Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

37 files changed, 5393 insertions, 0 deletions

diff --git a/src/debug/dwarf/attr_string.go b/src/debug/dwarf/attr_string.go
new file mode 100644
index 0000000..8a4fff8
--- /dev/null
+++ b/src/debug/dwarf/attr_string.go
@@ -0,0 +1,265 @@
+// Code generated by "stringer -type Attr -trimprefix=Attr"; DO NOT EDIT.
+
+package dwarf
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[AttrSibling-1]
+	_ = x[AttrLocation-2]
+	_ = x[AttrName-3]
+	_ = x[AttrOrdering-9]
+	_ = x[AttrByteSize-11]
+	_ = x[AttrBitOffset-12]
+	_ = x[AttrBitSize-13]
+	_ = x[AttrStmtList-16]
+	_ = x[AttrLowpc-17]
+	_ = x[AttrHighpc-18]
+	_ = x[AttrLanguage-19]
+	_ = x[AttrDiscr-21]
+	_ = x[AttrDiscrValue-22]
+	_ = x[AttrVisibility-23]
+	_ = x[AttrImport-24]
+	_ = x[AttrStringLength-25]
+	_ = x[AttrCommonRef-26]
+	_ = x[AttrCompDir-27]
+	_ = x[AttrConstValue-28]
+	_ = x[AttrContainingType-29]
+	_ = x[AttrDefaultValue-30]
+	_ = x[AttrInline-32]
+	_ = x[AttrIsOptional-33]
+	_ = x[AttrLowerBound-34]
+	_ = x[AttrProducer-37]
+	_ = x[AttrPrototyped-39]
+	_ = x[AttrReturnAddr-42]
+	_ = x[AttrStartScope-44]
+	_ = x[AttrStrideSize-46]
+	_ = x[AttrUpperBound-47]
+	_ = x[AttrAbstractOrigin-49]
+	_ = x[AttrAccessibility-50]
+	_ = x[AttrAddrClass-51]
+	_ = x[AttrArtificial-52]
+	_ = x[AttrBaseTypes-53]
+	_ = x[AttrCalling-54]
+	_ = x[AttrCount-55]
+	_ = x[AttrDataMemberLoc-56]
+	_ = x[AttrDeclColumn-57]
+	_ = x[AttrDeclFile-58]
+	_ = x[AttrDeclLine-59]
+	_ = x[AttrDeclaration-60]
+	_ = x[AttrDiscrList-61]
+	_ = x[AttrEncoding-62]
+	_ = x[AttrExternal-63]
+	_ = x[AttrFrameBase-64]
+	_ = x[AttrFriend-65]
+	_ = x[AttrIdentifierCase-66]
+	_ = x[AttrMacroInfo-67]
+	_ = x[AttrNamelistItem-68]
+	_ = x[AttrPriority-69]
+	_ = x[AttrSegment-70]
+	_ = x[AttrSpecification-71]
+	_ = x[AttrStaticLink-72]
+	_ = x[AttrType-73]
+	_ = x[AttrUseLocation-74]
+	_ = x[AttrVarParam-75]
+	_ = x[AttrVirtuality-76]
+	_ = x[AttrVtableElemLoc-77]
+	_ = x[AttrAllocated-78]
+	_ = x[AttrAssociated-79]
+	_ = x[AttrDataLocation-80]
+	_ = x[AttrStride-81]
+	_ = x[AttrEntrypc-82]
+	_ = x[AttrUseUTF8-83]
+	_ = x[AttrExtension-84]
+	_ = x[AttrRanges-85]
+	_ = x[AttrTrampoline-86]
+	_ = x[AttrCallColumn-87]
+	_ = x[AttrCallFile-88]
+	_ = x[AttrCallLine-89]
+	_ = x[AttrDescription-90]
+	_ = x[AttrBinaryScale-91]
+	_ = x[AttrDecimalScale-92]
+	_ = x[AttrSmall-93]
+	_ = x[AttrDecimalSign-94]
+	_ = x[AttrDigitCount-95]
+	_ = x[AttrPictureString-96]
+	_ = x[AttrMutable-97]
+	_ = x[AttrThreadsScaled-98]
+	_ = x[AttrExplicit-99]
+	_ = x[AttrObjectPointer-100]
+	_ = x[AttrEndianity-101]
+	_ = x[AttrElemental-102]
+	_ = x[AttrPure-103]
+	_ = x[AttrRecursive-104]
+	_ = x[AttrSignature-105]
+	_ = x[AttrMainSubprogram-106]
+	_ = x[AttrDataBitOffset-107]
+	_ = x[AttrConstExpr-108]
+	_ = x[AttrEnumClass-109]
+	_ = x[AttrLinkageName-110]
+	_ = x[AttrStringLengthBitSize-111]
+	_ = x[AttrStringLengthByteSize-112]
+	_ = x[AttrRank-113]
+	_ = x[AttrStrOffsetsBase-114]
+	_ = x[AttrAddrBase-115]
+	_ = x[AttrRnglistsBase-116]
+	_ = x[AttrDwoName-118]
+	_ = x[AttrReference-119]
+	_ = x[AttrRvalueReference-120]
+	_ = x[AttrMacros-121]
+	_ = x[AttrCallAllCalls-122]
+	_ = x[AttrCallAllSourceCalls-123]
+	_ = x[AttrCallAllTailCalls-124]
+	_ = x[AttrCallReturnPC-125]
+	_ = x[AttrCallValue-126]
+	_ = x[AttrCallOrigin-127]
+	_ = x[AttrCallParameter-128]
+	_ = x[AttrCallPC-129]
+	_ = x[AttrCallTailCall-130]
+	_ = x[AttrCallTarget-131]
+	_ = x[AttrCallTargetClobbered-132]
+	_ = x[AttrCallDataLocation-133]
+	_ = x[AttrCallDataValue-134]
+	_ = x[AttrNoreturn-135]
+	_ = x[AttrAlignment-136]
+	_ = x[AttrExportSymbols-137]
+	_ = x[AttrDeleted-138]
+	_ = x[AttrDefaulted-139]
+	_ = x[AttrLoclistsBase-140]
+}
+
+const _Attr_name = "SiblingLocationNameOrderingByteSizeBitOffsetBitSizeStmtListLowpcHighpcLanguageDiscrDiscrValueVisibilityImportStringLengthCommonRefCompDirConstValueContainingTypeDefaultValueInlineIsOptionalLowerBoundProducerPrototypedReturnAddrStartScopeStrideSizeUpperBoundAbstractOriginAccessibilityAddrClassArtificialBaseTypesCallingCountDataMemberLocDeclColumnDeclFileDeclLineDeclarationDiscrListEncodingExternalFrameBaseFriendIdentifierCaseMacroInfoNamelistItemPrioritySegmentSpecificationStaticLinkTypeUseLocationVarParamVirtualityVtableElemLocAllocatedAssociatedDataLocationStrideEntrypcUseUTF8ExtensionRangesTrampolineCallColumnCallFileCallLineDescriptionBinaryScaleDecimalScaleSmallDecimalSignDigitCountPictureStringMutableThreadsScaledExplicitObjectPointerEndianityElementalPureRecursiveSignatureMainSubprogramDataBitOffsetConstExprEnumClassLinkageNameStringLengthBitSizeStringLengthByteSizeRankStrOffsetsBaseAddrBaseRnglistsBaseDwoNameReferenceRvalueReferenceMacrosCallAllCallsCallAllSourceCallsCallAllTailCallsCallReturnPCCallValueCallOriginCallParameterCallPCCallTailCallCallTargetCallTargetClobberedCallDataLocationCallDataValueNoreturnAlignmentExportSymbolsDeletedDefaultedLoclistsBase"
+
+var _Attr_map = map[Attr]string{
+	1:   _Attr_name[0:7],
+	2:   _Attr_name[7:15],
+	3:   _Attr_name[15:19],
+	9:   _Attr_name[19:27],
+	11:  _Attr_name[27:35],
+	12:  _Attr_name[35:44],
+	13:  _Attr_name[44:51],
+	16:  _Attr_name[51:59],
+	17:  _Attr_name[59:64],
+	18:  _Attr_name[64:70],
+	19:  _Attr_name[70:78],
+	21:  _Attr_name[78:83],
+	22:  _Attr_name[83:93],
+	23:  _Attr_name[93:103],
+	24:  _Attr_name[103:109],
+	25:  _Attr_name[109:121],
+	26:  _Attr_name[121:130],
+	27:  _Attr_name[130:137],
+	28:  _Attr_name[137:147],
+	29:  _Attr_name[147:161],
+	30:  _Attr_name[161:173],
+	32:  _Attr_name[173:179],
+	33:  _Attr_name[179:189],
+	34:  _Attr_name[189:199],
+	37:  _Attr_name[199:207],
+	39:  _Attr_name[207:217],
+	42:  _Attr_name[217:227],
+	44:  _Attr_name[227:237],
+	46:  _Attr_name[237:247],
+	47:  _Attr_name[247:257],
+	49:  _Attr_name[257:271],
+	50:  _Attr_name[271:284],
+	51:  _Attr_name[284:293],
+	52:  _Attr_name[293:303],
+	53:  _Attr_name[303:312],
+	54:  _Attr_name[312:319],
+	55:  _Attr_name[319:324],
+	56:  _Attr_name[324:337],
+	57:  _Attr_name[337:347],
+	58:  _Attr_name[347:355],
+	59:  _Attr_name[355:363],
+	60:  _Attr_name[363:374],
+	61:  _Attr_name[374:383],
+	62:  _Attr_name[383:391],
+	63:  _Attr_name[391:399],
+	64:  _Attr_name[399:408],
+	65:  _Attr_name[408:414],
+	66:  _Attr_name[414:428],
+	67:  _Attr_name[428:437],
+	68:  _Attr_name[437:449],
+	69:  _Attr_name[449:457],
+	70:  _Attr_name[457:464],
+	71:  _Attr_name[464:477],
+	72:  _Attr_name[477:487],
+	73:  _Attr_name[487:491],
+	74:  _Attr_name[491:502],
+	75:  _Attr_name[502:510],
+	76:  _Attr_name[510:520],
+	77:  _Attr_name[520:533],
+	78:  _Attr_name[533:542],
+	79:  _Attr_name[542:552],
+	80:  _Attr_name[552:564],
+	81:  _Attr_name[564:570],
+	82:  _Attr_name[570:577],
+	83:  _Attr_name[577:584],
+	84:  _Attr_name[584:593],
+	85:  _Attr_name[593:599],
+	86:  _Attr_name[599:609],
+	87:  _Attr_name[609:619],
+	88:  _Attr_name[619:627],
+	89:  _Attr_name[627:635],
+	90:  _Attr_name[635:646],
+	91:  _Attr_name[646:657],
+	92:  _Attr_name[657:669],
+	93:  _Attr_name[669:674],
+	94:  _Attr_name[674:685],
+	95:  _Attr_name[685:695],
+	96:  _Attr_name[695:708],
+	97:  _Attr_name[708:715],
+	98:  _Attr_name[715:728],
+	99:  _Attr_name[728:736],
+	100: _Attr_name[736:749],
+	101: _Attr_name[749:758],
+	102: _Attr_name[758:767],
+	103: _Attr_name[767:771],
+	104: _Attr_name[771:780],
+	105: _Attr_name[780:789],
+	106: _Attr_name[789:803],
+	107: _Attr_name[803:816],
+	108: _Attr_name[816:825],
+	109: _Attr_name[825:834],
+	110: _Attr_name[834:845],
+	111: _Attr_name[845:864],
+	112: _Attr_name[864:884],
+	113: _Attr_name[884:888],
+	114: _Attr_name[888:902],
+	115: _Attr_name[902:910],
+	116: _Attr_name[910:922],
+	118: _Attr_name[922:929],
+	119: _Attr_name[929:938],
+	120: _Attr_name[938:953],
+	121: _Attr_name[953:959],
+	122: _Attr_name[959:971],
+	123: _Attr_name[971:989],
+	124: _Attr_name[989:1005],
+	125: _Attr_name[1005:1017],
+	126: _Attr_name[1017:1026],
+	127: _Attr_name[1026:1036],
+	128: _Attr_name[1036:1049],
+	129: _Attr_name[1049:1055],
+	130: _Attr_name[1055:1067],
+	131: _Attr_name[1067:1077],
+	132: _Attr_name[1077:1096],
+	133: _Attr_name[1096:1112],
+	134: _Attr_name[1112:1125],
+	135: _Attr_name[1125:1133],
+	136: _Attr_name[1133:1142],
+	137: _Attr_name[1142:1155],
+	138: _Attr_name[1155:1162],
+	139: _Attr_name[1162:1171],
+	140: _Attr_name[1171:1183],
+}
+
+func (i Attr) String() string {
+	if str, ok := _Attr_map[i]; ok {
+		return str
+	}
+	return "Attr(" + strconv.FormatInt(int64(i), 10) + ")"
+}
diff --git a/src/debug/dwarf/buf.go b/src/debug/dwarf/buf.go
new file mode 100644
index 0000000..c3822a0
--- /dev/null
+++ b/src/debug/dwarf/buf.go
@@ -0,0 +1,205 @@
+// 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.
+
+// Buffered reading and decoding of DWARF data streams.
+
+package dwarf
+
+import (
+	"bytes"
+	"encoding/binary"
+	"strconv"
+)
+
+// Data buffer being decoded.
+type buf struct {
+	dwarf  *Data
+	order  binary.ByteOrder
+	format dataFormat
+	name   string
+	off    Offset
+	data   []byte
+	err    error
+}
+
+// Data format, other than byte order. This affects the handling of
+// certain field formats.
+type dataFormat interface {
+	// DWARF version number. Zero means unknown.
+	version() int
+
+	// 64-bit DWARF format?
+	dwarf64() (dwarf64 bool, isKnown bool)
+
+	// Size of an address, in bytes. Zero means unknown.
+	addrsize() int
+}
+
+// Some parts of DWARF have no data format, e.g., abbrevs.
+type unknownFormat struct{}
+
+func (u unknownFormat) version() int {
+	return 0
+}
+
+func (u unknownFormat) dwarf64() (bool, bool) {
+	return false, false
+}
+
+func (u unknownFormat) addrsize() int {
+	return 0
+}
+
+func makeBuf(d *Data, format dataFormat, name string, off Offset, data []byte) buf {
+	return buf{d, d.order, format, name, off, data, nil}
+}
+
+func (b *buf) uint8() uint8 {
+	if len(b.data) < 1 {
+		b.error("underflow")
+		return 0
+	}
+	val := b.data[0]
+	b.data = b.data[1:]
+	b.off++
+	return val
+}
+
+func (b *buf) bytes(n int) []byte {
+	if len(b.data) < n {
+		b.error("underflow")
+		return nil
+	}
+	data := b.data[0:n]
+	b.data = b.data[n:]
+	b.off += Offset(n)
+	return data
+}
+
+func (b *buf) skip(n int) { b.bytes(n) }
+
+func (b *buf) string() string {
+	i := bytes.IndexByte(b.data, 0)
+	if i < 0 {
+		b.error("underflow")
+		return ""
+	}
+
+	s := string(b.data[0:i])
+	b.data = b.data[i+1:]
+	b.off += Offset(i + 1)
+	return s
+}
+
+func (b *buf) uint16() uint16 {
+	a := b.bytes(2)
+	if a == nil {
+		return 0
+	}
+	return b.order.Uint16(a)
+}
+
+func (b *buf) uint24() uint32 {
+	a := b.bytes(3)
+	if a == nil {
+		return 0
+	}
+	if b.dwarf.bigEndian {
+		return uint32(a[2]) | uint32(a[1])<<8 | uint32(a[0])<<16
+	} else {
+		return uint32(a[0]) | uint32(a[1])<<8 | uint32(a[2])<<16
+	}
+}
+
+func (b *buf) uint32() uint32 {
+	a := b.bytes(4)
+	if a == nil {
+		return 0
+	}
+	return b.order.Uint32(a)
+}
+
+func (b *buf) uint64() uint64 {
+	a := b.bytes(8)
+	if a == nil {
+		return 0
+	}
+	return b.order.Uint64(a)
+}
+
+// Read a varint, which is 7 bits per byte, little endian.
+// the 0x80 bit means read another byte.
+func (b *buf) varint() (c uint64, bits uint) {
+	for i := 0; i < len(b.data); i++ {
+		byte := b.data[i]
+		c |= uint64(byte&0x7F) << bits
+		bits += 7
+		if byte&0x80 == 0 {
+			b.off += Offset(i + 1)
+			b.data = b.data[i+1:]
+			return c, bits
+		}
+	}
+	return 0, 0
+}
+
+// Unsigned int is just a varint.
+func (b *buf) uint() uint64 {
+	x, _ := b.varint()
+	return x
+}
+
+// Signed int is a sign-extended varint.
+func (b *buf) int() int64 {
+	ux, bits := b.varint()
+	x := int64(ux)
+	if x&(1<<(bits-1)) != 0 {
+		x |= -1 << bits
+	}
+	return x
+}
+
+// Address-sized uint.
+func (b *buf) addr() uint64 {
+	switch b.format.addrsize() {
+	case 1:
+		return uint64(b.uint8())
+	case 2:
+		return uint64(b.uint16())
+	case 4:
+		return uint64(b.uint32())
+	case 8:
+		return b.uint64()
+	}
+	b.error("unknown address size")
+	return 0
+}
+
+func (b *buf) unitLength() (length Offset, dwarf64 bool) {
+	length = Offset(b.uint32())
+	if length == 0xffffffff {
+		dwarf64 = true
+		length = Offset(b.uint64())
+	} else if length >= 0xfffffff0 {
+		b.error("unit length has reserved value")
+	}
+	return
+}
+
+func (b *buf) error(s string) {
+	if b.err == nil {
+		b.data = nil
+		b.err = DecodeError{b.name, b.off, s}
+	}
+}
+
+type DecodeError struct {
+	Name   string
+	Offset Offset
+	Err    string
+}
+
+func (e DecodeError) Error() string {
+	return "decoding dwarf section " + e.Name + " at offset 0x" + strconv.FormatInt(int64(e.Offset), 16) + ": " + e.Err
+}
diff --git a/src/debug/dwarf/class_string.go b/src/debug/dwarf/class_string.go
new file mode 100644
index 0000000..76de7ca
--- /dev/null
+++ b/src/debug/dwarf/class_string.go
@@ -0,0 +1,37 @@
+// Code generated by "stringer -type=Class"; DO NOT EDIT.
+
+package dwarf
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[ClassUnknown-0]
+	_ = x[ClassAddress-1]
+	_ = x[ClassBlock-2]
+	_ = x[ClassConstant-3]
+	_ = x[ClassExprLoc-4]
+	_ = x[ClassFlag-5]
+	_ = x[ClassLinePtr-6]
+	_ = x[ClassLocListPtr-7]
+	_ = x[ClassMacPtr-8]
+	_ = x[ClassRangeListPtr-9]
+	_ = x[ClassReference-10]
+	_ = x[ClassReferenceSig-11]
+	_ = x[ClassString-12]
+	_ = x[ClassReferenceAlt-13]
+	_ = x[ClassStringAlt-14]
+}
+
+const _Class_name = "ClassUnknownClassAddressClassBlockClassConstantClassExprLocClassFlagClassLinePtrClassLocListPtrClassMacPtrClassRangeListPtrClassReferenceClassReferenceSigClassStringClassReferenceAltClassStringAlt"
+
+var _Class_index = [...]uint8{0, 12, 24, 34, 47, 59, 68, 80, 95, 106, 123, 137, 154, 165, 182, 196}
+
+func (i Class) String() string {
+	if i < 0 || i >= Class(len(_Class_index)-1) {
+		return "Class(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _Class_name[_Class_index[i]:_Class_index[i+1]]
+}
diff --git a/src/debug/dwarf/const.go b/src/debug/dwarf/const.go
new file mode 100644
index 0000000..c607091
--- /dev/null
+++ b/src/debug/dwarf/const.go
@@ -0,0 +1,475 @@
+// 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.
