src/cmd/link/internal/ld/go.go - go - 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.

 // go-specific code shared across loaders (5l, 6l, 8l).

 package ld

 import (
 	"bytes"
 	"cmd/internal/bio"
 	"cmd/internal/objabi"
 	"cmd/link/internal/sym"
 	"encoding/json"
 	"fmt"
 	"io"
 	"os"
 	"strings"
 )

 // go-specific code shared across loaders (5l, 6l, 8l).

 // replace all "". with pkg.
 func expandpkg(t0 string, pkg string) string {
 	return strings.Replace(t0, `"".`, pkg+".", -1)
 }

 func resolveABIAlias(s *sym.Symbol) *sym.Symbol {
 	if s.Type != sym.SABIALIAS {
 		return s
 	}
 	target := s.R[0].Sym
 	if target.Type == sym.SABIALIAS {
 		panic(fmt.Sprintf("ABI alias %s references another ABI alias %s", s, target))
 	}
 	return target
 }

 // TODO:
 //	generate debugging section in binary.
 //	once the dust settles, try to move some code to
 //		libmach, so that other linkers and ar can share.

 func ldpkg(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, filename string) {
 	if *flagG {
 		return
 	}

 	if int64(int(length)) != length {
 		fmt.Fprintf(os.Stderr, "%s: too much pkg data in %s\n", os.Args[0], filename)
 		if *flagU {
 			errorexit()
 		}
 		return
 	}

 	bdata := make([]byte, length)
 	if _, err := io.ReadFull(f, bdata); err != nil {
 		fmt.Fprintf(os.Stderr, "%s: short pkg read %s\n", os.Args[0], filename)
 		if *flagU {
 			errorexit()
 		}
 		return
 	}
 	data := string(bdata)

 	// process header lines
 	for data != "" {
 		var line string
 		if i := strings.Index(data, "\n"); i >= 0 {
 			line, data = data[:i], data[i+1:]
 		} else {
 			line, data = data, ""
 		}
 		if line == "safe" {
 			lib.Safe = true
 		}
 		if line == "main" {
 			lib.Main = true
 		}
 		if line == "" {
 			break
 		}
 	}

 	// look for cgo section
 	p0 := strings.Index(data, "\n$$  // cgo")
 	var p1 int
 	if p0 >= 0 {
 		p0 += p1
 		i := strings.IndexByte(data[p0+1:], '\n')
 		if i < 0 {
 			fmt.Fprintf(os.Stderr, "%s: found $$ // cgo but no newline in %s\n", os.Args[0], filename)
 			if *flagU {
 				errorexit()
 			}
 			return
 		}
 		p0 += 1 + i

 		p1 = strings.Index(data[p0:], "\n$$")
 		if p1 < 0 {
 			p1 = strings.Index(data[p0:], "\n!\n")
 		}
 		if p1 < 0 {
 			fmt.Fprintf(os.Stderr, "%s: cannot find end of // cgo section in %s\n", os.Args[0], filename)
 			if *flagU {
 				errorexit()
 			}
 			return
 		}
 		p1 += p0

 		loadcgo(ctxt, filename, objabi.PathToPrefix(lib.Pkg), data[p0:p1])
 	}
 }

 func loadcgo(ctxt *Link, file string, pkg string, p string) {
 	var directives [][]string
 	if err := json.NewDecoder(strings.NewReader(p)).Decode(&directives); err != nil {
 		fmt.Fprintf(os.Stderr, "%s: %s: failed decoding cgo directives: %v\n", os.Args[0], file, err)
 		nerrors++
 		return
 	}

 	for _, f := range directives {
 		switch f[0] {
 		case "cgo_import_dynamic":
 			if len(f) < 2 || len(f) > 4 {
 				break
 			}

 			local := f[1]
 			remote := local
 			if len(f) > 2 {
 				remote = f[2]
 			}
 			lib := ""
 			if len(f) > 3 {
 				lib = f[3]
 			}

 			if *FlagD {
 				fmt.Fprintf(os.Stderr, "%s: %s: cannot use dynamic imports with -d flag\n", os.Args[0], file)
 				nerrors++
 				return
 			}

 			if local == "_" && remote == "_" {
 				// allow #pragma dynimport _ _ "foo.so"
 				// to force a link of foo.so.
 				havedynamic = 1

 				if ctxt.HeadType == objabi.Hdarwin {
 					machoadddynlib(lib, ctxt.LinkMode)
 				} else {
 					dynlib = append(dynlib, lib)
 				}
 				continue
 			}

