src/cmd/link/internal/ld/dwarf_test.go - go - Git at Google

 // Copyright 2017 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.

 package ld

 import (
 	objfilepkg "cmd/internal/objfile" // renamed to avoid conflict with objfile function
 	"debug/dwarf"
 	"errors"
 	"fmt"
 	"internal/testenv"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"reflect"
 	"runtime"
 	"testing"
 )

 func TestRuntimeTypeDIEs(t *testing.T) {
 	testenv.MustHaveGoBuild(t)

 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}

 	dir, err := ioutil.TempDir("", "TestRuntimeTypeDIEs")
 	if err != nil {
 		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)

 	f := gobuild(t, dir, `package main; func main() { }`, false)
 	defer f.Close()

 	dwarf, err := f.DWARF()
 	if err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	want := map[string]bool{
 		"runtime._type":         true,
 		"runtime.arraytype":     true,
 		"runtime.chantype":      true,
 		"runtime.functype":      true,
 		"runtime.maptype":       true,
 		"runtime.ptrtype":       true,
 		"runtime.slicetype":     true,
 		"runtime.structtype":    true,
 		"runtime.interfacetype": true,
 		"runtime.itab":          true,
 		"runtime.imethod":       true,
 	}

 	found := findTypes(t, dwarf, want)
 	if len(found) != len(want) {
 		t.Errorf("found %v, want %v", found, want)
 	}
 }

 func findTypes(t *testing.T, dw *dwarf.Data, want map[string]bool) (found map[string]bool) {
 	found = make(map[string]bool)
 	rdr := dw.Reader()
 	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
 		if err != nil {
 			t.Fatalf("error reading DWARF: %v", err)
 		}
 		switch entry.Tag {
 		case dwarf.TagTypedef:
 			if name, ok := entry.Val(dwarf.AttrName).(string); ok && want[name] {
 				found[name] = true
 			}
 		}
 	}
 	return
 }

 func gobuild(t *testing.T, dir string, testfile string, opt bool) *objfilepkg.File {
 	src := filepath.Join(dir, "test.go")
 	dst := filepath.Join(dir, "out")

 	if err := ioutil.WriteFile(src, []byte(testfile), 0666); err != nil {
 		t.Fatal(err)
 	}

 	gcflags := "-gcflags=-N -l"
 	if opt {
 		gcflags = "-gcflags=-l=4"
 	}
 	cmd := exec.Command(testenv.GoToolPath(t), "build", gcflags, "-o", dst, src)
 	if b, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("build: %s\n", b)
 		t.Fatalf("build error: %v", err)
 	}

 	f, err := objfilepkg.Open(dst)
 	if err != nil {
 		t.Fatal(err)
 	}
 	return f
 }

 func TestEmbeddedStructMarker(t *testing.T) {
 	testenv.MustHaveGoBuild(t)

 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}

 	const prog = `
 package main

 import "fmt"

 type Foo struct { v int }
 type Bar struct {
 	Foo
 	name string
 }
 type Baz struct {
 	*Foo
 	name string
 }

 func main() {
 	bar := Bar{ Foo: Foo{v: 123}, name: "onetwothree"}
 	baz := Baz{ Foo: &bar.Foo, name: "123" }
 	fmt.Println(bar, baz)
 }`

 	want := map[string]map[string]bool{
 		"main.Foo": map[string]bool{"v": false},
 		"main.Bar": map[string]bool{"Foo": true, "name": false},
 		"main.Baz": map[string]bool{"Foo": true, "name": false},
 	}

 	dir, err := ioutil.TempDir("", "TestEmbeddedStructMarker")
 	if err != nil {
 		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)

 	f := gobuild(t, dir, prog, false)

 	defer f.Close()

 	d, err := f.DWARF()
 	if err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	rdr := d.Reader()
 	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
 		if err != nil {
 			t.Fatalf("error reading DWARF: %v", err)
 		}
 		switch entry.Tag {
 		case dwarf.TagStructType:
 			name := entry.Val(dwarf.AttrName).(string)
 			wantMembers := want[name]
 			if wantMembers == nil {
 				continue
 			}
 			gotMembers, err := findMembers(rdr)
 			if err != nil {
 				t.Fatalf("error reading DWARF: %v", err)
 			}

