoroot()
	goos = obj.Getgoos()

	Nacl = goos == "nacl"
	if Nacl {
		flag_largemodel = 1
	}

	outfile = ""
	obj.Flagcount("+", "compiling runtime", &compiling_runtime)
	obj.Flagcount("%", "debug non-static initializers", &Debug['%'])
	obj.Flagcount("A", "for bootstrapping, allow 'any' type", &Debug['A'])
	obj.Flagcount("B", "disable bounds checking", &Debug['B'])
	obj.Flagstr("D", "set relative `path` for local imports", &localimport)
	obj.Flagcount("E", "debug symbol export", &Debug['E'])
	obj.Flagfn1("I", "add `directory` to import search path", addidir)
	obj.Flagcount("K", "debug missing line numbers", &Debug['K'])
	obj.Flagcount("L", "use full (long) path in error messages", &Debug['L'])
	obj.Flagcount("M", "debug move generation", &Debug['M'])
	obj.Flagcount("N", "disable optimizations", &Debug['N'])
	obj.Flagcount("P", "debug peephole optimizer", &Debug['P'])
	obj.Flagcount("R", "debug register optimizer", &Debug['R'])
	obj.Flagcount("S", "print assembly listing", &Debug['S'])
	obj.Flagfn0("V", "print compiler version", doversion)
	obj.Flagcount("W", "debug parse tree after type checking", &Debug['W'])
	obj.Flagstr("asmhdr", "write assembly header to `file`", &asmhdr)
	obj.Flagstr("buildid", "record `id` as the build id in the export metadata", &buildid)
	obj.Flagcount("complete", "compiling complete package (no C or assembly)", &pure_go)
	obj.Flagstr("d", "print debug information about items in `list`", &debugstr)
	obj.Flagcount("e", "no limit on number of errors reported", &Debug['e'])
	obj.Flagcount("f", "debug stack frames", &Debug['f'])
	obj.Flagcount("g", "debug code generation", &Debug['g'])
	obj.Flagcount("h", "halt on error", &Debug['h'])
	obj.Flagcount("i", "debug line number stack", &Debug['i'])
	obj.Flagfn1("importmap", "add `definition` of the form source=actual to import map", addImportMap)
	obj.Flagstr("installsuffix", "set pkg directory `suffix`", &flag_installsuffix)
	obj.Flagcount("j", "debug runtime-initialized variables", &Debug['j'])
	obj.Flagcount("l", "disable inlining", &Debug['l'])
	obj.Flagcount("live", "debug liveness analysis", &debuglive)
	obj.Flagcount("m", "print optimization decisions", &Debug['m'])
	obj.Flagcount("msan", "build code compatible with C/C++ memory sanitizer", &flag_msan)
	obj.Flagcount("newexport", "use new export format", &newexport) // TODO(gri) remove eventually (issue 13241)
	obj.Flagcount("nolocalimports", "reject local (relative) imports", &nolocalimports)
	obj.Flagstr("o", "write output to `file`", &outfile)
	obj.Flagstr("p", "set expected package import `path`", &myimportpath)
	obj.Flagcount("pack", "write package file instead of object file", &writearchive)
	obj.Flagcount("r", "debug generated wrappers", &Debug['r'])
	obj.Flagcount("race", "enable race detector", &flag_race)
	obj.Flagcount("s", "warn about composite literals that can be simplified", &Debug['s'])
	obj.Flagstr("trimpath", "remove `prefix` from recorded source file paths", &Ctxt.LineHist.TrimPathPrefix)
	obj.Flagcount("u", "reject unsafe code", &safemode)
	obj.Flagcount("v", "increase debug verbosity", &Debug['v'])
	obj.Flagcount("w", "debug type checking", &Debug['w'])
	use_writebarrier = 1
	obj.Flagcount("wb", "enable write barrier", &use_writebarrier)
	obj.Flagcount("x", "debug lexer", &Debug['x'])
	obj.Flagcount("y", "debug declarations in canned imports (with -d)", &Debug['y'])
	var flag_shared int
	var flag_dynlink bool
	switch Thearch.Thechar {
	case '5', '6', '7', '8', '9':
		obj.Flagcount("shared", "generate code that can be linked into a shared library", &flag_shared)
	}
	if Thearch.Thechar == '6' {
		obj.Flagcount("largemodel", "generate code that assumes a large memory model", &flag_largemodel)
	}
	switch Thearch.Thechar {
	case '5', '6', '7', '8', '9':
		flag.BoolVar(&flag_dynlink, "dynlink", false, "support references to Go symbols defined in other shared libraries")
	}
	obj.Flagstr("cpuprofile", "write cpu profile to `file`", &cpuprofile)
	obj.Flagstr("memprofile", "write memory profile to `file`", &memprofile)
	obj.Flagint64("memprofilerate", "set runtime.MemProfileRate to `rate`", &memprofilerate)
	obj.Flagparse(usage)

	if flag_dynlink {
		flag_shared = 1
	}
	Ctxt.Flag_shared = int32(flag_shared)
	Ctxt.Flag_dynlink = flag_dynlink
	Ctxt.Flag_optimize = Debug['N'] == 0

	Ctxt.Debugasm = int32(Debug['S'])
	Ctxt.Debugvlog = int32(Debug['v'])

	if flag.NArg() < 1 {
		usage()
	}

	startProfile()

	if flag_race != 0 {
		racepkg = mkpkg("runtime/race")
		racepkg.Name = "race"
	}
	if flag_msan != 0 {
		msanpkg = mkpkg("runtime/msan")
		msanpkg.Name = "msan"
	}
	if flag_race != 0 && flag_msan != 0 {
		log.Fatal("cannot use both -race and -msan")
	} else if flag_race != 0 || flag_msan != 0 {
		instrumenting = true
	}

	// parse -d argument
	if debugstr != "" {
	Split:
		for _, name := range strings.Split(debugstr, ",") {
			if name == "" {
				continue
			}
			val := 1
			if i := strings.Index(name, "="); i >= 0 {
				var err error
				val, err = strconv.Atoi(name[i+1:])
				if err != nil {
					log.Fatalf("invalid debug value %v", name)
				}
				name = name[:i]
			}
			for _, t := range debugtab {
				if t.name == name {
					if t.val != nil {
						*t.val = val
						continue Split
					}
				}
			}
			// special case for ssa for now
			if strings.HasPrefix(name, "ssa/") {
				// expect form ssa/phase/flag
				// e.g. -d=ssa/generic_cse/time
				// _ in phase name also matches space
				phase := name[4:]
				flag := "debug" // default flag is debug
				if i := strings.Index(phase, "/"); i >= 0 {
					flag = phase[i+1:]
					phase = phase[:i]
				}
				err := ssa.PhaseOption(phase, flag, val)
				if err != "" {
					log.Fatalf(err)
				}
				continue Split
			}
			log.Fatalf("unknown debug key -d %s\n", name)
		}
	}

	// enable inlining.  for now:
	//	default: inlining on.  (debug['l'] == 1)
	//	-l: inlining off  (debug['l'] == 0)
	//	-ll, -lll: inlining on again, with extra debugging (debug['l'] > 1)
	if Debug['l'] <= 1 {
		Debug['l'] = 1 - Debug['l']
	}