 			local = expandpkg(local, pkg)
 			q := ""
 			if i := strings.Index(remote, "#"); i >= 0 {
 				remote, q = remote[:i], remote[i+1:]
 			}
 			s := ctxt.Syms.Lookup(local, 0)
 			if s.Type == 0 || s.Type == sym.SXREF || s.Type == sym.SHOSTOBJ {
 				s.SetDynimplib(lib)
 				s.SetExtname(remote)
 				s.SetDynimpvers(q)
 				if s.Type != sym.SHOSTOBJ {
 					s.Type = sym.SDYNIMPORT
 				}
 				havedynamic = 1
 			}

 			continue

 		case "cgo_import_static":
 			if len(f) != 2 {
 				break
 			}
 			local := f[1]

 			s := ctxt.Syms.Lookup(local, 0)
 			s.Type = sym.SHOSTOBJ
 			s.Size = 0
 			continue

 		case "cgo_export_static", "cgo_export_dynamic":
 			if len(f) < 2 || len(f) > 3 {
 				break
 			}
 			local := f[1]
 			remote := local
 			if len(f) > 2 {
 				remote = f[2]
 			}
 			local = expandpkg(local, pkg)

 			// The compiler arranges for an ABI0 wrapper
 			// to be available for all cgo-exported
 			// functions. Link.loadlib will resolve any
 			// ABI aliases we find here (since we may not
 			// yet know it's an alias).
 			s := ctxt.Syms.Lookup(local, 0)

 			switch ctxt.BuildMode {
 			case BuildModeCShared, BuildModeCArchive, BuildModePlugin:
 				if s == ctxt.Syms.Lookup("main", 0) {
 					continue
 				}
 			}

 			// export overrides import, for openbsd/cgo.
 			// see issue 4878.
 			if s.Dynimplib() != "" {
 				s.ResetDyninfo()
 				s.SetExtname("")
 				s.Type = 0
 			}

 			if !s.Attr.CgoExport() {
 				s.SetExtname(remote)
 				dynexp = append(dynexp, s)
 			} else if s.Extname() != remote {
 				fmt.Fprintf(os.Stderr, "%s: conflicting cgo_export directives: %s as %s and %s\n", os.Args[0], s.Name, s.Extname(), remote)
 				nerrors++
 				return
 			}

 			if f[0] == "cgo_export_static" {
 				s.Attr |= sym.AttrCgoExportStatic
 			} else {
 				s.Attr |= sym.AttrCgoExportDynamic
 			}
 			continue

 		case "cgo_dynamic_linker":
 			if len(f) != 2 {
 				break
 			}

 			if *flagInterpreter == "" {
 				if interpreter != "" && interpreter != f[1] {
 					fmt.Fprintf(os.Stderr, "%s: conflict dynlinker: %s and %s\n", os.Args[0], interpreter, f[1])
 					nerrors++
 					return
 				}

 				interpreter = f[1]
 			}
 			continue

 		case "cgo_ldflag":
 			if len(f) != 2 {
 				break
 			}
 			ldflag = append(ldflag, f[1])
 			continue
 		}

 		fmt.Fprintf(os.Stderr, "%s: %s: invalid cgo directive: %q\n", os.Args[0], file, f)
 		nerrors++
 	}
 }

 var seenlib = make(map[string]bool)

 func adddynlib(ctxt *Link, lib string) {
 	if seenlib[lib] || ctxt.LinkMode == LinkExternal {
 		return
 	}
 	seenlib[lib] = true

 	if ctxt.IsELF {
 		s := ctxt.Syms.Lookup(".dynstr", 0)
 		if s.Size == 0 {
 			Addstring(s, "")
 		}
 		Elfwritedynent(ctxt, ctxt.Syms.Lookup(".dynamic", 0), DT_NEEDED, uint64(Addstring(s, lib)))
 	} else {
 		Errorf(nil, "adddynlib: unsupported binary format")
 	}
 }

 func Adddynsym(ctxt *Link, s *sym.Symbol) {
 	if s.Dynid >= 0 || ctxt.LinkMode == LinkExternal {
 		return
 	}

