parser.go - platform/build/kati - Gitiles

 // Copyright 2015 Google Inc. All rights reserved
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 package kati

 //go:generate go run testcase/gen_testcase_parse_benchmark.go
 //
 // $ go generate
 // $ go test -bench .

 import (
 	"bufio"
 	"bytes"
 	"crypto/sha1"
 	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"strings"
 	"sync"
 	"time"
 )

 type makefile struct {
 	filename string
 	stmts    []ast
 }

 type ifState struct {
 	ast     *ifAST
 	inElse  bool
 	numNest int
 }

 type parser struct {
 	rd          *bufio.Reader
 	mk          makefile
 	lineno      int
 	elineno     int // lineno == elineno unless there is trailing '\'.
 	linenoFixed bool
 	done        bool
 	outStmts    *[]ast
 	inRecipe    bool
 	ifStack     []ifState

 	defineVar []byte
 	inDef     []byte

 	defOpt    string
 	numIfNest int
 	err       error
 }

 func newParser(rd io.Reader, filename string) *parser {
 	p := &parser{
 		rd: bufio.NewReader(rd),
 	}
 	p.mk.filename = filename
 	p.outStmts = &p.mk.stmts
 	return p
 }

 func (p *parser) srcpos() srcpos {
 	return srcpos{
 		filename: p.mk.filename,
 		lineno:   p.lineno,
 	}
 }

 func (p *parser) addStatement(stmt ast) {
 	*p.outStmts = append(*p.outStmts, stmt)
 	switch stmt.(type) {
 	case *maybeRuleAST:
 		p.inRecipe = true
 	case *assignAST, *includeAST, *exportAST:
 		p.inRecipe = false
 	}
 }

 func (p *parser) readLine() []byte {
 	if !p.linenoFixed {
 		p.lineno = p.elineno + 1
 	}
 	var line []byte
 	for !p.done {
 		buf, err := p.rd.ReadBytes('\n')
 		if !p.linenoFixed {
 			p.elineno++
 		}
 		if err == io.EOF {
 			p.done = true
 		} else if err != nil {
 			p.err = fmt.Errorf("readline %s: %v", p.srcpos(), err)
 			p.done = true
 		}
 		line = append(line, buf...)
 		buf = bytes.TrimRight(buf, "\r\n")
 		backslash := false
 		for len(buf) > 1 && buf[len(buf)-1] == '\\' {
 			buf = buf[:len(buf)-1]
 			backslash = !backslash
 		}
 		if !backslash {
 			break
 		}
 	}
 	line = bytes.TrimRight(line, "\r\n")
 	return line
 }

 func newAssignAST(p *parser, lhsBytes []byte, rhsBytes []byte, op string) (*assignAST, error) {
 	lhs, _, err := parseExpr(lhsBytes, nil, parseOp{alloc: true})
 	if err != nil {
 		return nil, err
 	}
 	rhs, _, err := parseExpr(rhsBytes, nil, parseOp{alloc: true})
 	if err != nil {
 		return nil, err
 	}
 	opt := ""
 	if p != nil {
 		opt = p.defOpt
 	}
 	return &assignAST{
 		lhs: lhs,
 		rhs: rhs,
 		op:  op,
 		opt: opt,
 	}, nil
 }

 func (p *parser) handleDirective(line []byte, directives map[string]directiveFunc) bool {
 	w, data := firstWord(line)
 	if d, ok := directives[string(w)]; ok {
 		d(p, data)
 		return true
 	}
 	return false
 }

 func (p *parser) handleRuleOrAssign(line []byte) {
 	rline := line
 	var semi []byte
 	if i := findLiteralChar(line, []byte{';'}, true); i >= 0 {
 		// preserve after semicolon
 		semi = append(semi, line[i+1:]...)
 		rline = concatline(line[:i])
 	} else {
 		rline = concatline(line)
 	}
 	if p.handleAssign(line) {
 		return
 	}
 	// not assignment
 	p.parseMaybeRule(rline, semi)
 	return
 }

 func (p *parser) handleAssign(line []byte) bool {
 	aline, _ := removeComment(concatline(line))
 	aline = trimLeftSpaceBytes(aline)
 	if len(aline) == 0 {
 		return false
 	}
 	// fmt.Printf("assign: %q=>%q\n", line, aline)
 	i := findLiteralChar(aline, []byte{':', '='}, true)
 	if i >= 0 {
 		if aline[i] == '=' {
 			p.parseAssign(aline, i)
 			return true
 		}
 		if aline[i] == ':' && i+1 < len(aline) && aline[i+1] == '=' {
 			p.parseAssign(aline, i+1)
 			return true
 		}
 	}
 	return false
 }

 func (p *parser) parseAssign(line []byte, sep int) {
 	lhs, op, rhs := line[:sep], line[sep:sep+1], line[sep+1:]
 	if sep > 0 {
 		switch line[sep-1] {
 		case ':', '+', '?':
 			lhs, op = line[:sep-1], line[sep-1:sep+1]
 		}
 	}
 	logf("parseAssign %s %s", line, op)
 	lhs = trimSpaceBytes(lhs)
 	rhs = trimLeftSpaceBytes(rhs)
 	aast, err := newAssignAST(p, lhs, rhs, string(op))
 	if err != nil {
 		p.err = err
 		return
 	}
 	aast.srcpos = p.srcpos()
 	p.addStatement(aast)
 }