+
+// Constants
+
+package dwarf
+
+//go:generate stringer -type Attr -trimprefix=Attr
+
+// An Attr identifies the attribute type in a DWARF Entry's Field.
+type Attr uint32
+
+const (
+	AttrSibling        Attr = 0x01
+	AttrLocation       Attr = 0x02
+	AttrName           Attr = 0x03
+	AttrOrdering       Attr = 0x09
+	AttrByteSize       Attr = 0x0B
+	AttrBitOffset      Attr = 0x0C
+	AttrBitSize        Attr = 0x0D
+	AttrStmtList       Attr = 0x10
+	AttrLowpc          Attr = 0x11
+	AttrHighpc         Attr = 0x12
+	AttrLanguage       Attr = 0x13
+	AttrDiscr          Attr = 0x15
+	AttrDiscrValue     Attr = 0x16
+	AttrVisibility     Attr = 0x17
+	AttrImport         Attr = 0x18
+	AttrStringLength   Attr = 0x19
+	AttrCommonRef      Attr = 0x1A
+	AttrCompDir        Attr = 0x1B
+	AttrConstValue     Attr = 0x1C
+	AttrContainingType Attr = 0x1D
+	AttrDefaultValue   Attr = 0x1E
+	AttrInline         Attr = 0x20
+	AttrIsOptional     Attr = 0x21
+	AttrLowerBound     Attr = 0x22
+	AttrProducer       Attr = 0x25
+	AttrPrototyped     Attr = 0x27
+	AttrReturnAddr     Attr = 0x2A
+	AttrStartScope     Attr = 0x2C
+	AttrStrideSize     Attr = 0x2E
+	AttrUpperBound     Attr = 0x2F
+	AttrAbstractOrigin Attr = 0x31
+	AttrAccessibility  Attr = 0x32
+	AttrAddrClass      Attr = 0x33
+	AttrArtificial     Attr = 0x34
+	AttrBaseTypes      Attr = 0x35
+	AttrCalling        Attr = 0x36
+	AttrCount          Attr = 0x37
+	AttrDataMemberLoc  Attr = 0x38
+	AttrDeclColumn     Attr = 0x39
+	AttrDeclFile       Attr = 0x3A
+	AttrDeclLine       Attr = 0x3B
+	AttrDeclaration    Attr = 0x3C
+	AttrDiscrList      Attr = 0x3D
+	AttrEncoding       Attr = 0x3E
+	AttrExternal       Attr = 0x3F
+	AttrFrameBase      Attr = 0x40
+	AttrFriend         Attr = 0x41
+	AttrIdentifierCase Attr = 0x42
+	AttrMacroInfo      Attr = 0x43
+	AttrNamelistItem   Attr = 0x44
+	AttrPriority       Attr = 0x45
+	AttrSegment        Attr = 0x46
+	AttrSpecification  Attr = 0x47
+	AttrStaticLink     Attr = 0x48
+	AttrType           Attr = 0x49
+	AttrUseLocation    Attr = 0x4A
+	AttrVarParam       Attr = 0x4B
+	AttrVirtuality     Attr = 0x4C
+	AttrVtableElemLoc  Attr = 0x4D
+	// The following are new in DWARF 3.
+	AttrAllocated     Attr = 0x4E
+	AttrAssociated    Attr = 0x4F
+	AttrDataLocation  Attr = 0x50
+	AttrStride        Attr = 0x51
+	AttrEntrypc       Attr = 0x52
+	AttrUseUTF8       Attr = 0x53
+	AttrExtension     Attr = 0x54
+	AttrRanges        Attr = 0x55
+	AttrTrampoline    Attr = 0x56
+	AttrCallColumn    Attr = 0x57
+	AttrCallFile      Attr = 0x58
+	AttrCallLine      Attr = 0x59
+	AttrDescription   Attr = 0x5A
+	AttrBinaryScale   Attr = 0x5B
+	AttrDecimalScale  Attr = 0x5C
+	AttrSmall         Attr = 0x5D
+	AttrDecimalSign   Attr = 0x5E
+	AttrDigitCount    Attr = 0x5F
+	AttrPictureString Attr = 0x60
+	AttrMutable       Attr = 0x61
+	AttrThreadsScaled Attr = 0x62
+	AttrExplicit      Attr = 0x63
+	AttrObjectPointer Attr = 0x64
+	AttrEndianity     Attr = 0x65
+	AttrElemental     Attr = 0x66
+	AttrPure          Attr = 0x67
+	AttrRecursive     Attr = 0x68
+	// The following are new in DWARF 4.
+	AttrSignature      Attr = 0x69
+	AttrMainSubprogram Attr = 0x6A
+	AttrDataBitOffset  Attr = 0x6B
+	AttrConstExpr      Attr = 0x6C
+	AttrEnumClass      Attr = 0x6D
+	AttrLinkageName    Attr = 0x6E
+	// The following are new in DWARF 5.
+	AttrStringLengthBitSize  Attr = 0x6F
+	AttrStringLengthByteSize Attr = 0x70
+	AttrRank                 Attr = 0x71
+	AttrStrOffsetsBase       Attr = 0x72
+	AttrAddrBase             Attr = 0x73
+	AttrRnglistsBase         Attr = 0x74
+	AttrDwoName              Attr = 0x76
+	AttrReference            Attr = 0x77
+	AttrRvalueReference      Attr = 0x78
+	AttrMacros               Attr = 0x79
+	AttrCallAllCalls         Attr = 0x7A
+	AttrCallAllSourceCalls   Attr = 0x7B
+	AttrCallAllTailCalls     Attr = 0x7C
+	AttrCallReturnPC         Attr = 0x7D
+	AttrCallValue            Attr = 0x7E
+	AttrCallOrigin           Attr = 0x7F
+	AttrCallParameter        Attr = 0x80
+	AttrCallPC               Attr = 0x81
+	AttrCallTailCall         Attr = 0x82
+	AttrCallTarget           Attr = 0x83
+	AttrCallTargetClobbered  Attr = 0x84
+	AttrCallDataLocation     Attr = 0x85
+	AttrCallDataValue        Attr = 0x86
+	AttrNoreturn             Attr = 0x87
+	AttrAlignment            Attr = 0x88
+	AttrExportSymbols        Attr = 0x89
+	AttrDeleted              Attr = 0x8A
+	AttrDefaulted            Attr = 0x8B
+	AttrLoclistsBase         Attr = 0x8C
+)
+
+func (a Attr) GoString() string {
+	if str, ok := _Attr_map[a]; ok {
+		return "dwarf.Attr" + str
+	}
+	return "dwarf." + a.String()
+}
+
+// A format is a DWARF data encoding format.
+type format uint32
+
+const (
+	// value formats
+	formAddr        format = 0x01
+	formDwarfBlock2 format = 0x03
+	formDwarfBlock4 format = 0x04
+	formData2       format = 0x05
+	formData4       format = 0x06
+	formData8       format = 0x07
+	formString      format = 0x08
+	formDwarfBlock  format = 0x09
+	formDwarfBlock1 format = 0x0A
+	formData1       format = 0x0B
+	formFlag        format = 0x0C
+	formSdata       format = 0x0D
+	formStrp        format = 0x0E
+	formUdata       format = 0x0F
+	formRefAddr     format = 0x10
+	formRef1        format = 0x11
+	formRef2        format = 0x12
+	formRef4        format = 0x13
+	formRef8        format = 0x14
+	formRefUdata    format = 0x15
+	formIndirect    format = 0x16
+	// The following are new in DWARF 4.
+	formSecOffset   format = 0x17
+	formExprloc     format = 0x18
+	formFlagPresent format = 0x19
+	formRefSig8     format = 0x20
+	// The following are new in DWARF 5.
+	formStrx          format = 0x1A
+	formAddrx         format = 0x1B
+	formRefSup4       format = 0x1C
+	formStrpSup       format = 0x1D
+	formData16        format = 0x1E
+	formLineStrp      format = 0x1F
+	formImplicitConst format = 0x21
+	formLoclistx      format = 0x22
+	formRnglistx      format = 0x23
+	formRefSup8       format = 0x24
+	formStrx1         format = 0x25
+	formStrx2         format = 0x26
+	formStrx3         format = 0x27
+	formStrx4         format = 0x28
+	formAddrx1        format = 0x29
+	formAddrx2        format = 0x2A
+	formAddrx3        format = 0x2B
+	formAddrx4        format = 0x2C
+	// Extensions for multi-file compression (.dwz)
+	// http://www.dwarfstd.org/ShowIssue.php?issue=120604.1
+	formGnuRefAlt  format = 0x1f20
+	formGnuStrpAlt format = 0x1f21
+)
+
+//go:generate stringer -type Tag -trimprefix=Tag
+
+// A Tag is the classification (the type) of an Entry.
+type Tag uint32
+
+const (
+	TagArrayType              Tag = 0x01
+	TagClassType              Tag = 0x02
+	TagEntryPoint             Tag = 0x03
+	TagEnumerationType        Tag = 0x04
+	TagFormalParameter        Tag = 0x05
+	TagImportedDeclaration    Tag = 0x08
+	TagLabel                  Tag = 0x0A
+	TagLexDwarfBlock          Tag = 0x0B
+	TagMember                 Tag = 0x0D
+	TagPointerType            Tag = 0x0F
+	TagReferenceType          Tag = 0x10
+	TagCompileUnit            Tag = 0x11
+	TagStringType             Tag = 0x12
+	TagStructType             Tag = 0x13
+	TagSubroutineType         Tag = 0x15
+	TagTypedef                Tag = 0x16
+	TagUnionType              Tag = 0x17
+	TagUnspecifiedParameters  Tag = 0x18
+	TagVariant                Tag = 0x19
+	TagCommonDwarfBlock       Tag = 0x1A
+	TagCommonInclusion        Tag = 0x1B
+	TagInheritance            Tag = 0x1C
+	TagInlinedSubroutine      Tag = 0x1D
+	TagModule                 Tag = 0x1E
+	TagPtrToMemberType        Tag = 0x1F
+	TagSetType                Tag = 0x20
+	TagSubrangeType           Tag = 0x21
+	TagWithStmt               Tag = 0x22
+	TagAccessDeclaration      Tag = 0x23
+	TagBaseType               Tag = 0x24
+	TagCatchDwarfBlock        Tag = 0x25
+	TagConstType              Tag = 0x26
+	TagConstant               Tag = 0x27
+	TagEnumerator             Tag = 0x28
+	TagFileType               Tag = 0x29
+	TagFriend                 Tag = 0x2A
+	TagNamelist               Tag = 0x2B
+	TagNamelistItem           Tag = 0x2C
+	TagPackedType             Tag = 0x2D
+	TagSubprogram             Tag = 0x2E
+	TagTemplateTypeParameter  Tag = 0x2F
+	TagTemplateValueParameter Tag = 0x30
+	TagThrownType             Tag = 0x31
+	TagTryDwarfBlock          Tag = 0x32
+	TagVariantPart            Tag = 0x33
+	TagVariable               Tag = 0x34
+	TagVolatileType           Tag = 0x35
+	// The following are new in DWARF 3.
+	TagDwarfProcedure  Tag = 0x36
+	TagRestrictType    Tag = 0x37
+	TagInterfaceType   Tag = 0x38
+	TagNamespace       Tag = 0x39
+	TagImportedModule  Tag = 0x3A
+	TagUnspecifiedType Tag = 0x3B
+	TagPartialUnit     Tag = 0x3C
+	TagImportedUnit    Tag = 0x3D
+	TagMutableType     Tag = 0x3E // Later removed from DWARF.
+	TagCondition       Tag = 0x3F
+	TagSharedType      Tag = 0x40
+	// The following are new in DWARF 4.
+	TagTypeUnit            Tag = 0x41
+	TagRvalueReferenceType Tag = 0x42
+	TagTemplateAlias       Tag = 0x43
+	// The following are new in DWARF 5.
+	TagCoarrayType       Tag = 0x44
+	TagGenericSubrange   Tag = 0x45
+	TagDynamicType       Tag = 0x46
+	TagAtomicType        Tag = 0x47
+	TagCallSite          Tag = 0x48
+	TagCallSiteParameter Tag = 0x49
+	TagSkeletonUnit      Tag = 0x4A
+	TagImmutableType     Tag = 0x4B
+)
+
+func (t Tag) GoString() string {
+	if t <= TagTemplateAlias {
+		return "dwarf.Tag" + t.String()
+	}
+	return "dwarf." + t.String()
+}
+
+// Location expression operators.
+// The debug info encodes value locations like 8(R3)
+// as a sequence of these op codes.
+// This package does not implement full expressions;
+// the opPlusUconst operator is expected by the type parser.
+const (
+	opAddr       = 0x03 /* 1 op, const addr */
+	opDeref      = 0x06
+	opConst1u    = 0x08 /* 1 op, 1 byte const */
+	opConst1s    = 0x09 /*	" signed */
+	opConst2u    = 0x0A /* 1 op, 2 byte const  */
+	opConst2s    = 0x0B /*	" signed */
+	opConst4u    = 0x0C /* 1 op, 4 byte const */
+	opConst4s    = 0x0D /*	" signed */
+	opConst8u    = 0x0E /* 1 op, 8 byte const */
+	opConst8s    = 0x0F /*	" signed */
+	opConstu     = 0x10 /* 1 op, LEB128 const */
+	opConsts     = 0x11 /*	" signed */
+	opDup        = 0x12
+	opDrop       = 0x13
+	opOver       = 0x14
+	opPick       = 0x15 /* 1 op, 1 byte stack index */
+	opSwap       = 0x16
+	opRot        = 0x17
+	opXderef     = 0x18
+	opAbs        = 0x19
+	opAnd        = 0x1A
+	opDiv        = 0x1B
+	opMinus      = 0x1C
+	opMod        = 0x1D
+	opMul        = 0x1E
+	opNeg        = 0x1F
+	opNot        = 0x20
+	opOr         = 0x21
+	opPlus       = 0x22
+	opPlusUconst = 0x23 /* 1 op, ULEB128 addend */
+	opShl        = 0x24
+	opShr        = 0x25
+	opShra       = 0x26
+	opXor        = 0x27
+	opSkip       = 0x2F /* 1 op, signed 2-byte constant */
+	opBra        = 0x28 /* 1 op, signed 2-byte constant */
+	opEq         = 0x29
+	opGe         = 0x2A
+	opGt         = 0x2B
+	opLe         = 0x2C
+	opLt         = 0x2D
+	opNe         = 0x2E
+	opLit0       = 0x30
+	/* OpLitN = OpLit0 + N for N = 0..31 */
+	opReg0 = 0x50
+	/* OpRegN = OpReg0 + N for N = 0..31 */
+	opBreg0 = 0x70 /* 1 op, signed LEB128 constant */
+	/* OpBregN = OpBreg0 + N for N = 0..31 */
+	opRegx       = 0x90 /* 1 op, ULEB128 register */
+	opFbreg      = 0x91 /* 1 op, SLEB128 offset */
+	opBregx      = 0x92 /* 2 op, ULEB128 reg; SLEB128 off */
+	opPiece      = 0x93 /* 1 op, ULEB128 size of piece */
+	opDerefSize  = 0x94 /* 1-byte size of data retrieved */
+	opXderefSize = 0x95 /* 1-byte size of data retrieved */
+	opNop        = 0x96
+	// The following are new in DWARF 3.
+	opPushObjAddr    = 0x97
+	opCall2          = 0x98 /* 2-byte offset of DIE */
+	opCall4          = 0x99 /* 4-byte offset of DIE */
+	opCallRef        = 0x9A /* 4- or 8- byte offset of DIE */
+	opFormTLSAddress = 0x9B
+	opCallFrameCFA   = 0x9C
+	opBitPiece       = 0x9D
+	// The following are new in DWARF 4.
+	opImplicitValue = 0x9E
+	opStackValue    = 0x9F
+	// The following a new in DWARF 5.
+	opImplicitPointer = 0xA0
+	opAddrx           = 0xA1
+	opConstx          = 0xA2
+	opEntryValue      = 0xA3
+	opConstType       = 0xA4
+	opRegvalType      = 0xA5
+	opDerefType       = 0xA6
+	opXderefType      = 0xA7
+	opConvert         = 0xA8
+	opReinterpret     = 0xA9
+	/* 0xE0-0xFF reserved for user-specific */
+)
+
+// Basic type encodings -- the value for AttrEncoding in a TagBaseType Entry.
+const (
+	encAddress      = 0x01
+	encBoolean      = 0x02
+	encComplexFloat = 0x03
+	encFloat        = 0x04
+	encSigned       = 0x05
+	encSignedChar   = 0x06
+	encUnsigned     = 0x07
+	encUnsignedChar = 0x08
+	// The following are new in DWARF 3.
+	encImaginaryFloat = 0x09
+	encPackedDecimal  = 0x0A
+	encNumericString  = 0x0B
+	encEdited         = 0x0C
+	encSignedFixed    = 0x0D
+	encUnsignedFixed  = 0x0E
+	encDecimalFloat   = 0x0F
+	// The following are new in DWARF 4.
+	encUTF = 0x10
+	// The following are new in DWARF 5.
+	encUCS   = 0x11
+	encASCII = 0x12
+)
+
+// Statement program standard opcode encodings.
+const (
+	lnsCopy           = 1
+	lnsAdvancePC      = 2
+	lnsAdvanceLine    = 3
+	lnsSetFile        = 4
+	lnsSetColumn      = 5
+	lnsNegateStmt     = 6
+	lnsSetBasicBlock  = 7
+	lnsConstAddPC     = 8
+	lnsFixedAdvancePC = 9
+
+	// DWARF 3
+	lnsSetPrologueEnd   = 10
+	lnsSetEpilogueBegin = 11
+	lnsSetISA           = 12
+)
+
+// Statement program extended opcode encodings.
+const (
+	lneEndSequence = 1
+	lneSetAddress  = 2
+	lneDefineFile  = 3
+
+	// DWARF 4
+	lneSetDiscriminator = 4
+)
+
+// Line table directory directory and file name entry formats.
+// These are new in DWARF 5.
+const (
+	lnctPath           = 0x01
+	lnctDirectoryIndex = 0x02
+	lnctTimestamp      = 0x03
+	lnctSize           = 0x04
+	lnctMD5            = 0x05
+)
+
+// Location list entry codes.
+// These are new in DWARF 5.
+const (
+	lleEndOfList       = 0x00
+	lleBaseAddressx    = 0x01
+	lleStartxEndx      = 0x02
+	lleStartxLength    = 0x03
+	lleOffsetPair      = 0x04
+	lleDefaultLocation = 0x05
+	lleBaseAddress     = 0x06
+	lleStartEnd        = 0x07
+	lleStartLength     = 0x08
+)
+
+// Unit header unit type encodings.
+// These are new in DWARF 5.
+const (
+	utCompile      = 0x01
+	utType         = 0x02
+	utPartial      = 0x03
+	utSkeleton     = 0x04
+	utSplitCompile = 0x05
+	utSplitType    = 0x06
+)
+
+// Opcodes for DWARFv5 debug_rnglists section.