 			if !reflect.DeepEqual(gotMembers, wantMembers) {
 				t.Errorf("type %v: got map[member]embedded = %+v, want %+v", name, wantMembers, gotMembers)
 			}
 			delete(want, name)
 		}
 	}
 	if len(want) != 0 {
 		t.Errorf("failed to check all expected types: missing types = %+v", want)
 	}
 }

 func findMembers(rdr *dwarf.Reader) (map[string]bool, error) {
 	memberEmbedded := map[string]bool{}
 	// TODO(hyangah): define in debug/dwarf package
 	const goEmbeddedStruct = dwarf.Attr(0x2903)
 	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
 		if err != nil {
 			return nil, err
 		}
 		switch entry.Tag {
 		case dwarf.TagMember:
 			name := entry.Val(dwarf.AttrName).(string)
 			embedded := entry.Val(goEmbeddedStruct).(bool)
 			memberEmbedded[name] = embedded
 		case 0:
 			return memberEmbedded, nil
 		}
 	}
 	return memberEmbedded, nil
 }

 func TestSizes(t *testing.T) {
 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}

 	// DWARF sizes should never be -1.
 	// See issue #21097
 	const prog = `
 package main
 var x func()
 var y [4]func()
 func main() {
 	x = nil
 	y[0] = nil
 }
 `
 	dir, err := ioutil.TempDir("", "TestSizes")
 	if err != nil {
 		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)
 	f := gobuild(t, dir, prog, false)
 	defer f.Close()
 	d, err := f.DWARF()
 	if err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}
 	rdr := d.Reader()
 	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
 		if err != nil {
 			t.Fatalf("error reading DWARF: %v", err)
 		}
 		switch entry.Tag {
 		case dwarf.TagArrayType, dwarf.TagPointerType, dwarf.TagStructType, dwarf.TagBaseType, dwarf.TagSubroutineType, dwarf.TagTypedef:
 		default:
 			continue
 		}
 		typ, err := d.Type(entry.Offset)
 		if err != nil {
 			t.Fatalf("can't read type: %v", err)
 		}
 		if typ.Size() < 0 {
 			t.Errorf("subzero size %s %s %T", typ, entry.Tag, typ)
 		}
 	}
 }

 func TestFieldOverlap(t *testing.T) {
 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}

 	// This test grew out of issue 21094, where specific sudog<T> DWARF types
 	// had elem fields set to values instead of pointers.
 	const prog = `
 package main

 var c chan string

 func main() {
 	c <- "foo"
 }
 `
 	dir, err := ioutil.TempDir("", "TestFieldOverlap")
 	if err != nil {
 		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)

 	f := gobuild(t, dir, prog, false)
 	defer f.Close()

 	d, err := f.DWARF()
 	if err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	rdr := d.Reader()
 	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
 		if err != nil {
 			t.Fatalf("error reading DWARF: %v", err)
 		}
 		if entry.Tag != dwarf.TagStructType {
 			continue
 		}
 		typ, err := d.Type(entry.Offset)
 		if err != nil {
 			t.Fatalf("can't read type: %v", err)
 		}
 		s := typ.(*dwarf.StructType)
 		for i := 0; i < len(s.Field); i++ {
 			end := s.Field[i].ByteOffset + s.Field[i].Type.Size()
 			var limit int64
 			if i == len(s.Field)-1 {
 				limit = s.Size()
 			} else {
 				limit = s.Field[i+1].ByteOffset
 			}
 			if end > limit {
 				name := entry.Val(dwarf.AttrName).(string)
 				t.Fatalf("field %s.%s overlaps next field", name, s.Field[i].Name)
 			}
 		}
 	}
 }

 func TestVarDeclCoordsAndSubrogramDeclFile(t *testing.T) {
 	testenv.MustHaveGoBuild(t)

 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}

 	const prog = `
 package main

 func main() {
 	var i int
 	i = i
 }
 `
 	dir, err := ioutil.TempDir("", "TestVarDeclCoords")
 	if err != nil {
 		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)

 	f := gobuild(t, dir, prog, false)

 	d, err := f.DWARF()
 	if err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	rdr := d.Reader()
 	ex := examiner{}
 	if err := ex.populate(rdr); err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	// Locate the main.main DIE
 	mains := ex.Named("main.main")
 	if len(mains) == 0 {
 		t.Fatalf("unable to locate DIE for main.main")
 	}
 	if len(mains) != 1 {
 		t.Fatalf("more than one main.main DIE")
 	}
 	maindie := mains[0]

