libgo/go/cmd/cgo/main.go - gcc - Git at Google

 // 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.

 // Cgo; see doc.go for an overview.

 // TODO(rsc):
 //	Emit correct line number annotations.
 //	Make gc understand the annotations.

 package main

 import (
 	"crypto/md5"
 	"flag"
 	"fmt"
 	"go/ast"
 	"go/printer"
 	"go/token"
 	"internal/buildcfg"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"reflect"
 	"runtime"
 	"sort"
 	"strings"

 	"cmd/internal/edit"
 	"cmd/internal/objabi"
 )

 // A Package collects information about the package we're going to write.
 type Package struct {
 	PackageName string // name of package
 	PackagePath string
 	PtrSize     int64
 	IntSize     int64
 	GccOptions  []string
 	GccIsClang  bool
 	CgoFlags    map[string][]string // #cgo flags (CFLAGS, LDFLAGS)
 	Written     map[string]bool
 	Name        map[string]*Name // accumulated Name from Files
 	ExpFunc     []*ExpFunc       // accumulated ExpFunc from Files
 	Decl        []ast.Decl
 	GoFiles     []string        // list of Go files
 	GccFiles    []string        // list of gcc output files
 	Preamble    string          // collected preamble for _cgo_export.h
 	typedefs    map[string]bool // type names that appear in the types of the objects we're interested in
 	typedefList []typedefInfo
 }

 // A typedefInfo is an element on Package.typedefList: a typedef name
 // and the position where it was required.
 type typedefInfo struct {
 	typedef string
 	pos     token.Pos
 }

 // A File collects information about a single Go input file.
 type File struct {
 	AST      *ast.File           // parsed AST
 	Comments []*ast.CommentGroup // comments from file
 	Package  string              // Package name
 	Preamble string              // C preamble (doc comment on import "C")
 	Ref      []*Ref              // all references to C.xxx in AST
 	Calls    []*Call             // all calls to C.xxx in AST
 	ExpFunc  []*ExpFunc          // exported functions for this file
 	Name     map[string]*Name    // map from Go name to Name
 	NamePos  map[*Name]token.Pos // map from Name to position of the first reference
 	Edit     *edit.Buffer
 }

 func (f *File) offset(p token.Pos) int {
 	return fset.Position(p).Offset
 }

 func nameKeys(m map[string]*Name) []string {
 	var ks []string
 	for k := range m {
 		ks = append(ks, k)
 	}
 	sort.Strings(ks)
 	return ks
 }

 // A Call refers to a call of a C.xxx function in the AST.
 type Call struct {
 	Call     *ast.CallExpr
 	Deferred bool
 	Done     bool
 }

 // A Ref refers to an expression of the form C.xxx in the AST.
 type Ref struct {
 	Name    *Name
 	Expr    *ast.Expr
 	Context astContext
 	Done    bool
 }

 func (r *Ref) Pos() token.Pos {
 	return (*r.Expr).Pos()
 }

 var nameKinds = []string{"iconst", "fconst", "sconst", "type", "var", "fpvar", "func", "macro", "not-type"}

 // A Name collects information about C.xxx.
 type Name struct {
 	Go       string // name used in Go referring to package C
 	Mangle   string // name used in generated Go
 	C        string // name used in C
 	Define   string // #define expansion
 	Kind     string // one of the nameKinds
 	Type     *Type  // the type of xxx
 	FuncType *FuncType
 	AddError bool
 	Const    string // constant definition
 }

 // IsVar reports whether Kind is either "var" or "fpvar"
 func (n *Name) IsVar() bool {
 	return n.Kind == "var" || n.Kind == "fpvar"
 }

 // IsConst reports whether Kind is either "iconst", "fconst" or "sconst"
 func (n *Name) IsConst() bool {
 	return strings.HasSuffix(n.Kind, "const")
 }

 // An ExpFunc is an exported function, callable from C.
 // Such functions are identified in the Go input file
 // by doc comments containing the line //export ExpName
 type ExpFunc struct {
 	Func    *ast.FuncDecl
 	ExpName string // name to use from C
 	Doc     string
 }

 // A TypeRepr contains the string representation of a type.
 type TypeRepr struct {
 	Repr       string
 	FormatArgs []interface{}
 }