+const (
+	rleEndOfList    = 0x0
+	rleBaseAddressx = 0x1
+	rleStartxEndx   = 0x2
+	rleStartxLength = 0x3
+	rleOffsetPair   = 0x4
+	rleBaseAddress  = 0x5
+	rleStartEnd     = 0x6
+	rleStartLength  = 0x7
+)
diff --git a/src/debug/dwarf/dwarf5ranges_test.go b/src/debug/dwarf/dwarf5ranges_test.go
new file mode 100644
index 0000000..8bc50bc
--- /dev/null
+++ b/src/debug/dwarf/dwarf5ranges_test.go
@@ -0,0 +1,41 @@
+// Copyright 2020 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 dwarf
+
+import (
+	"encoding/binary"
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestDwarf5Ranges(t *testing.T) {
+	rngLists, err := os.ReadFile("testdata/debug_rnglists")
+	if err != nil {
+		t.Fatalf("could not read test data: %v", err)
+	}
+
+	d := &Data{}
+	d.order = binary.LittleEndian
+	if err := d.AddSection(".debug_rnglists", rngLists); err != nil {
+		t.Fatal(err)
+	}
+	u := &unit{
+		asize: 8,
+		vers:  5,
+		is64:  true,
+	}
+	ret, err := d.dwarf5Ranges(u, nil, 0x5fbd, 0xc, [][2]uint64{})
+	if err != nil {
+		t.Fatalf("could not read rnglist: %v", err)
+	}
+	t.Logf("%#v", ret)
+
+	tgt := [][2]uint64{{0x0000000000006712, 0x000000000000679f}, {0x00000000000067af}, {0x00000000000067b3}}
+
+	if reflect.DeepEqual(ret, tgt) {
+		t.Errorf("expected %#v got %#x", tgt, ret)
+	}
+}
diff --git a/src/debug/dwarf/entry.go b/src/debug/dwarf/entry.go
new file mode 100644
index 0000000..3fc73b8
--- /dev/null
+++ b/src/debug/dwarf/entry.go
@@ -0,0 +1,1154 @@
+// 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.
+
+// DWARF debug information entry parser.
+// An entry is a sequence of data items of a given format.
+// The first word in the entry is an index into what DWARF
+// calls the ``abbreviation table.''  An abbreviation is really
+// just a type descriptor: it's an array of attribute tag/value format pairs.
+
+package dwarf
+
+import (
+	"encoding/binary"
+	"errors"
+	"strconv"
+)
+
+// a single entry's description: a sequence of attributes
+type abbrev struct {
+	tag      Tag
+	children bool
+	field    []afield
+}
+
+type afield struct {
+	attr  Attr
+	fmt   format
+	class Class
+	val   int64 // for formImplicitConst
+}
+
+// a map from entry format ids to their descriptions
+type abbrevTable map[uint32]abbrev
+
+// ParseAbbrev returns the abbreviation table that starts at byte off
+// in the .debug_abbrev section.
+func (d *Data) parseAbbrev(off uint64, vers int) (abbrevTable, error) {
+	if m, ok := d.abbrevCache[off]; ok {
+		return m, nil
+	}
+
+	data := d.abbrev
+	if off > uint64(len(data)) {
+		data = nil
+	} else {
+		data = data[off:]
+	}
+	b := makeBuf(d, unknownFormat{}, "abbrev", 0, data)
+
+	// Error handling is simplified by the buf getters
+	// returning an endless stream of 0s after an error.
+	m := make(abbrevTable)
+	for {
+		// Table ends with id == 0.
+		id := uint32(b.uint())
+		if id == 0 {
+			break
+		}
+
+		// Walk over attributes, counting.
+		n := 0
+		b1 := b // Read from copy of b.
+		b1.uint()
+		b1.uint8()
+		for {
+			tag := b1.uint()
+			fmt := b1.uint()
+			if tag == 0 && fmt == 0 {
+				break
+			}
+			if format(fmt) == formImplicitConst {
+				b1.int()
+			}
+			n++
+		}
+		if b1.err != nil {
+			return nil, b1.err
+		}
+
+		// Walk over attributes again, this time writing them down.
+		var a abbrev
+		a.tag = Tag(b.uint())
+		a.children = b.uint8() != 0
+		a.field = make([]afield, n)
+		for i := range a.field {
+			a.field[i].attr = Attr(b.uint())
+			a.field[i].fmt = format(b.uint())
+			a.field[i].class = formToClass(a.field[i].fmt, a.field[i].attr, vers, &b)
+			if a.field[i].fmt == formImplicitConst {
+				a.field[i].val = b.int()
+			}
+		}
+		b.uint()
+		b.uint()
+
+		m[id] = a
+	}
+	if b.err != nil {
+		return nil, b.err
+	}
+	d.abbrevCache[off] = m
+	return m, nil
+}
+
+// attrIsExprloc indicates attributes that allow exprloc values that
+// are encoded as block values in DWARF 2 and 3. See DWARF 4, Figure
+// 20.
+var attrIsExprloc = map[Attr]bool{
+	AttrLocation:      true,
+	AttrByteSize:      true,
+	AttrBitOffset:     true,
+	AttrBitSize:       true,
+	AttrStringLength:  true,
+	AttrLowerBound:    true,
+	AttrReturnAddr:    true,
+	AttrStrideSize:    true,
+	AttrUpperBound:    true,
+	AttrCount:         true,
+	AttrDataMemberLoc: true,
+	AttrFrameBase:     true,
+	AttrSegment:       true,
+	AttrStaticLink:    true,
+	AttrUseLocation:   true,
+	AttrVtableElemLoc: true,
+	AttrAllocated:     true,
+	AttrAssociated:    true,
+	AttrDataLocation:  true,
+	AttrStride:        true,
+}
+
+// attrPtrClass indicates the *ptr class of attributes that have
+// encoding formSecOffset in DWARF 4 or formData* in DWARF 2 and 3.
+var attrPtrClass = map[Attr]Class{
+	AttrLocation:      ClassLocListPtr,
+	AttrStmtList:      ClassLinePtr,
+	AttrStringLength:  ClassLocListPtr,
+	AttrReturnAddr:    ClassLocListPtr,
+	AttrStartScope:    ClassRangeListPtr,
+	AttrDataMemberLoc: ClassLocListPtr,
+	AttrFrameBase:     ClassLocListPtr,
+	AttrMacroInfo:     ClassMacPtr,
+	AttrSegment:       ClassLocListPtr,
+	AttrStaticLink:    ClassLocListPtr,
+	AttrUseLocation:   ClassLocListPtr,
+	AttrVtableElemLoc: ClassLocListPtr,
+	AttrRanges:        ClassRangeListPtr,
+	// The following are new in DWARF 5.
+	AttrStrOffsetsBase: ClassStrOffsetsPtr,
+	AttrAddrBase:       ClassAddrPtr,
+	AttrRnglistsBase:   ClassRngListsPtr,
+	AttrLoclistsBase:   ClassLocListPtr,
+}
+
+// formToClass returns the DWARF 4 Class for the given form. If the
+// DWARF version is less then 4, it will disambiguate some forms
+// depending on the attribute.
+func formToClass(form format, attr Attr, vers int, b *buf) Class {
+	switch form {
+	default:
+		b.error("cannot determine class of unknown attribute form")
+		return 0
+
+	case formIndirect:
+		return ClassUnknown
+
+	case formAddr, formAddrx, formAddrx1, formAddrx2, formAddrx3, formAddrx4:
+		return ClassAddress
+
+	case formDwarfBlock1, formDwarfBlock2, formDwarfBlock4, formDwarfBlock:
+		// In DWARF 2 and 3, ClassExprLoc was encoded as a
+		// block. DWARF 4 distinguishes ClassBlock and
+		// ClassExprLoc, but there are no attributes that can
+		// be both, so we also promote ClassBlock values in
+		// DWARF 4 that should be ClassExprLoc in case
+		// producers get this wrong.
+		if attrIsExprloc[attr] {
+			return ClassExprLoc
+		}
+		return ClassBlock
+
+	case formData1, formData2, formData4, formData8, formSdata, formUdata, formData16, formImplicitConst:
+		// In DWARF 2 and 3, ClassPtr was encoded as a
+		// constant. Unlike ClassExprLoc/ClassBlock, some
+		// DWARF 4 attributes need to distinguish Class*Ptr
+		// from ClassConstant, so we only do this promotion
+		// for versions 2 and 3.
+		if class, ok := attrPtrClass[attr]; vers < 4 && ok {
+			return class
+		}
+		return ClassConstant
+
+	case formFlag, formFlagPresent:
+		return ClassFlag
+
+	case formRefAddr, formRef1, formRef2, formRef4, formRef8, formRefUdata, formRefSup4, formRefSup8:
+		return ClassReference
+
+	case formRefSig8:
+		return ClassReferenceSig
+
+	case formString, formStrp, formStrx, formStrpSup, formLineStrp, formStrx1, formStrx2, formStrx3, formStrx4:
+		return ClassString
+
+	case formSecOffset:
+		// DWARF 4 defines four *ptr classes, but doesn't
+		// distinguish them in the encoding. Disambiguate
+		// these classes using the attribute.
+		if class, ok := attrPtrClass[attr]; ok {
+			return class
+		}
+		return ClassUnknown
+
+	case formExprloc:
+		return ClassExprLoc
+
+	case formGnuRefAlt:
+		return ClassReferenceAlt
+
+	case formGnuStrpAlt:
+		return ClassStringAlt
+
+	case formLoclistx:
+		return ClassLocList
+
+	case formRnglistx:
+		return ClassRngList
+	}
+}
+
+// An entry is a sequence of attribute/value pairs.
+type Entry struct {
+	Offset   Offset // offset of Entry in DWARF info
+	Tag      Tag    // tag (kind of Entry)
+	Children bool   // whether Entry is followed by children
+	Field    []Field
+}
+
+// A Field is a single attribute/value pair in an Entry.
+//
+// A value can be one of several "attribute classes" defined by DWARF.
+// The Go types corresponding to each class are:
+//
+//    DWARF class       Go type        Class
+//    -----------       -------        -----
+//    address           uint64         ClassAddress
+//    block             []byte         ClassBlock
+//    constant          int64          ClassConstant
+//    flag              bool           ClassFlag
+//    reference
+//      to info         dwarf.Offset   ClassReference
+//      to type unit    uint64         ClassReferenceSig
+//    string            string         ClassString
+//    exprloc           []byte         ClassExprLoc
+//    lineptr           int64          ClassLinePtr
+//    loclistptr        int64          ClassLocListPtr
+//    macptr            int64          ClassMacPtr
+//    rangelistptr      int64          ClassRangeListPtr
+//
+// For unrecognized or vendor-defined attributes, Class may be
+// ClassUnknown.
+type Field struct {
+	Attr  Attr
+	Val   interface{}
+	Class Class
+}
+
+// A Class is the DWARF 4 class of an attribute value.
+//
+// In general, a given attribute's value may take on one of several
+// possible classes defined by DWARF, each of which leads to a
+// slightly different interpretation of the attribute.
+//
+// DWARF version 4 distinguishes attribute value classes more finely
+// than previous versions of DWARF. The reader will disambiguate
+// coarser classes from earlier versions of DWARF into the appropriate
+// DWARF 4 class. For example, DWARF 2 uses "constant" for constants
+// as well as all types of section offsets, but the reader will
+// canonicalize attributes in DWARF 2 files that refer to section
+// offsets to one of the Class*Ptr classes, even though these classes
+// were only defined in DWARF 3.
+type Class int
+
+const (
+	// ClassUnknown represents values of unknown DWARF class.
+	ClassUnknown Class = iota
+
+	// ClassAddress represents values of type uint64 that are
+	// addresses on the target machine.
+	ClassAddress
+
+	// ClassBlock represents values of type []byte whose
+	// interpretation depends on the attribute.
+	ClassBlock
+
+	// ClassConstant represents values of type int64 that are
+	// constants. The interpretation of this constant depends on
+	// the attribute.
+	ClassConstant
+
+	// ClassExprLoc represents values of type []byte that contain
+	// an encoded DWARF expression or location description.
+	ClassExprLoc
+
+	// ClassFlag represents values of type bool.
+	ClassFlag
+
+	// ClassLinePtr represents values that are an int64 offset
+	// into the "line" section.
+	ClassLinePtr
+
+	// ClassLocListPtr represents values that are an int64 offset
+	// into the "loclist" section.
+	ClassLocListPtr
+
+	// ClassMacPtr represents values that are an int64 offset into
+	// the "mac" section.
+	ClassMacPtr
+
+	// ClassMacPtr represents values that are an int64 offset into
+	// the "rangelist" section.
+	ClassRangeListPtr
+
+	// ClassReference represents values that are an Offset offset
+	// of an Entry in the info section (for use with Reader.Seek).
+	// The DWARF specification combines ClassReference and
+	// ClassReferenceSig into class "reference".
+	ClassReference
+
+	// ClassReferenceSig represents values that are a uint64 type
+	// signature referencing a type Entry.
+	ClassReferenceSig
+
+	// ClassString represents values that are strings. If the
+	// compilation unit specifies the AttrUseUTF8 flag (strongly
+	// recommended), the string value will be encoded in UTF-8.
+	// Otherwise, the encoding is unspecified.
+	ClassString
+
+	// ClassReferenceAlt represents values of type int64 that are
+	// an offset into the DWARF "info" section of an alternate
+	// object file.
+	ClassReferenceAlt
+
+	// ClassStringAlt represents values of type int64 that are an
+	// offset into the DWARF string section of an alternate object
+	// file.
+	ClassStringAlt
+
+	// ClassAddrPtr represents values that are an int64 offset
+	// into the "addr" section.
+	ClassAddrPtr
+
+	// ClassLocList represents values that are an int64 offset
+	// into the "loclists" section.
+	ClassLocList
+
+	// ClassRngList represents values that are an int64 offset
+	// from the base of the "rnglists" section.
+	ClassRngList
+
+	// ClassRngListsPtr represents values that are an int64 offset
+	// into the "rnglists" section. These are used as the base for
+	// ClassRngList values.
+	ClassRngListsPtr
+
+	// ClassStrOffsetsPtr represents values that are an int64
+	// offset into the "str_offsets" section.
+	ClassStrOffsetsPtr
+)
+
+//go:generate stringer -type=Class
+
+func (i Class) GoString() string {
+	return "dwarf." + i.String()
+}
+
+// Val returns the value associated with attribute Attr in Entry,
+// or nil if there is no such attribute.
+//
+// A common idiom is to merge the check for nil return with
+// the check that the value has the expected dynamic type, as in:
+//	v, ok := e.Val(AttrSibling).(int64)
+//
+func (e *Entry) Val(a Attr) interface{} {
+	if f := e.AttrField(a); f != nil {
+		return f.Val
+	}
+	return nil
+}
+
+// AttrField returns the Field associated with attribute Attr in
+// Entry, or nil if there is no such attribute.
+func (e *Entry) AttrField(a Attr) *Field {
+	for i, f := range e.Field {
+		if f.Attr == a {
+			return &e.Field[i]
+		}
+	}
+	return nil
+}
+
+// An Offset represents the location of an Entry within the DWARF info.
+// (See Reader.Seek.)
+type Offset uint32
+
+// Entry reads a single entry from buf, decoding
+// according to the given abbreviation table.
+func (b *buf) entry(cu *Entry, atab abbrevTable, ubase Offset, vers int) *Entry {
+	off := b.off
+	id := uint32(b.uint())
+	if id == 0 {
+		return &Entry{}
+	}
+	a, ok := atab[id]
+	if !ok {
+		b.error("unknown abbreviation table index")
+		return nil
+	}
+	e := &Entry{
+		Offset:   off,
+		Tag:      a.tag,
+		Children: a.children,
+		Field:    make([]Field, len(a.field)),
+	}
+
+	// If we are currently parsing the compilation unit,
+	// we can't evaluate Addrx or Strx until we've seen the
+	// relevant base entry.
+	type delayed struct {
+		idx int
+		off uint64
+		fmt format
+	}
+	var delay []delayed
+
+	resolveStrx := func(strBase, off uint64) string {
+		off += strBase
+		if uint64(int(off)) != off {
+			b.error("DW_FORM_strx offset out of range")
+		}
+
+		b1 := makeBuf(b.dwarf, b.format, "str_offsets", 0, b.dwarf.strOffsets)
+		b1.skip(int(off))
+		is64, _ := b.format.dwarf64()
+		if is64 {
+			off = b1.uint64()
+		} else {
+			off = uint64(b1.uint32())
+		}
+		if b1.err != nil {
+			b.err = b1.err
+			return ""
+		}
+		if uint64(int(off)) != off {
+			b.error("DW_FORM_strx indirect offset out of range")
+		}
+		b1 = makeBuf(b.dwarf, b.format, "str", 0, b.dwarf.str)
+		b1.skip(int(off))
+		val := b1.string()
+		if b1.err != nil {
+			b.err = b1.err
+		}
+		return val
+	}
+
+	for i := range e.Field {
+		e.Field[i].Attr = a.field[i].attr
+		e.Field[i].Class = a.field[i].class
+		fmt := a.field[i].fmt
+		if fmt == formIndirect {
+			fmt = format(b.uint())
+			e.Field[i].Class = formToClass(fmt, a.field[i].attr, vers, b)
+		}
+		var val interface{}
+		switch fmt {
+		default:
+			b.error("unknown entry attr format 0x" + strconv.FormatInt(int64(fmt), 16))
+
+		// address
+		case formAddr:
+			val = b.addr()
+		case formAddrx, formAddrx1, formAddrx2, formAddrx3, formAddrx4:
+			var off uint64
+			switch fmt {
+			case formAddrx:
+				off = b.uint()
+			case formAddrx1:
+				off = uint64(b.uint8())
+			case formAddrx2:
+				off = uint64(b.uint16())
+			case formAddrx3:
+				off = uint64(b.uint24())
+			case formAddrx4:
+				off = uint64(b.uint32())
+			}
+			if b.dwarf.addr == nil {
+				b.error("DW_FORM_addrx with no .debug_addr section")
+			}
+			if b.err != nil {
+				return nil
+			}
+
+			// We have to adjust by the offset of the
+			// compilation unit. This won't work if the
+			// program uses Reader.Seek to skip over the
+			// unit. Not much we can do about that.
+			var addrBase int64
+			if cu != nil {
+				addrBase, _ = cu.Val(AttrAddrBase).(int64)
+			} else if a.tag == TagCompileUnit {
+				delay = append(delay, delayed{i, off, formAddrx})
+				break
+			}
+
+			var err error
+			val, err = b.dwarf.debugAddr(b.format, uint64(addrBase), off)
+			if err != nil {
+				if b.err == nil {
+					b.err = err
+				}
+				return nil
+			}
+
+		// block
+		case formDwarfBlock1:
+			val = b.bytes(int(b.uint8()))
+		case formDwarfBlock2:
+			val = b.bytes(int(b.uint16()))
+		case formDwarfBlock4:
+			val = b.bytes(int(b.uint32()))
+		case formDwarfBlock:
+			val = b.bytes(int(b.uint()))
+
+		// constant
+		case formData1:
+			val = int64(b.uint8())
+		case formData2:
+			val = int64(b.uint16())
+		case formData4:
+			val = int64(b.uint32())
+		case formData8:
+			val = int64(b.uint64())
+		case formData16:
+			val = b.bytes(16)
+		case formSdata:
+			val = int64(b.int())
+		case formUdata:
+			val = int64(b.uint())
+		case formImplicitConst:
+			val = a.field[i].val
+
+		// flag
+		case formFlag:
+			val = b.uint8() == 1
+		// New in DWARF 4.