 func (p *parser) parseMaybeRule(line, semi []byte) {
 	if line[0] == '\t' {
 		p.err = p.srcpos().errorf("*** commands commence before first target.")
 		return
 	}
 	expr, _, err := parseExpr(line, nil, parseOp{})
 	if err != nil {
 		p.err = p.srcpos().errorf("parse error: %s: %v", string(line), err)
 		return
 	}
 	// TODO(ukai): remove ast, and eval here.
 	rast := &maybeRuleAST{
 		expr: expr,
 		semi: semi,
 	}
 	rast.srcpos = p.srcpos()
 	p.addStatement(rast)
 }

 func (p *parser) parseInclude(op string, line []byte) {
 	// TODO(ukai): parse expr here
 	iast := &includeAST{
 		expr: string(line),
 		op:   op,
 	}
 	iast.srcpos = p.srcpos()
 	p.addStatement(iast)
 }

 func (p *parser) parseIfdef(op string, data []byte) {
 	lhs, _, err := parseExpr(data, nil, parseOp{alloc: true})
 	if err != nil {
 		p.err = p.srcpos().error(err)
 		return
 	}
 	iast := &ifAST{
 		op:  op,
 		lhs: lhs,
 	}
 	iast.srcpos = p.srcpos()
 	p.addStatement(iast)
 	p.ifStack = append(p.ifStack, ifState{ast: iast, numNest: p.numIfNest})
 	p.outStmts = &iast.trueStmts
 }

 func (p *parser) parseTwoQuotes(s []byte, op string) ([]string, bool, error) {
 	var args []string
 	for i := 0; i < 2; i++ {
 		s = trimSpaceBytes(s)
 		if len(s) == 0 {
 			return nil, false, nil
 		}
 		quote := s[0]
 		if quote != '\'' && quote != '"' {
 			return nil, false, nil
 		}
 		end := bytes.IndexByte(s[1:], quote) + 1
 		if end < 0 {
 			return nil, false, nil
 		}
 		args = append(args, string(s[1:end]))
 		s = s[end+1:]
 	}
 	if len(s) > 0 {
 		return nil, false, p.srcpos().errorf(`extraneous text after %q directive`, op)
 	}
 	return args, true, nil
 }

 // parse
 //  "(lhs, rhs)"
 //  "lhs, rhs"
 func (p *parser) parseEq(s []byte, op string) (string, string, bool, error) {
 	if s[0] == '(' && s[len(s)-1] == ')' {
 		in := s[1 : len(s)-1]
 		logf("parseEq ( %q )", in)
 		term := []byte{','}
 		v, n, err := parseExpr(in, term, parseOp{matchParen: true})
 		if err != nil {
 			return "", "", false, err
 		}
 		lhs := v.String()
 		n++
 		n += skipSpaces(in[n:], nil)
 		v, n, err = parseExpr(in[n:], nil, parseOp{matchParen: true})
 		if err != nil {
 			return "", "", false, err
 		}
 		rhs := v.String()
 		return lhs, rhs, true, nil
 	}
 	args, ok, err := p.parseTwoQuotes(s, op)
 	if !ok {
 		return "", "", false, err
 	}
 	return args[0], args[1], true, nil
 }

 func (p *parser) parseIfeq(op string, data []byte) {
 	lhsBytes, rhsBytes, ok, err := p.parseEq(data, op)
 	if err != nil {
 		p.err = err
 		return
 	}
 	if !ok {
 		p.err = p.srcpos().errorf(`*** invalid syntax in conditional.`)
 		return
 	}

 	lhs, _, err := parseExpr([]byte(lhsBytes), nil, parseOp{matchParen: true})
 	if err != nil {
 		p.err = p.srcpos().error(err)
 		return
 	}
 	rhs, _, err := parseExpr([]byte(rhsBytes), nil, parseOp{matchParen: true})
 	if err != nil {
 		p.err = p.srcpos().error(err)
 		return
 	}

 	iast := &ifAST{
 		op:  op,
 		lhs: lhs,
 		rhs: rhs,
 	}
 	iast.srcpos = p.srcpos()
 	p.addStatement(iast)
 	p.ifStack = append(p.ifStack, ifState{ast: iast, numNest: p.numIfNest})
 	p.outStmts = &iast.trueStmts
 }

 func (p *parser) checkIfStack(curKeyword string) error {
 	if len(p.ifStack) == 0 {
 		return p.srcpos().errorf(`*** extraneous %q.`, curKeyword)
 	}
 	return nil
 }