 	// Vet the main.main DIE
 	if maindie.Tag != dwarf.TagSubprogram {
 		t.Fatalf("unexpected tag %v on main.main DIE", maindie.Tag)
 	}

 	// Walk main's children and select variable "i".
 	mainIdx := ex.idxFromOffset(maindie.Offset)
 	childDies := ex.Children(mainIdx)
 	var iEntry *dwarf.Entry
 	for _, child := range childDies {
 		if child.Tag == dwarf.TagVariable && child.Val(dwarf.AttrName).(string) == "i" {
 			iEntry = child
 			break
 		}
 	}
 	if iEntry == nil {
 		t.Fatalf("didn't find DW_TAG_variable for i in main.main")
 	}

 	// Verify line/file attributes.
 	line := iEntry.Val(dwarf.AttrDeclLine)
 	if line == nil || line.(int64) != 5 {
 		t.Errorf("DW_AT_decl_line for i is %v, want 5", line)
 	}

 	file := maindie.Val(dwarf.AttrDeclFile)
 	if file == nil || file.(int64) != 1 {
 		t.Errorf("DW_AT_decl_file for main is %v, want 1", file)
 	}
 }

 // Helper class for supporting queries on DIEs within a DWARF .debug_info
 // section. Invoke the populate() method below passing in a dwarf.Reader,
 // which will read in all DIEs and keep track of parent/child
 // relationships. Queries can then be made to ask for DIEs by name or
 // by offset. This will hopefully reduce boilerplate for future test
 // writing.

 type examiner struct {
 	dies        []*dwarf.Entry
 	idxByOffset map[dwarf.Offset]int
 	kids        map[int][]int
 	byname      map[string][]int
 }

 // Populate the examiner using the DIEs read from rdr.
 func (ex *examiner) populate(rdr *dwarf.Reader) error {
 	ex.idxByOffset = make(map[dwarf.Offset]int)
 	ex.kids = make(map[int][]int)
 	ex.byname = make(map[string][]int)
 	var nesting []int
 	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
 		if err != nil {
 			return err
 		}
 		if entry.Tag == 0 {
 			// terminator
 			if len(nesting) == 0 {
 				return errors.New("nesting stack underflow")
 			}
 			nesting = nesting[:len(nesting)-1]
 			continue
 		}
 		idx := len(ex.dies)
 		ex.dies = append(ex.dies, entry)
 		if _, found := ex.idxByOffset[entry.Offset]; found {
 			return errors.New("DIE clash on offset")
 		}
 		ex.idxByOffset[entry.Offset] = idx
 		if name, ok := entry.Val(dwarf.AttrName).(string); ok {
 			ex.byname[name] = append(ex.byname[name], idx)
 		}
 		if len(nesting) > 0 {
 			parent := nesting[len(nesting)-1]
 			ex.kids[parent] = append(ex.kids[parent], idx)
 		}
 		if entry.Children {
 			nesting = append(nesting, idx)
 		}
 	}
 	if len(nesting) > 0 {
 		return errors.New("unterminated child sequence")
 	}
 	return nil
 }

 func indent(ilevel int) {
 	for i := 0; i < ilevel; i++ {
 		fmt.Printf("  ")
 	}
 }

 // For debugging new tests
 func (ex *examiner) dumpEntry(idx int, dumpKids bool, ilevel int) error {
 	if idx >= len(ex.dies) {
 		msg := fmt.Sprintf("bad DIE %d: index out of range\n", idx)
 		return errors.New(msg)
 	}
 	entry := ex.dies[idx]
 	indent(ilevel)
 	fmt.Printf("%d: %v\n", idx, entry.Tag)
 	for _, f := range entry.Field {
 		indent(ilevel)
 		fmt.Printf("at=%v val=%v\n", f.Attr, f.Val)
 	}
 	if dumpKids {
 		ksl := ex.kids[idx]
 		for _, k := range ksl {
 			ex.dumpEntry(k, true, ilevel+2)
 		}
 	}
 	return nil
 }