+		case formFlagPresent:
+			// The attribute is implicitly indicated as present, and no value is
+			// encoded in the debugging information entry itself.
+			val = true
+
+		// reference to other entry
+		case formRefAddr:
+			vers := b.format.version()
+			if vers == 0 {
+				b.error("unknown version for DW_FORM_ref_addr")
+			} else if vers == 2 {
+				val = Offset(b.addr())
+			} else {
+				is64, known := b.format.dwarf64()
+				if !known {
+					b.error("unknown size for DW_FORM_ref_addr")
+				} else if is64 {
+					val = Offset(b.uint64())
+				} else {
+					val = Offset(b.uint32())
+				}
+			}
+		case formRef1:
+			val = Offset(b.uint8()) + ubase
+		case formRef2:
+			val = Offset(b.uint16()) + ubase
+		case formRef4:
+			val = Offset(b.uint32()) + ubase
+		case formRef8:
+			val = Offset(b.uint64()) + ubase
+		case formRefUdata:
+			val = Offset(b.uint()) + ubase
+
+		// string
+		case formString:
+			val = b.string()
+		case formStrp, formLineStrp:
+			var off uint64 // offset into .debug_str
+			is64, known := b.format.dwarf64()
+			if !known {
+				b.error("unknown size for DW_FORM_strp/line_strp")
+			} else if is64 {
+				off = b.uint64()
+			} else {
+				off = uint64(b.uint32())
+			}
+			if uint64(int(off)) != off {
+				b.error("DW_FORM_strp/line_strp offset out of range")
+			}
+			if b.err != nil {
+				return nil
+			}
+			var b1 buf
+			if fmt == formStrp {
+				b1 = makeBuf(b.dwarf, b.format, "str", 0, b.dwarf.str)
+			} else {
+				if len(b.dwarf.lineStr) == 0 {
+					b.error("DW_FORM_line_strp with no .debug_line_str section")
+				}
+				b1 = makeBuf(b.dwarf, b.format, "line_str", 0, b.dwarf.lineStr)
+			}
+			b1.skip(int(off))
+			val = b1.string()
+			if b1.err != nil {
+				b.err = b1.err
+				return nil
+			}
+		case formStrx, formStrx1, formStrx2, formStrx3, formStrx4:
+			var off uint64
+			switch fmt {
+			case formStrx:
+				off = b.uint()
+			case formStrx1:
+				off = uint64(b.uint8())
+			case formStrx2:
+				off = uint64(b.uint16())
+			case formStrx3:
+				off = uint64(b.uint24())
+			case formStrx4:
+				off = uint64(b.uint32())
+			}
+			if len(b.dwarf.strOffsets) == 0 {
+				b.error("DW_FORM_strx with no .debug_str_offsets section")
+			}
+			is64, known := b.format.dwarf64()
+			if !known {
+				b.error("unknown offset size for DW_FORM_strx")
+			}
+			if b.err != nil {
+				return nil
+			}
+			if is64 {
+				off *= 8
+			} else {
+				off *= 4
+			}
+
+			// We have to adjust by the offset of the
+			// compilation unit. This won't work if the
+			// program uses Reader.Seek to skip over the
+			// unit. Not much we can do about that.
+			var strBase int64
+			if cu != nil {
+				strBase, _ = cu.Val(AttrStrOffsetsBase).(int64)
+			} else if a.tag == TagCompileUnit {
+				delay = append(delay, delayed{i, off, formStrx})
+				break
+			}
+
+			val = resolveStrx(uint64(strBase), off)
+
+		case formStrpSup:
+			is64, known := b.format.dwarf64()
+			if !known {
+				b.error("unknown size for DW_FORM_strp_sup")
+			} else if is64 {
+				val = b.uint64()
+			} else {
+				val = b.uint32()
+			}
+
+		// lineptr, loclistptr, macptr, rangelistptr
+		// New in DWARF 4, but clang can generate them with -gdwarf-2.
+		// Section reference, replacing use of formData4 and formData8.
+		case formSecOffset, formGnuRefAlt, formGnuStrpAlt:
+			is64, known := b.format.dwarf64()
+			if !known {
+				b.error("unknown size for form 0x" + strconv.FormatInt(int64(fmt), 16))
+			} else if is64 {
+				val = int64(b.uint64())
+			} else {
+				val = int64(b.uint32())
+			}
+
+		// exprloc
+		// New in DWARF 4.
+		case formExprloc:
+			val = b.bytes(int(b.uint()))
+
+		// reference
+		// New in DWARF 4.
+		case formRefSig8:
+			// 64-bit type signature.
+			val = b.uint64()
+		case formRefSup4:
+			val = b.uint32()
+		case formRefSup8:
+			val = b.uint64()
+
+		// loclist
+		case formLoclistx:
+			val = b.uint()
+
+		// rnglist
+		case formRnglistx:
+			val = b.uint()
+		}
+
+		e.Field[i].Val = val
+	}
+	if b.err != nil {
+		return nil
+	}
+
+	for _, del := range delay {
+		switch del.fmt {
+		case formAddrx:
+			addrBase, _ := e.Val(AttrAddrBase).(int64)
+			val, err := b.dwarf.debugAddr(b.format, uint64(addrBase), del.off)
+			if err != nil {
+				b.err = err
+				return nil
+			}
+			e.Field[del.idx].Val = val
+		case formStrx:
+			strBase, _ := e.Val(AttrStrOffsetsBase).(int64)
+			e.Field[del.idx].Val = resolveStrx(uint64(strBase), del.off)
+			if b.err != nil {
+				return nil
+			}
+		}
+	}
+
+	return e
+}
+
+// A Reader allows reading Entry structures from a DWARF ``info'' section.
+// The Entry structures are arranged in a tree. The Reader's Next function
+// return successive entries from a pre-order traversal of the tree.
+// If an entry has children, its Children field will be true, and the children
+// follow, terminated by an Entry with Tag 0.
+type Reader struct {
+	b            buf
+	d            *Data
+	err          error
+	unit         int
+	lastUnit     bool   // set if last entry returned by Next is TagCompileUnit/TagPartialUnit
+	lastChildren bool   // .Children of last entry returned by Next
+	lastSibling  Offset // .Val(AttrSibling) of last entry returned by Next
+	cu           *Entry // current compilation unit
+}
+
+// Reader returns a new Reader for Data.
+// The reader is positioned at byte offset 0 in the DWARF ``info'' section.
+func (d *Data) Reader() *Reader {
+	r := &Reader{d: d}
+	r.Seek(0)
+	return r
+}
+
+// AddressSize returns the size in bytes of addresses in the current compilation
+// unit.
+func (r *Reader) AddressSize() int {
+	return r.d.unit[r.unit].asize
+}
+
+// ByteOrder returns the byte order in the current compilation unit.
+func (r *Reader) ByteOrder() binary.ByteOrder {
+	return r.b.order
+}
+
+// Seek positions the Reader at offset off in the encoded entry stream.
+// Offset 0 can be used to denote the first entry.
+func (r *Reader) Seek(off Offset) {
+	d := r.d
+	r.err = nil
+	r.lastChildren = false
+	if off == 0 {
+		if len(d.unit) == 0 {
+			return
+		}
+		u := &d.unit[0]
+		r.unit = 0
+		r.b = makeBuf(r.d, u, "info", u.off, u.data)
+		r.cu = nil
+		return
+	}
+
+	i := d.offsetToUnit(off)
+	if i == -1 {
+		r.err = errors.New("offset out of range")
+		return
+	}
+	if i != r.unit {
+		r.cu = nil
+	}
+	u := &d.unit[i]
+	r.unit = i
+	r.b = makeBuf(r.d, u, "info", off, u.data[off-u.off:])
+}
+
+// maybeNextUnit advances to the next unit if this one is finished.
+func (r *Reader) maybeNextUnit() {
+	for len(r.b.data) == 0 && r.unit+1 < len(r.d.unit) {
+		r.nextUnit()
+	}
+}
+
+// nextUnit advances to the next unit.
+func (r *Reader) nextUnit() {
+	r.unit++
+	u := &r.d.unit[r.unit]
+	r.b = makeBuf(r.d, u, "info", u.off, u.data)
+	r.cu = nil
+}
+
+// Next reads the next entry from the encoded entry stream.
+// It returns nil, nil when it reaches the end of the section.
+// It returns an error if the current offset is invalid or the data at the
+// offset cannot be decoded as a valid Entry.
+func (r *Reader) Next() (*Entry, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+	r.maybeNextUnit()
+	if len(r.b.data) == 0 {
+		return nil, nil
+	}
+	u := &r.d.unit[r.unit]
+	e := r.b.entry(r.cu, u.atable, u.base, u.vers)
+	if r.b.err != nil {
+		r.err = r.b.err
+		return nil, r.err
+	}
+	r.lastUnit = false
+	if e != nil {
+		r.lastChildren = e.Children
+		if r.lastChildren {
+			r.lastSibling, _ = e.Val(AttrSibling).(Offset)
+		}
+		if e.Tag == TagCompileUnit || e.Tag == TagPartialUnit {
+			r.lastUnit = true
+			r.cu = e
+		}
+	} else {
+		r.lastChildren = false
+	}
+	return e, nil
+}
+
+// SkipChildren skips over the child entries associated with
+// the last Entry returned by Next. If that Entry did not have
+// children or Next has not been called, SkipChildren is a no-op.
+func (r *Reader) SkipChildren() {
+	if r.err != nil || !r.lastChildren {
+		return
+	}
+
+	// If the last entry had a sibling attribute,
+	// that attribute gives the offset of the next
+	// sibling, so we can avoid decoding the
+	// child subtrees.
+	if r.lastSibling >= r.b.off {
+		r.Seek(r.lastSibling)
+		return
+	}
+
+	if r.lastUnit && r.unit+1 < len(r.d.unit) {
+		r.nextUnit()
+		return
+	}
+
+	for {
+		e, err := r.Next()
+		if err != nil || e == nil || e.Tag == 0 {
+			break
+		}
+		if e.Children {
+			r.SkipChildren()
+		}
+	}
+}
+
+// clone returns a copy of the reader. This is used by the typeReader
+// interface.
+func (r *Reader) clone() typeReader {
+	return r.d.Reader()
+}
+
+// offset returns the current buffer offset. This is used by the
+// typeReader interface.
+func (r *Reader) offset() Offset {
+	return r.b.off
+}
+
+// SeekPC returns the Entry for the compilation unit that includes pc,
+// and positions the reader to read the children of that unit.  If pc
+// is not covered by any unit, SeekPC returns ErrUnknownPC and the
+// position of the reader is undefined.
+//
+// Because compilation units can describe multiple regions of the
+// executable, in the worst case SeekPC must search through all the
+// ranges in all the compilation units. Each call to SeekPC starts the
+// search at the compilation unit of the last call, so in general
+// looking up a series of PCs will be faster if they are sorted. If
+// the caller wishes to do repeated fast PC lookups, it should build
+// an appropriate index using the Ranges method.
+func (r *Reader) SeekPC(pc uint64) (*Entry, error) {
+	unit := r.unit
+	for i := 0; i < len(r.d.unit); i++ {
+		if unit >= len(r.d.unit) {
+			unit = 0
+		}
+		r.err = nil
+		r.lastChildren = false
+		r.unit = unit
+		r.cu = nil
+		u := &r.d.unit[unit]
+		r.b = makeBuf(r.d, u, "info", u.off, u.data)
+		e, err := r.Next()
+		if err != nil {
+			return nil, err
+		}
+		ranges, err := r.d.Ranges(e)
+		if err != nil {
+			return nil, err
+		}
+		for _, pcs := range ranges {
+			if pcs[0] <= pc && pc < pcs[1] {
+				return e, nil
+			}
+		}
+		unit++
+	}
+	return nil, ErrUnknownPC
+}
+
+// Ranges returns the PC ranges covered by e, a slice of [low,high) pairs.
+// Only some entry types, such as TagCompileUnit or TagSubprogram, have PC
+// ranges; for others, this will return nil with no error.
+func (d *Data) Ranges(e *Entry) ([][2]uint64, error) {
+	var ret [][2]uint64
+
+	low, lowOK := e.Val(AttrLowpc).(uint64)
+
+	var high uint64
+	var highOK bool
+	highField := e.AttrField(AttrHighpc)
+	if highField != nil {
+		switch highField.Class {
+		case ClassAddress:
+			high, highOK = highField.Val.(uint64)
+		case ClassConstant:
+			off, ok := highField.Val.(int64)
+			if ok {
+				high = low + uint64(off)
+				highOK = true
+			}
+		}
+	}
+
+	if lowOK && highOK {
+		ret = append(ret, [2]uint64{low, high})
+	}
+
+	var u *unit
+	if uidx := d.offsetToUnit(e.Offset); uidx >= 0 && uidx < len(d.unit) {
+		u = &d.unit[uidx]
+	}
+
+	if u != nil && u.vers >= 5 && d.rngLists != nil {
+		// DWARF version 5 and later
+		field := e.AttrField(AttrRanges)
+		if field == nil {
+			return ret, nil
+		}
+		switch field.Class {
+		case ClassRangeListPtr:
+			ranges, rangesOK := field.Val.(int64)
+			if !rangesOK {
+				return ret, nil
+			}
+			cu, base, err := d.baseAddressForEntry(e)
+			if err != nil {
+				return nil, err
+			}
+			return d.dwarf5Ranges(u, cu, base, ranges, ret)
+
+		case ClassRngList:
+			// TODO: support DW_FORM_rnglistx
+			return ret, nil
+
+		default:
+			return ret, nil
+		}
+	}
+
+	// DWARF version 2 through 4
+	ranges, rangesOK := e.Val(AttrRanges).(int64)
+	if rangesOK && d.ranges != nil {
+		_, base, err := d.baseAddressForEntry(e)
+		if err != nil {
+			return nil, err
+		}
+		return d.dwarf2Ranges(u, base, ranges, ret)
+	}
+
+	return ret, nil
+}
+
+// baseAddressForEntry returns the initial base address to be used when
+// looking up the range list of entry e.
+// DWARF specifies that this should be the lowpc attribute of the enclosing
+// compilation unit, however comments in gdb/dwarf2read.c say that some
+// versions of GCC use the entrypc attribute, so we check that too.
+func (d *Data) baseAddressForEntry(e *Entry) (*Entry, uint64, error) {
+	var cu *Entry
+	if e.Tag == TagCompileUnit {
+		cu = e
+	} else {
+		i := d.offsetToUnit(e.Offset)
+		if i == -1 {
+			return nil, 0, errors.New("no unit for entry")
+		}
+		u := &d.unit[i]
+		b := makeBuf(d, u, "info", u.off, u.data)
+		cu = b.entry(nil, u.atable, u.base, u.vers)
+		if b.err != nil {
+			return nil, 0, b.err
+		}
+	}
+
+	if cuEntry, cuEntryOK := cu.Val(AttrEntrypc).(uint64); cuEntryOK {
+		return cu, cuEntry, nil
+	} else if cuLow, cuLowOK := cu.Val(AttrLowpc).(uint64); cuLowOK {
+		return cu, cuLow, nil
+	}
+
+	return cu, 0, nil
+}
+
+func (d *Data) dwarf2Ranges(u *unit, base uint64, ranges int64, ret [][2]uint64) ([][2]uint64, error) {
+	buf := makeBuf(d, u, "ranges", Offset(ranges), d.ranges[ranges:])
+	for len(buf.data) > 0 {
+		low := buf.addr()
+		high := buf.addr()
+
+		if low == 0 && high == 0 {
+			break
+		}
+
+		if low == ^uint64(0)>>uint((8-u.addrsize())*8) {
+			base = high
+		} else {
+			ret = append(ret, [2]uint64{base + low, base + high})
+		}
+	}
+
+	return ret, nil
+}
+
+// dwarf5Ranges interpets a debug_rnglists sequence, see DWARFv5 section
+// 2.17.3 (page 53).
+func (d *Data) dwarf5Ranges(u *unit, cu *Entry, base uint64, ranges int64, ret [][2]uint64) ([][2]uint64, error) {
+	var addrBase int64
+	if cu != nil {
+		addrBase, _ = cu.Val(AttrAddrBase).(int64)
+	}
+
+	buf := makeBuf(d, u, "rnglists", 0, d.rngLists)
+	buf.skip(int(ranges))
+	for {
+		opcode := buf.uint8()
+		switch opcode {
+		case rleEndOfList:
+			if buf.err != nil {
+				return nil, buf.err
+			}
+			return ret, nil
+
+		case rleBaseAddressx:
+			baseIdx := buf.uint()
+			var err error
+			base, err = d.debugAddr(u, uint64(addrBase), baseIdx)
+			if err != nil {
+				return nil, err
+			}
+
+		case rleStartxEndx:
+			startIdx := buf.uint()
+			endIdx := buf.uint()
+
+			start, err := d.debugAddr(u, uint64(addrBase), startIdx)
+			if err != nil {
+				return nil, err
+			}
+			end, err := d.debugAddr(u, uint64(addrBase), endIdx)
+			if err != nil {
+				return nil, err
+			}
+			ret = append(ret, [2]uint64{start, end})
+
+		case rleStartxLength:
+			startIdx := buf.uint()
+			len := buf.uint()
+			start, err := d.debugAddr(u, uint64(addrBase), startIdx)
+			if err != nil {
+				return nil, err
+			}
+			ret = append(ret, [2]uint64{start, start + len})
+
+		case rleOffsetPair:
+			off1 := buf.uint()
+			off2 := buf.uint()
+			ret = append(ret, [2]uint64{base + off1, base + off2})
+
+		case rleBaseAddress:
+			base = buf.addr()
+
+		case rleStartEnd:
+			start := buf.addr()
+			end := buf.addr()
+			ret = append(ret, [2]uint64{start, end})
+
+		case rleStartLength:
+			start := buf.addr()
+			len := buf.uint()
+			ret = append(ret, [2]uint64{start, start + len})
+		}
+	}
+}
+
+// debugAddr returns the address at idx in debug_addr
+func (d *Data) debugAddr(format dataFormat, addrBase, idx uint64) (uint64, error) {
+	off := idx*uint64(format.addrsize()) + addrBase
+
+	if uint64(int(off)) != off {
+		return 0, errors.New("offset out of range")
+	}
+
+	b := makeBuf(d, format, "addr", 0, d.addr)
+	b.skip(int(off))
+	val := b.addr()
+	if b.err != nil {
+		return 0, b.err
+	}
+	return val, nil
+}
diff --git a/src/debug/dwarf/entry_test.go b/src/debug/dwarf/entry_test.go
new file mode 100644
index 0000000..b54f8b4
--- /dev/null
+++ b/src/debug/dwarf/entry_test.go
@@ -0,0 +1,295 @@
+// 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.
+
+package dwarf_test
+
+import (
+	. "debug/dwarf"
+	"encoding/binary"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+func TestSplit(t *testing.T) {
+	// debug/dwarf doesn't (currently) support split DWARF, but
+	// the attributes that pointed to the split DWARF used to
+	// cause loading the DWARF data to fail entirely (issue
+	// #12592). Test that we can at least read the DWARF data.