 	if ctxt.IsELF {
 		elfadddynsym(ctxt, s)
 	} else if ctxt.HeadType == objabi.Hdarwin {
 		Errorf(s, "adddynsym: missed symbol (Extname=%s)", s.Extname())
 	} else if ctxt.HeadType == objabi.Hwindows {
 		// already taken care of
 	} else {
 		Errorf(s, "adddynsym: unsupported binary format")
 	}
 }

 func fieldtrack(ctxt *Link) {
 	// record field tracking references
 	var buf bytes.Buffer
 	for _, s := range ctxt.Syms.Allsym {
 		if strings.HasPrefix(s.Name, "go.track.") {
 			s.Attr |= sym.AttrSpecial // do not lay out in data segment
 			s.Attr |= sym.AttrNotInSymbolTable
 			if s.Attr.Reachable() {
 				buf.WriteString(s.Name[9:])
 				for p := ctxt.Reachparent[s]; p != nil; p = ctxt.Reachparent[p] {
 					buf.WriteString("\t")
 					buf.WriteString(p.Name)
 				}
 				buf.WriteString("\n")
 			}

 			s.Type = sym.SCONST
 			s.Value = 0
 		}
 	}

 	if *flagFieldTrack == "" {
 		return
 	}
 	s := ctxt.Syms.ROLookup(*flagFieldTrack, 0)
 	if s == nil || !s.Attr.Reachable() {
 		return
 	}
 	s.Type = sym.SDATA
 	addstrdata(ctxt, *flagFieldTrack, buf.String())
 }

 func (ctxt *Link) addexport() {
 	// TODO(aix)
 	if ctxt.HeadType == objabi.Hdarwin || ctxt.HeadType == objabi.Haix {
 		return
 	}

 	for _, exp := range dynexp {
 		Adddynsym(ctxt, exp)
 	}
 	for _, lib := range dynlib {
 		adddynlib(ctxt, lib)
 	}
 }

 type Pkg struct {
 	mark    bool
 	checked bool
 	path    string
 	impby   []*Pkg
 }

 var pkgall []*Pkg

 func (p *Pkg) cycle() *Pkg {
 	if p.checked {
 		return nil
 	}

 	if p.mark {
 		nerrors++
 		fmt.Printf("import cycle:\n")
 		fmt.Printf("\t%s\n", p.path)
 		return p
 	}

 	p.mark = true
 	for _, q := range p.impby {
 		if bad := q.cycle(); bad != nil {
 			p.mark = false
 			p.checked = true
 			fmt.Printf("\timports %s\n", p.path)
 			if bad == p {
 				return nil
 			}
 			return bad
 		}
 	}

 	p.checked = true
 	p.mark = false
 	return nil
 }

 func importcycles() {
 	for _, p := range pkgall {
 		p.cycle()
 	}
 }
	// 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-specific code shared across loaders (5l, 6l, 8l).

	package ld

	import (
	"bytes"
	"cmd/internal/bio"
	"cmd/internal/objabi"
	"cmd/link/internal/sym"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"strings"
	)

	// go-specific code shared across loaders (5l, 6l, 8l).

	// replace all "". with pkg.
	func expandpkg(t0 string, pkg string) string {
	return strings.Replace(t0, `"".`, pkg+".", -1)
	}

	func resolveABIAlias(s sym.Symbol) sym.Symbol {
	if s.Type != sym.SABIALIAS {
	return s
	}
	target := s.R[0].Sym
	if target.Type == sym.SABIALIAS {
	panic(fmt.Sprintf("ABI alias %s references another ABI alias %s", s, target))
	}
	return target
	}

	// TODO:
	// generate debugging section in binary.
	// once the dust settles, try to move some code to
	// libmach, so that other linkers and ar can share.

	func ldpkg(ctxt Link, f bio.Reader, lib *sym.Library, length int64, filename string) {
	if *flagG {
	return
	}

	if int64(int(length)) != length {
	fmt.Fprintf(os.Stderr, "%s: too much pkg data in %s\n", os.Args[0], filename)
	if *flagU {
	errorexit()
	}
	return
	}

	bdata := make([]byte, length)
	if _, err := io.ReadFull(f, bdata); err != nil {
	fmt.Fprintf(os.Stderr, "%s: short pkg read %s\n", os.Args[0], filename)
	if *flagU {
	errorexit()
	}
	return
	}
	data := string(bdata)

	// process header lines
	for data != "" {
	var line string
	if i := strings.Index(data, "\n"); i >= 0 {
	line, data = data[:i], data[i+1:]
	} else {
	line, data = data, ""
	}
	if line == "safe" {
	lib.Safe = true
	}
	if line == "main" {
	lib.Main = true
	}
	if line == "" {
	break
	}
	}