 // A Type collects information about a type in both the C and Go worlds.
 type Type struct {
 	Size       int64
 	Align      int64
 	C          *TypeRepr
 	Go         ast.Expr
 	EnumValues map[string]int64
 	Typedef    string
 	BadPointer bool // this pointer type should be represented as a uintptr (deprecated)
 }

 // A FuncType collects information about a function type in both the C and Go worlds.
 type FuncType struct {
 	Params []*Type
 	Result *Type
 	Go     *ast.FuncType
 }

 func usage() {
 	fmt.Fprint(os.Stderr, "usage: cgo -- [compiler options] file.go ...\n")
 	flag.PrintDefaults()
 	os.Exit(2)
 }

 var ptrSizeMap = map[string]int64{
 	"386":         4,
 	"alpha":       8,
 	"amd64":       8,
 	"arm":         4,
 	"arm64":       8,
 	"m68k":        4,
 	"mips":        4,
 	"mipsle":      4,
 	"mips64":      8,
 	"mips64le":    8,
 	"mips64p32":   4,
 	"mips64p32le": 4,
 	"nios2":       4,
 	"ppc":         4,
 	"ppc64":       8,
 	"ppc64le":     8,
 	"riscv":       4,
 	"riscv64":     8,
 	"s390":        4,
 	"s390x":       8,
 	"sh":          4,
 	"shbe":        4,
 	"sparc":       4,
 	"sparc64":     8,
 }

 var intSizeMap = map[string]int64{
 	"386":         4,
 	"alpha":       8,
 	"amd64":       8,
 	"arm":         4,
 	"arm64":       8,
 	"m68k":        4,
 	"mips":        4,
 	"mipsle":      4,
 	"mips64":      8,
 	"mips64le":    8,
 	"mips64p32":   8,
 	"mips64p32le": 8,
 	"nios2":       4,
 	"ppc":         4,
 	"ppc64":       8,
 	"ppc64le":     8,
 	"riscv":       4,
 	"riscv64":     8,
 	"s390":        4,
 	"s390x":       8,
 	"sh":          4,
 	"shbe":        4,
 	"sparc":       4,
 	"sparc64":     8,
 }

 var cPrefix string

 var fset = token.NewFileSet()

 var dynobj = flag.String("dynimport", "", "if non-empty, print dynamic import data for that file")
 var dynout = flag.String("dynout", "", "write -dynimport output to this file")
 var dynpackage = flag.String("dynpackage", "main", "set Go package for -dynimport output")
 var dynlinker = flag.Bool("dynlinker", false, "record dynamic linker information in -dynimport mode")

 // This flag is for bootstrapping a new Go implementation,
 // to generate Go types that match the data layout and
 // constant values used in the host's C libraries and system calls.
 var godefs = flag.Bool("godefs", false, "for bootstrap: write Go definitions for C file to standard output")

 var srcDir = flag.String("srcdir", "", "source directory")
 var objDir = flag.String("objdir", "", "object directory")
 var importPath = flag.String("importpath", "", "import path of package being built (for comments in generated files)")
 var exportHeader = flag.String("exportheader", "", "where to write export header if any exported functions")

 var gccgo = flag.Bool("gccgo", false, "generate files for use with gccgo")
 var gccgoprefix = flag.String("gccgoprefix", "", "-fgo-prefix option used with gccgo")
 var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used with gccgo")
 var gccgoMangler func(string) string
 var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
 var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
 var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")

 var goarch, goos, gomips, gomips64 string
 var gccBaseCmd []string

 func main() {
 	objabi.AddVersionFlag() // -V
 	flag.Usage = usage
 	flag.Parse()

 	if *dynobj != "" {
 		// cgo -dynimport is essentially a separate helper command
 		// built into the cgo binary. It scans a gcc-produced executable
 		// and dumps information about the imported symbols and the
 		// imported libraries. The 'go build' rules for cgo prepare an
 		// appropriate executable and then use its import information
 		// instead of needing to make the linkers duplicate all the
 		// specialized knowledge gcc has about where to look for imported
 		// symbols and which ones to use.
 		dynimport(*dynobj)
 		return
 	}