 // Given a DIE offset, return the previously read dwarf.Entry, or nil
 func (ex *examiner) entryFromOffset(off dwarf.Offset) *dwarf.Entry {
 	if idx, found := ex.idxByOffset[off]; found && idx != -1 {
 		return ex.entryFromIdx(idx)
 	}
 	return nil
 }

 // Return the ID that that examiner uses to refer to the DIE at offset off
 func (ex *examiner) idxFromOffset(off dwarf.Offset) int {
 	if idx, found := ex.idxByOffset[off]; found {
 		return idx
 	}
 	return -1
 }

 // Return the dwarf.Entry pointer for the DIE with id 'idx'
 func (ex *examiner) entryFromIdx(idx int) *dwarf.Entry {
 	if idx >= len(ex.dies) {
 		return nil
 	}
 	return ex.dies[idx]
 }

 // Returns a list of child entries for a die with ID 'idx'
 func (ex *examiner) Children(idx int) []*dwarf.Entry {
 	sl := ex.kids[idx]
 	ret := make([]*dwarf.Entry, len(sl))
 	for i, k := range sl {
 		ret[i] = ex.entryFromIdx(k)
 	}
 	return ret
 }

 // Return a list of all DIEs with name 'name'. When searching for DIEs
 // by name, keep in mind that the returned results will include child
 // DIEs such as params/variables. For example, asking for all DIEs named
 // "p" for even a small program will give you 400-500 entries.
 func (ex *examiner) Named(name string) []*dwarf.Entry {
 	sl := ex.byname[name]
 	ret := make([]*dwarf.Entry, len(sl))
 	for i, k := range sl {
 		ret[i] = ex.entryFromIdx(k)
 	}
 	return ret
 }

 func TestInlinedRoutineRecords(t *testing.T) {
 	testenv.MustHaveGoBuild(t)

 	if runtime.GOOS == "plan9" {
 		t.Skip("skipping on plan9; no DWARF symbol table in executables")
 	}

 	const prog = `
 package main

 var G int

 func cand(x, y int) int {
     return (x + y) ^ (y - x)
 }

 func main() {
     x := cand(G*G,G|7%G)
     G = x
 }
 `
 	dir, err := ioutil.TempDir("", "TestInlinedRoutineRecords")
 	if err != nil {
 		t.Fatalf("could not create directory: %v", err)
 	}
 	defer os.RemoveAll(dir)

 	// Note: this is a regular go build here, without "-l -N". The
 	// test is intended to verify DWARF that is only generated when the
 	// inliner is active.
 	f := gobuild(t, dir, prog, true)

 	d, err := f.DWARF()
 	if err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	// The inlined subroutines we expect to visit
 	expectedInl := []string{"main.cand"}

 	rdr := d.Reader()
 	ex := examiner{}
 	if err := ex.populate(rdr); err != nil {
 		t.Fatalf("error reading DWARF: %v", err)
 	}

 	// Locate the main.main DIE
 	mains := ex.Named("main.main")
 	if len(mains) == 0 {
 		t.Fatalf("unable to locate DIE for main.main")
 	}
 	if len(mains) != 1 {
 		t.Fatalf("more than one main.main DIE")
 	}
 	maindie := mains[0]

 	// Vet the main.main DIE
 	if maindie.Tag != dwarf.TagSubprogram {
 		t.Fatalf("unexpected tag %v on main.main DIE", maindie.Tag)
 	}

 	// Walk main's children and pick out the inlined subroutines
 	mainIdx := ex.idxFromOffset(maindie.Offset)
 	childDies := ex.Children(mainIdx)
 	exCount := 0
 	for _, child := range childDies {
 		if child.Tag == dwarf.TagInlinedSubroutine {
 			// Found an inlined subroutine, locate abstract origin.
 			ooff, originOK := child.Val(dwarf.AttrAbstractOrigin).(dwarf.Offset)
 			if !originOK {
 				t.Fatalf("no abstract origin attr for inlined subroutine at offset %v", child.Offset)
 			}
 			originDIE := ex.entryFromOffset(ooff)
 			if originDIE == nil {
 				t.Fatalf("can't locate origin DIE at off %v", ooff)
 			}

 			if exCount >= len(expectedInl) {
 				t.Fatalf("too many inlined subroutines found in main.main")
 			}