	// look for cgo section
	p0 := strings.Index(data, "\n$$ // cgo")
	var p1 int
	if p0 >= 0 {
	p0 += p1
	i := strings.IndexByte(data[p0+1:], '\n')
	if i < 0 {
	fmt.Fprintf(os.Stderr, "%s: found $$ // cgo but no newline in %s\n", os.Args[0], filename)
	if *flagU {
	errorexit()
	}
	return
	}
	p0 += 1 + i

	p1 = strings.Index(data[p0:], "\n$$")
	if p1 < 0 {
	p1 = strings.Index(data[p0:], "\n!\n")
	}
	if p1 < 0 {
	fmt.Fprintf(os.Stderr, "%s: cannot find end of // cgo section in %s\n", os.Args[0], filename)
	if *flagU {
	errorexit()
	}
	return
	}
	p1 += p0

	loadcgo(ctxt, filename, objabi.PathToPrefix(lib.Pkg), data[p0:p1])
	}
	}

	func loadcgo(ctxt *Link, file string, pkg string, p string) {
	var directives [][]string
	if err := json.NewDecoder(strings.NewReader(p)).Decode(&directives); err != nil {
	fmt.Fprintf(os.Stderr, "%s: %s: failed decoding cgo directives: %v\n", os.Args[0], file, err)
	nerrors++
	return
	}

	for _, f := range directives {
	switch f[0] {
	case "cgo_import_dynamic":
	if len(f) < 2 \|\| len(f) > 4 {
	break
	}

	local := f[1]
	remote := local
	if len(f) > 2 {
	remote = f[2]
	}
	lib := ""
	if len(f) > 3 {
	lib = f[3]
	}

	if *FlagD {
	fmt.Fprintf(os.Stderr, "%s: %s: cannot use dynamic imports with -d flag\n", os.Args[0], file)
	nerrors++
	return
	}

	if local == "_" && remote == "_" {
	// allow #pragma dynimport _ _ "foo.so"
	// to force a link of foo.so.
	havedynamic = 1

	if ctxt.HeadType == objabi.Hdarwin {
	machoadddynlib(lib, ctxt.LinkMode)
	} else {
	dynlib = append(dynlib, lib)
	}
	continue
	}

	local = expandpkg(local, pkg)
	q := ""
	if i := strings.Index(remote, "#"); i >= 0 {
	remote, q = remote[:i], remote[i+1:]
	}
	s := ctxt.Syms.Lookup(local, 0)
	if s.Type == 0 \|\| s.Type == sym.SXREF \|\| s.Type == sym.SHOSTOBJ {
	s.SetDynimplib(lib)
	s.SetExtname(remote)
	s.SetDynimpvers(q)
	if s.Type != sym.SHOSTOBJ {
	s.Type = sym.SDYNIMPORT
	}
	havedynamic = 1
	}

	continue

	case "cgo_import_static":
	if len(f) != 2 {
	break
	}
	local := f[1]

	s := ctxt.Syms.Lookup(local, 0)
	s.Type = sym.SHOSTOBJ
	s.Size = 0
	continue

	case "cgo_export_static", "cgo_export_dynamic":
	if len(f) < 2 \|\| len(f) > 3 {
	break
	}
	local := f[1]
	remote := local
	if len(f) > 2 {
	remote = f[2]
	}
	local = expandpkg(local, pkg)

	// The compiler arranges for an ABI0 wrapper
	// to be available for all cgo-exported
	// functions. Link.loadlib will resolve any
	// ABI aliases we find here (since we may not
	// yet know it's an alias).
	s := ctxt.Syms.Lookup(local, 0)

	switch ctxt.BuildMode {
	case BuildModeCShared, BuildModeCArchive, BuildModePlugin:
	if s == ctxt.Syms.Lookup("main", 0) {
	continue
	}
	}