 	if *godefs {
 		// Generating definitions pulled from header files,
 		// to be checked into Go repositories.
 		// Line numbers are just noise.
 		conf.Mode &^= printer.SourcePos
 	}

 	args := flag.Args()
 	if len(args) < 1 {
 		usage()
 	}

 	// Find first arg that looks like a go file and assume everything before
 	// that are options to pass to gcc.
 	var i int
 	for i = len(args); i > 0; i-- {
 		if !strings.HasSuffix(args[i-1], ".go") {
 			break
 		}
 	}
 	if i == len(args) {
 		usage()
 	}

 	goFiles := args[i:]

 	for _, arg := range args[:i] {
 		if arg == "-fsanitize=thread" {
 			tsanProlog = yesTsanProlog
 		}
 		if arg == "-fsanitize=memory" {
 			msanProlog = yesMsanProlog
 		}
 	}

 	p := newPackage(args[:i])

 	// We need a C compiler to be available. Check this.
 	var err error
 	gccBaseCmd, err = checkGCCBaseCmd()
 	if err != nil {
 		fatalf("%v", err)
 		os.Exit(2)
 	}

 	// Record CGO_LDFLAGS from the environment for external linking.
 	if ldflags := os.Getenv("CGO_LDFLAGS"); ldflags != "" {
 		args, err := splitQuoted(ldflags)
 		if err != nil {
 			fatalf("bad CGO_LDFLAGS: %q (%s)", ldflags, err)
 		}
 		p.addToFlag("LDFLAGS", args)
 	}

 	// Need a unique prefix for the global C symbols that
 	// we use to coordinate between gcc and ourselves.
 	// We already put _cgo_ at the beginning, so the main
 	// concern is other cgo wrappers for the same functions.
 	// Use the beginning of the md5 of the input to disambiguate.
 	h := md5.New()
 	io.WriteString(h, *importPath)
 	fs := make([]*File, len(goFiles))
 	for i, input := range goFiles {
 		if *srcDir != "" {
 			input = filepath.Join(*srcDir, input)
 		}

 		// Create absolute path for file, so that it will be used in error
 		// messages and recorded in debug line number information.
 		// This matches the rest of the toolchain. See golang.org/issue/5122.
 		if aname, err := filepath.Abs(input); err == nil {
 			input = aname
 		}

 		b, err := ioutil.ReadFile(input)
 		if err != nil {
 			fatalf("%s", err)
 		}
 		if _, err = h.Write(b); err != nil {
 			fatalf("%s", err)
 		}

 		// Apply trimpath to the file path. The path won't be read from after this point.
 		input, _ = objabi.ApplyRewrites(input, *trimpath)
 		goFiles[i] = input

 		f := new(File)
 		f.Edit = edit.NewBuffer(b)
 		f.ParseGo(input, b)
 		f.DiscardCgoDirectives()
 		fs[i] = f
 	}

 	cPrefix = fmt.Sprintf("_%x", h.Sum(nil)[0:6])

 	if *objDir == "" {
 		// make sure that _obj directory exists, so that we can write
 		// all the output files there.
 		os.Mkdir("_obj", 0777)
 		*objDir = "_obj"
 	}
 	*objDir += string(filepath.Separator)

 	for i, input := range goFiles {
 		f := fs[i]
 		p.Translate(f)
 		for _, cref := range f.Ref {
 			switch cref.Context {
 			case ctxCall, ctxCall2:
 				if cref.Name.Kind != "type" {
 					break
 				}
 				old := *cref.Expr
 				*cref.Expr = cref.Name.Type.Go
 				f.Edit.Replace(f.offset(old.Pos()), f.offset(old.End()), gofmt(cref.Name.Type.Go))
 			}
 		}
 		if nerrors > 0 {
 			os.Exit(2)
 		}
 		p.PackagePath = f.Package
 		p.Record(f)
 		if *godefs {
 			os.Stdout.WriteString(p.godefs(f))
 		} else {
 			p.writeOutput(f, input)
 		}
 	}