+	d := elfData(t, "testdata/split.elf")
+	r := d.Reader()
+	e, err := r.Next()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if e.Tag != TagCompileUnit {
+		t.Fatalf("bad tag: have %s, want %s", e.Tag, TagCompileUnit)
+	}
+	// Check that we were able to parse the unknown section offset
+	// field, even if we can't figure out its DWARF class.
+	const AttrGNUAddrBase Attr = 0x2133
+	f := e.AttrField(AttrGNUAddrBase)
+	if _, ok := f.Val.(int64); !ok {
+		t.Fatalf("bad attribute value type: have %T, want int64", f.Val)
+	}
+	if f.Class != ClassUnknown {
+		t.Fatalf("bad class: have %s, want %s", f.Class, ClassUnknown)
+	}
+}
+
+// wantRange maps from a PC to the ranges of the compilation unit
+// containing that PC.
+type wantRange struct {
+	pc     uint64
+	ranges [][2]uint64
+}
+
+func TestReaderSeek(t *testing.T) {
+	want := []wantRange{
+		{0x40059d, [][2]uint64{{0x40059d, 0x400601}}},
+		{0x400600, [][2]uint64{{0x40059d, 0x400601}}},
+		{0x400601, [][2]uint64{{0x400601, 0x400611}}},
+		{0x4005f0, [][2]uint64{{0x40059d, 0x400601}}}, // loop test
+		{0x10, nil},
+		{0x400611, nil},
+	}
+	testRanges(t, "testdata/line-gcc.elf", want)
+
+	want = []wantRange{
+		{0x401122, [][2]uint64{{0x401122, 0x401166}}},
+		{0x401165, [][2]uint64{{0x401122, 0x401166}}},
+		{0x401166, [][2]uint64{{0x401166, 0x401179}}},
+	}
+	testRanges(t, "testdata/line-gcc-dwarf5.elf", want)
+
+	want = []wantRange{
+		{0x401130, [][2]uint64{{0x401130, 0x40117e}}},
+		{0x40117d, [][2]uint64{{0x401130, 0x40117e}}},
+		{0x40117e, nil},
+	}
+	testRanges(t, "testdata/line-clang-dwarf5.elf", want)
+}
+
+func TestRangesSection(t *testing.T) {
+	want := []wantRange{
+		{0x400500, [][2]uint64{{0x400500, 0x400549}, {0x400400, 0x400408}}},
+		{0x400400, [][2]uint64{{0x400500, 0x400549}, {0x400400, 0x400408}}},
+		{0x400548, [][2]uint64{{0x400500, 0x400549}, {0x400400, 0x400408}}},
+		{0x400407, [][2]uint64{{0x400500, 0x400549}, {0x400400, 0x400408}}},
+		{0x400408, nil},
+		{0x400449, nil},
+		{0x4003ff, nil},
+	}
+	testRanges(t, "testdata/ranges.elf", want)
+}
+
+func testRanges(t *testing.T, name string, want []wantRange) {
+	d := elfData(t, name)
+	r := d.Reader()
+	for _, w := range want {
+		entry, err := r.SeekPC(w.pc)
+		if err != nil {
+			if w.ranges != nil {
+				t.Errorf("%s: missing Entry for %#x", name, w.pc)
+			}
+			if err != ErrUnknownPC {
+				t.Errorf("%s: expected ErrUnknownPC for %#x, got %v", name, w.pc, err)
+			}
+			continue
+		}
+
+		ranges, err := d.Ranges(entry)
+		if err != nil {
+			t.Errorf("%s: %v", name, err)
+			continue
+		}
+		if !reflect.DeepEqual(ranges, w.ranges) {
+			t.Errorf("%s: for %#x got %x, expected %x", name, w.pc, ranges, w.ranges)
+		}
+	}
+}
+
+func TestReaderRanges(t *testing.T) {
+	type subprograms []struct {
+		name   string
+		ranges [][2]uint64
+	}
+	tests := []struct {
+		filename    string
+		subprograms subprograms
+	}{
+		{
+			"testdata/line-gcc.elf",
+			subprograms{
+				{"f1", [][2]uint64{{0x40059d, 0x4005e7}}},
+				{"main", [][2]uint64{{0x4005e7, 0x400601}}},
+				{"f2", [][2]uint64{{0x400601, 0x400611}}},
+			},
+		},
+		{
+			"testdata/line-gcc-dwarf5.elf",
+			subprograms{
+				{"main", [][2]uint64{{0x401147, 0x401166}}},
+				{"f1", [][2]uint64{{0x401122, 0x401147}}},
+				{"f2", [][2]uint64{{0x401166, 0x401179}}},
+			},
+		},
+		{
+			"testdata/line-clang-dwarf5.elf",
+			subprograms{
+				{"main", [][2]uint64{{0x401130, 0x401144}}},
+				{"f1", [][2]uint64{{0x401150, 0x40117e}}},
+				{"f2", [][2]uint64{{0x401180, 0x401197}}},
+			},
+		},
+	}
+
+	for _, test := range tests {
+		d := elfData(t, test.filename)
+		subprograms := test.subprograms
+
+		r := d.Reader()
+		i := 0
+		for entry, err := r.Next(); entry != nil && err == nil; entry, err = r.Next() {
+			if entry.Tag != TagSubprogram {
+				continue
+			}
+
+			if i > len(subprograms) {
+				t.Fatalf("%s: too many subprograms (expected at most %d)", test.filename, i)
+			}
+
+			if got := entry.Val(AttrName).(string); got != subprograms[i].name {
+				t.Errorf("%s: subprogram %d name is %s, expected %s", test.filename, i, got, subprograms[i].name)
+			}
+			ranges, err := d.Ranges(entry)
+			if err != nil {
+				t.Errorf("%s: subprogram %d: %v", test.filename, i, err)
+				continue
+			}
+			if !reflect.DeepEqual(ranges, subprograms[i].ranges) {
+				t.Errorf("%s: subprogram %d ranges are %x, expected %x", test.filename, i, ranges, subprograms[i].ranges)
+			}
+			i++
+		}
+
+		if i < len(subprograms) {
+			t.Errorf("%s: saw only %d subprograms, expected %d", test.filename, i, len(subprograms))
+		}
+	}
+}
+
+func Test64Bit(t *testing.T) {
+	// I don't know how to generate a 64-bit DWARF debug
+	// compilation unit except by using XCOFF, so this is
+	// hand-written.
+	tests := []struct {
+		name      string
+		info      []byte
+		addrSize  int
+		byteOrder binary.ByteOrder
+	}{
+		{
+			"32-bit little",
+			[]byte{0x30, 0, 0, 0, // comp unit length
+				4, 0, // DWARF version 4
+				0, 0, 0, 0, // abbrev offset
+				8, // address size
+				0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+			},
+			8, binary.LittleEndian,
+		},
+		{
+			"64-bit little",
+			[]byte{0xff, 0xff, 0xff, 0xff, // 64-bit DWARF
+				0x30, 0, 0, 0, 0, 0, 0, 0, // comp unit length
+				4, 0, // DWARF version 4
+				0, 0, 0, 0, 0, 0, 0, 0, // abbrev offset
+				8, // address size
+				0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+			},
+			8, binary.LittleEndian,
+		},
+		{
+			"64-bit big",
+			[]byte{0xff, 0xff, 0xff, 0xff, // 64-bit DWARF
+				0, 0, 0, 0, 0, 0, 0, 0x30, // comp unit length
+				0, 4, // DWARF version 4
+				0, 0, 0, 0, 0, 0, 0, 0, // abbrev offset
+				8, // address size
+				0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+				0, 0, 0, 0, 0, 0, 0, 0,
+			},
+			8, binary.BigEndian,
+		},
+	}
+
+	for _, test := range tests {
+		data, err := New(nil, nil, nil, test.info, nil, nil, nil, nil)
+		if err != nil {
+			t.Errorf("%s: %v", test.name, err)
+		}
+
+		r := data.Reader()
+		if r.AddressSize() != test.addrSize {
+			t.Errorf("%s: got address size %d, want %d", test.name, r.AddressSize(), test.addrSize)
+		}
+		if r.ByteOrder() != test.byteOrder {
+			t.Errorf("%s: got byte order %s, want %s", test.name, r.ByteOrder(), test.byteOrder)
+		}
+	}
+}
+
+func TestUnitIteration(t *testing.T) {
+	// Iterate over all ELF test files we have and ensure that
+	// we get the same set of compilation units skipping (method 0)
+	// and not skipping (method 1) CU children.
+	files, err := filepath.Glob(filepath.Join("testdata", "*.elf"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, file := range files {
+		t.Run(file, func(t *testing.T) {
+			d := elfData(t, file)
+			var units [2][]interface{}
+			for method := range units {
+				for r := d.Reader(); ; {
+					ent, err := r.Next()
+					if err != nil {
+						t.Fatal(err)
+					}
+					if ent == nil {
+						break
+					}
+					if ent.Tag == TagCompileUnit {
+						units[method] = append(units[method], ent.Val(AttrName))
+					}
+					if method == 0 {
+						if ent.Tag != TagCompileUnit {
+							t.Fatalf("found unexpected tag %v on top level", ent.Tag)
+						}
+						r.SkipChildren()
+					}
+				}
+			}
+			t.Logf("skipping CUs:     %v", units[0])
+			t.Logf("not-skipping CUs: %v", units[1])
+			if !reflect.DeepEqual(units[0], units[1]) {
+				t.Fatal("set of CUs differ")
+			}
+		})
+	}
+}
diff --git a/src/debug/dwarf/export_test.go b/src/debug/dwarf/export_test.go
new file mode 100644
index 0000000..b8a25ff
--- /dev/null
+++ b/src/debug/dwarf/export_test.go
@@ -0,0 +1,7 @@
+// 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 dwarf
+
+var PathJoin = pathJoin
diff --git a/src/debug/dwarf/line.go b/src/debug/dwarf/line.go
new file mode 100644
index 0000000..c4937ca
--- /dev/null
+++ b/src/debug/dwarf/line.go
@@ -0,0 +1,848 @@
+// Copyright 2015 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 dwarf
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"path"
+	"strings"
+)
+
+// A LineReader reads a sequence of LineEntry structures from a DWARF
+// "line" section for a single compilation unit. LineEntries occur in
+// order of increasing PC and each LineEntry gives metadata for the
+// instructions from that LineEntry's PC to just before the next
+// LineEntry's PC. The last entry will have its EndSequence field set.
+type LineReader struct {
+	buf buf
+
+	// Original .debug_line section data. Used by Seek.
+	section []byte
+
+	str     []byte // .debug_str
+	lineStr []byte // .debug_line_str
+
+	// Header information
+	version              uint16
+	addrsize             int
+	segmentSelectorSize  int
+	minInstructionLength int
+	maxOpsPerInstruction int
+	defaultIsStmt        bool
+	lineBase             int
+	lineRange            int
+	opcodeBase           int
+	opcodeLengths        []int
+	directories          []string
+	fileEntries          []*LineFile
+
+	programOffset Offset // section offset of line number program
+	endOffset     Offset // section offset of byte following program
+
+	initialFileEntries int // initial length of fileEntries
+
+	// Current line number program state machine registers
+	state     LineEntry // public state
+	fileIndex int       // private state
+}
+
+// A LineEntry is a row in a DWARF line table.
+type LineEntry struct {
+	// Address is the program-counter value of a machine
+	// instruction generated by the compiler. This LineEntry
+	// applies to each instruction from Address to just before the
+	// Address of the next LineEntry.
+	Address uint64
+
+	// OpIndex is the index of an operation within a VLIW
+	// instruction. The index of the first operation is 0. For
+	// non-VLIW architectures, it will always be 0. Address and
+	// OpIndex together form an operation pointer that can
+	// reference any individual operation within the instruction
+	// stream.
+	OpIndex int
+
+	// File is the source file corresponding to these
+	// instructions.
+	File *LineFile
+
+	// Line is the source code line number corresponding to these
+	// instructions. Lines are numbered beginning at 1. It may be
+	// 0 if these instructions cannot be attributed to any source
+	// line.
+	Line int
+
+	// Column is the column number within the source line of these
+	// instructions. Columns are numbered beginning at 1. It may
+	// be 0 to indicate the "left edge" of the line.
+	Column int
+
+	// IsStmt indicates that Address is a recommended breakpoint
+	// location, such as the beginning of a line, statement, or a
+	// distinct subpart of a statement.
+	IsStmt bool
+
+	// BasicBlock indicates that Address is the beginning of a
+	// basic block.
+	BasicBlock bool
+
+	// PrologueEnd indicates that Address is one (of possibly
+	// many) PCs where execution should be suspended for a
+	// breakpoint on entry to the containing function.
+	//
+	// Added in DWARF 3.
+	PrologueEnd bool
+
+	// EpilogueBegin indicates that Address is one (of possibly
+	// many) PCs where execution should be suspended for a
+	// breakpoint on exit from this function.
+	//
+	// Added in DWARF 3.
+	EpilogueBegin bool
+
+	// ISA is the instruction set architecture for these
+	// instructions. Possible ISA values should be defined by the
+	// applicable ABI specification.
+	//
+	// Added in DWARF 3.
+	ISA int
+
+	// Discriminator is an arbitrary integer indicating the block
+	// to which these instructions belong. It serves to
+	// distinguish among multiple blocks that may all have with
+	// the same source file, line, and column. Where only one
+	// block exists for a given source position, it should be 0.
+	//
+	// Added in DWARF 3.
+	Discriminator int
+
+	// EndSequence indicates that Address is the first byte after
+	// the end of a sequence of target machine instructions. If it
+	// is set, only this and the Address field are meaningful. A
+	// line number table may contain information for multiple
+	// potentially disjoint instruction sequences. The last entry
+	// in a line table should always have EndSequence set.
+	EndSequence bool
+}
+
+// A LineFile is a source file referenced by a DWARF line table entry.
+type LineFile struct {
+	Name   string
+	Mtime  uint64 // Implementation defined modification time, or 0 if unknown
+	Length int    // File length, or 0 if unknown
+}
+
+// LineReader returns a new reader for the line table of compilation
+// unit cu, which must be an Entry with tag TagCompileUnit.
+//
+// If this compilation unit has no line table, it returns nil, nil.
+func (d *Data) LineReader(cu *Entry) (*LineReader, error) {
+	if d.line == nil {
+		// No line tables available.
+		return nil, nil
+	}
+
+	// Get line table information from cu.
+	off, ok := cu.Val(AttrStmtList).(int64)
+	if !ok {
+		// cu has no line table.
+		return nil, nil
+	}
+	if off > int64(len(d.line)) {
+		return nil, errors.New("AttrStmtList value out of range")
+	}
+	// AttrCompDir is optional if all file names are absolute. Use
+	// the empty string if it's not present.
+	compDir, _ := cu.Val(AttrCompDir).(string)
+
+	// Create the LineReader.
+	u := &d.unit[d.offsetToUnit(cu.Offset)]
+	buf := makeBuf(d, u, "line", Offset(off), d.line[off:])
+	// The compilation directory is implicitly directories[0].
+	r := LineReader{
+		buf:     buf,
+		section: d.line,
+		str:     d.str,
+		lineStr: d.lineStr,
+	}
+
+	// Read the header.
+	if err := r.readHeader(compDir); err != nil {
+		return nil, err
+	}
+
+	// Initialize line reader state.
+	r.Reset()
+
+	return &r, nil
+}
+
+// readHeader reads the line number program header from r.buf and sets
+// all of the header fields in r.
+func (r *LineReader) readHeader(compDir string) error {
+	buf := &r.buf
+
+	// Read basic header fields [DWARF2 6.2.4].
+	hdrOffset := buf.off
+	unitLength, dwarf64 := buf.unitLength()
+	r.endOffset = buf.off + unitLength
+	if r.endOffset > buf.off+Offset(len(buf.data)) {
+		return DecodeError{"line", hdrOffset, fmt.Sprintf("line table end %d exceeds section size %d", r.endOffset, buf.off+Offset(len(buf.data)))}
+	}
+	r.version = buf.uint16()
+	if buf.err == nil && (r.version < 2 || r.version > 5) {
+		// DWARF goes to all this effort to make new opcodes
+		// backward-compatible, and then adds fields right in
+		// the middle of the header in new versions, so we're
+		// picky about only supporting known line table
+		// versions.
+		return DecodeError{"line", hdrOffset, fmt.Sprintf("unknown line table version %d", r.version)}
+	}
+	if r.version >= 5 {
+		r.addrsize = int(buf.uint8())
+		r.segmentSelectorSize = int(buf.uint8())
+	} else {
+		r.addrsize = buf.format.addrsize()
+		r.segmentSelectorSize = 0
+	}
+	var headerLength Offset
+	if dwarf64 {
+		headerLength = Offset(buf.uint64())
+	} else {
+		headerLength = Offset(buf.uint32())
+	}
+	r.programOffset = buf.off + headerLength
+	r.minInstructionLength = int(buf.uint8())
+	if r.version >= 4 {
+		// [DWARF4 6.2.4]
+		r.maxOpsPerInstruction = int(buf.uint8())
+	} else {
+		r.maxOpsPerInstruction = 1
+	}
+	r.defaultIsStmt = buf.uint8() != 0
+	r.lineBase = int(int8(buf.uint8()))
+	r.lineRange = int(buf.uint8())
+
+	// Validate header.
+	if buf.err != nil {
+		return buf.err
+	}
+	if r.maxOpsPerInstruction == 0 {
+		return DecodeError{"line", hdrOffset, "invalid maximum operations per instruction: 0"}
+	}
+	if r.lineRange == 0 {
+		return DecodeError{"line", hdrOffset, "invalid line range: 0"}
+	}
+
+	// Read standard opcode length table. This table starts with opcode 1.
+	r.opcodeBase = int(buf.uint8())
+	r.opcodeLengths = make([]int, r.opcodeBase)
+	for i := 1; i < r.opcodeBase; i++ {
+		r.opcodeLengths[i] = int(buf.uint8())
+	}
+
+	// Validate opcode lengths.
+	if buf.err != nil {
+		return buf.err
+	}
+	for i, length := range r.opcodeLengths {
+		if known, ok := knownOpcodeLengths[i]; ok && known != length {
+			return DecodeError{"line", hdrOffset, fmt.Sprintf("opcode %d expected to have length %d, but has length %d", i, known, length)}
+		}
+	}
+
+	if r.version < 5 {
+		// Read include directories table.
+		r.directories = []string{compDir}
+		for {
+			directory := buf.string()
+			if buf.err != nil {
+				return buf.err
+			}
+			if len(directory) == 0 {
+				break
+			}
+			if !pathIsAbs(directory) {
+				// Relative paths are implicitly relative to
+				// the compilation directory.
+				directory = pathJoin(compDir, directory)
+			}
+			r.directories = append(r.directories, directory)
+		}
+
+		// Read file name list. File numbering starts with 1,
+		// so leave the first entry nil.
+		r.fileEntries = make([]*LineFile, 1)
+		for {
+			if done, err := r.readFileEntry(); err != nil {
+				return err
+			} else if done {
+				break
+			}
+		}
+	} else {
+		dirFormat := r.readLNCTFormat()
+		c := buf.uint()
+		r.directories = make([]string, c)
+		for i := range r.directories {
+			dir, _, _, err := r.readLNCT(dirFormat, dwarf64)
+			if err != nil {
+				return err
+			}
+			r.directories[i] = dir
+		}
+		fileFormat := r.readLNCTFormat()
+		c = buf.uint()
+		r.fileEntries = make([]*LineFile, c)
+		for i := range r.fileEntries {
+			name, mtime, size, err := r.readLNCT(fileFormat, dwarf64)
+			if err != nil {
+				return err
+			}
+			r.fileEntries[i] = &LineFile{name, mtime, int(size)}
+		}
+	}
+
+	r.initialFileEntries = len(r.fileEntries)
+
+	return buf.err
+}
+
+// lnctForm is a pair of an LNCT code and a form. This represents an
+// entry in the directory name or file name description in the DWARF 5
+// line number program header.