	// export overrides import, for openbsd/cgo.
	// see issue 4878.
	if s.Dynimplib() != "" {
	s.ResetDyninfo()
	s.SetExtname("")
	s.Type = 0
	}

	if !s.Attr.CgoExport() {
	s.SetExtname(remote)
	dynexp = append(dynexp, s)
	} else if s.Extname() != remote {
	fmt.Fprintf(os.Stderr, "%s: conflicting cgo_export directives: %s as %s and %s\n", os.Args[0], s.Name, s.Extname(), remote)
	nerrors++
	return
	}

	if f[0] == "cgo_export_static" {
	s.Attr \|= sym.AttrCgoExportStatic
	} else {
	s.Attr \|= sym.AttrCgoExportDynamic
	}
	continue

	case "cgo_dynamic_linker":
	if len(f) != 2 {
	break
	}

	if *flagInterpreter == "" {
	if interpreter != "" && interpreter != f[1] {
	fmt.Fprintf(os.Stderr, "%s: conflict dynlinker: %s and %s\n", os.Args[0], interpreter, f[1])
	nerrors++
	return
	}

	interpreter = f[1]
	}
	continue

	case "cgo_ldflag":
	if len(f) != 2 {
	break
	}
	ldflag = append(ldflag, f[1])
	continue
	}

	fmt.Fprintf(os.Stderr, "%s: %s: invalid cgo directive: %q\n", os.Args[0], file, f)
	nerrors++
	}
	}

	var seenlib = make(map[string]bool)

	func adddynlib(ctxt *Link, lib string) {
	if seenlib[lib] \|\| ctxt.LinkMode == LinkExternal {
	return
	}
	seenlib[lib] = true

	if ctxt.IsELF {
	s := ctxt.Syms.Lookup(".dynstr", 0)
	if s.Size == 0 {
	Addstring(s, "")
	}
	Elfwritedynent(ctxt, ctxt.Syms.Lookup(".dynamic", 0), DT_NEEDED, uint64(Addstring(s, lib)))
	} else {
	Errorf(nil, "adddynlib: unsupported binary format")
	}
	}

	func Adddynsym(ctxt Link, s sym.Symbol) {
	if s.Dynid >= 0 \|\| ctxt.LinkMode == LinkExternal {
	return
	}

	if ctxt.IsELF {
	elfadddynsym(ctxt, s)
	} else if ctxt.HeadType == objabi.Hdarwin {
	Errorf(s, "adddynsym: missed symbol (Extname=%s)", s.Extname())
	} else if ctxt.HeadType == objabi.Hwindows {
	// already taken care of
	} else {
	Errorf(s, "adddynsym: unsupported binary format")
	}
	}

	func fieldtrack(ctxt *Link) {
	// record field tracking references
	var buf bytes.Buffer
	for _, s := range ctxt.Syms.Allsym {
	if strings.HasPrefix(s.Name, "go.track.") {
	s.Attr \|= sym.AttrSpecial // do not lay out in data segment
	s.Attr \|= sym.AttrNotInSymbolTable
	if s.Attr.Reachable() {
	buf.WriteString(s.Name[9:])
	for p := ctxt.Reachparent[s]; p != nil; p = ctxt.Reachparent[p] {
	buf.WriteString("\t")
	buf.WriteString(p.Name)
	}
	buf.WriteString("\n")
	}

	s.Type = sym.SCONST
	s.Value = 0
	}
	}

	if *flagFieldTrack == "" {
	return
	}
	s := ctxt.Syms.ROLookup(*flagFieldTrack, 0)
	if s == nil \|\| !s.Attr.Reachable() {
	return
	}
	s.Type = sym.SDATA
	addstrdata(ctxt, *flagFieldTrack, buf.String())
	}

	func (ctxt *Link) addexport() {
	// TODO(aix)
	if ctxt.HeadType == objabi.Hdarwin \|\| ctxt.HeadType == objabi.Haix {
	return
	}

	for _, exp := range dynexp {
	Adddynsym(ctxt, exp)
	}
	for _, lib := range dynlib {
	adddynlib(ctxt, lib)
	}
	}

	type Pkg struct {
	mark bool
	checked bool
	path string
	impby []*Pkg
	}

	var pkgall []*Pkg

	func (p Pkg) cycle() Pkg {
	if p.checked {
	return nil
	}

	if p.mark {
	nerrors++
	fmt.Printf("import cycle:\n")
	fmt.Printf("\t%s\n", p.path)
	return p
	}

	p.mark = true
	for _, q := range p.impby {
	if bad := q.cycle(); bad != nil {
	p.mark = false
	p.checked = true
	fmt.Printf("\timports %s\n", p.path)
	if bad == p {
	return nil
	}
	return bad
	}
	}

	p.checked = true
	p.mark = false
	return nil
	}

	func importcycles() {
	for _, p := range pkgall {
	p.cycle()
	}
	}