 	if !*godefs {
 		p.writeDefs()
 	}
 	if nerrors > 0 {
 		os.Exit(2)
 	}
 }

 // newPackage returns a new Package that will invoke
 // gcc with the additional arguments specified in args.
 func newPackage(args []string) *Package {
 	goarch = runtime.GOARCH
 	if s := os.Getenv("GOARCH"); s != "" {
 		goarch = s
 	}
 	goos = runtime.GOOS
 	if s := os.Getenv("GOOS"); s != "" {
 		goos = s
 	}
 	buildcfg.Check()
 	gomips = buildcfg.GOMIPS
 	gomips64 = buildcfg.GOMIPS64
 	ptrSize := ptrSizeMap[goarch]
 	if ptrSize == 0 {
 		fatalf("unknown ptrSize for $GOARCH %q", goarch)
 	}
 	intSize := intSizeMap[goarch]
 	if intSize == 0 {
 		fatalf("unknown intSize for $GOARCH %q", goarch)
 	}

 	// Reset locale variables so gcc emits English errors [sic].
 	os.Setenv("LANG", "en_US.UTF-8")
 	os.Setenv("LC_ALL", "C")

 	p := &Package{
 		PtrSize:  ptrSize,
 		IntSize:  intSize,
 		CgoFlags: make(map[string][]string),
 		Written:  make(map[string]bool),
 	}
 	p.addToFlag("CFLAGS", args)
 	return p
 }

 // Record what needs to be recorded about f.
 func (p *Package) Record(f *File) {
 	if p.PackageName == "" {
 		p.PackageName = f.Package
 	} else if p.PackageName != f.Package {
 		error_(token.NoPos, "inconsistent package names: %s, %s", p.PackageName, f.Package)
 	}

 	if p.Name == nil {
 		p.Name = f.Name
 	} else {
 		for k, v := range f.Name {
 			if p.Name[k] == nil {
 				p.Name[k] = v
 			} else if p.incompleteTypedef(p.Name[k].Type) {
 				p.Name[k] = v
 			} else if p.incompleteTypedef(v.Type) {
 				// Nothing to do.
 			} else if _, ok := nameToC[k]; ok {
 				// Names we predefine may appear inconsistent
 				// if some files typedef them and some don't.
 				// Issue 26743.
 			} else if !reflect.DeepEqual(p.Name[k], v) {
 				error_(token.NoPos, "inconsistent definitions for C.%s", fixGo(k))
 			}
 		}
 	}

 	if f.ExpFunc != nil {
 		p.ExpFunc = append(p.ExpFunc, f.ExpFunc...)
 		p.Preamble += "\n" + f.Preamble
 	}
 	p.Decl = append(p.Decl, f.AST.Decls...)
 }

 // incompleteTypedef reports whether t appears to be an incomplete
 // typedef definition.
 func (p *Package) incompleteTypedef(t *Type) bool {
 	return t == nil || (t.Size == 0 && t.Align == -1)
 }
	// 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.

	// Cgo; see doc.go for an overview.

	// TODO(rsc):
	// Emit correct line number annotations.
	// Make gc understand the annotations.

	package main

	import (
	"crypto/md5"
	"flag"
	"fmt"
	"go/ast"
	"go/printer"
	"go/token"
	"internal/buildcfg"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"sort"
	"strings"

	"cmd/internal/edit"
	"cmd/internal/objabi"
	)

	// A Package collects information about the package we're going to write.
	type Package struct {
	PackageName string // name of package
	PackagePath string
	PtrSize int64
	IntSize int64
	GccOptions []string
	GccIsClang bool
	CgoFlags map[string][]string // #cgo flags (CFLAGS, LDFLAGS)
	Written map[string]bool
	Name map[string]*Name // accumulated Name from Files
	ExpFunc []*ExpFunc // accumulated ExpFunc from Files
	Decl []ast.Decl
	GoFiles []string // list of Go files
	GccFiles []string // list of gcc output files
	Preamble string // collected preamble for _cgo_export.h
	typedefs map[string]bool // type names that appear in the types of the objects we're interested in
	typedefList []typedefInfo
	}

	// A typedefInfo is an element on Package.typedefList: a typedef name
	// and the position where it was required.
	type typedefInfo struct {
	typedef string
	pos token.Pos
	}