+type lnctForm struct {
+	lnct int
+	form format
+}
+
+// readLNCTFormat reads an LNCT format description.
+func (r *LineReader) readLNCTFormat() []lnctForm {
+	c := r.buf.uint8()
+	ret := make([]lnctForm, c)
+	for i := range ret {
+		ret[i].lnct = int(r.buf.uint())
+		ret[i].form = format(r.buf.uint())
+	}
+	return ret
+}
+
+// readLNCT reads a sequence of LNCT entries and returns path information.
+func (r *LineReader) readLNCT(s []lnctForm, dwarf64 bool) (path string, mtime uint64, size uint64, err error) {
+	var dir string
+	for _, lf := range s {
+		var str string
+		var val uint64
+		switch lf.form {
+		case formString:
+			str = r.buf.string()
+		case formStrp, formLineStrp:
+			var off uint64
+			if dwarf64 {
+				off = r.buf.uint64()
+			} else {
+				off = uint64(r.buf.uint32())
+			}
+			if uint64(int(off)) != off {
+				return "", 0, 0, DecodeError{"line", r.buf.off, "strp/line_strp offset out of range"}
+			}
+			var b1 buf
+			if lf.form == formStrp {
+				b1 = makeBuf(r.buf.dwarf, r.buf.format, "str", 0, r.str)
+			} else {
+				b1 = makeBuf(r.buf.dwarf, r.buf.format, "line_str", 0, r.lineStr)
+			}
+			b1.skip(int(off))
+			str = b1.string()
+			if b1.err != nil {
+				return "", 0, 0, DecodeError{"line", r.buf.off, b1.err.Error()}
+			}
+		case formStrpSup:
+			// Supplemental sections not yet supported.
+			if dwarf64 {
+				r.buf.uint64()
+			} else {
+				r.buf.uint32()
+			}
+		case formStrx:
+			// .debug_line.dwo sections not yet supported.
+			r.buf.uint()
+		case formStrx1:
+			r.buf.uint8()
+		case formStrx2:
+			r.buf.uint16()
+		case formStrx3:
+			r.buf.uint24()
+		case formStrx4:
+			r.buf.uint32()
+		case formData1:
+			val = uint64(r.buf.uint8())
+		case formData2:
+			val = uint64(r.buf.uint16())
+		case formData4:
+			val = uint64(r.buf.uint32())
+		case formData8:
+			val = r.buf.uint64()
+		case formData16:
+			r.buf.bytes(16)
+		case formDwarfBlock:
+			r.buf.bytes(int(r.buf.uint()))
+		case formUdata:
+			val = r.buf.uint()
+		}
+
+		switch lf.lnct {
+		case lnctPath:
+			path = str
+		case lnctDirectoryIndex:
+			if val >= uint64(len(r.directories)) {
+				return "", 0, 0, DecodeError{"line", r.buf.off, "directory index out of range"}
+			}
+			dir = r.directories[val]
+		case lnctTimestamp:
+			mtime = val
+		case lnctSize:
+			size = val
+		case lnctMD5:
+			// Ignored.
+		}
+	}
+
+	if dir != "" && path != "" {
+		path = pathJoin(dir, path)
+	}
+
+	return path, mtime, size, nil
+}
+
+// readFileEntry reads a file entry from either the header or a
+// DW_LNE_define_file extended opcode and adds it to r.fileEntries. A
+// true return value indicates that there are no more entries to read.
+func (r *LineReader) readFileEntry() (bool, error) {
+	name := r.buf.string()
+	if r.buf.err != nil {
+		return false, r.buf.err
+	}
+	if len(name) == 0 {
+		return true, nil
+	}
+	off := r.buf.off
+	dirIndex := int(r.buf.uint())
+	if !pathIsAbs(name) {
+		if dirIndex >= len(r.directories) {
+			return false, DecodeError{"line", off, "directory index too large"}
+		}
+		name = pathJoin(r.directories[dirIndex], name)
+	}
+	mtime := r.buf.uint()
+	length := int(r.buf.uint())
+
+	// If this is a dynamically added path and the cursor was
+	// backed up, we may have already added this entry. Avoid
+	// updating existing line table entries in this case. This
+	// avoids an allocation and potential racy access to the slice
+	// backing store if the user called Files.
+	if len(r.fileEntries) < cap(r.fileEntries) {
+		fe := r.fileEntries[:len(r.fileEntries)+1]
+		if fe[len(fe)-1] != nil {
+			// We already processed this addition.
+			r.fileEntries = fe
+			return false, nil
+		}
+	}
+	r.fileEntries = append(r.fileEntries, &LineFile{name, mtime, length})
+	return false, nil
+}
+
+// updateFile updates r.state.File after r.fileIndex has
+// changed or r.fileEntries has changed.
+func (r *LineReader) updateFile() {
+	if r.fileIndex < len(r.fileEntries) {
+		r.state.File = r.fileEntries[r.fileIndex]
+	} else {
+		r.state.File = nil
+	}
+}
+
+// Next sets *entry to the next row in this line table and moves to
+// the next row. If there are no more entries and the line table is
+// properly terminated, it returns io.EOF.
+//
+// Rows are always in order of increasing entry.Address, but
+// entry.Line may go forward or backward.
+func (r *LineReader) Next(entry *LineEntry) error {
+	if r.buf.err != nil {
+		return r.buf.err
+	}
+
+	// Execute opcodes until we reach an opcode that emits a line
+	// table entry.
+	for {
+		if len(r.buf.data) == 0 {
+			return io.EOF
+		}
+		emit := r.step(entry)
+		if r.buf.err != nil {
+			return r.buf.err
+		}
+		if emit {
+			return nil
+		}
+	}
+}
+
+// knownOpcodeLengths gives the opcode lengths (in varint arguments)
+// of known standard opcodes.
+var knownOpcodeLengths = map[int]int{
+	lnsCopy:             0,
+	lnsAdvancePC:        1,
+	lnsAdvanceLine:      1,
+	lnsSetFile:          1,
+	lnsNegateStmt:       0,
+	lnsSetBasicBlock:    0,
+	lnsConstAddPC:       0,
+	lnsSetPrologueEnd:   0,
+	lnsSetEpilogueBegin: 0,
+	lnsSetISA:           1,
+	// lnsFixedAdvancePC takes a uint8 rather than a varint; it's
+	// unclear what length the header is supposed to claim, so
+	// ignore it.
+}
+
+// step processes the next opcode and updates r.state. If the opcode
+// emits a row in the line table, this updates *entry and returns
+// true.
+func (r *LineReader) step(entry *LineEntry) bool {
+	opcode := int(r.buf.uint8())
+
+	if opcode >= r.opcodeBase {
+		// Special opcode [DWARF2 6.2.5.1, DWARF4 6.2.5.1]
+		adjustedOpcode := opcode - r.opcodeBase
+		r.advancePC(adjustedOpcode / r.lineRange)
+		lineDelta := r.lineBase + adjustedOpcode%r.lineRange
+		r.state.Line += lineDelta
+		goto emit
+	}
+
+	switch opcode {
+	case 0:
+		// Extended opcode [DWARF2 6.2.5.3]
+		length := Offset(r.buf.uint())
+		startOff := r.buf.off
+		opcode := r.buf.uint8()
+
+		switch opcode {
+		case lneEndSequence:
+			r.state.EndSequence = true
+			*entry = r.state
+			r.resetState()
+
+		case lneSetAddress:
+			switch r.addrsize {
+			case 1:
+				r.state.Address = uint64(r.buf.uint8())
+			case 2:
+				r.state.Address = uint64(r.buf.uint16())
+			case 4:
+				r.state.Address = uint64(r.buf.uint32())
+			case 8:
+				r.state.Address = r.buf.uint64()
+			default:
+				r.buf.error("unknown address size")
+			}
+
+		case lneDefineFile:
+			if done, err := r.readFileEntry(); err != nil {
+				r.buf.err = err
+				return false
+			} else if done {
+				r.buf.err = DecodeError{"line", startOff, "malformed DW_LNE_define_file operation"}
+				return false
+			}
+			r.updateFile()
+
+		case lneSetDiscriminator:
+			// [DWARF4 6.2.5.3]
+			r.state.Discriminator = int(r.buf.uint())
+		}
+
+		r.buf.skip(int(startOff + length - r.buf.off))
+
+		if opcode == lneEndSequence {
+			return true
+		}
+
+	// Standard opcodes [DWARF2 6.2.5.2]
+	case lnsCopy:
+		goto emit
+
+	case lnsAdvancePC:
+		r.advancePC(int(r.buf.uint()))
+
+	case lnsAdvanceLine:
+		r.state.Line += int(r.buf.int())
+
+	case lnsSetFile:
+		r.fileIndex = int(r.buf.uint())
+		r.updateFile()
+
+	case lnsSetColumn:
+		r.state.Column = int(r.buf.uint())
+
+	case lnsNegateStmt:
+		r.state.IsStmt = !r.state.IsStmt
+
+	case lnsSetBasicBlock:
+		r.state.BasicBlock = true
+
+	case lnsConstAddPC:
+		r.advancePC((255 - r.opcodeBase) / r.lineRange)
+
+	case lnsFixedAdvancePC:
+		r.state.Address += uint64(r.buf.uint16())
+
+	// DWARF3 standard opcodes [DWARF3 6.2.5.2]
+	case lnsSetPrologueEnd:
+		r.state.PrologueEnd = true
+
+	case lnsSetEpilogueBegin:
+		r.state.EpilogueBegin = true
+
+	case lnsSetISA:
+		r.state.ISA = int(r.buf.uint())
+
+	default:
+		// Unhandled standard opcode. Skip the number of
+		// arguments that the prologue says this opcode has.
+		for i := 0; i < r.opcodeLengths[opcode]; i++ {
+			r.buf.uint()
+		}
+	}
+	return false
+
+emit:
+	*entry = r.state
+	r.state.BasicBlock = false
+	r.state.PrologueEnd = false
+	r.state.EpilogueBegin = false
+	r.state.Discriminator = 0
+	return true
+}
+
+// advancePC advances "operation pointer" (the combination of Address
+// and OpIndex) in r.state by opAdvance steps.
+func (r *LineReader) advancePC(opAdvance int) {
+	opIndex := r.state.OpIndex + opAdvance
+	r.state.Address += uint64(r.minInstructionLength * (opIndex / r.maxOpsPerInstruction))
+	r.state.OpIndex = opIndex % r.maxOpsPerInstruction
+}
+
+// A LineReaderPos represents a position in a line table.
+type LineReaderPos struct {
+	// off is the current offset in the DWARF line section.
+	off Offset
+	// numFileEntries is the length of fileEntries.
+	numFileEntries int
+	// state and fileIndex are the statement machine state at
+	// offset off.
+	state     LineEntry
+	fileIndex int
+}
+
+// Tell returns the current position in the line table.
+func (r *LineReader) Tell() LineReaderPos {
+	return LineReaderPos{r.buf.off, len(r.fileEntries), r.state, r.fileIndex}
+}
+
+// Seek restores the line table reader to a position returned by Tell.
+//
+// The argument pos must have been returned by a call to Tell on this
+// line table.
+func (r *LineReader) Seek(pos LineReaderPos) {
+	r.buf.off = pos.off
+	r.buf.data = r.section[r.buf.off:r.endOffset]
+	r.fileEntries = r.fileEntries[:pos.numFileEntries]
+	r.state = pos.state
+	r.fileIndex = pos.fileIndex
+}
+
+// Reset repositions the line table reader at the beginning of the
+// line table.
+func (r *LineReader) Reset() {
+	// Reset buffer to the line number program offset.
+	r.buf.off = r.programOffset
+	r.buf.data = r.section[r.buf.off:r.endOffset]
+
+	// Reset file entries list.
+	r.fileEntries = r.fileEntries[:r.initialFileEntries]
+
+	// Reset line number program state.
+	r.resetState()
+}
+
+// resetState resets r.state to its default values
+func (r *LineReader) resetState() {
+	// Reset the state machine registers to the defaults given in
+	// [DWARF4 6.2.2].
+	r.state = LineEntry{
+		Address:       0,
+		OpIndex:       0,
+		File:          nil,
+		Line:          1,
+		Column:        0,
+		IsStmt:        r.defaultIsStmt,
+		BasicBlock:    false,
+		PrologueEnd:   false,
+		EpilogueBegin: false,
+		ISA:           0,
+		Discriminator: 0,
+	}
+	r.fileIndex = 1
+	r.updateFile()
+}
+
+// Files returns the file name table of this compilation unit as of
+// the current position in the line table. The file name table may be
+// referenced from attributes in this compilation unit such as
+// AttrDeclFile.
+//
+// Entry 0 is always nil, since file index 0 represents "no file".
+//
+// The file name table of a compilation unit is not fixed. Files
+// returns the file table as of the current position in the line
+// table. This may contain more entries than the file table at an
+// earlier position in the line table, though existing entries never
+// change.
+func (r *LineReader) Files() []*LineFile {
+	return r.fileEntries
+}
+
+// ErrUnknownPC is the error returned by LineReader.ScanPC when the
+// seek PC is not covered by any entry in the line table.
+var ErrUnknownPC = errors.New("ErrUnknownPC")
+
+// SeekPC sets *entry to the LineEntry that includes pc and positions
+// the reader on the next entry in the line table. If necessary, this
+// will seek backwards to find pc.
+//
+// If pc is not covered by any entry in this line table, SeekPC
+// returns ErrUnknownPC. In this case, *entry and the final seek
+// position are unspecified.
+//
+// Note that DWARF line tables only permit sequential, forward scans.
+// Hence, in the worst case, this takes time linear in the size of the
+// line table. If the caller wishes to do repeated fast PC lookups, it
+// should build an appropriate index of the line table.
+func (r *LineReader) SeekPC(pc uint64, entry *LineEntry) error {
+	if err := r.Next(entry); err != nil {
+		return err
+	}
+	if entry.Address > pc {
+		// We're too far. Start at the beginning of the table.
+		r.Reset()
+		if err := r.Next(entry); err != nil {
+			return err
+		}
+		if entry.Address > pc {
+			// The whole table starts after pc.
+			r.Reset()
+			return ErrUnknownPC
+		}
+	}
+
+	// Scan until we pass pc, then back up one.
+	for {
+		var next LineEntry
+		pos := r.Tell()
+		if err := r.Next(&next); err != nil {
+			if err == io.EOF {
+				return ErrUnknownPC
+			}
+			return err
+		}
+		if next.Address > pc {
+			if entry.EndSequence {
+				// pc is in a hole in the table.
+				return ErrUnknownPC
+			}
+			// entry is the desired entry. Back up the
+			// cursor to "next" and return success.
+			r.Seek(pos)
+			return nil
+		}
+		*entry = next
+	}
+}
+
+// pathIsAbs reports whether path is an absolute path (or "full path
+// name" in DWARF parlance). This is in "whatever form makes sense for
+// the host system", so this accepts both UNIX-style and DOS-style
+// absolute paths. We avoid the filepath package because we want this
+// to behave the same regardless of our host system and because we
+// don't know what system the paths came from.
+func pathIsAbs(path string) bool {
+	_, path = splitDrive(path)
+	return len(path) > 0 && (path[0] == '/' || path[0] == '\\')
+}
+
+// pathJoin joins dirname and filename. filename must be relative.
+// DWARF paths can be UNIX-style or DOS-style, so this handles both.
+func pathJoin(dirname, filename string) string {
+	if len(dirname) == 0 {
+		return filename
+	}
+	// dirname should be absolute, which means we can determine
+	// whether it's a DOS path reasonably reliably by looking for
+	// a drive letter or UNC path.
+	drive, dirname := splitDrive(dirname)
+	if drive == "" {
+		// UNIX-style path.
+		return path.Join(dirname, filename)
+	}
+	// DOS-style path.
+	drive2, filename := splitDrive(filename)
+	if drive2 != "" {
+		if !strings.EqualFold(drive, drive2) {
+			// Different drives. There's not much we can
+			// do here, so just ignore the directory.
+			return drive2 + filename
+		}
+		// Drives are the same. Ignore drive on filename.
+	}
+	if !(strings.HasSuffix(dirname, "/") || strings.HasSuffix(dirname, `\`)) && dirname != "" {
+		sep := `\`
+		if strings.HasPrefix(dirname, "/") {
+			sep = `/`
+		}
+		dirname += sep
+	}
+	return drive + dirname + filename
+}
+
+// splitDrive splits the DOS drive letter or UNC share point from
+// path, if any. path == drive + rest
+func splitDrive(path string) (drive, rest string) {
+	if len(path) >= 2 && path[1] == ':' {
+		if c := path[0]; 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' {
+			return path[:2], path[2:]
+		}
+	}
+	if len(path) > 3 && (path[0] == '\\' || path[0] == '/') && (path[1] == '\\' || path[1] == '/') {
+		// Normalize the path so we can search for just \ below.
+		npath := strings.Replace(path, "/", `\`, -1)
+		// Get the host part, which must be non-empty.
+		slash1 := strings.IndexByte(npath[2:], '\\') + 2
+		if slash1 > 2 {
+			// Get the mount-point part, which must be non-empty.