 func (p *parser) parseElse(data []byte) {
 	err := p.checkIfStack("else")
 	if err != nil {
 		p.err = err
 		return
 	}
 	state := &p.ifStack[len(p.ifStack)-1]
 	if state.inElse {
 		p.err = p.srcpos().errorf(`*** only one "else" per conditional.`)
 		return
 	}
 	state.inElse = true
 	p.outStmts = &state.ast.falseStmts

 	nextIf := data
 	if len(nextIf) == 0 {
 		return
 	}
 	var ifDirectives = map[string]directiveFunc{
 		"ifdef":  ifdefDirective,
 		"ifndef": ifndefDirective,
 		"ifeq":   ifeqDirective,
 		"ifneq":  ifneqDirective,
 	}
 	p.numIfNest = state.numNest + 1
 	if p.handleDirective(nextIf, ifDirectives) {
 		p.numIfNest = 0
 		return
 	}
 	p.numIfNest = 0
 	warnNoPrefix(p.srcpos(), "extraneous text after `else` directive")
 	return
 }

 func (p *parser) parseEndif(data []byte) {
 	err := p.checkIfStack("endif")
 	if err != nil {
 		p.err = err
 		return
 	}
 	state := p.ifStack[len(p.ifStack)-1]
 	for t := 0; t <= state.numNest; t++ {
 		p.ifStack = p.ifStack[0 : len(p.ifStack)-1]
 		if len(p.ifStack) == 0 {
 			p.outStmts = &p.mk.stmts
 		} else {
 			state := p.ifStack[len(p.ifStack)-1]
 			if state.inElse {
 				p.outStmts = &state.ast.falseStmts
 			} else {
 				p.outStmts = &state.ast.trueStmts
 			}
 		}
 	}
 	return
 }

 func (p *parser) parseDefine(data []byte) {
 	p.defineVar = nil
 	p.inDef = nil
 	p.defineVar = append(p.defineVar, trimSpaceBytes(data)...)
 	return
 }

 type directiveFunc func(*parser, []byte)

 var makeDirectives map[string]directiveFunc

 func init() {
 	makeDirectives = map[string]directiveFunc{
 		"include":  includeDirective,
 		"-include": sincludeDirective,
 		"sinclude": sincludeDirective,
 		"ifdef":    ifdefDirective,
 		"ifndef":   ifndefDirective,
 		"ifeq":     ifeqDirective,
 		"ifneq":    ifneqDirective,
 		"else":     elseDirective,
 		"endif":    endifDirective,
 		"define":   defineDirective,
 		"override": overrideDirective,
 		"export":   exportDirective,
 		"unexport": unexportDirective,
 	}
 }

 func includeDirective(p *parser, data []byte) {
 	p.parseInclude("include", data)
 }

 func sincludeDirective(p *parser, data []byte) {
 	p.parseInclude("-include", data)
 }

 func ifdefDirective(p *parser, data []byte) {
 	p.parseIfdef("ifdef", data)
 }

 func ifndefDirective(p *parser, data []byte) {
 	p.parseIfdef("ifndef", data)
 }

 func ifeqDirective(p *parser, data []byte) {
 	p.parseIfeq("ifeq", data)
 }

 func ifneqDirective(p *parser, data []byte) {
 	p.parseIfeq("ifneq", data)
 }

 func elseDirective(p *parser, data []byte) {
 	p.parseElse(data)
 }

 func endifDirective(p *parser, data []byte) {
 	p.parseEndif(data)
 }

 func defineDirective(p *parser, data []byte) {
 	p.parseDefine(data)
 }

 func overrideDirective(p *parser, data []byte) {
 	p.defOpt = "override"
 	defineDirective := map[string]directiveFunc{
 		"define": defineDirective,
 	}
 	logf("override define? %q", data)
 	if p.handleDirective(data, defineDirective) {
 		return
 	}
 	// e.g. overrider foo := bar
 	// line will be "foo := bar".
 	if p.handleAssign(data) {
 		return
 	}
 	p.defOpt = ""
 	var line []byte
 	line = append(line, []byte("override ")...)
 	line = append(line, data...)
 	p.handleRuleOrAssign(line)
 }

 func handleExport(p *parser, data []byte, export bool) (hasEqual bool) {
 	i := bytes.IndexByte(data, '=')
 	if i > 0 {
 		hasEqual = true
 		switch data[i-1] {
 		case ':', '+', '?':
 			i--
 		}
 		data = data[:i]
 	}

 	east := &exportAST{
 		expr:   data,
 		export: export,
 	}
 	east.srcpos = p.srcpos()
 	p.addStatement(east)
 	return hasEqual
 }

 func exportDirective(p *parser, data []byte) {
 	p.defOpt = "export"
 	defineDirective := map[string]directiveFunc{
 		"define": defineDirective,
 	}
 	logf("export define? %q", data)
 	if p.handleDirective(data, defineDirective) {
 		return
 	}

 	if !handleExport(p, data, true) {
 		return
 	}

 	// e.g. export foo := bar
 	// line will be "foo := bar".
 	if p.handleAssign(data) {
 		return
 	}
 	p.defOpt = ""
 	var line []byte
 	line = append(line, []byte("export ")...)
 	line = append(line, data...)
 	p.handleRuleOrAssign(line)
 }