	Thearch.Betypeinit()
	if Widthptr == 0 {
		Fatalf("betypeinit failed")
	}

	lexinit()
	typeinit()
	lexinit1()

	blockgen = 1
	dclcontext = PEXTERN
	nerrors = 0
	lexlineno = 1

	loadsys()

	for _, infile = range flag.Args() {
		if trace && Debug['x'] != 0 {
			fmt.Printf("--- %s ---\n", infile)
		}

		linehistpush(infile)

		bin, err := obj.Bopenr(infile)
		if err != nil {
			fmt.Printf("open %s: %v\n", infile, err)
			errorexit()
		}

		// Skip initial BOM if present.
		if obj.Bgetrune(bin) != BOM {
			obj.Bungetrune(bin)
		}

		block = 1
		iota_ = -1000000

		imported_unsafe = false

		parse_file(bin)
		if nsyntaxerrors != 0 {
			errorexit()
		}

		// Instead of converting EOF into '\n' in getc and count it as an extra line
		// for the line history to work, and which then has to be corrected elsewhere,
		// just add a line here.
		lexlineno++

		linehistpop()
		obj.Bterm(bin)
	}

	testdclstack()
	mkpackage(localpkg.Name) // final import not used checks
	lexfini()

	typecheckok = true
	if Debug['f'] != 0 {
		frame(1)
	}

	// Process top-level declarations in phases.

	// Phase 1: const, type, and names and types of funcs.
	//   This will gather all the information about types
	//   and methods but doesn't depend on any of it.
	defercheckwidth()

	for l := xtop; l != nil; l = l.Next {
		if l.N.Op != ODCL && l.N.Op != OAS && l.N.Op != OAS2 {
			typecheck(&l.N, Etop)
		}
	}

	// Phase 2: Variable assignments.
	//   To check interface assignments, depends on phase 1.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCL || l.N.Op == OAS || l.N.Op == OAS2 {
			typecheck(&l.N, Etop)
		}
	}
	resumecheckwidth()

	// Phase 3: Type check function bodies.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC || l.N.Op == OCLOSURE {
			Curfn = l.N
			decldepth = 1
			saveerrors()
			typecheckslice(l.N.Nbody.Slice(), Etop)
			checkreturn(l.N)
			if nerrors != 0 {
				l.N.Nbody.Set(nil) // type errors; do not compile
			}
		}
	}

	// Phase 4: Decide how to capture closed variables.
	// This needs to run before escape analysis,
	// because variables captured by value do not escape.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC && l.N.Func.Closure != nil {
			Curfn = l.N
			capturevars(l.N)
		}
	}

	Curfn = nil

	if nsavederrors+nerrors != 0 {
		errorexit()
	}

	// Phase 5: Inlining
	if Debug['l'] > 1 {
		// Typecheck imported function bodies if debug['l'] > 1,
		// otherwise lazily when used or re-exported.
		for _, n := range importlist {
			if len(n.Func.Inl.Slice()) != 0 {
				saveerrors()
				typecheckinl(n)
			}
		}

		if nsavederrors+nerrors != 0 {
			errorexit()
		}
	}

	if Debug['l'] != 0 {
		// Find functions that can be inlined and clone them before walk expands them.
		visitBottomUp(xtop, func(list []*Node, recursive bool) {
			// TODO: use a range statement here if the order does not matter
			for i := len(list) - 1; i >= 0; i-- {
				n := list[i]
				if n.Op == ODCLFUNC {
					caninl(n)
					inlcalls(n)
				}
			}
		})
	}

	// Phase 6: Escape analysis.
	// Required for moving heap allocations onto stack,
	// which in turn is required by the closure implementation,
	// which stores the addresses of stack variables into the closure.
	// If the closure does not escape, it needs to be on the stack
	// or else the stack copier will not update it.
	// Large values are also moved off stack in escape analysis;
	// because large values may contain pointers, it must happen early.
	escapes(xtop)

	// Phase 7: Transform closure bodies to properly reference captured variables.
	// This needs to happen before walk, because closures must be transformed
	// before walk reaches a call of a closure.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC && l.N.Func.Closure != nil {
			Curfn = l.N
			transformclosure(l.N)
		}
	}

	Curfn = nil

	// Phase 8: Compile top level functions.
	for l := xtop; l != nil; l = l.Next {
		if l.N.Op == ODCLFUNC {
			funccompile(l.N)
		}
	}

	if nsavederrors+nerrors == 0 {
		fninit(xtop)
	}

	if compiling_runtime != 0 {
		checknowritebarrierrec()
	}

	// Phase 9: Check external declarations.
	for i, n := range externdcl {
		if n.Op == ONAME {
			typecheck(&externdcl[i], Erv)
		}
	}

	if nerrors+nsavederrors != 0 {
		errorexit()
	}

	dumpobj()

	if asmhdr != "" {
		dumpasmhdr()
	}

	if nerrors+nsavederrors != 0 {
		errorexit()
	}

	Flusherrors()
}

var importMap = map[string]string{}

func addImportMap(s string) {
	if strings.Count(s, "=") != 1 {
		log.Fatal("-importmap argument must be of the form source=actual")
	}
	i := strings.Index(s, "=")
	source, actual := s[:i], s[i+1:]
	if source == "" || actual == "" {
		log.Fatal("-importmap argument must be of the form source=actual; source and actual must be non-empty")
	}
	importMap[source] = actual
}

func saveerrors() {
	nsavederrors += nerrors
	nerrors = 0
}

func arsize(b *obj.Biobuf, name string) int {
	var buf [ArhdrSize]byte
	if _, err := io.ReadFull(b, buf[:]); err != nil {
		return -1
	}
	aname := strings.Trim(string(buf[0:16]), " ")
	if !strings.HasPrefix(aname, name) {
		return -1
	}
	asize := strings.Trim(string(buf[48:58]), " ")
	i, _ := strconv.Atoi(asize)
	return i
}

func skiptopkgdef(b *obj.Biobuf) bool {
	// archive header
	p := obj.Brdline(b, '\n')
	if p == "" {
		return false
	}
	if obj.Blinelen(b) != 8 {
		return false
	}
	if p != "!<arch>\n" {
		return false
	}

	// package export block should be first
	sz := arsize(b, "__.PKGDEF")
	return sz > 0
}

var idirs []string

func addidir(dir string) {
	if dir != "" {
		idirs = append(idirs, dir)
	}
}

func isDriveLetter(b byte) bool {
	return 'a' <= b && b <= 'z' || 'A' <= b && b <= 'Z'
}

// is this path a local name?  begins with ./ or ../ or /
func islocalname(name string) bool {
	return strings.HasPrefix(name, "/") ||
		Ctxt.Windows != 0 && len(name) >= 3 && isDriveLetter(name[0]) && name[1] == ':' && name[2] == '/' ||
		strings.HasPrefix(name, "./") || name == "." ||
		strings.HasPrefix(name, "../") || name == ".."
}

func findpkg(name string) (file string, ok bool) {
	if islocalname(name) {
		if safemode != 0 || nolocalimports != 0 {
			return "", false
		}

		// try .a before .6.  important for building libraries:
		// if there is an array.6 in the array.a library,
		// want to find all of array.a, not just array.6.
		file = fmt.Sprintf("%s.a", name)
		if _, err := os.Stat(file); err == nil {
			return file, true
		}
		file = fmt.Sprintf("%s.o", name)
		if _, err := os.Stat(file); err == nil {
			return file, true
		}
		return "", false
	}