+			slash2 := strings.IndexByte(npath[slash1+1:], '\\') + slash1 + 1
+			if slash2 > slash1 {
+				return path[:slash2], path[slash2:]
+			}
+		}
+	}
+	return "", path
+}
diff --git a/src/debug/dwarf/line_test.go b/src/debug/dwarf/line_test.go
new file mode 100644
index 0000000..b13818e
--- /dev/null
+++ b/src/debug/dwarf/line_test.go
@@ -0,0 +1,368 @@
+// Copyright 2015 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 dwarf_test
+
+import (
+	. "debug/dwarf"
+	"io"
+	"strings"
+	"testing"
+)
+
+var (
+	file1C = &LineFile{Name: "/home/austin/go.dev/src/debug/dwarf/testdata/line1.c"}
+	file1H = &LineFile{Name: "/home/austin/go.dev/src/debug/dwarf/testdata/line1.h"}
+	file2C = &LineFile{Name: "/home/austin/go.dev/src/debug/dwarf/testdata/line2.c"}
+)
+
+func TestLineELFGCC(t *testing.T) {
+	// Generated by:
+	//   # gcc --version | head -n1
+	//   gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2
+	//   # gcc -g -o line-gcc.elf line*.c
+
+	// Line table based on readelf --debug-dump=rawline,decodedline
+	want := []LineEntry{
+		{Address: 0x40059d, File: file1H, Line: 2, IsStmt: true},
+		{Address: 0x4005a5, File: file1H, Line: 2, IsStmt: true},
+		{Address: 0x4005b4, File: file1H, Line: 5, IsStmt: true},
+		{Address: 0x4005bd, File: file1H, Line: 6, IsStmt: true, Discriminator: 2},
+		{Address: 0x4005c7, File: file1H, Line: 5, IsStmt: true, Discriminator: 2},
+		{Address: 0x4005cb, File: file1H, Line: 5, IsStmt: false, Discriminator: 1},
+		{Address: 0x4005d1, File: file1H, Line: 7, IsStmt: true},
+		{Address: 0x4005e7, File: file1C, Line: 6, IsStmt: true},
+		{Address: 0x4005eb, File: file1C, Line: 7, IsStmt: true},
+		{Address: 0x4005f5, File: file1C, Line: 8, IsStmt: true},
+		{Address: 0x4005ff, File: file1C, Line: 9, IsStmt: true},
+		{Address: 0x400601, EndSequence: true},
+
+		{Address: 0x400601, File: file2C, Line: 4, IsStmt: true},
+		{Address: 0x400605, File: file2C, Line: 5, IsStmt: true},
+		{Address: 0x40060f, File: file2C, Line: 6, IsStmt: true},
+		{Address: 0x400611, EndSequence: true},
+	}
+	files := [][]*LineFile{{nil, file1H, file1C}, {nil, file2C}}
+
+	testLineTable(t, want, files, elfData(t, "testdata/line-gcc.elf"))
+}
+
+func TestLineGCCWindows(t *testing.T) {
+	// Generated by:
+	//   > gcc --version
+	//   gcc (tdm64-1) 4.9.2
+	//   > gcc -g -o line-gcc-win.bin line1.c C:\workdir\go\src\debug\dwarf\testdata\line2.c
+
+	toWindows := func(lf *LineFile) *LineFile {
+		lf2 := *lf
+		lf2.Name = strings.Replace(lf2.Name, "/home/austin/go.dev/", "C:\\workdir\\go\\", -1)
+		lf2.Name = strings.Replace(lf2.Name, "/", "\\", -1)
+		return &lf2
+	}
+	file1C := toWindows(file1C)
+	file1H := toWindows(file1H)
+	file2C := toWindows(file2C)
+
+	// Line table based on objdump --dwarf=rawline,decodedline
+	want := []LineEntry{
+		{Address: 0x401530, File: file1H, Line: 2, IsStmt: true},
+		{Address: 0x401538, File: file1H, Line: 5, IsStmt: true},
+		{Address: 0x401541, File: file1H, Line: 6, IsStmt: true, Discriminator: 3},
+		{Address: 0x40154b, File: file1H, Line: 5, IsStmt: true, Discriminator: 3},
+		{Address: 0x40154f, File: file1H, Line: 5, IsStmt: false, Discriminator: 1},
+		{Address: 0x401555, File: file1H, Line: 7, IsStmt: true},
+		{Address: 0x40155b, File: file1C, Line: 6, IsStmt: true},
+		{Address: 0x401563, File: file1C, Line: 6, IsStmt: true},
+		{Address: 0x401568, File: file1C, Line: 7, IsStmt: true},
+		{Address: 0x40156d, File: file1C, Line: 8, IsStmt: true},
+		{Address: 0x401572, File: file1C, Line: 9, IsStmt: true},
+		{Address: 0x401578, EndSequence: true},
+
+		{Address: 0x401580, File: file2C, Line: 4, IsStmt: true},
+		{Address: 0x401588, File: file2C, Line: 5, IsStmt: true},
+		{Address: 0x401595, File: file2C, Line: 6, IsStmt: true},
+		{Address: 0x40159b, EndSequence: true},
+	}
+	files := [][]*LineFile{{nil, file1H, file1C}, {nil, file2C}}
+
+	testLineTable(t, want, files, peData(t, "testdata/line-gcc-win.bin"))
+}
+
+func TestLineELFClang(t *testing.T) {
+	// Generated by:
+	//   # clang --version | head -n1
+	//   Ubuntu clang version 3.4-1ubuntu3 (tags/RELEASE_34/final) (based on LLVM 3.4)
+	//   # clang -g -o line-clang.elf line*.
+
+	want := []LineEntry{
+		{Address: 0x400530, File: file1C, Line: 6, IsStmt: true},
+		{Address: 0x400534, File: file1C, Line: 7, IsStmt: true, PrologueEnd: true},
+		{Address: 0x400539, File: file1C, Line: 8, IsStmt: true},
+		{Address: 0x400545, File: file1C, Line: 9, IsStmt: true},
+		{Address: 0x400550, File: file1H, Line: 2, IsStmt: true},
+		{Address: 0x400554, File: file1H, Line: 5, IsStmt: true, PrologueEnd: true},
+		{Address: 0x400568, File: file1H, Line: 6, IsStmt: true},
+		{Address: 0x400571, File: file1H, Line: 5, IsStmt: true},
+		{Address: 0x400581, File: file1H, Line: 7, IsStmt: true},
+		{Address: 0x400583, EndSequence: true},
+
+		{Address: 0x400590, File: file2C, Line: 4, IsStmt: true},
+		{Address: 0x4005a0, File: file2C, Line: 5, IsStmt: true, PrologueEnd: true},
+		{Address: 0x4005a7, File: file2C, Line: 6, IsStmt: true},
+		{Address: 0x4005b0, EndSequence: true},
+	}
+	files := [][]*LineFile{{nil, file1C, file1H}, {nil, file2C}}
+
+	testLineTable(t, want, files, elfData(t, "testdata/line-clang.elf"))
+}
+
+func TestLineSeek(t *testing.T) {
+	d := elfData(t, "testdata/line-gcc.elf")
+
+	// Get the line table for the first CU.
+	cu, err := d.Reader().Next()
+	if err != nil {
+		t.Fatal("d.Reader().Next:", err)
+	}
+	lr, err := d.LineReader(cu)
+	if err != nil {
+		t.Fatal("d.LineReader:", err)
+	}
+
+	// Read entries forward.
+	var line LineEntry
+	var posTable []LineReaderPos
+	var table []LineEntry
+	for {
+		posTable = append(posTable, lr.Tell())
+
+		err := lr.Next(&line)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			t.Fatal("lr.Next:", err)
+		}
+		table = append(table, line)
+	}
+
+	// Test that Reset returns to the first line.
+	lr.Reset()
+	if err := lr.Next(&line); err != nil {
+		t.Fatal("lr.Next after Reset failed:", err)
+	} else if line != table[0] {
+		t.Fatal("lr.Next after Reset returned", line, "instead of", table[0])
+	}
+
+	// Check that entries match when seeking backward.
+	for i := len(posTable) - 1; i >= 0; i-- {
+		lr.Seek(posTable[i])
+		err := lr.Next(&line)
+		if i == len(posTable)-1 {
+			if err != io.EOF {
+				t.Fatal("expected io.EOF after seek to end, got", err)
+			}
+		} else if err != nil {
+			t.Fatal("lr.Next after seek to", posTable[i], "failed:", err)
+		} else if line != table[i] {
+			t.Fatal("lr.Next after seek to", posTable[i], "returned", line, "instead of", table[i])
+		}
+	}
+
+	// Check that seeking to a PC returns the right line.
+	if err := lr.SeekPC(table[0].Address-1, &line); err != ErrUnknownPC {
+		t.Fatalf("lr.SeekPC to %#x returned %v instead of ErrUnknownPC", table[0].Address-1, err)
+	}
+	for i, testLine := range table {
+		if testLine.EndSequence {
+			if err := lr.SeekPC(testLine.Address, &line); err != ErrUnknownPC {
+				t.Fatalf("lr.SeekPC to %#x returned %v instead of ErrUnknownPC", testLine.Address, err)
+			}
+			continue
+		}
+
+		nextPC := table[i+1].Address
+		for pc := testLine.Address; pc < nextPC; pc++ {
+			if err := lr.SeekPC(pc, &line); err != nil {
+				t.Fatalf("lr.SeekPC to %#x failed: %v", pc, err)
+			} else if line != testLine {
+				t.Fatalf("lr.SeekPC to %#x returned %v instead of %v", pc, line, testLine)
+			}
+		}
+	}
+}
+
+func testLineTable(t *testing.T, want []LineEntry, files [][]*LineFile, d *Data) {
+	// Get line table from d.
+	var got []LineEntry
+	dr := d.Reader()
+	for {
+		ent, err := dr.Next()
+		if err != nil {
+			t.Fatal("dr.Next:", err)
+		} else if ent == nil {
+			break
+		}
+
+		if ent.Tag != TagCompileUnit {
+			dr.SkipChildren()
+			continue
+		}
+
+		// Ignore system compilation units (this happens in
+		// the Windows binary). We'll still decode the line
+		// table, but won't check it.
+		name := ent.Val(AttrName).(string)
+		ignore := strings.HasPrefix(name, "C:/crossdev/") || strings.HasPrefix(name, "../../")
+
+		// Decode CU's line table.
+		lr, err := d.LineReader(ent)
+		if err != nil {
+			t.Fatal("d.LineReader:", err)
+		} else if lr == nil {
+			continue
+		}
+
+		for {
+			var line LineEntry
+			err := lr.Next(&line)
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				t.Fatal("lr.Next:", err)
+			}
+			// Ignore sources from the Windows build environment.
+			if ignore {
+				continue
+			}
+			got = append(got, line)
+		}
+
+		// Check file table.
+		if !ignore {
+			if !compareFiles(files[0], lr.Files()) {
+				t.Log("File tables do not match. Got:")
+				dumpFiles(t, lr.Files())
+				t.Log("Want:")
+				dumpFiles(t, files[0])
+				t.Fail()
+			}
+			files = files[1:]
+		}
+	}
+
+	// Compare line tables.
+	if !compareLines(got, want) {
+		t.Log("Line tables do not match. Got:")
+		dumpLines(t, got)
+		t.Log("Want:")
+		dumpLines(t, want)
+		t.FailNow()
+	}
+}
+
+func compareFiles(a, b []*LineFile) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] == nil && b[i] == nil {
+			continue
+		}
+		if a[i] != nil && b[i] != nil && a[i].Name == b[i].Name {
+			continue
+		}
+		return false
+	}
+	return true
+}
+
+func dumpFiles(t *testing.T, files []*LineFile) {
+	for i, f := range files {
+		name := "<nil>"
+		if f != nil {
+			name = f.Name
+		}
+		t.Logf("  %d %s", i, name)
+	}
+}
+
+func compareLines(a, b []LineEntry) bool {
+	if len(a) != len(b) {
+		return false
+	}
+
+	for i := range a {
+		al, bl := a[i], b[i]
+		// If both are EndSequence, then the only other valid
+		// field is Address. Otherwise, test equality of all
+		// fields.
+		if al.EndSequence && bl.EndSequence && al.Address == bl.Address {
+			continue
+		}
+		if al.File.Name != bl.File.Name {
+			return false
+		}
+		al.File = nil
+		bl.File = nil
+		if al != bl {
+			return false
+		}
+	}
+	return true
+}
+
+func dumpLines(t *testing.T, lines []LineEntry) {
+	for _, l := range lines {
+		t.Logf("  %+v File:%+v", l, l.File)
+	}
+}
+
+type joinTest struct {
+	dirname, filename string
+	path              string
+}
+
+var joinTests = []joinTest{
+	{"a", "b", "a/b"},
+	{"a", "", "a"},
+	{"", "b", "b"},
+	{"/a", "b", "/a/b"},
+	{"/a/", "b", "/a/b"},
+
+	{`C:\Windows\`, `System32`, `C:\Windows\System32`},
+	{`C:\Windows\`, ``, `C:\Windows\`},
+	{`C:\`, `Windows`, `C:\Windows`},
+	{`C:\Windows\`, `C:System32`, `C:\Windows\System32`},
+	{`C:\Windows`, `a/b`, `C:\Windows\a/b`},
+	{`\\host\share\`, `foo`, `\\host\share\foo`},
+	{`\\host\share\`, `foo\bar`, `\\host\share\foo\bar`},
+	{`//host/share/`, `foo/bar`, `//host/share/foo/bar`},
+
+	// Note: the Go compiler currently emits DWARF line table paths
+	// with '/' instead of '\' (see issues #19784, #36495). These
+	// tests are to cover cases that might come up for Windows Go
+	// binaries.
+	{`c:/workdir/go/src/x`, `y.go`, `c:/workdir/go/src/x/y.go`},
+	{`d:/some/thing/`, `b.go`, `d:/some/thing/b.go`},
+	{`e:\blah\`, `foo.c`, `e:\blah\foo.c`},
+
+	// The following are "best effort". We shouldn't see relative
+	// base directories in DWARF, but these test that pathJoin
+	// doesn't fail miserably if it sees one.
+	{`C:`, `a`, `C:a`},
+	{`C:`, `a\b`, `C:a\b`},
+	{`C:.`, `a`, `C:.\a`},
+	{`C:a`, `b`, `C:a\b`},
+}
+
+func TestPathJoin(t *testing.T) {
+	for _, test := range joinTests {
+		got := PathJoin(test.dirname, test.filename)
+		if test.path != got {
+			t.Errorf("pathJoin(%q, %q) = %q, want %q", test.dirname, test.filename, got, test.path)
+		}
+	}
+}
diff --git a/src/debug/dwarf/open.go b/src/debug/dwarf/open.go
new file mode 100644
index 0000000..e94103a
--- /dev/null
+++ b/src/debug/dwarf/open.go
@@ -0,0 +1,130 @@
+// 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.
+
+// Package dwarf provides access to DWARF debugging information loaded from
+// executable files, as defined in the DWARF 2.0 Standard at
+// http://dwarfstd.org/doc/dwarf-2.0.0.pdf
+package dwarf
+
+import (
+	"encoding/binary"
+	"errors"
+)
+
+// Data represents the DWARF debugging information
+// loaded from an executable file (for example, an ELF or Mach-O executable).
+type Data struct {
+	// raw data
+	abbrev   []byte
+	aranges  []byte
+	frame    []byte
+	info     []byte
+	line     []byte
+	pubnames []byte
+	ranges   []byte
+	str      []byte
+
+	// New sections added in DWARF 5.
+	addr       []byte
+	lineStr    []byte
+	strOffsets []byte
+	rngLists   []byte
+
+	// parsed data
+	abbrevCache map[uint64]abbrevTable
+	bigEndian   bool
+	order       binary.ByteOrder
+	typeCache   map[Offset]Type
+	typeSigs    map[uint64]*typeUnit
+	unit        []unit
+}
+
+var errSegmentSelector = errors.New("non-zero segment_selector size not supported")
+
+// New returns a new Data object initialized from the given parameters.
+// Rather than calling this function directly, clients should typically use
+// the DWARF method of the File type of the appropriate package debug/elf,
+// debug/macho, or debug/pe.
+//
+// The []byte arguments are the data from the corresponding debug section
+// in the object file; for example, for an ELF object, abbrev is the contents of
+// the ".debug_abbrev" section.
+func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Data, error) {
+	d := &Data{
+		abbrev:      abbrev,
+		aranges:     aranges,
+		frame:       frame,
+		info:        info,
+		line:        line,
+		pubnames:    pubnames,
+		ranges:      ranges,
+		str:         str,
+		abbrevCache: make(map[uint64]abbrevTable),
+		typeCache:   make(map[Offset]Type),
+		typeSigs:    make(map[uint64]*typeUnit),
+	}
+
+	// Sniff .debug_info to figure out byte order.
+	// 32-bit DWARF: 4 byte length, 2 byte version.
+	// 64-bit DWARf: 4 bytes of 0xff, 8 byte length, 2 byte version.
+	if len(d.info) < 6 {
+		return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
+	}
+	offset := 4
+	if d.info[0] == 0xff && d.info[1] == 0xff && d.info[2] == 0xff && d.info[3] == 0xff {
+		if len(d.info) < 14 {
+			return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
+		}
+		offset = 12
+	}
+	// Fetch the version, a tiny 16-bit number (1, 2, 3, 4, 5).
+	x, y := d.info[offset], d.info[offset+1]
+	switch {
+	case x == 0 && y == 0:
+		return nil, DecodeError{"info", 4, "unsupported version 0"}
+	case x == 0:
+		d.bigEndian = true
+		d.order = binary.BigEndian
+	case y == 0:
+		d.bigEndian = false
+		d.order = binary.LittleEndian
+	default:
+		return nil, DecodeError{"info", 4, "cannot determine byte order"}
+	}
+
+	u, err := d.parseUnits()
+	if err != nil {
+		return nil, err
+	}
+	d.unit = u
+	return d, nil
+}
+
+// AddTypes will add one .debug_types section to the DWARF data. A
+// typical object with DWARF version 4 debug info will have multiple
+// .debug_types sections. The name is used for error reporting only,
+// and serves to distinguish one .debug_types section from another.
+func (d *Data) AddTypes(name string, types []byte) error {
+	return d.parseTypes(name, types)
+}
+
+// AddSection adds another DWARF section by name. The name should be a
+// DWARF section name such as ".debug_addr", ".debug_str_offsets", and
+// so forth. This approach is used for new DWARF sections added in
+// DWARF 5 and later.
+func (d *Data) AddSection(name string, contents []byte) error {
+	var err error
+	switch name {
+	case ".debug_addr":
+		d.addr = contents
+	case ".debug_line_str":
+		d.lineStr = contents
+	case ".debug_str_offsets":
+		d.strOffsets = contents
+	case ".debug_rnglists":
+		d.rngLists = contents
+	}
+	// Just ignore names that we don't yet support.
+	return err
+}
diff --git a/src/debug/dwarf/tag_string.go b/src/debug/dwarf/tag_string.go
new file mode 100644
index 0000000..b79ea17
--- /dev/null
+++ b/src/debug/dwarf/tag_string.go
@@ -0,0 +1,119 @@
+// Code generated by "stringer -type Tag -trimprefix=Tag"; DO NOT EDIT.