	// A File collects information about a single Go input file.
	type File struct {
	AST *ast.File // parsed AST
	Comments []*ast.CommentGroup // comments from file
	Package string // Package name
	Preamble string // C preamble (doc comment on import "C")
	Ref []*Ref // all references to C.xxx in AST
	Calls []*Call // all calls to C.xxx in AST
	ExpFunc []*ExpFunc // exported functions for this file
	Name map[string]*Name // map from Go name to Name
	NamePos map[*Name]token.Pos // map from Name to position of the first reference
	Edit *edit.Buffer
	}

	func (f *File) offset(p token.Pos) int {
	return fset.Position(p).Offset
	}

	func nameKeys(m map[string]*Name) []string {
	var ks []string
	for k := range m {
	ks = append(ks, k)
	}
	sort.Strings(ks)
	return ks
	}

	// A Call refers to a call of a C.xxx function in the AST.
	type Call struct {
	Call *ast.CallExpr
	Deferred bool
	Done bool
	}

	// A Ref refers to an expression of the form C.xxx in the AST.
	type Ref struct {
	Name *Name
	Expr *ast.Expr
	Context astContext
	Done bool
	}

	func (r *Ref) Pos() token.Pos {
	return (*r.Expr).Pos()
	}

	var nameKinds = []string{"iconst", "fconst", "sconst", "type", "var", "fpvar", "func", "macro", "not-type"}

	// A Name collects information about C.xxx.
	type Name struct {
	Go string // name used in Go referring to package C
	Mangle string // name used in generated Go
	C string // name used in C
	Define string // #define expansion
	Kind string // one of the nameKinds
	Type *Type // the type of xxx
	FuncType *FuncType
	AddError bool
	Const string // constant definition
	}

	// IsVar reports whether Kind is either "var" or "fpvar"
	func (n *Name) IsVar() bool {
	return n.Kind == "var" \|\| n.Kind == "fpvar"
	}

	// IsConst reports whether Kind is either "iconst", "fconst" or "sconst"
	func (n *Name) IsConst() bool {
	return strings.HasSuffix(n.Kind, "const")
	}

	// An ExpFunc is an exported function, callable from C.
	// Such functions are identified in the Go input file
	// by doc comments containing the line //export ExpName
	type ExpFunc struct {
	Func *ast.FuncDecl
	ExpName string // name to use from C
	Doc string
	}

	// A TypeRepr contains the string representation of a type.
	type TypeRepr struct {
	Repr string
	FormatArgs []interface{}
	}

	// A Type collects information about a type in both the C and Go worlds.
	type Type struct {
	Size int64
	Align int64
	C *TypeRepr
	Go ast.Expr
	EnumValues map[string]int64
	Typedef string
	BadPointer bool // this pointer type should be represented as a uintptr (deprecated)
	}

	// A FuncType collects information about a function type in both the C and Go worlds.
	type FuncType struct {
	Params []*Type
	Result *Type
	Go *ast.FuncType
	}

	func usage() {
	fmt.Fprint(os.Stderr, "usage: cgo -- [compiler options] file.go ...\n")
	flag.PrintDefaults()
	os.Exit(2)
	}

	var ptrSizeMap = map[string]int64{
	"386": 4,
	"alpha": 8,
	"amd64": 8,
	"arm": 4,
	"arm64": 8,
	"m68k": 4,
	"mips": 4,
	"mipsle": 4,
	"mips64": 8,
	"mips64le": 8,
	"mips64p32": 4,
	"mips64p32le": 4,
	"nios2": 4,
	"ppc": 4,
	"ppc64": 8,
	"ppc64le": 8,
	"riscv": 4,
	"riscv64": 8,
	"s390": 4,
	"s390x": 8,
	"sh": 4,
	"shbe": 4,
	"sparc": 4,
	"sparc64": 8,
	}

	var intSizeMap = map[string]int64{
	"386": 4,
	"alpha": 8,
	"amd64": 8,
	"arm": 4,
	"arm64": 8,
	"m68k": 4,
	"mips": 4,
	"mipsle": 4,
	"mips64": 8,
	"mips64le": 8,
	"mips64p32": 8,
	"mips64p32le": 8,
	"nios2": 4,
	"ppc": 4,
	"ppc64": 8,
	"ppc64le": 8,
	"riscv": 4,
	"riscv64": 8,
	"s390": 4,
	"s390x": 8,
	"sh": 4,
	"shbe": 4,
	"sparc": 4,
	"sparc64": 8,
	}

	var cPrefix string

	var fset = token.NewFileSet()

	var dynobj = flag.String("dynimport", "", "if non-empty, print dynamic import data for that file")
	var dynout = flag.String("dynout", "", "write -dynimport output to this file")
	var dynpackage = flag.String("dynpackage", "main", "set Go package for -dynimport output")
	var dynlinker = flag.Bool("dynlinker", false, "record dynamic linker information in -dynimport mode")