	// local imports should be canonicalized already.
	// don't want to see "encoding/../encoding/base64"
	// as different from "encoding/base64".
	if q := path.Clean(name); q != name {
		Yyerror("non-canonical import path %q (should be %q)", name, q)
		return "", false
	}

	for _, dir := range idirs {
		file = fmt.Sprintf("%s/%s.a", dir, name)
		if _, err := os.Stat(file); err == nil {
			return file, true
		}
		file = fmt.Sprintf("%s/%s.o", dir, name)
		if _, err := os.Stat(file); err == nil {
			return file, true
		}
	}

	if goroot != "" {
		suffix := ""
		suffixsep := ""
		if flag_installsuffix != "" {
			suffixsep = "_"
			suffix = flag_installsuffix
		} else if flag_race != 0 {
			suffixsep = "_"
			suffix = "race"
		} else if flag_msan != 0 {
			suffixsep = "_"
			suffix = "msan"
		}

		file = fmt.Sprintf("%s/pkg/%s_%s%s%s/%s.a", goroot, goos, goarch, suffixsep, suffix, name)
		if _, err := os.Stat(file); err == nil {
			return file, true
		}
		file = fmt.Sprintf("%s/pkg/%s_%s%s%s/%s.o", goroot, goos, goarch, suffixsep, suffix, name)
		if _, err := os.Stat(file); err == nil {
			return file, true
		}
	}

	return "", false
}

// loadsys loads the definitions for the low-level runtime and unsafe functions,
// so that the compiler can generate calls to them,
// but does not make the names "runtime" or "unsafe" visible as packages.
func loadsys() {
	if Debug['A'] != 0 {
		return
	}

	block = 1
	iota_ = -1000000
	incannedimport = 1

	importpkg = Runtimepkg
	parse_import(obj.Binitr(strings.NewReader(runtimeimport)), nil)

	importpkg = unsafepkg
	parse_import(obj.Binitr(strings.NewReader(unsafeimport)), nil)

	importpkg = nil
	incannedimport = 0
}

func importfile(f *Val, indent []byte) {
	if importpkg != nil {
		Fatalf("importpkg not nil")
	}

	path_, ok := f.U.(string)
	if !ok {
		Yyerror("import statement not a string")
		return
	}

	if len(path_) == 0 {
		Yyerror("import path is empty")
		return
	}

	if isbadimport(path_) {
		return
	}

	// The package name main is no longer reserved,
	// but we reserve the import path "main" to identify
	// the main package, just as we reserve the import
	// path "math" to identify the standard math package.
	if path_ == "main" {
		Yyerror("cannot import \"main\"")
		errorexit()
	}

	if myimportpath != "" && path_ == myimportpath {
		Yyerror("import %q while compiling that package (import cycle)", path_)
		errorexit()
	}

	if mapped, ok := importMap[path_]; ok {
		path_ = mapped
	}

	if path_ == "unsafe" {
		if safemode != 0 {
			Yyerror("cannot import package unsafe")
			errorexit()
		}

		importpkg = unsafepkg
		imported_unsafe = true
		return
	}

	if islocalname(path_) {
		if path_[0] == '/' {
			Yyerror("import path cannot be absolute path")
			return
		}

		prefix := Ctxt.Pathname
		if localimport != "" {
			prefix = localimport
		}
		path_ = path.Join(prefix, path_)

		if isbadimport(path_) {
			return
		}
	}

	file, found := findpkg(path_)
	if !found {
		Yyerror("can't find import: %q", path_)
		errorexit()
	}

	importpkg = mkpkg(path_)

	if importpkg.Imported {
		return
	}

	importpkg.Imported = true

	imp, err := obj.Bopenr(file)
	if err != nil {
		Yyerror("can't open import: %q: %v", path_, err)
		errorexit()
	}
	defer obj.Bterm(imp)

	if strings.HasSuffix(file, ".a") {
		if !skiptopkgdef(imp) {
			Yyerror("import %s: not a package file", file)
			errorexit()
		}
	}

	// check object header
	p := obj.Brdstr(imp, '\n', 1)

	if p != "empty archive" {
		if !strings.HasPrefix(p, "go object ") {
			Yyerror("import %s: not a go object file", file)
			errorexit()
		}

		q := fmt.Sprintf("%s %s %s %s", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
		if p[10:] != q {
			Yyerror("import %s: object is [%s] expected [%s]", file, p[10:], q)
			errorexit()
		}
	}

	// assume files move (get installed)
	// so don't record the full path.
	linehistpragma(file[len(file)-len(path_)-2:]) // acts as #pragma lib

	// In the importfile, if we find:
	// $$\n  (old format): position the input right after $$\n and return
	// $$B\n (new format): import directly, then feed the lexer a dummy statement

	// look for $$
	var c int
	for {
		c = obj.Bgetc(imp)
		if c < 0 {
			break
		}
		if c == '$' {
			c = obj.Bgetc(imp)
			if c == '$' || c < 0 {
				break
			}
		}
	}

	// get character after $$
	if c >= 0 {
		c = obj.Bgetc(imp)
	}

	switch c {
	case '\n':
		// old export format
		parse_import(imp, indent)

	case 'B':
		// new export format
		obj.Bgetc(imp) // skip \n after $$B
		Import(imp)

	default:
		Yyerror("no import in %q", path_)
		errorexit()
	}

	if safemode != 0 && !importpkg.Safe {
		Yyerror("cannot import unsafe package %q", importpkg.Path)
	}
}

func isSpace(c rune) bool {
	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
}

func isLetter(c rune) bool {
	return 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_'
}

func isDigit(c rune) bool {
	return '0' <= c && c <= '9'
}

func plan9quote(s string) string {
	if s == "" {
		return "''"
	}
	for _, c := range s {
		if c <= ' ' || c == '\'' {
			return "'" + strings.Replace(s, "'", "''", -1) + "'"
		}
	}
	return s
}

type Pragma uint16

const (
	Nointerface       Pragma = 1 << iota
	Noescape                 // func parameters don't escape
	Norace                   // func must not have race detector annotations
	Nosplit                  // func should not execute on separate stack
	Noinline                 // func should not be inlined
	Systemstack              // func must run on system stack
	Nowritebarrier           // emit compiler error instead of write barrier
	Nowritebarrierrec        // error on write barrier in this or recursive callees
	CgoUnsafeArgs            // treat a pointer to one arg as a pointer to them all
)

type lexer struct {
	// source
	bin    *obj.Biobuf
	peekr1 rune
	peekr2 rune // second peekc for ...

	nlsemi bool // if set, '\n' and EOF translate to ';'

	// pragma flags
	// accumulated by lexer; reset by parser
	pragma Pragma

	// current token
	tok  int32
	sym_ *Sym   // valid if tok == LNAME
	val  Val    // valid if tok == LLITERAL
	op   Op     // valid if tok == LOPER, LASOP, or LINCOP, or prec > 0
	prec OpPrec // operator precedence; 0 if not a binary operator
}

type OpPrec int

const (
	// Precedences of binary operators (must be > 0).
	PCOMM OpPrec = 1 + iota
	POROR
	PANDAND
	PCMP
	PADD
	PMUL
)

const (
	// The value of single-char tokens is just their character's Unicode value.
	// They are all below utf8.RuneSelf. Shift other tokens up to avoid conflicts.