 func unexportDirective(p *parser, data []byte) {
 	handleExport(p, data, false)
 	return
 }

 func (p *parser) parse() (mk makefile, err error) {
 	for !p.done {
 		line := p.readLine()
 		logf("line: %q", line)
 		if p.defineVar != nil {
 			p.processDefine(line)
 			if p.err != nil {
 				return makefile{}, p.err
 			}
 			continue
 		}
 		p.defOpt = ""
 		if p.inRecipe {
 			if len(line) > 0 && line[0] == '\t' {
 				cast := &commandAST{cmd: string(line[1:])}
 				cast.srcpos = p.srcpos()
 				p.addStatement(cast)
 				continue
 			}
 		}
 		p.parseLine(line)
 		if p.err != nil {
 			return makefile{}, p.err
 		}
 	}
 	return p.mk, p.err
 }

 func (p *parser) parseLine(line []byte) {
 	cline := concatline(line)
 	if len(cline) == 0 {
 		return
 	}
 	logf("concatline:%q", cline)
 	var dline []byte
 	cline, _ = removeComment(cline)
 	dline = append(dline, cline...)
 	dline = trimSpaceBytes(dline)
 	if len(dline) == 0 {
 		return
 	}
 	logf("directive?: %q", dline)
 	if p.handleDirective(dline, makeDirectives) {
 		return
 	}
 	logf("rule or assign?: %q", line)
 	p.handleRuleOrAssign(line)
 }

 func (p *parser) processDefine(line []byte) {
 	line = concatline(line)
 	logf("concatline:%q", line)
 	if !p.isEndef(line) {
 		if len(p.inDef) != 0 {
 			p.inDef = append(p.inDef, '\n')
 		}
 		p.inDef = append(p.inDef, line...)
 		return
 	}
 	logf("multilineAssign %q %q", p.defineVar, p.inDef)
 	aast, err := newAssignAST(p, p.defineVar, p.inDef, "=")
 	if err != nil {
 		p.err = p.srcpos().errorf("assign error %q=%q: %v", p.defineVar, p.inDef, err)
 		return
 	}
 	aast.srcpos = p.srcpos()
 	aast.srcpos.lineno -= bytes.Count(p.inDef, []byte{'\n'})
 	p.addStatement(aast)
 	p.defineVar = nil
 	p.inDef = nil
 	return
 }

 func (p *parser) isEndef(line []byte) bool {
 	if bytes.Equal(line, []byte("endef")) {
 		return true
 	}
 	w, data := firstWord(line)
 	if bytes.Equal(w, []byte("endef")) {
 		data, _ = removeComment(data)
 		data = trimLeftSpaceBytes(data)
 		if len(data) > 0 {
 			warnNoPrefix(p.srcpos(), `extraneous text after "endef" directive`)
 		}
 		return true
 	}
 	return false
 }

 func defaultMakefile() (string, error) {
 	candidates := []string{"GNUmakefile", "makefile", "Makefile"}
 	for _, filename := range candidates {
 		if exists(filename) {
 			return filename, nil
 		}
 	}
 	return "", errors.New("no targets specified and no makefile found")
 }

 func parseMakefileReader(rd io.Reader, loc srcpos) (makefile, error) {
 	parser := newParser(rd, loc.filename)
 	parser.lineno = loc.lineno
 	parser.elineno = loc.lineno
 	parser.linenoFixed = true
 	return parser.parse()
 }

 func parseMakefileString(s string, loc srcpos) (makefile, error) {
 	return parseMakefileReader(strings.NewReader(s), loc)
 }

 func parseMakefileBytes(s []byte, loc srcpos) (makefile, error) {
 	return parseMakefileReader(bytes.NewReader(s), loc)
 }

 type mkCacheEntry struct {
 	mk   makefile
 	hash [sha1.Size]byte
 	err  error
 	ts   int64
 }

 type makefileCacheT struct {
 	mu sync.Mutex
 	mk map[string]mkCacheEntry
 }

 var makefileCache = &makefileCacheT{
 	mk: make(map[string]mkCacheEntry),
 }

 func (mc *makefileCacheT) lookup(filename string) (makefile, [sha1.Size]byte, bool, error) {
 	var hash [sha1.Size]byte
 	mc.mu.Lock()
 	c, present := mc.mk[filename]
 	mc.mu.Unlock()
 	if !present {
 		return makefile{}, hash, false, nil
 	}
 	ts := getTimestamp(filename)
 	if ts < 0 || ts >= c.ts {
 		return makefile{}, hash, false, nil
 	}
 	return c.mk, c.hash, true, c.err
 }