 			// Name should check out.
 			expected := expectedInl[exCount]
 			if name, ok := originDIE.Val(dwarf.AttrName).(string); ok {
 				if name != expected {
 					t.Fatalf("expected inlined routine %s got %s", name, expected)
 				}
 			}
 			exCount++
 		}
 	}
 	if exCount != len(expectedInl) {
 		t.Fatalf("not enough inlined subroutines found in main.main")
 	}
 }
	// Copyright 2017 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.

	package ld

	import (
	objfilepkg "cmd/internal/objfile" // renamed to avoid conflict with objfile function
	"debug/dwarf"
	"errors"
	"fmt"
	"internal/testenv"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"reflect"
	"runtime"
	"testing"
	)

	func TestRuntimeTypeDIEs(t *testing.T) {
	testenv.MustHaveGoBuild(t)

	if runtime.GOOS == "plan9" {
	t.Skip("skipping on plan9; no DWARF symbol table in executables")
	}

	dir, err := ioutil.TempDir("", "TestRuntimeTypeDIEs")
	if err != nil {
	t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)

	f := gobuild(t, dir, `package main; func main() { }`, false)
	defer f.Close()

	dwarf, err := f.DWARF()
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	want := map[string]bool{
	"runtime._type": true,
	"runtime.arraytype": true,
	"runtime.chantype": true,
	"runtime.functype": true,
	"runtime.maptype": true,
	"runtime.ptrtype": true,
	"runtime.slicetype": true,
	"runtime.structtype": true,
	"runtime.interfacetype": true,
	"runtime.itab": true,
	"runtime.imethod": true,
	}

	found := findTypes(t, dwarf, want)
	if len(found) != len(want) {
	t.Errorf("found %v, want %v", found, want)
	}
	}

	func findTypes(t testing.T, dw dwarf.Data, want map[string]bool) (found map[string]bool) {
	found = make(map[string]bool)
	rdr := dw.Reader()
	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}
	switch entry.Tag {
	case dwarf.TagTypedef:
	if name, ok := entry.Val(dwarf.AttrName).(string); ok && want[name] {
	found[name] = true
	}
	}
	}
	return
	}

	func gobuild(t testing.T, dir string, testfile string, opt bool) objfilepkg.File {
	src := filepath.Join(dir, "test.go")
	dst := filepath.Join(dir, "out")

	if err := ioutil.WriteFile(src, []byte(testfile), 0666); err != nil {
	t.Fatal(err)
	}

	gcflags := "-gcflags=-N -l"
	if opt {
	gcflags = "-gcflags=-l=4"
	}
	cmd := exec.Command(testenv.GoToolPath(t), "build", gcflags, "-o", dst, src)
	if b, err := cmd.CombinedOutput(); err != nil {
	t.Logf("build: %s\n", b)
	t.Fatalf("build error: %v", err)
	}

	f, err := objfilepkg.Open(dst)
	if err != nil {
	t.Fatal(err)
	}
	return f
	}

	func TestEmbeddedStructMarker(t *testing.T) {
	testenv.MustHaveGoBuild(t)

	if runtime.GOOS == "plan9" {
	t.Skip("skipping on plan9; no DWARF symbol table in executables")
	}

	const prog = `
	package main

	import "fmt"

	type Foo struct { v int }
	type Bar struct {
	Foo
	name string
	}
	type Baz struct {
	*Foo
	name string
	}

	func main() {
	bar := Bar{ Foo: Foo{v: 123}, name: "onetwothree"}
	baz := Baz{ Foo: &bar.Foo, name: "123" }
	fmt.Println(bar, baz)
	}`

	want := map[string]map[string]bool{
	"main.Foo": map[string]bool{"v": false},
	"main.Bar": map[string]bool{"Foo": true, "name": false},
	"main.Baz": map[string]bool{"Foo": true, "name": false},
	}

	dir, err := ioutil.TempDir("", "TestEmbeddedStructMarker")
	if err != nil {
	t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)

	f := gobuild(t, dir, prog, false)

	defer f.Close()