	// This flag is for bootstrapping a new Go implementation,
	// to generate Go types that match the data layout and
	// constant values used in the host's C libraries and system calls.
	var godefs = flag.Bool("godefs", false, "for bootstrap: write Go definitions for C file to standard output")

	var srcDir = flag.String("srcdir", "", "source directory")
	var objDir = flag.String("objdir", "", "object directory")
	var importPath = flag.String("importpath", "", "import path of package being built (for comments in generated files)")
	var exportHeader = flag.String("exportheader", "", "where to write export header if any exported functions")

	var gccgo = flag.Bool("gccgo", false, "generate files for use with gccgo")
	var gccgoprefix = flag.String("gccgoprefix", "", "-fgo-prefix option used with gccgo")
	var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used with gccgo")
	var gccgoMangler func(string) string
	var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
	var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
	var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")

	var goarch, goos, gomips, gomips64 string
	var gccBaseCmd []string

	func main() {
	objabi.AddVersionFlag() // -V
	flag.Usage = usage
	flag.Parse()

	if *dynobj != "" {
	// cgo -dynimport is essentially a separate helper command
	// built into the cgo binary. It scans a gcc-produced executable
	// and dumps information about the imported symbols and the
	// imported libraries. The 'go build' rules for cgo prepare an
	// appropriate executable and then use its import information
	// instead of needing to make the linkers duplicate all the
	// specialized knowledge gcc has about where to look for imported
	// symbols and which ones to use.
	dynimport(*dynobj)
	return
	}

	if *godefs {
	// Generating definitions pulled from header files,
	// to be checked into Go repositories.
	// Line numbers are just noise.
	conf.Mode &^= printer.SourcePos
	}

	args := flag.Args()
	if len(args) < 1 {
	usage()
	}

	// Find first arg that looks like a go file and assume everything before
	// that are options to pass to gcc.
	var i int
	for i = len(args); i > 0; i-- {
	if !strings.HasSuffix(args[i-1], ".go") {
	break
	}
	}
	if i == len(args) {
	usage()
	}

	goFiles := args[i:]

	for _, arg := range args[:i] {
	if arg == "-fsanitize=thread" {
	tsanProlog = yesTsanProlog
	}
	if arg == "-fsanitize=memory" {
	msanProlog = yesMsanProlog
	}
	}

	p := newPackage(args[:i])

	// We need a C compiler to be available. Check this.
	var err error
	gccBaseCmd, err = checkGCCBaseCmd()
	if err != nil {
	fatalf("%v", err)
	os.Exit(2)
	}

	// Record CGO_LDFLAGS from the environment for external linking.
	if ldflags := os.Getenv("CGO_LDFLAGS"); ldflags != "" {
	args, err := splitQuoted(ldflags)
	if err != nil {
	fatalf("bad CGO_LDFLAGS: %q (%s)", ldflags, err)
	}
	p.addToFlag("LDFLAGS", args)
	}

	// Need a unique prefix for the global C symbols that
	// we use to coordinate between gcc and ourselves.
	// We already put _cgo_ at the beginning, so the main
	// concern is other cgo wrappers for the same functions.
	// Use the beginning of the md5 of the input to disambiguate.
	h := md5.New()
	io.WriteString(h, *importPath)
	fs := make([]*File, len(goFiles))
	for i, input := range goFiles {
	if *srcDir != "" {
	input = filepath.Join(*srcDir, input)
	}

	// Create absolute path for file, so that it will be used in error
	// messages and recorded in debug line number information.
	// This matches the rest of the toolchain. See golang.org/issue/5122.
	if aname, err := filepath.Abs(input); err == nil {
	input = aname
	}

	b, err := ioutil.ReadFile(input)
	if err != nil {
	fatalf("%s", err)
	}
	if _, err = h.Write(b); err != nil {
	fatalf("%s", err)
	}