	// names and literals
	LNAME = utf8.RuneSelf + iota
	LLITERAL

	// operator-based operations
	LOPER
	LASOP
	LINCOP

	// miscellaneous
	LCOLAS
	LCOMM
	LDDD

	// keywords
	LBREAK
	LCASE
	LCHAN
	LCONST
	LCONTINUE
	LDEFAULT
	LDEFER
	LELSE
	LFALL
	LFOR
	LFUNC
	LGO
	LGOTO
	LIF
	LIMPORT
	LINTERFACE
	LMAP
	LPACKAGE
	LRANGE
	LRETURN
	LSELECT
	LSTRUCT
	LSWITCH
	LTYPE
	LVAR

	LIGNORE
)

func (l *lexer) next() {
	nlsemi := l.nlsemi
	l.nlsemi = false
	l.prec = 0

l0:
	// skip white space
	c := l.getr()
	for isSpace(c) {
		if c == '\n' && nlsemi {
			if Debug['x'] != 0 {
				fmt.Printf("lex: implicit semi\n")
			}
			// Insert implicit semicolon on previous line,
			// before the newline character.
			lineno = lexlineno - 1
			l.tok = ';'
			return
		}
		c = l.getr()
	}

	// start of token
	lineno = lexlineno

	// identifiers and keywords
	// (for better error messages consume all chars >= utf8.RuneSelf for identifiers)
	if isLetter(c) || c >= utf8.RuneSelf {
		l.ident(c)
		if l.tok == LIGNORE {
			goto l0
		}
		return
	}
	// c < utf8.RuneSelf

	var c1 rune
	var op Op
	var prec OpPrec

	switch c {
	case EOF:
		l.ungetr(EOF) // return EOF again in future next call
		// Treat EOF as "end of line" for the purposes
		// of inserting a semicolon.
		if nlsemi {
			if Debug['x'] != 0 {
				fmt.Printf("lex: implicit semi\n")
			}
			l.tok = ';'
			return
		}
		l.tok = -1
		return

	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
		l.number(c)
		return

	case '.':
		c1 = l.getr()
		if isDigit(c1) {
			l.ungetr(c1)
			l.number('.')
			return
		}

		if c1 == '.' {
			c1 = l.getr()
			if c1 == '.' {
				c = LDDD
				goto lx
			}

			l.ungetr(c1)
			c1 = '.'
		}

	case '"':
		l.stdString()
		return

	case '`':
		l.rawString()
		return

	case '\'':
		l.rune()
		return

	case '/':
		c1 = l.getr()
		if c1 == '*' {
			c = l.getr()
			for {
				if c == '*' {
					c = l.getr()
					if c == '/' {
						break
					}
					continue
				}
				if c == EOF {
					Yyerror("eof in comment")
					errorexit()
				}
				c = l.getr()
			}

			// A comment containing newlines acts like a newline.
			if lexlineno > lineno && nlsemi {
				if Debug['x'] != 0 {
					fmt.Printf("lex: implicit semi\n")
				}
				l.tok = ';'
				return
			}
			goto l0
		}

		if c1 == '/' {
			c = l.getlinepragma()
			for {
				if c == '\n' || c == EOF {
					l.ungetr(c)
					goto l0
				}

				c = l.getr()
			}
		}

		op = ODIV
		prec = PMUL
		goto binop1

	case ':':
		c1 = l.getr()
		if c1 == '=' {
			c = LCOLAS
			goto lx
		}

	case '*':
		op = OMUL
		prec = PMUL
		goto binop

	case '%':
		op = OMOD
		prec = PMUL
		goto binop

	case '+':
		op = OADD
		goto incop

	case '-':
		op = OSUB
		goto incop

	case '>':
		c = LOPER
		c1 = l.getr()
		if c1 == '>' {
			op = ORSH
			prec = PMUL
			goto binop
		}

		l.prec = PCMP
		if c1 == '=' {
			l.op = OGE
			goto lx
		}
		l.op = OGT

	case '<':
		c = LOPER
		c1 = l.getr()
		if c1 == '<' {
			op = OLSH
			prec = PMUL
			goto binop
		}

		if c1 == '-' {
			c = LCOMM
			// Not a binary operator, but parsed as one
			// so we can give a good error message when used
			// in an expression context.
			l.prec = PCOMM
			l.op = OSEND
			goto lx
		}

		l.prec = PCMP
		if c1 == '=' {
			l.op = OLE
			goto lx
		}
		l.op = OLT

	case '=':
		c1 = l.getr()
		if c1 == '=' {
			c = LOPER
			l.prec = PCMP
			l.op = OEQ
			goto lx
		}

	case '!':
		c1 = l.getr()
		if c1 == '=' {
			c = LOPER
			l.prec = PCMP
			l.op = ONE
			goto lx
		}

	case '&':
		c1 = l.getr()
		if c1 == '&' {
			c = LOPER
			l.prec = PANDAND
			l.op = OANDAND
			goto lx
		}

		if c1 == '^' {
			c = LOPER
			op = OANDNOT
			prec = PMUL
			goto binop
		}

		op = OAND
		prec = PMUL
		goto binop1

	case '|':
		c1 = l.getr()
		if c1 == '|' {
			c = LOPER
			l.prec = POROR
			l.op = OOROR
			goto lx
		}

		op = OOR
		prec = PADD
		goto binop1

	case '^':
		op = OXOR
		prec = PADD
		goto binop

	case '(', '[', '{', ',', ';':
		goto lx

	case ')', ']', '}':
		l.nlsemi = true
		goto lx

	case '#', '$', '?', '@', '\\':
		if importpkg != nil {
			goto lx
		}
		fallthrough

	default:
		// anything else is illegal
		Yyerror("syntax error: illegal character %#U", c)
		goto l0
	}

	l.ungetr(c1)

lx:
	if Debug['x'] != 0 {
		if c >= utf8.RuneSelf {
			fmt.Printf("%v lex: TOKEN %s\n", linestr(lineno), lexname(c))
		} else {
			fmt.Printf("%v lex: TOKEN '%c'\n", linestr(lineno), c)
		}
	}

	l.tok = c
	return

incop:
	c1 = l.getr()
	if c1 == c {
		l.nlsemi = true
		l.op = op
		c = LINCOP
		goto lx
	}
	prec = PADD
	goto binop1

binop:
	c1 = l.getr()
binop1:
	if c1 != '=' {
		l.ungetr(c1)
		l.op = op
		l.prec = prec
		goto lx
	}

	l.op = op
	if Debug['x'] != 0 {
		fmt.Printf("lex: TOKEN ASOP %s=\n", goopnames[op])
	}
	l.tok = LASOP
}

func (l *lexer) ident(c rune) {
	cp := &lexbuf
	cp.Reset()

	// accelerate common case (7bit ASCII)
	for isLetter(c) || isDigit(c) {
		cp.WriteByte(byte(c))
		c = l.getr()
	}