	d, err := f.DWARF()
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	rdr := d.Reader()
	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}
	switch entry.Tag {
	case dwarf.TagStructType:
	name := entry.Val(dwarf.AttrName).(string)
	wantMembers := want[name]
	if wantMembers == nil {
	continue
	}
	gotMembers, err := findMembers(rdr)
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	if !reflect.DeepEqual(gotMembers, wantMembers) {
	t.Errorf("type %v: got map[member]embedded = %+v, want %+v", name, wantMembers, gotMembers)
	}
	delete(want, name)
	}
	}
	if len(want) != 0 {
	t.Errorf("failed to check all expected types: missing types = %+v", want)
	}
	}

	func findMembers(rdr *dwarf.Reader) (map[string]bool, error) {
	memberEmbedded := map[string]bool{}
	// TODO(hyangah): define in debug/dwarf package
	const goEmbeddedStruct = dwarf.Attr(0x2903)
	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
	if err != nil {
	return nil, err
	}
	switch entry.Tag {
	case dwarf.TagMember:
	name := entry.Val(dwarf.AttrName).(string)
	embedded := entry.Val(goEmbeddedStruct).(bool)
	memberEmbedded[name] = embedded
	case 0:
	return memberEmbedded, nil
	}
	}
	return memberEmbedded, nil
	}

	func TestSizes(t *testing.T) {
	if runtime.GOOS == "plan9" {
	t.Skip("skipping on plan9; no DWARF symbol table in executables")
	}

	// DWARF sizes should never be -1.
	// See issue #21097
	const prog = `
	package main
	var x func()
	var y [4]func()
	func main() {
	x = nil
	y[0] = nil
	}
	`
	dir, err := ioutil.TempDir("", "TestSizes")
	if err != nil {
	t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)
	f := gobuild(t, dir, prog, false)
	defer f.Close()
	d, err := f.DWARF()
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}
	rdr := d.Reader()
	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}
	switch entry.Tag {
	case dwarf.TagArrayType, dwarf.TagPointerType, dwarf.TagStructType, dwarf.TagBaseType, dwarf.TagSubroutineType, dwarf.TagTypedef:
	default:
	continue
	}
	typ, err := d.Type(entry.Offset)
	if err != nil {
	t.Fatalf("can't read type: %v", err)
	}
	if typ.Size() < 0 {
	t.Errorf("subzero size %s %s %T", typ, entry.Tag, typ)
	}
	}
	}

	func TestFieldOverlap(t *testing.T) {
	if runtime.GOOS == "plan9" {
	t.Skip("skipping on plan9; no DWARF symbol table in executables")
	}

	// This test grew out of issue 21094, where specific sudog<T> DWARF types
	// had elem fields set to values instead of pointers.
	const prog = `
	package main

	var c chan string

	func main() {
	c <- "foo"
	}
	`
	dir, err := ioutil.TempDir("", "TestFieldOverlap")
	if err != nil {
	t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)

	f := gobuild(t, dir, prog, false)
	defer f.Close()

	d, err := f.DWARF()
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	rdr := d.Reader()
	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}
	if entry.Tag != dwarf.TagStructType {
	continue
	}
	typ, err := d.Type(entry.Offset)
	if err != nil {
	t.Fatalf("can't read type: %v", err)
	}
	s := typ.(*dwarf.StructType)
	for i := 0; i < len(s.Field); i++ {
	end := s.Field[i].ByteOffset + s.Field[i].Type.Size()
	var limit int64
	if i == len(s.Field)-1 {
	limit = s.Size()
	} else {
	limit = s.Field[i+1].ByteOffset
	}
	if end > limit {
	name := entry.Val(dwarf.AttrName).(string)
	t.Fatalf("field %s.%s overlaps next field", name, s.Field[i].Name)
	}
	}
	}
	}

	func TestVarDeclCoordsAndSubrogramDeclFile(t *testing.T) {
	testenv.MustHaveGoBuild(t)

	if runtime.GOOS == "plan9" {
	t.Skip("skipping on plan9; no DWARF symbol table in executables")
	}

	const prog = `
	package main

	func main() {
	var i int
	i = i
	}
	`
	dir, err := ioutil.TempDir("", "TestVarDeclCoords")
	if err != nil {
	t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)

	f := gobuild(t, dir, prog, false)

	d, err := f.DWARF()
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	rdr := d.Reader()
	ex := examiner{}
	if err := ex.populate(rdr); err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	// Locate the main.main DIE
	mains := ex.Named("main.main")
	if len(mains) == 0 {
	t.Fatalf("unable to locate DIE for main.main")
	}
	if len(mains) != 1 {
	t.Fatalf("more than one main.main DIE")
	}
	maindie := mains[0]