 func (mc *makefileCacheT) parse(filename string) (makefile, [sha1.Size]byte, error) {
 	logf("parse Makefile %q", filename)
 	mk, hash, ok, err := makefileCache.lookup(filename)
 	if ok {
 		if LogFlag {
 			logf("makefile cache hit for %q", filename)
 		}
 		return mk, hash, err
 	}
 	if LogFlag {
 		logf("reading makefile %q", filename)
 	}
 	c, err := ioutil.ReadFile(filename)
 	if err != nil {
 		return makefile{}, hash, err
 	}
 	hash = sha1.Sum(c)
 	mk, err = parseMakefile(c, filename)
 	if err != nil {
 		return makefile{}, hash, err
 	}
 	makefileCache.mu.Lock()
 	makefileCache.mk[filename] = mkCacheEntry{
 		mk:   mk,
 		hash: hash,
 		err:  err,
 		ts:   time.Now().Unix(),
 	}
 	makefileCache.mu.Unlock()
 	return mk, hash, err
 }

 func parseMakefile(s []byte, filename string) (makefile, error) {
 	parser := newParser(bytes.NewReader(s), filename)
 	return parser.parse()
 }
	// Copyright 2015 Google Inc. All rights reserved
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	package kati

	//go:generate go run testcase/gen_testcase_parse_benchmark.go
	//
	// $ go generate
	// $ go test -bench .

	import (
	"bufio"
	"bytes"
	"crypto/sha1"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"strings"
	"sync"
	"time"
	)

	type makefile struct {
	filename string
	stmts []ast
	}

	type ifState struct {
	ast *ifAST
	inElse bool
	numNest int
	}

	type parser struct {
	rd *bufio.Reader
	mk makefile
	lineno int
	elineno int // lineno == elineno unless there is trailing '\'.
	linenoFixed bool
	done bool
	outStmts *[]ast
	inRecipe bool
	ifStack []ifState

	defineVar []byte
	inDef []byte

	defOpt string
	numIfNest int
	err error
	}

	func newParser(rd io.Reader, filename string) *parser {
	p := &parser{
	rd: bufio.NewReader(rd),
	}
	p.mk.filename = filename
	p.outStmts = &p.mk.stmts
	return p
	}

	func (p *parser) srcpos() srcpos {
	return srcpos{
	filename: p.mk.filename,
	lineno: p.lineno,
	}
	}

	func (p *parser) addStatement(stmt ast) {
	p.outStmts = append(p.outStmts, stmt)
	switch stmt.(type) {
	case *maybeRuleAST:
	p.inRecipe = true
	case assignAST, includeAST, *exportAST:
	p.inRecipe = false
	}
	}

	func (p *parser) readLine() []byte {
	if !p.linenoFixed {
	p.lineno = p.elineno + 1
	}
	var line []byte
	for !p.done {
	buf, err := p.rd.ReadBytes('\n')
	if !p.linenoFixed {
	p.elineno++
	}
	if err == io.EOF {
	p.done = true
	} else if err != nil {
	p.err = fmt.Errorf("readline %s: %v", p.srcpos(), err)
	p.done = true
	}
	line = append(line, buf...)
	buf = bytes.TrimRight(buf, "\r\n")
	backslash := false
	for len(buf) > 1 && buf[len(buf)-1] == '\\' {
	buf = buf[:len(buf)-1]
	backslash = !backslash
	}
	if !backslash {
	break
	}
	}
	line = bytes.TrimRight(line, "\r\n")
	return line
	}

	func newAssignAST(p parser, lhsBytes []byte, rhsBytes []byte, op string) (assignAST, error) {
	lhs, _, err := parseExpr(lhsBytes, nil, parseOp{alloc: true})
	if err != nil {
	return nil, err
	}
	rhs, _, err := parseExpr(rhsBytes, nil, parseOp{alloc: true})
	if err != nil {
	return nil, err
	}
	opt := ""
	if p != nil {
	opt = p.defOpt
	}
	return &assignAST{
	lhs: lhs,
	rhs: rhs,
	op: op,
	opt: opt,
	}, nil
	}

	func (p *parser) handleDirective(line []byte, directives map[string]directiveFunc) bool {
	w, data := firstWord(line)
	if d, ok := directives[string(w)]; ok {
	d(p, data)
	return true
	}
	return false
	}

	func (p *parser) handleRuleOrAssign(line []byte) {
	rline := line
	var semi []byte
	if i := findLiteralChar(line, []byte{';'}, true); i >= 0 {
	// preserve after semicolon
	semi = append(semi, line[i+1:]...)
	rline = concatline(line[:i])
	} else {
	rline = concatline(line)
	}
	if p.handleAssign(line) {
	return
	}
	// not assignment
	p.parseMaybeRule(rline, semi)
	return
	}

	func (p *parser) handleAssign(line []byte) bool {
	aline, _ := removeComment(concatline(line))
	aline = trimLeftSpaceBytes(aline)
	if len(aline) == 0 {
	return false
	}
	// fmt.Printf("assign: %q=>%q\n", line, aline)
	i := findLiteralChar(aline, []byte{':', '='}, true)
	if i >= 0 {
	if aline[i] == '=' {
	p.parseAssign(aline, i)
	return true
	}
	if aline[i] == ':' && i+1 < len(aline) && aline[i+1] == '=' {
	p.parseAssign(aline, i+1)
	return true
	}
	}
	return false
	}