	// Apply trimpath to the file path. The path won't be read from after this point.
	input, _ = objabi.ApplyRewrites(input, *trimpath)
	goFiles[i] = input

	f := new(File)
	f.Edit = edit.NewBuffer(b)
	f.ParseGo(input, b)
	f.DiscardCgoDirectives()
	fs[i] = f
	}

	cPrefix = fmt.Sprintf("_%x", h.Sum(nil)[0:6])

	if *objDir == "" {
	// make sure that _obj directory exists, so that we can write
	// all the output files there.
	os.Mkdir("_obj", 0777)
	*objDir = "_obj"
	}
	*objDir += string(filepath.Separator)

	for i, input := range goFiles {
	f := fs[i]
	p.Translate(f)
	for _, cref := range f.Ref {
	switch cref.Context {
	case ctxCall, ctxCall2:
	if cref.Name.Kind != "type" {
	break
	}
	old := *cref.Expr
	*cref.Expr = cref.Name.Type.Go
	f.Edit.Replace(f.offset(old.Pos()), f.offset(old.End()), gofmt(cref.Name.Type.Go))
	}
	}
	if nerrors > 0 {
	os.Exit(2)
	}
	p.PackagePath = f.Package
	p.Record(f)
	if *godefs {
	os.Stdout.WriteString(p.godefs(f))
	} else {
	p.writeOutput(f, input)
	}
	}

	if !*godefs {
	p.writeDefs()
	}
	if nerrors > 0 {
	os.Exit(2)
	}
	}

	// newPackage returns a new Package that will invoke
	// gcc with the additional arguments specified in args.
	func newPackage(args []string) *Package {
	goarch = runtime.GOARCH
	if s := os.Getenv("GOARCH"); s != "" {
	goarch = s
	}
	goos = runtime.GOOS
	if s := os.Getenv("GOOS"); s != "" {
	goos = s
	}
	buildcfg.Check()
	gomips = buildcfg.GOMIPS
	gomips64 = buildcfg.GOMIPS64
	ptrSize := ptrSizeMap[goarch]
	if ptrSize == 0 {
	fatalf("unknown ptrSize for $GOARCH %q", goarch)
	}
	intSize := intSizeMap[goarch]
	if intSize == 0 {
	fatalf("unknown intSize for $GOARCH %q", goarch)
	}

	// Reset locale variables so gcc emits English errors [sic].
	os.Setenv("LANG", "en_US.UTF-8")
	os.Setenv("LC_ALL", "C")

	p := &Package{
	PtrSize: ptrSize,
	IntSize: intSize,
	CgoFlags: make(map[string][]string),
	Written: make(map[string]bool),
	}
	p.addToFlag("CFLAGS", args)
	return p
	}

	// Record what needs to be recorded about f.
	func (p Package) Record(f File) {
	if p.PackageName == "" {
	p.PackageName = f.Package
	} else if p.PackageName != f.Package {
	error_(token.NoPos, "inconsistent package names: %s, %s", p.PackageName, f.Package)
	}

	if p.Name == nil {
	p.Name = f.Name
	} else {
	for k, v := range f.Name {
	if p.Name[k] == nil {
	p.Name[k] = v
	} else if p.incompleteTypedef(p.Name[k].Type) {
	p.Name[k] = v
	} else if p.incompleteTypedef(v.Type) {
	// Nothing to do.
	} else if _, ok := nameToC[k]; ok {
	// Names we predefine may appear inconsistent
	// if some files typedef them and some don't.
	// Issue 26743.
	} else if !reflect.DeepEqual(p.Name[k], v) {
	error_(token.NoPos, "inconsistent definitions for C.%s", fixGo(k))
	}
	}
	}

	if f.ExpFunc != nil {
	p.ExpFunc = append(p.ExpFunc, f.ExpFunc...)
	p.Preamble += "\n" + f.Preamble
	}
	p.Decl = append(p.Decl, f.AST.Decls...)
	}

	// incompleteTypedef reports whether t appears to be an incomplete
	// typedef definition.
	func (p Package) incompleteTypedef(t Type) bool {
	return t == nil \|\| (t.Size == 0 && t.Align == -1)
	}