	// Vet the main.main DIE
	if maindie.Tag != dwarf.TagSubprogram {
	t.Fatalf("unexpected tag %v on main.main DIE", maindie.Tag)
	}

	// Walk main's children and select variable "i".
	mainIdx := ex.idxFromOffset(maindie.Offset)
	childDies := ex.Children(mainIdx)
	var iEntry *dwarf.Entry
	for _, child := range childDies {
	if child.Tag == dwarf.TagVariable && child.Val(dwarf.AttrName).(string) == "i" {
	iEntry = child
	break
	}
	}
	if iEntry == nil {
	t.Fatalf("didn't find DW_TAG_variable for i in main.main")
	}

	// Verify line/file attributes.
	line := iEntry.Val(dwarf.AttrDeclLine)
	if line == nil \|\| line.(int64) != 5 {
	t.Errorf("DW_AT_decl_line for i is %v, want 5", line)
	}

	file := maindie.Val(dwarf.AttrDeclFile)
	if file == nil \|\| file.(int64) != 1 {
	t.Errorf("DW_AT_decl_file for main is %v, want 1", file)
	}
	}

	// Helper class for supporting queries on DIEs within a DWARF .debug_info
	// section. Invoke the populate() method below passing in a dwarf.Reader,
	// which will read in all DIEs and keep track of parent/child
	// relationships. Queries can then be made to ask for DIEs by name or
	// by offset. This will hopefully reduce boilerplate for future test
	// writing.

	type examiner struct {
	dies []*dwarf.Entry
	idxByOffset map[dwarf.Offset]int
	kids map[int][]int
	byname map[string][]int
	}

	// Populate the examiner using the DIEs read from rdr.
	func (ex examiner) populate(rdr dwarf.Reader) error {
	ex.idxByOffset = make(map[dwarf.Offset]int)
	ex.kids = make(map[int][]int)
	ex.byname = make(map[string][]int)
	var nesting []int
	for entry, err := rdr.Next(); entry != nil; entry, err = rdr.Next() {
	if err != nil {
	return err
	}
	if entry.Tag == 0 {
	// terminator
	if len(nesting) == 0 {
	return errors.New("nesting stack underflow")
	}
	nesting = nesting[:len(nesting)-1]
	continue
	}
	idx := len(ex.dies)
	ex.dies = append(ex.dies, entry)
	if _, found := ex.idxByOffset[entry.Offset]; found {
	return errors.New("DIE clash on offset")
	}
	ex.idxByOffset[entry.Offset] = idx
	if name, ok := entry.Val(dwarf.AttrName).(string); ok {
	ex.byname[name] = append(ex.byname[name], idx)
	}
	if len(nesting) > 0 {
	parent := nesting[len(nesting)-1]
	ex.kids[parent] = append(ex.kids[parent], idx)
	}
	if entry.Children {
	nesting = append(nesting, idx)
	}
	}
	if len(nesting) > 0 {
	return errors.New("unterminated child sequence")
	}
	return nil
	}

	func indent(ilevel int) {
	for i := 0; i < ilevel; i++ {
	fmt.Printf(" ")
	}
	}

	// For debugging new tests
	func (ex *examiner) dumpEntry(idx int, dumpKids bool, ilevel int) error {
	if idx >= len(ex.dies) {
	msg := fmt.Sprintf("bad DIE %d: index out of range\n", idx)
	return errors.New(msg)
	}
	entry := ex.dies[idx]
	indent(ilevel)
	fmt.Printf("%d: %v\n", idx, entry.Tag)
	for _, f := range entry.Field {
	indent(ilevel)
	fmt.Printf("at=%v val=%v\n", f.Attr, f.Val)
	}
	if dumpKids {
	ksl := ex.kids[idx]
	for _, k := range ksl {
	ex.dumpEntry(k, true, ilevel+2)
	}
	}
	return nil
	}