	func (p *parser) parseAssign(line []byte, sep int) {
	lhs, op, rhs := line[:sep], line[sep:sep+1], line[sep+1:]
	if sep > 0 {
	switch line[sep-1] {
	case ':', '+', '?':
	lhs, op = line[:sep-1], line[sep-1:sep+1]
	}
	}
	logf("parseAssign %s %s", line, op)
	lhs = trimSpaceBytes(lhs)
	rhs = trimLeftSpaceBytes(rhs)
	aast, err := newAssignAST(p, lhs, rhs, string(op))
	if err != nil {
	p.err = err
	return
	}
	aast.srcpos = p.srcpos()
	p.addStatement(aast)
	}

	func (p *parser) parseMaybeRule(line, semi []byte) {
	if line[0] == '\t' {
	p.err = p.srcpos().errorf("*** commands commence before first target.")
	return
	}
	expr, _, err := parseExpr(line, nil, parseOp{})
	if err != nil {
	p.err = p.srcpos().errorf("parse error: %s: %v", string(line), err)
	return
	}
	// TODO(ukai): remove ast, and eval here.
	rast := &maybeRuleAST{
	expr: expr,
	semi: semi,
	}
	rast.srcpos = p.srcpos()
	p.addStatement(rast)
	}

	func (p *parser) parseInclude(op string, line []byte) {
	// TODO(ukai): parse expr here
	iast := &includeAST{
	expr: string(line),
	op: op,
	}
	iast.srcpos = p.srcpos()
	p.addStatement(iast)
	}

	func (p *parser) parseIfdef(op string, data []byte) {
	lhs, _, err := parseExpr(data, nil, parseOp{alloc: true})
	if err != nil {
	p.err = p.srcpos().error(err)
	return
	}
	iast := &ifAST{
	op: op,
	lhs: lhs,
	}
	iast.srcpos = p.srcpos()
	p.addStatement(iast)
	p.ifStack = append(p.ifStack, ifState{ast: iast, numNest: p.numIfNest})
	p.outStmts = &iast.trueStmts
	}

	func (p *parser) parseTwoQuotes(s []byte, op string) ([]string, bool, error) {
	var args []string
	for i := 0; i < 2; i++ {
	s = trimSpaceBytes(s)
	if len(s) == 0 {
	return nil, false, nil
	}
	quote := s[0]
	if quote != '\'' && quote != '"' {
	return nil, false, nil
	}
	end := bytes.IndexByte(s[1:], quote) + 1
	if end < 0 {
	return nil, false, nil
	}
	args = append(args, string(s[1:end]))
	s = s[end+1:]
	}
	if len(s) > 0 {
	return nil, false, p.srcpos().errorf(`extraneous text after %q directive`, op)
	}
	return args, true, nil
	}

	// parse
	// "(lhs, rhs)"
	// "lhs, rhs"
	func (p *parser) parseEq(s []byte, op string) (string, string, bool, error) {
	if s[0] == '(' && s[len(s)-1] == ')' {
	in := s[1 : len(s)-1]
	logf("parseEq ( %q )", in)
	term := []byte{','}
	v, n, err := parseExpr(in, term, parseOp{matchParen: true})
	if err != nil {
	return "", "", false, err
	}
	lhs := v.String()
	n++
	n += skipSpaces(in[n:], nil)
	v, n, err = parseExpr(in[n:], nil, parseOp{matchParen: true})
	if err != nil {
	return "", "", false, err
	}
	rhs := v.String()
	return lhs, rhs, true, nil
	}
	args, ok, err := p.parseTwoQuotes(s, op)
	if !ok {
	return "", "", false, err
	}
	return args[0], args[1], true, nil
	}

	func (p *parser) parseIfeq(op string, data []byte) {
	lhsBytes, rhsBytes, ok, err := p.parseEq(data, op)
	if err != nil {
	p.err = err
	return
	}
	if !ok {
	p.err = p.srcpos().errorf(`*** invalid syntax in conditional.`)
	return
	}

	lhs, _, err := parseExpr([]byte(lhsBytes), nil, parseOp{matchParen: true})
	if err != nil {
	p.err = p.srcpos().error(err)
	return
	}
	rhs, _, err := parseExpr([]byte(rhsBytes), nil, parseOp{matchParen: true})
	if err != nil {
	p.err = p.srcpos().error(err)
	return
	}

	iast := &ifAST{
	op: op,
	lhs: lhs,
	rhs: rhs,
	}
	iast.srcpos = p.srcpos()
	p.addStatement(iast)
	p.ifStack = append(p.ifStack, ifState{ast: iast, numNest: p.numIfNest})
	p.outStmts = &iast.trueStmts
	}

	func (p *parser) checkIfStack(curKeyword string) error {
	if len(p.ifStack) == 0 {
	return p.srcpos().errorf(`*** extraneous %q.`, curKeyword)
	}
	return nil
	}

	func (p *parser) parseElse(data []byte) {
	err := p.checkIfStack("else")
	if err != nil {
	p.err = err
	return
	}
	state := &p.ifStack[len(p.ifStack)-1]
	if state.inElse {
	p.err = p.srcpos().errorf(`*** only one "else" per conditional.`)
	return
	}
	state.inElse = true
	p.outStmts = &state.ast.falseStmts