	// general case
	for {
		if c >= utf8.RuneSelf {
			if unicode.IsLetter(c) || c == '_' || unicode.IsDigit(c) || importpkg != nil && c == 0xb7 {
				if cp.Len() == 0 && unicode.IsDigit(c) {
					Yyerror("identifier cannot begin with digit %#U", c)
				}
			} else {
				Yyerror("invalid identifier character %#U", c)
			}
			cp.WriteRune(c)
		} else if isLetter(c) || isDigit(c) {
			cp.WriteByte(byte(c))
		} else {
			break
		}
		c = l.getr()
	}

	cp = nil
	l.ungetr(c)

	name := lexbuf.Bytes()

	if len(name) >= 2 {
		if tok, ok := keywords[string(name)]; ok {
			if Debug['x'] != 0 {
				fmt.Printf("lex: %s\n", lexname(tok))
			}
			switch tok {
			case LBREAK, LCONTINUE, LFALL, LRETURN:
				l.nlsemi = true
			}
			l.tok = tok
			return
		}
	}

	s := LookupBytes(name)
	if Debug['x'] != 0 {
		fmt.Printf("lex: ident %s\n", s)
	}
	l.sym_ = s
	l.nlsemi = true
	l.tok = LNAME
}

var keywords = map[string]int32{
	"break":       LBREAK,
	"case":        LCASE,
	"chan":        LCHAN,
	"const":       LCONST,
	"continue":    LCONTINUE,
	"default":     LDEFAULT,
	"defer":       LDEFER,
	"else":        LELSE,
	"fallthrough": LFALL,
	"for":         LFOR,
	"func":        LFUNC,
	"go":          LGO,
	"goto":        LGOTO,
	"if":          LIF,
	"import":      LIMPORT,
	"interface":   LINTERFACE,
	"map":         LMAP,
	"package":     LPACKAGE,
	"range":       LRANGE,
	"return":      LRETURN,
	"select":      LSELECT,
	"struct":      LSTRUCT,
	"switch":      LSWITCH,
	"type":        LTYPE,
	"var":         LVAR,

	// 💩
	"notwithstanding":      LIGNORE,
	"thetruthofthematter":  LIGNORE,
	"despiteallobjections": LIGNORE,
	"whereas":              LIGNORE,
	"insofaras":            LIGNORE,
}

func (l *lexer) number(c rune) {
	var str string
	cp := &lexbuf
	cp.Reset()

	// parse mantissa before decimal point or exponent
	isInt := false
	malformedOctal := false
	if c != '.' {
		if c != '0' {
			// decimal or float
			for isDigit(c) {
				cp.WriteByte(byte(c))
				c = l.getr()
			}

		} else {
			// c == 0
			cp.WriteByte('0')
			c = l.getr()
			if c == 'x' || c == 'X' {
				isInt = true // must be int
				cp.WriteByte(byte(c))
				c = l.getr()
				for isDigit(c) || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F' {
					cp.WriteByte(byte(c))
					c = l.getr()
				}
				if lexbuf.Len() == 2 {
					Yyerror("malformed hex constant")
				}
			} else {
				// decimal 0, octal, or float
				for isDigit(c) {
					if c > '7' {
						malformedOctal = true
					}
					cp.WriteByte(byte(c))
					c = l.getr()
				}
			}
		}
	}

	// unless we have a hex number, parse fractional part or exponent, if any
	if !isInt {
		isInt = true // assume int unless proven otherwise

		// fraction
		if c == '.' {
			isInt = false
			cp.WriteByte('.')
			c = l.getr()
			for isDigit(c) {
				cp.WriteByte(byte(c))
				c = l.getr()
			}
			// Falling through to exponent parsing here permits invalid
			// floating-point numbers with fractional mantissa and base-2
			// (p or P) exponent. We don't care because base-2 exponents
			// can only show up in machine-generated textual export data
			// which will use correct formatting.
		}

		// exponent
		// base-2 exponent (p or P) is only allowed in export data (see #9036)
		// TODO(gri) Once we switch to binary import data, importpkg will
		// always be nil in this function. Simplify the code accordingly.
		if c == 'e' || c == 'E' || importpkg != nil && (c == 'p' || c == 'P') {
			isInt = false
			cp.WriteByte(byte(c))
			c = l.getr()
			if c == '+' || c == '-' {
				cp.WriteByte(byte(c))
				c = l.getr()
			}
			if !isDigit(c) {
				Yyerror("malformed floating point constant exponent")
			}
			for isDigit(c) {
				cp.WriteByte(byte(c))
				c = l.getr()
			}
		}

		// imaginary constant
		if c == 'i' {
			str = lexbuf.String()
			x := new(Mpcplx)
			Mpmovecflt(&x.Real, 0.0)
			mpatoflt(&x.Imag, str)
			if x.Imag.Val.IsInf() {
				Yyerror("overflow in imaginary constant")
				Mpmovecflt(&x.Imag, 0.0)
			}
			l.val.U = x

			if Debug['x'] != 0 {
				fmt.Printf("lex: imaginary literal\n")
			}
			goto done
		}
	}

	l.ungetr(c)

	if isInt {
		if malformedOctal {
			Yyerror("malformed octal constant")
		}

		str = lexbuf.String()
		x := new(Mpint)
		mpatofix(x, str)
		if x.Ovf {
			Yyerror("overflow in constant")
			Mpmovecfix(x, 0)
		}
		l.val.U = x

		if Debug['x'] != 0 {
			fmt.Printf("lex: integer literal\n")
		}

	} else { // float

		str = lexbuf.String()
		x := newMpflt()
		mpatoflt(x, str)
		if x.Val.IsInf() {
			Yyerror("overflow in float constant")
			Mpmovecflt(x, 0.0)
		}
		l.val.U = x

		if Debug['x'] != 0 {
			fmt.Printf("lex: floating literal\n")
		}
	}

done:
	litbuf = "literal " + str
	l.nlsemi = true
	l.tok = LLITERAL
}

func (l *lexer) stdString() {
	lexbuf.Reset()
	lexbuf.WriteString(`"<string>"`)

	cp := &strbuf
	cp.Reset()

	for {
		r, b, ok := l.onechar('"')
		if !ok {
			break
		}
		if r == 0 {
			cp.WriteByte(b)
		} else {
			cp.WriteRune(r)
		}
	}

	l.val.U = internString(cp.Bytes())
	if Debug['x'] != 0 {
		fmt.Printf("lex: string literal\n")
	}
	litbuf = "string literal"
	l.nlsemi = true
	l.tok = LLITERAL
}

func (l *lexer) rawString() {
	lexbuf.Reset()
	lexbuf.WriteString("`<string>`")

	cp := &strbuf
	cp.Reset()

	for {
		c := l.getr()
		if c == '\r' {
			continue
		}
		if c == EOF {
			Yyerror("eof in string")
			break
		}
		if c == '`' {
			break
		}
		cp.WriteRune(c)
	}

	l.val.U = internString(cp.Bytes())
	if Debug['x'] != 0 {
		fmt.Printf("lex: string literal\n")
	}
	litbuf = "string literal"
	l.nlsemi = true
	l.tok = LLITERAL
}

func (l *lexer) rune() {
	r, b, ok := l.onechar('\'')
	if !ok {
		Yyerror("empty character literal or unescaped ' in character literal")
		r = '\''
	}
	if r == 0 {
		r = rune(b)
	}

	if c := l.getr(); c != '\'' {
		Yyerror("missing '")
		l.ungetr(c)
	}

	x := new(Mpint)
	l.val.U = x
	Mpmovecfix(x, int64(r))
	x.Rune = true
	if Debug['x'] != 0 {
		fmt.Printf("lex: codepoint literal\n")
	}
	litbuf = "rune literal"
	l.nlsemi = true
	l.tok = LLITERAL
}

var internedStrings = map[string]string{}

func internString(b []byte) string {
	s, ok := internedStrings[string(b)] // string(b) here doesn't allocate
	if !ok {
		s = string(b)
		internedStrings[s] = s
	}
	return s
}

func more(pp *string) bool {
	p := *pp
	for p != "" && isSpace(rune(p[0])) {
		p = p[1:]
	}
	*pp = p
	return p != ""
}