	// Given a DIE offset, return the previously read dwarf.Entry, or nil
	func (ex examiner) entryFromOffset(off dwarf.Offset) dwarf.Entry {
	if idx, found := ex.idxByOffset[off]; found && idx != -1 {
	return ex.entryFromIdx(idx)
	}
	return nil
	}

	// Return the ID that that examiner uses to refer to the DIE at offset off
	func (ex *examiner) idxFromOffset(off dwarf.Offset) int {
	if idx, found := ex.idxByOffset[off]; found {
	return idx
	}
	return -1
	}

	// Return the dwarf.Entry pointer for the DIE with id 'idx'
	func (ex examiner) entryFromIdx(idx int) dwarf.Entry {
	if idx >= len(ex.dies) {
	return nil
	}
	return ex.dies[idx]
	}

	// Returns a list of child entries for a die with ID 'idx'
	func (ex examiner) Children(idx int) []dwarf.Entry {
	sl := ex.kids[idx]
	ret := make([]*dwarf.Entry, len(sl))
	for i, k := range sl {
	ret[i] = ex.entryFromIdx(k)
	}
	return ret
	}

	// Return a list of all DIEs with name 'name'. When searching for DIEs
	// by name, keep in mind that the returned results will include child
	// DIEs such as params/variables. For example, asking for all DIEs named
	// "p" for even a small program will give you 400-500 entries.
	func (ex examiner) Named(name string) []dwarf.Entry {
	sl := ex.byname[name]
	ret := make([]*dwarf.Entry, len(sl))
	for i, k := range sl {
	ret[i] = ex.entryFromIdx(k)
	}
	return ret
	}

	func TestInlinedRoutineRecords(t *testing.T) {
	testenv.MustHaveGoBuild(t)

	if runtime.GOOS == "plan9" {
	t.Skip("skipping on plan9; no DWARF symbol table in executables")
	}

	const prog = `
	package main

	var G int

	func cand(x, y int) int {
	return (x + y) ^ (y - x)
	}

	func main() {
	x := cand(G*G,G\|7%G)
	G = x
	}
	`
	dir, err := ioutil.TempDir("", "TestInlinedRoutineRecords")
	if err != nil {
	t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)

	// Note: this is a regular go build here, without "-l -N". The
	// test is intended to verify DWARF that is only generated when the
	// inliner is active.
	f := gobuild(t, dir, prog, true)

	d, err := f.DWARF()
	if err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	// The inlined subroutines we expect to visit
	expectedInl := []string{"main.cand"}

	rdr := d.Reader()
	ex := examiner{}
	if err := ex.populate(rdr); err != nil {
	t.Fatalf("error reading DWARF: %v", err)
	}

	// Locate the main.main DIE
	mains := ex.Named("main.main")
	if len(mains) == 0 {
	t.Fatalf("unable to locate DIE for main.main")
	}
	if len(mains) != 1 {
	t.Fatalf("more than one main.main DIE")
	}
	maindie := mains[0]

	// Vet the main.main DIE
	if maindie.Tag != dwarf.TagSubprogram {
	t.Fatalf("unexpected tag %v on main.main DIE", maindie.Tag)
	}

	// Walk main's children and pick out the inlined subroutines
	mainIdx := ex.idxFromOffset(maindie.Offset)
	childDies := ex.Children(mainIdx)
	exCount := 0
	for _, child := range childDies {
	if child.Tag == dwarf.TagInlinedSubroutine {
	// Found an inlined subroutine, locate abstract origin.
	ooff, originOK := child.Val(dwarf.AttrAbstractOrigin).(dwarf.Offset)
	if !originOK {
	t.Fatalf("no abstract origin attr for inlined subroutine at offset %v", child.Offset)
	}
	originDIE := ex.entryFromOffset(ooff)
	if originDIE == nil {
	t.Fatalf("can't locate origin DIE at off %v", ooff)
	}

	if exCount >= len(expectedInl) {
	t.Fatalf("too many inlined subroutines found in main.main")
	}

	// Name should check out.
	expected := expectedInl[exCount]
	if name, ok := originDIE.Val(dwarf.AttrName).(string); ok {
	if name != expected {
	t.Fatalf("expected inlined routine %s got %s", name, expected)
	}
	}
	exCount++
	}
	}
	if exCount != len(expectedInl) {
	t.Fatalf("not enough inlined subroutines found in main.main")
	}
	}