	nextIf := data
	if len(nextIf) == 0 {
	return
	}
	var ifDirectives = map[string]directiveFunc{
	"ifdef": ifdefDirective,
	"ifndef": ifndefDirective,
	"ifeq": ifeqDirective,
	"ifneq": ifneqDirective,
	}
	p.numIfNest = state.numNest + 1
	if p.handleDirective(nextIf, ifDirectives) {
	p.numIfNest = 0
	return
	}
	p.numIfNest = 0
	warnNoPrefix(p.srcpos(), "extraneous text after `else` directive")
	return
	}

	func (p *parser) parseEndif(data []byte) {
	err := p.checkIfStack("endif")
	if err != nil {
	p.err = err
	return
	}
	state := p.ifStack[len(p.ifStack)-1]
	for t := 0; t <= state.numNest; t++ {
	p.ifStack = p.ifStack[0 : len(p.ifStack)-1]
	if len(p.ifStack) == 0 {
	p.outStmts = &p.mk.stmts
	} else {
	state := p.ifStack[len(p.ifStack)-1]
	if state.inElse {
	p.outStmts = &state.ast.falseStmts
	} else {
	p.outStmts = &state.ast.trueStmts
	}
	}
	}
	return
	}

	func (p *parser) parseDefine(data []byte) {
	p.defineVar = nil
	p.inDef = nil
	p.defineVar = append(p.defineVar, trimSpaceBytes(data)...)
	return
	}

	type directiveFunc func(*parser, []byte)

	var makeDirectives map[string]directiveFunc

	func init() {
	makeDirectives = map[string]directiveFunc{
	"include": includeDirective,
	"-include": sincludeDirective,
	"sinclude": sincludeDirective,
	"ifdef": ifdefDirective,
	"ifndef": ifndefDirective,
	"ifeq": ifeqDirective,
	"ifneq": ifneqDirective,
	"else": elseDirective,
	"endif": endifDirective,
	"define": defineDirective,
	"override": overrideDirective,
	"export": exportDirective,
	"unexport": unexportDirective,
	}
	}

	func includeDirective(p *parser, data []byte) {
	p.parseInclude("include", data)
	}

	func sincludeDirective(p *parser, data []byte) {
	p.parseInclude("-include", data)
	}

	func ifdefDirective(p *parser, data []byte) {
	p.parseIfdef("ifdef", data)
	}

	func ifndefDirective(p *parser, data []byte) {
	p.parseIfdef("ifndef", data)
	}

	func ifeqDirective(p *parser, data []byte) {
	p.parseIfeq("ifeq", data)
	}

	func ifneqDirective(p *parser, data []byte) {
	p.parseIfeq("ifneq", data)
	}

	func elseDirective(p *parser, data []byte) {
	p.parseElse(data)
	}

	func endifDirective(p *parser, data []byte) {
	p.parseEndif(data)
	}

	func defineDirective(p *parser, data []byte) {
	p.parseDefine(data)
	}

	func overrideDirective(p *parser, data []byte) {
	p.defOpt = "override"
	defineDirective := map[string]directiveFunc{
	"define": defineDirective,
	}
	logf("override define? %q", data)
	if p.handleDirective(data, defineDirective) {
	return
	}
	// e.g. overrider foo := bar
	// line will be "foo := bar".
	if p.handleAssign(data) {
	return
	}
	p.defOpt = ""
	var line []byte
	line = append(line, []byte("override ")...)
	line = append(line, data...)
	p.handleRuleOrAssign(line)
	}

	func handleExport(p *parser, data []byte, export bool) (hasEqual bool) {
	i := bytes.IndexByte(data, '=')
	if i > 0 {
	hasEqual = true
	switch data[i-1] {
	case ':', '+', '?':
	i--
	}
	data = data[:i]
	}

	east := &exportAST{
	expr: data,
	export: export,
	}
	east.srcpos = p.srcpos()
	p.addStatement(east)
	return hasEqual
	}

	func exportDirective(p *parser, data []byte) {
	p.defOpt = "export"
	defineDirective := map[string]directiveFunc{
	"define": defineDirective,
	}
	logf("export define? %q", data)
	if p.handleDirective(data, defineDirective) {
	return
	}

	if !handleExport(p, data, true) {
	return
	}

	// e.g. export foo := bar
	// line will be "foo := bar".
	if p.handleAssign(data) {
	return
	}
	p.defOpt = ""
	var line []byte
	line = append(line, []byte("export ")...)
	line = append(line, data...)
	p.handleRuleOrAssign(line)
	}

	func unexportDirective(p *parser, data []byte) {
	handleExport(p, data, false)
	return
	}