// read and interpret syntax that looks like
// //line parse.y:15
// as a discontinuity in sequential line numbers.
// the next line of input comes from parse.y:15
func (l *lexer) getlinepragma() rune {
	c := l.getr()
	if c == 'g' { // check for //go: directive
		cp := &lexbuf
		cp.Reset()
		cp.WriteByte('g') // already read
		for {
			c = l.getr()
			if c == EOF || c >= utf8.RuneSelf {
				return c
			}
			if c == '\n' {
				break
			}
			cp.WriteByte(byte(c))
		}
		cp = nil

		text := strings.TrimSuffix(lexbuf.String(), "\r")

		if strings.HasPrefix(text, "go:cgo_") {
			pragcgo(text)
		}

		verb := text
		if i := strings.Index(text, " "); i >= 0 {
			verb = verb[:i]
		}

		switch verb {
		case "go:linkname":
			if !imported_unsafe {
				Yyerror("//go:linkname only allowed in Go files that import \"unsafe\"")
			}
			f := strings.Fields(text)
			if len(f) != 3 {
				Yyerror("usage: //go:linkname localname linkname")
				break
			}
			Lookup(f[1]).Linkname = f[2]
		case "go:nointerface":
			if obj.Fieldtrack_enabled != 0 {
				l.pragma |= Nointerface
			}
		case "go:noescape":
			l.pragma |= Noescape
		case "go:norace":
			l.pragma |= Norace
		case "go:nosplit":
			l.pragma |= Nosplit
		case "go:noinline":
			l.pragma |= Noinline
		case "go:systemstack":
			if compiling_runtime == 0 {
				Yyerror("//go:systemstack only allowed in runtime")
			}
			l.pragma |= Systemstack
		case "go:nowritebarrier":
			if compiling_runtime == 0 {
				Yyerror("//go:nowritebarrier only allowed in runtime")
			}
			l.pragma |= Nowritebarrier
		case "go:nowritebarrierrec":
			if compiling_runtime == 0 {
				Yyerror("//go:nowritebarrierrec only allowed in runtime")
			}
			l.pragma |= Nowritebarrierrec | Nowritebarrier // implies Nowritebarrier
		case "go:cgo_unsafe_args":
			l.pragma |= CgoUnsafeArgs
		}
		return c
	}

	// check for //line directive
	if c != 'l' {
		return c
	}
	for i := 1; i < 5; i++ {
		c = l.getr()
		if c != rune("line "[i]) {
			return c
		}
	}

	cp := &lexbuf
	cp.Reset()
	linep := 0
	for {
		c = l.getr()
		if c == EOF {
			return c
		}
		if c == '\n' {
			break
		}
		if c == ' ' {
			continue
		}
		if c == ':' {
			linep = cp.Len() + 1
		}
		cp.WriteByte(byte(c))
	}
	cp = nil

	if linep == 0 {
		return c
	}
	text := strings.TrimSuffix(lexbuf.String(), "\r")
	n, err := strconv.Atoi(text[linep:])
	if err != nil {
		return c // todo: make this an error instead? it is almost certainly a bug.
	}
	if n > 1e8 {
		Yyerror("line number out of range")
		errorexit()
	}
	if n <= 0 {
		return c
	}

	linehistupdate(text[:linep-1], n)
	return c
}

func getimpsym(pp *string) string {
	more(pp) // skip spaces
	p := *pp
	if p == "" || p[0] == '"' {
		return ""
	}
	i := 0
	for i < len(p) && !isSpace(rune(p[i])) && p[i] != '"' {
		i++
	}
	sym := p[:i]
	*pp = p[i:]
	return sym
}

func getquoted(pp *string) (string, bool) {
	more(pp) // skip spaces
	p := *pp
	if p == "" || p[0] != '"' {
		return "", false
	}
	p = p[1:]
	i := strings.Index(p, `"`)
	if i < 0 {
		return "", false
	}
	*pp = p[i+1:]
	return p[:i], true
}

// Copied nearly verbatim from the C compiler's #pragma parser.
// TODO: Rewrite more cleanly once the compiler is written in Go.
func pragcgo(text string) {
	var q string

	if i := strings.Index(text, " "); i >= 0 {
		text, q = text[:i], text[i:]
	}

	verb := text[3:] // skip "go:"

	if verb == "cgo_dynamic_linker" || verb == "dynlinker" {
		p, ok := getquoted(&q)
		if !ok {
			Yyerror("usage: //go:cgo_dynamic_linker \"path\"")
			return
		}
		pragcgobuf += fmt.Sprintf("cgo_dynamic_linker %v\n", plan9quote(p))
		return

	}

	if verb == "dynexport" {
		verb = "cgo_export_dynamic"
	}
	if verb == "cgo_export_static" || verb == "cgo_export_dynamic" {
		local := getimpsym(&q)
		var remote string
		if local == "" {
			goto err2
		}
		if !more(&q) {
			pragcgobuf += fmt.Sprintf("%s %v\n", verb, plan9quote(local))
			return
		}

		remote = getimpsym(&q)
		if remote == "" {
			goto err2
		}
		pragcgobuf += fmt.Sprintf("%s %v %v\n", verb, plan9quote(local), plan9quote(remote))
		return

	err2:
		Yyerror("usage: //go:%s local [remote]", verb)
		return
	}

	if verb == "cgo_import_dynamic" || verb == "dynimport" {
		var ok bool
		local := getimpsym(&q)
		var p string
		var remote string
		if local == "" {
			goto err3
		}
		if !more(&q) {
			pragcgobuf += fmt.Sprintf("cgo_import_dynamic %v\n", plan9quote(local))
			return
		}

		remote = getimpsym(&q)
		if remote == "" {
			goto err3
		}
		if !more(&q) {
			pragcgobuf += fmt.Sprintf("cgo_import_dynamic %v %v\n", plan9quote(local), plan9quote(remote))
			return
		}

		p, ok = getquoted(&q)
		if !ok {
			goto err3
		}
		pragcgobuf += fmt.Sprintf("cgo_import_dynamic %v %v %v\n", plan9quote(local), plan9quote(remote), plan9quote(p))
		return

	err3:
		Yyerror("usage: //go:cgo_import_dynamic local [remote [\"library\"]]")
		return
	}

	if verb == "cgo_import_static" {
		local := getimpsym(&q)
		if local == "" || more(&q) {
			Yyerror("usage: //go:cgo_import_static local")
			return
		}
		pragcgobuf += fmt.Sprintf("cgo_import_static %v\n", plan9quote(local))
		return

	}

	if verb == "cgo_ldflag" {
		p, ok := getquoted(&q)
		if !ok {
			Yyerror("usage: //go:cgo_ldflag \"arg\"")
			return
		}
		pragcgobuf += fmt.Sprintf("cgo_ldflag %v\n", plan9quote(p))
		return

	}
}

func (l *lexer) getr() rune {
	// unread rune != 0 available
	if r := l.peekr1; r != 0 {
		l.peekr1 = l.peekr2
		l.peekr2 = 0
		if r == '\n' && importpkg == nil {
			lexlineno++
		}
		return r
	}

redo:
	// common case: 7bit ASCII
	c := obj.Bgetc(l.bin)
	if c < utf8.RuneSelf {
		if c == 0 {
			yyerrorl(lexlineno, "illegal NUL byte")
			return 0
		}
		if c == '\n' && importpkg == nil {
			lexlineno++
		}
		return rune(c)
	}
	// c >= utf8.RuneSelf

	// uncommon case: non-ASCII
	var buf [utf8.UTFMax]byte
	buf[0] = byte(c)
	buf[1] = byte(obj.Bgetc(l.bin))
	i := 2
	for ; i < len(buf) && !utf8.FullRune(buf[:i]); i++ {
		buf[i] = byte(obj.Bgetc(l.bin))
	}

	r, w := utf8.DecodeRune(buf[:i])
	if r == utf8.RuneError && w == 1 {
		// The string conversion here makes a copy for passing
		// to fmt.Printf, so that buf itself does not escape and
		// can be allocated on the stack.
		yyerrorl(lexlineno, "illegal UTF-8 sequence % x", string(buf[:i]))
	}

	if r == BOM {
		yyerrorl(lexlineno, "Unicode (UTF-8) BOM in middle of file")
		goto redo
	}

	return r
}

func (l *lexer) ungetr(r rune) {
	l.peekr2 = l.peekr1
	l.peekr1 = r
	if r == '\n' && importpkg == nil {
		lexlineno--
	}
}

// onechar lexes a single character within a rune or interpreted string literal,
// handling escape sequences as necessary.
func (l *lexer) onechar(quote rune) (r rune, b byte, ok bool) {
	c := l.getr()
	switch c {
	case EOF:
		Yyerror("eof in string")
		l.ungetr(EOF)
		return

	case '\n':
		Yyerror("newline in string")
		l.ungetr('\n')
		return

	case '\\':
		break

	case quote:
		return

	default:
		return c, 0, true
	}

	c = l.getr()
	switch c {
	case 'x':
		return 0, byte(l.hexchar(2)), true

	case 'u':
		return l.unichar(4), 0, true

	case 'U':
		return l.unichar(8), 0, true

	case '0', '1', '2', '3', '4', '5', '6', '7':
		x := c - '0'
		for i := 2; i > 0; i-- {
			c = l.getr()
			if c >= '0' && c <= '7' {
				x = x*8 + c - '0'
				continue
			}

			Yyerror("non-octal character in escape sequence: %c", c)
			l.ungetr(c)
		}

		if x > 255 {
			Yyerror("octal escape value > 255: %d", x)
		}

		return 0, byte(x), true

	case 'a':
		c = '\a'
	case 'b':
		c = '\b'
	case 'f':
		c = '\f'
	case 'n':
		c = '\n'
	case 'r':
		c = '\r'
	case 't':
		c = '\t'
	case 'v':
		c = '\v'
	case '\\':
		c = '\\'

	default:
		if c != quote {
			Yyerror("unknown escape sequence: %c", c)
		}
	}

	return c, 0, true
}

func (l *lexer) unichar(n int) rune {
	x := l.hexchar(n)
	if x > utf8.MaxRune || 0xd800 <= x && x < 0xe000 {
		Yyerror("invalid Unicode code point in escape sequence: %#x", x)
		x = utf8.RuneError
	}
	return rune(x)
}

func (l *lexer) hexchar(n int) uint32 {
	var x uint32

	for ; n > 0; n-- {
		var d uint32
		switch c := l.getr(); {
		case isDigit(c):
			d = uint32(c - '0')
		case 'a' <= c && c <= 'f':
			d = uint32(c - 'a' + 10)
		case 'A' <= c && c <= 'F':
			d = uint32(c - 'A' + 10)
		default:
			Yyerror("non-hex character in escape sequence: %c", c)
			l.ungetr(c)
			return x
		}
		x = x*16 + d
	}

	return x
}

var basicTypes = [...]struct {
	name  string
	etype EType
}{
	{"int8", TINT8},
	{"int16", TINT16},
	{"int32", TINT32},
	{"int64", TINT64},
	{"uint8", TUINT8},
	{"uint16", TUINT16},
	{"uint32", TUINT32},
	{"uint64", TUINT64},
	{"float32", TFLOAT32},
	{"float64", TFLOAT64},
	{"complex64", TCOMPLEX64},
	{"complex128", TCOMPLEX128},
	{"bool", TBOOL},
	{"string", TSTRING},
	{"any", TANY},
}

var typedefs = [...]struct {
	name     string
	etype    EType
	width    *int
	sameas32 EType
	sameas64 EType
}{
	{"int", TINT, &Widthint, TINT32, TINT64},
	{"uint", TUINT, &Widthint, TUINT32, TUINT64},
	{"uintptr", TUINTPTR, &Widthptr, TUINT32, TUINT64},
}

var builtinFuncs = [...]struct {
	name string
	op   Op
}{
	{"append", OAPPEND},
	{"cap", OCAP},
	{"close", OCLOSE},
	{"complex", OCOMPLEX},
	{"copy", OCOPY},
	{"delete", ODELETE},
	{"imag", OIMAG},
	{"len", OLEN},
	{"make", OMAKE},
	{"new", ONEW},
	{"panic", OPANIC},
	{"print", OPRINT},
	{"println", OPRINTN},
	{"real", OREAL},
	{"recover", ORECOVER},
}

// lexinit initializes known symbols and the basic types.
func lexinit() {
	for _, s := range basicTypes {
		etype := s.etype
		if int(etype) >= len(Types) {
			Fatalf("lexinit: %s bad etype", s.name)
		}
		s2 := Pkglookup(s.name, builtinpkg)
		t := Types[etype]
		if t == nil {
			t = typ(etype)
			t.Sym = s2
			if etype != TANY && etype != TSTRING {
				dowidth(t)
			}
			Types[etype] = t
		}
		s2.Def = typenod(t)
		s2.Def.Name = new(Name)
	}

	for _, s := range builtinFuncs {
		// TODO(marvin): Fix Node.EType type union.
		s2 := Pkglookup(s.name, builtinpkg)
		s2.Def = Nod(ONAME, nil, nil)
		s2.Def.Sym = s2
		s2.Def.Etype = EType(s.op)
	}

	// logically, the type of a string literal.
	// types[TSTRING] is the named type string
	// (the type of x in var x string or var x = "hello").
	// this is the ideal form
	// (the type of x in const x = "hello").
	idealstring = typ(TSTRING)

	idealbool = typ(TBOOL)

	s := Pkglookup("true", builtinpkg)
	s.Def = Nodbool(true)
	s.Def.Sym = Lookup("true")
	s.Def.Name = new(Name)
	s.Def.Type = idealbool

	s = Pkglookup("false", builtinpkg)
	s.Def = Nodbool(false)
	s.Def.Sym = Lookup("false")
	s.Def.Name = new(Name)
	s.Def.Type = idealbool

	s = Lookup("_")
	s.Block = -100
	s.Def = Nod(ONAME, nil, nil)
	s.Def.Sym = s
	Types[TBLANK] = typ(TBLANK)
	s.Def.Type = Types[TBLANK]
	nblank = s.Def

	s = Pkglookup("_", builtinpkg)
	s.Block = -100
	s.Def = Nod(ONAME, nil, nil)
	s.Def.Sym = s
	Types[TBLANK] = typ(TBLANK)
	s.Def.Type = Types[TBLANK]