	func (p *parser) parse() (mk makefile, err error) {
	for !p.done {
	line := p.readLine()
	logf("line: %q", line)
	if p.defineVar != nil {
	p.processDefine(line)
	if p.err != nil {
	return makefile{}, p.err
	}
	continue
	}
	p.defOpt = ""
	if p.inRecipe {
	if len(line) > 0 && line[0] == '\t' {
	cast := &commandAST{cmd: string(line[1:])}
	cast.srcpos = p.srcpos()
	p.addStatement(cast)
	continue
	}
	}
	p.parseLine(line)
	if p.err != nil {
	return makefile{}, p.err
	}
	}
	return p.mk, p.err
	}

	func (p *parser) parseLine(line []byte) {
	cline := concatline(line)
	if len(cline) == 0 {
	return
	}
	logf("concatline:%q", cline)
	var dline []byte
	cline, _ = removeComment(cline)
	dline = append(dline, cline...)
	dline = trimSpaceBytes(dline)
	if len(dline) == 0 {
	return
	}
	logf("directive?: %q", dline)
	if p.handleDirective(dline, makeDirectives) {
	return
	}
	logf("rule or assign?: %q", line)
	p.handleRuleOrAssign(line)
	}

	func (p *parser) processDefine(line []byte) {
	line = concatline(line)
	logf("concatline:%q", line)
	if !p.isEndef(line) {
	if len(p.inDef) != 0 {
	p.inDef = append(p.inDef, '\n')
	}
	p.inDef = append(p.inDef, line...)
	return
	}
	logf("multilineAssign %q %q", p.defineVar, p.inDef)
	aast, err := newAssignAST(p, p.defineVar, p.inDef, "=")
	if err != nil {
	p.err = p.srcpos().errorf("assign error %q=%q: %v", p.defineVar, p.inDef, err)
	return
	}
	aast.srcpos = p.srcpos()
	aast.srcpos.lineno -= bytes.Count(p.inDef, []byte{'\n'})
	p.addStatement(aast)
	p.defineVar = nil
	p.inDef = nil
	return
	}

	func (p *parser) isEndef(line []byte) bool {
	if bytes.Equal(line, []byte("endef")) {
	return true
	}
	w, data := firstWord(line)
	if bytes.Equal(w, []byte("endef")) {
	data, _ = removeComment(data)
	data = trimLeftSpaceBytes(data)
	if len(data) > 0 {
	warnNoPrefix(p.srcpos(), `extraneous text after "endef" directive`)
	}
	return true
	}
	return false
	}

	func defaultMakefile() (string, error) {
	candidates := []string{"GNUmakefile", "makefile", "Makefile"}
	for _, filename := range candidates {
	if exists(filename) {
	return filename, nil
	}
	}
	return "", errors.New("no targets specified and no makefile found")
	}

	func parseMakefileReader(rd io.Reader, loc srcpos) (makefile, error) {
	parser := newParser(rd, loc.filename)
	parser.lineno = loc.lineno
	parser.elineno = loc.lineno
	parser.linenoFixed = true
	return parser.parse()
	}

	func parseMakefileString(s string, loc srcpos) (makefile, error) {
	return parseMakefileReader(strings.NewReader(s), loc)
	}

	func parseMakefileBytes(s []byte, loc srcpos) (makefile, error) {
	return parseMakefileReader(bytes.NewReader(s), loc)
	}

	type mkCacheEntry struct {
	mk makefile
	hash [sha1.Size]byte
	err error
	ts int64
	}

	type makefileCacheT struct {
	mu sync.Mutex
	mk map[string]mkCacheEntry
	}

	var makefileCache = &makefileCacheT{
	mk: make(map[string]mkCacheEntry),
	}

	func (mc *makefileCacheT) lookup(filename string) (makefile, [sha1.Size]byte, bool, error) {
	var hash [sha1.Size]byte
	mc.mu.Lock()
	c, present := mc.mk[filename]
	mc.mu.Unlock()
	if !present {
	return makefile{}, hash, false, nil
	}
	ts := getTimestamp(filename)
	if ts < 0 \|\| ts >= c.ts {
	return makefile{}, hash, false, nil
	}
	return c.mk, c.hash, true, c.err
	}

	func (mc *makefileCacheT) parse(filename string) (makefile, [sha1.Size]byte, error) {
	logf("parse Makefile %q", filename)
	mk, hash, ok, err := makefileCache.lookup(filename)
	if ok {
	if LogFlag {
	logf("makefile cache hit for %q", filename)
	}
	return mk, hash, err
	}
	if LogFlag {
	logf("reading makefile %q", filename)
	}
	c, err := ioutil.ReadFile(filename)
	if err != nil {
	return makefile{}, hash, err
	}
	hash = sha1.Sum(c)
	mk, err = parseMakefile(c, filename)
	if err != nil {
	return makefile{}, hash, err
	}
	makefileCache.mu.Lock()
	makefileCache.mk[filename] = mkCacheEntry{
	mk: mk,
	hash: hash,
	err: err,
	ts: time.Now().Unix(),
	}
	makefileCache.mu.Unlock()
	return mk, hash, err
	}

	func parseMakefile(s []byte, filename string) (makefile, error) {
	parser := newParser(bytes.NewReader(s), filename)
	return parser.parse()
	}