	Types[TNIL] = typ(TNIL)
	s = Pkglookup("nil", builtinpkg)
	var v Val
	v.U = new(NilVal)
	s.Def = nodlit(v)
	s.Def.Sym = s
	s.Def.Name = new(Name)

	s = Pkglookup("iota", builtinpkg)
	s.Def = Nod(OIOTA, nil, nil)
	s.Def.Sym = s
	s.Def.Name = new(Name)
}

func lexinit1() {
	// t = interface { Error() string }
	rcvr := typ(TSTRUCT)

	rcvr.Type = typ(TFIELD)
	rcvr.Type.Type = Ptrto(typ(TSTRUCT))
	rcvr.Funarg = true
	in := typ(TSTRUCT)
	in.Funarg = true
	out := typ(TSTRUCT)
	out.Type = typ(TFIELD)
	out.Type.Type = Types[TSTRING]
	out.Funarg = true
	f := typ(TFUNC)
	*getthis(f) = rcvr
	*Getoutarg(f) = out
	*getinarg(f) = in
	f.Thistuple = 1
	f.Intuple = 0
	f.Outnamed = false
	f.Outtuple = 1
	t := typ(TINTER)
	t.Type = typ(TFIELD)
	t.Type.Sym = Lookup("Error")
	t.Type.Type = f

	// error type
	s := Pkglookup("error", builtinpkg)
	errortype = t
	errortype.Sym = s
	s.Def = typenod(errortype)

	// byte alias
	s = Pkglookup("byte", builtinpkg)
	bytetype = typ(TUINT8)
	bytetype.Sym = s
	s.Def = typenod(bytetype)
	s.Def.Name = new(Name)

	// rune alias
	s = Pkglookup("rune", builtinpkg)
	runetype = typ(TINT32)
	runetype.Sym = s
	s.Def = typenod(runetype)
	s.Def.Name = new(Name)

	// backend-dependent builtin types (e.g. int).
	for _, s := range typedefs {
		s1 := Pkglookup(s.name, builtinpkg)

		sameas := s.sameas32
		if *s.width == 8 {
			sameas = s.sameas64
		}

		Simtype[s.etype] = sameas
		minfltval[s.etype] = minfltval[sameas]
		maxfltval[s.etype] = maxfltval[sameas]
		Minintval[s.etype] = Minintval[sameas]
		Maxintval[s.etype] = Maxintval[sameas]

		t := typ(s.etype)
		t.Sym = s1
		Types[s.etype] = t
		s1.Def = typenod(t)
		s1.Def.Name = new(Name)
		s1.Origpkg = builtinpkg

		dowidth(t)
	}
}

func lexfini() {
	for _, s := range builtinpkg.Syms {
		if s.Def == nil {
			continue
		}
		s1 := Lookup(s.Name)
		if s1.Def != nil {
			continue
		}

		s1.Def = s.Def
		s1.Block = s.Block
	}

	nodfp = Nod(ONAME, nil, nil)
	nodfp.Type = Types[TINT32]
	nodfp.Xoffset = 0
	nodfp.Class = PPARAM
	nodfp.Sym = Lookup(".fp")
}

var lexn = map[rune]string{
	LNAME:    "NAME",
	LLITERAL: "LITERAL",

	LOPER:  "OPER",
	LASOP:  "ASOP",
	LINCOP: "INCOP",

	LCOLAS: "COLAS",
	LCOMM:  "COMM",
	LDDD:   "DDD",

	LBREAK:     "BREAK",
	LCASE:      "CASE",
	LCHAN:      "CHAN",
	LCONST:     "CONST",
	LCONTINUE:  "CONTINUE",
	LDEFAULT:   "DEFAULT",
	LDEFER:     "DEFER",
	LELSE:      "ELSE",
	LFALL:      "FALL",
	LFOR:       "FOR",
	LFUNC:      "FUNC",
	LGO:        "GO",
	LGOTO:      "GOTO",
	LIF:        "IF",
	LIMPORT:    "IMPORT",
	LINTERFACE: "INTERFACE",
	LMAP:       "MAP",
	LPACKAGE:   "PACKAGE",
	LRANGE:     "RANGE",
	LRETURN:    "RETURN",
	LSELECT:    "SELECT",
	LSTRUCT:    "STRUCT",
	LSWITCH:    "SWITCH",
	LTYPE:      "TYPE",
	LVAR:       "VAR",
}

func lexname(lex rune) string {
	if s, ok := lexn[lex]; ok {
		return s
	}
	return fmt.Sprintf("LEX-%d", lex)
}

func pkgnotused(lineno int32, path string, name string) {
	// If the package was imported with a name other than the final
	// import path element, show it explicitly in the error message.
	// Note that this handles both renamed imports and imports of
	// packages containing unconventional package declarations.
	// Note that this uses / always, even on Windows, because Go import
	// paths always use forward slashes.
	elem := path
	if i := strings.LastIndex(elem, "/"); i >= 0 {
		elem = elem[i+1:]
	}
	if name == "" || elem == name {
		yyerrorl(lineno, "imported and not used: %q", path)
	} else {
		yyerrorl(lineno, "imported and not used: %q as %s", path, name)
	}
}

func mkpackage(pkgname string) {
	if localpkg.Name == "" {
		if pkgname == "_" {
			Yyerror("invalid package name _")
		}
		localpkg.Name = pkgname
	} else {
		if pkgname != localpkg.Name {
			Yyerror("package %s; expected %s", pkgname, localpkg.Name)
		}
		for _, s := range localpkg.Syms {
			if s.Def == nil {
				continue
			}
			if s.Def.Op == OPACK {
				// throw away top-level package name leftover
				// from previous file.
				// leave s->block set to cause redeclaration
				// errors if a conflicting top-level name is
				// introduced by a different file.
				if !s.Def.Used && nsyntaxerrors == 0 {
					pkgnotused(s.Def.Lineno, s.Def.Name.Pkg.Path, s.Name)
				}
				s.Def = nil
				continue
			}

			if s.Def.Sym != s {
				// throw away top-level name left over
				// from previous import . "x"
				if s.Def.Name != nil && s.Def.Name.Pack != nil && !s.Def.Name.Pack.Used && nsyntaxerrors == 0 {
					pkgnotused(s.Def.Name.Pack.Lineno, s.Def.Name.Pack.Name.Pkg.Path, "")
					s.Def.Name.Pack.Used = true
				}

				s.Def = nil
				continue
			}
		}
	}

	if outfile == "" {
		p := infile
		if i := strings.LastIndex(p, "/"); i >= 0 {
			p = p[i+1:]
		}
		if Ctxt.Windows != 0 {
			if i := strings.LastIndex(p, `\`); i >= 0 {
				p = p[i+1:]
			}
		}
		if i := strings.LastIndex(p, "."); i >= 0 {
			p = p[:i]
		}
		suffix := ".o"
		if writearchive > 0 {
			suffix = ".a"
		}
		outfile = p + suffix
	}
}