+
+package dwarf
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[TagArrayType-1]
+	_ = x[TagClassType-2]
+	_ = x[TagEntryPoint-3]
+	_ = x[TagEnumerationType-4]
+	_ = x[TagFormalParameter-5]
+	_ = x[TagImportedDeclaration-8]
+	_ = x[TagLabel-10]
+	_ = x[TagLexDwarfBlock-11]
+	_ = x[TagMember-13]
+	_ = x[TagPointerType-15]
+	_ = x[TagReferenceType-16]
+	_ = x[TagCompileUnit-17]
+	_ = x[TagStringType-18]
+	_ = x[TagStructType-19]
+	_ = x[TagSubroutineType-21]
+	_ = x[TagTypedef-22]
+	_ = x[TagUnionType-23]
+	_ = x[TagUnspecifiedParameters-24]
+	_ = x[TagVariant-25]
+	_ = x[TagCommonDwarfBlock-26]
+	_ = x[TagCommonInclusion-27]
+	_ = x[TagInheritance-28]
+	_ = x[TagInlinedSubroutine-29]
+	_ = x[TagModule-30]
+	_ = x[TagPtrToMemberType-31]
+	_ = x[TagSetType-32]
+	_ = x[TagSubrangeType-33]
+	_ = x[TagWithStmt-34]
+	_ = x[TagAccessDeclaration-35]
+	_ = x[TagBaseType-36]
+	_ = x[TagCatchDwarfBlock-37]
+	_ = x[TagConstType-38]
+	_ = x[TagConstant-39]
+	_ = x[TagEnumerator-40]
+	_ = x[TagFileType-41]
+	_ = x[TagFriend-42]
+	_ = x[TagNamelist-43]
+	_ = x[TagNamelistItem-44]
+	_ = x[TagPackedType-45]
+	_ = x[TagSubprogram-46]
+	_ = x[TagTemplateTypeParameter-47]
+	_ = x[TagTemplateValueParameter-48]
+	_ = x[TagThrownType-49]
+	_ = x[TagTryDwarfBlock-50]
+	_ = x[TagVariantPart-51]
+	_ = x[TagVariable-52]
+	_ = x[TagVolatileType-53]
+	_ = x[TagDwarfProcedure-54]
+	_ = x[TagRestrictType-55]
+	_ = x[TagInterfaceType-56]
+	_ = x[TagNamespace-57]
+	_ = x[TagImportedModule-58]
+	_ = x[TagUnspecifiedType-59]
+	_ = x[TagPartialUnit-60]
+	_ = x[TagImportedUnit-61]
+	_ = x[TagMutableType-62]
+	_ = x[TagCondition-63]
+	_ = x[TagSharedType-64]
+	_ = x[TagTypeUnit-65]
+	_ = x[TagRvalueReferenceType-66]
+	_ = x[TagTemplateAlias-67]
+	_ = x[TagCoarrayType-68]
+	_ = x[TagGenericSubrange-69]
+	_ = x[TagDynamicType-70]
+	_ = x[TagAtomicType-71]
+	_ = x[TagCallSite-72]
+	_ = x[TagCallSiteParameter-73]
+	_ = x[TagSkeletonUnit-74]
+	_ = x[TagImmutableType-75]
+}
+
+const (
+	_Tag_name_0 = "ArrayTypeClassTypeEntryPointEnumerationTypeFormalParameter"
+	_Tag_name_1 = "ImportedDeclaration"
+	_Tag_name_2 = "LabelLexDwarfBlock"
+	_Tag_name_3 = "Member"
+	_Tag_name_4 = "PointerTypeReferenceTypeCompileUnitStringTypeStructType"
+	_Tag_name_5 = "SubroutineTypeTypedefUnionTypeUnspecifiedParametersVariantCommonDwarfBlockCommonInclusionInheritanceInlinedSubroutineModulePtrToMemberTypeSetTypeSubrangeTypeWithStmtAccessDeclarationBaseTypeCatchDwarfBlockConstTypeConstantEnumeratorFileTypeFriendNamelistNamelistItemPackedTypeSubprogramTemplateTypeParameterTemplateValueParameterThrownTypeTryDwarfBlockVariantPartVariableVolatileTypeDwarfProcedureRestrictTypeInterfaceTypeNamespaceImportedModuleUnspecifiedTypePartialUnitImportedUnitMutableTypeConditionSharedTypeTypeUnitRvalueReferenceTypeTemplateAliasCoarrayTypeGenericSubrangeDynamicTypeAtomicTypeCallSiteCallSiteParameterSkeletonUnitImmutableType"
+)
+
+var (
+	_Tag_index_0 = [...]uint8{0, 9, 18, 28, 43, 58}
+	_Tag_index_2 = [...]uint8{0, 5, 18}
+	_Tag_index_4 = [...]uint8{0, 11, 24, 35, 45, 55}
+	_Tag_index_5 = [...]uint16{0, 14, 21, 30, 51, 58, 74, 89, 100, 117, 123, 138, 145, 157, 165, 182, 190, 205, 214, 222, 232, 240, 246, 254, 266, 276, 286, 307, 329, 339, 352, 363, 371, 383, 397, 409, 422, 431, 445, 460, 471, 483, 494, 503, 513, 521, 540, 553, 564, 579, 590, 600, 608, 625, 637, 650}
+)
+
+func (i Tag) String() string {
+	switch {
+	case 1 <= i && i <= 5:
+		i -= 1
+		return _Tag_name_0[_Tag_index_0[i]:_Tag_index_0[i+1]]
+	case i == 8:
+		return _Tag_name_1
+	case 10 <= i && i <= 11:
+		i -= 10
+		return _Tag_name_2[_Tag_index_2[i]:_Tag_index_2[i+1]]
+	case i == 13:
+		return _Tag_name_3
+	case 15 <= i && i <= 19:
+		i -= 15
+		return _Tag_name_4[_Tag_index_4[i]:_Tag_index_4[i+1]]
+	case 21 <= i && i <= 75:
+		i -= 21
+		return _Tag_name_5[_Tag_index_5[i]:_Tag_index_5[i+1]]
+	default:
+		return "Tag(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+}
diff --git a/src/debug/dwarf/testdata/cppunsuptypes.cc b/src/debug/dwarf/testdata/cppunsuptypes.cc
new file mode 100644
index 0000000..e9281c7
--- /dev/null
+++ b/src/debug/dwarf/testdata/cppunsuptypes.cc
@@ -0,0 +1,34 @@
+// Copyright 2019 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.
+
+// cppunsuptypes.elf built with g++ 7.3
+//    g++ -g -c -o cppunsuptypes.elf cppunsuptypes.cc
+
+int i = 3;
+double d = 3;
+
+// anonymous reference type
+int &culprit = i;
+
+// named reference type
+typedef double &dref;
+dref dr = d;
+
+// incorporated into another type
+typedef struct {
+  dref q;
+  int &r;
+} hasrefs;
+
+hasrefs hr = { d, i };
+
+// This code is intended to trigger a DWARF "pointer to member" type DIE
+struct CS { int dm; };
+
+int foo()
+{
+  int CS::* pdm = &CS::dm;
+  CS cs = {42};
+  return cs.*pdm;
+}
diff --git a/src/debug/dwarf/testdata/cppunsuptypes.elf b/src/debug/dwarf/testdata/cppunsuptypes.elf
new file mode 100644
index 0000000..e955512
--- /dev/null
+++ b/src/debug/dwarf/testdata/cppunsuptypes.elf
diff --git a/src/debug/dwarf/testdata/cycle.c b/src/debug/dwarf/testdata/cycle.c
new file mode 100644
index 0000000..a0b53df
--- /dev/null
+++ b/src/debug/dwarf/testdata/cycle.c
@@ -0,0 +1,7 @@
+typedef struct aaa *AAA;
+typedef AAA BBB;
+struct aaa { BBB val; };
+
+AAA x(void) {
+    return (AAA)0;
+}
diff --git a/src/debug/dwarf/testdata/cycle.elf b/src/debug/dwarf/testdata/cycle.elf
new file mode 100644
index 0000000..e0b66ca
--- /dev/null
+++ b/src/debug/dwarf/testdata/cycle.elf
diff --git a/src/debug/dwarf/testdata/debug_rnglists b/src/debug/dwarf/testdata/debug_rnglists
new file mode 100644
index 0000000..985ec6c
--- /dev/null
+++ b/src/debug/dwarf/testdata/debug_rnglists
diff --git a/src/debug/dwarf/testdata/line-clang-dwarf5.elf b/src/debug/dwarf/testdata/line-clang-dwarf5.elf
new file mode 100644
index 0000000..7b80c9c
--- /dev/null
+++ b/src/debug/dwarf/testdata/line-clang-dwarf5.elf
diff --git a/src/debug/dwarf/testdata/line-clang.elf b/src/debug/dwarf/testdata/line-clang.elf
new file mode 100644
index 0000000..b63cc78
--- /dev/null
+++ b/src/debug/dwarf/testdata/line-clang.elf
diff --git a/src/debug/dwarf/testdata/line-gcc-dwarf5.elf b/src/debug/dwarf/testdata/line-gcc-dwarf5.elf
new file mode 100644
index 0000000..34ce17c
--- /dev/null
+++ b/src/debug/dwarf/testdata/line-gcc-dwarf5.elf
diff --git a/src/debug/dwarf/testdata/line-gcc-win.bin b/src/debug/dwarf/testdata/line-gcc-win.bin
new file mode 100644
index 0000000..583ad44
--- /dev/null
+++ b/src/debug/dwarf/testdata/line-gcc-win.bin
diff --git a/src/debug/dwarf/testdata/line-gcc.elf b/src/debug/dwarf/testdata/line-gcc.elf
new file mode 100644
index 0000000..50500a8
--- /dev/null
+++ b/src/debug/dwarf/testdata/line-gcc.elf
diff --git a/src/debug/dwarf/testdata/line1.c b/src/debug/dwarf/testdata/line1.c
new file mode 100644
index 0000000..f358647
--- /dev/null
+++ b/src/debug/dwarf/testdata/line1.c
@@ -0,0 +1,9 @@
+#include "line1.h"
+
+void f2();
+
+int main()
+{
+	f1();
+	f2();
+}
diff --git a/src/debug/dwarf/testdata/line1.h b/src/debug/dwarf/testdata/line1.h
new file mode 100644
index 0000000..974d4c8
--- /dev/null
+++ b/src/debug/dwarf/testdata/line1.h
@@ -0,0 +1,7 @@
+static void f1()
+{
+	char buf[10];
+	int i;
+	for(i = 0; i < 10; i++)
+		buf[i] = 1;
+}
diff --git a/src/debug/dwarf/testdata/line2.c b/src/debug/dwarf/testdata/line2.c
new file mode 100644
index 0000000..38d8998
--- /dev/null
+++ b/src/debug/dwarf/testdata/line2.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+
+void f2()
+{
+	printf("hello\n");
+}
diff --git a/src/debug/dwarf/testdata/ranges.c b/src/debug/dwarf/testdata/ranges.c
new file mode 100644
index 0000000..2f208e5
--- /dev/null
+++ b/src/debug/dwarf/testdata/ranges.c
@@ -0,0 +1,25 @@
+// gcc -g -O2 -freorder-blocks-and-partition
+
+const char *arr[10000];
+const char *hot = "hot";
+const char *cold = "cold";
+
+__attribute__((noinline))
+void fn(int path) {
+	int i;
+
+	if (path) {
+		for (i = 0; i < sizeof arr / sizeof arr[0]; i++) {
+			arr[i] = hot;
+		}
+	} else {
+		for (i = 0; i < sizeof arr / sizeof arr[0]; i++) {
+			arr[i] = cold;
+		}
+	}
+}
+
+int main(int argc, char *argv[]) {
+	fn(argc);
+	return 0;
+}
diff --git a/src/debug/dwarf/testdata/ranges.elf b/src/debug/dwarf/testdata/ranges.elf
new file mode 100755
index 0000000..7f54138
--- /dev/null
+++ b/src/debug/dwarf/testdata/ranges.elf
diff --git a/src/debug/dwarf/testdata/split.c b/src/debug/dwarf/testdata/split.c
new file mode 100644
index 0000000..0ef3427
--- /dev/null
+++ b/src/debug/dwarf/testdata/split.c
@@ -0,0 +1,5 @@
+// gcc -gsplit-dwarf split.c -o split.elf
+
+int main() 
+{
+}
diff --git a/src/debug/dwarf/testdata/split.elf b/src/debug/dwarf/testdata/split.elf
new file mode 100644
index 0000000..99ee2c2
--- /dev/null
+++ b/src/debug/dwarf/testdata/split.elf
diff --git a/src/debug/dwarf/testdata/typedef.c b/src/debug/dwarf/testdata/typedef.c
new file mode 100644
index 0000000..4780a0b
--- /dev/null
+++ b/src/debug/dwarf/testdata/typedef.c
@@ -0,0 +1,85 @@
+// 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.
+
+/*
+Linux ELF:
+gcc -gdwarf-2 -m64 -c typedef.c && gcc -gdwarf-2 -m64 -o typedef.elf typedef.o
+
+OS X Mach-O:
+gcc -gdwarf-2 -m64 -c typedef.c -o typedef.macho
+*/
+#include <complex.h>
+
+typedef volatile int* t_ptr_volatile_int;
+typedef const char *t_ptr_const_char;
+typedef long t_long;
+typedef unsigned short t_ushort;
+typedef int t_func_int_of_float_double(float, double);
+typedef int (*t_ptr_func_int_of_float_double)(float, double);
+typedef int (*t_ptr_func_int_of_float_complex)(float complex);
+typedef int (*t_ptr_func_int_of_double_complex)(double complex);
+typedef int (*t_ptr_func_int_of_long_double_complex)(long double complex);
+typedef int *t_func_ptr_int_of_char_schar_uchar(char, signed char, unsigned char);
+typedef void t_func_void_of_char(char);
+typedef void t_func_void_of_void(void);
+typedef void t_func_void_of_ptr_char_dots(char*, ...);
+typedef struct my_struct {
+	volatile int vi;
+	char x : 1;
+	int y : 4;
+	int z[0];
+	long long array[40];
+	int zz[0];
+} t_my_struct;
+typedef struct my_struct1 {
+	int zz [1];
+} t_my_struct1;
+typedef union my_union {
+	volatile int vi;
+	char x : 1;
+	int y : 4;
+	long long array[40];
+} t_my_union;
+typedef enum my_enum {
+	e1 = 1,
+	e2 = 2,
+	e3 = -5,
+	e4 = 1000000000000000LL,
+} t_my_enum;
+
+typedef struct list t_my_list;
+struct list {
+	short val;
+	t_my_list *next;
+};
+
+typedef struct tree {
+	struct tree *left, *right;
+	unsigned long long val;
+} t_my_tree;
+
+t_ptr_volatile_int *a2;
+t_ptr_const_char **a3a;
+t_long *a4;
+t_ushort *a5;
+t_func_int_of_float_double *a6;
+t_ptr_func_int_of_float_double *a7;
+t_func_ptr_int_of_char_schar_uchar *a8;
+t_func_void_of_char *a9;
+t_func_void_of_void *a10;
+t_func_void_of_ptr_char_dots *a11;
+t_my_struct *a12;
+t_my_struct1 *a12a;
+t_my_union *a12b;
+t_my_enum *a13;
+t_my_list *a14;
+t_my_tree *a15;
+t_ptr_func_int_of_float_complex *a16;
+t_ptr_func_int_of_double_complex *a17;
+t_ptr_func_int_of_long_double_complex *a18;
+
+int main()
+{
+	return 0;
+}
diff --git a/src/debug/dwarf/testdata/typedef.elf b/src/debug/dwarf/testdata/typedef.elf
new file mode 100755
index 0000000..b2062d2
--- /dev/null
+++ b/src/debug/dwarf/testdata/typedef.elf
diff --git a/src/debug/dwarf/testdata/typedef.elf4 b/src/debug/dwarf/testdata/typedef.elf4
new file mode 100644
index 0000000..3d5a5a1
--- /dev/null
+++ b/src/debug/dwarf/testdata/typedef.elf4
diff --git a/src/debug/dwarf/testdata/typedef.macho b/src/debug/dwarf/testdata/typedef.macho
new file mode 100644
index 0000000..f75afcc
--- /dev/null
+++ b/src/debug/dwarf/testdata/typedef.macho
diff --git a/src/debug/dwarf/type.go b/src/debug/dwarf/type.go
new file mode 100644
index 0000000..316db25
--- /dev/null
+++ b/src/debug/dwarf/type.go
@@ -0,0 +1,751 @@
+// 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.
+
+// DWARF type information structures.
+// The format is heavily biased toward C, but for simplicity
+// the String methods use a pseudo-Go syntax.
+
+package dwarf
+
+import "strconv"
+
+// A Type conventionally represents a pointer to any of the
+// specific Type structures (CharType, StructType, etc.).
+type Type interface {
+	Common() *CommonType
+	String() string
+	Size() int64
+}
+
+// A CommonType holds fields common to multiple types.
+// If a field is not known or not applicable for a given type,
+// the zero value is used.
+type CommonType struct {
+	ByteSize int64  // size of value of this type, in bytes
+	Name     string // name that can be used to refer to type
+}
+
+func (c *CommonType) Common() *CommonType { return c }
+
+func (c *CommonType) Size() int64 { return c.ByteSize }
+
+// Basic types
+
+// A BasicType holds fields common to all basic types.
+type BasicType struct {
+	CommonType
+	BitSize   int64
+	BitOffset int64
+}
+
+func (b *BasicType) Basic() *BasicType { return b }
+
+func (t *BasicType) String() string {
+	if t.Name != "" {
+		return t.Name
+	}
+	return "?"
+}
+
+// A CharType represents a signed character type.
+type CharType struct {
+	BasicType
+}
+
+// A UcharType represents an unsigned character type.
+type UcharType struct {
+	BasicType
+}
+
+// An IntType represents a signed integer type.
+type IntType struct {
+	BasicType
+}
+
+// A UintType represents an unsigned integer type.
+type UintType struct {
+	BasicType
+}
+
+// A FloatType represents a floating point type.
+type FloatType struct {
+	BasicType
+}
+
+// A ComplexType represents a complex floating point type.
+type ComplexType struct {
+	BasicType
+}
+
+// A BoolType represents a boolean type.
+type BoolType struct {
+	BasicType
+}
+
+// An AddrType represents a machine address type.
+type AddrType struct {
+	BasicType
+}
+
+// An UnspecifiedType represents an implicit, unknown, ambiguous or nonexistent type.
+type UnspecifiedType struct {
+	BasicType
+}
+
+// qualifiers
+
+// A QualType represents a type that has the C/C++ "const", "restrict", or "volatile" qualifier.
+type QualType struct {
+	CommonType
+	Qual string
+	Type Type
+}
+
+func (t *QualType) String() string { return t.Qual + " " + t.Type.String() }
+
+func (t *QualType) Size() int64 { return t.Type.Size() }
+
+// An ArrayType represents a fixed size array type.
+type ArrayType struct {
+	CommonType
+	Type          Type
+	StrideBitSize int64 // if > 0, number of bits to hold each element
+	Count         int64 // if == -1, an incomplete array, like char x[].
+}
+
+func (t *ArrayType) String() string {
+	return "[" + strconv.FormatInt(t.Count, 10) + "]" + t.Type.String()
+}
+
+func (t *ArrayType) Size() int64 {
+	if t.Count == -1 {
+		return 0
+	}
+	return t.Count * t.Type.Size()
+}
+
+// A VoidType represents the C void type.
+type VoidType struct {
+	CommonType
+}
+
+func (t *VoidType) String() string { return "void" }
+
+// A PtrType represents a pointer type.
+type PtrType struct {
+	CommonType
+	Type Type
+}
+
+func (t *PtrType) String() string { return "*" + t.Type.String() }
+
+// A StructType represents a struct, union, or C++ class type.
+type StructType struct {
+	CommonType
+	StructName string
+	Kind       string // "struct", "union", or "class".
+	Field      []*StructField
+	Incomplete bool // if true, struct, union, class is declared but not defined
+}
+
+// A StructField represents a field in a struct, union, or C++ class type.
+type StructField struct {
+	Name       string
+	Type       Type
+	ByteOffset int64
+	ByteSize   int64 // usually zero; use Type.Size() for normal fields
+	BitOffset  int64 // within the ByteSize bytes at ByteOffset
+	BitSize    int64 // zero if not a bit field
+}
+
+func (t *StructType) String() string {
+	if t.StructName != "" {
+		return t.Kind + " " + t.StructName
+	}
+	return t.Defn()
+}
+
+func (t *StructType) Defn() string {
+	s := t.Kind
+	if t.StructName != "" {
+		s += " " + t.StructName
+	}
+	if t.Incomplete {
+		s += " /*incomplete*/"
+		return s
+	}
+	s += " {"
+	for i, f := range t.Field {
+		if i > 0 {
+			s += "; "
+		}
+		s += f.Name + " " + f.Type.String()
+		s += "@" + strconv.FormatInt(f.ByteOffset, 10)
+		if f.BitSize > 0 {
+			s += " : " + strconv.FormatInt(f.BitSize, 10)
+			s += "@" + strconv.FormatInt(f.BitOffset, 10)
+		}
+	}
+	s += "}"
+	return s
+}
+
+// An EnumType represents an enumerated type.
+// The only indication of its native integer type is its ByteSize
+// (inside CommonType).
+type EnumType struct {
+	CommonType
+	EnumName string
+	Val      []*EnumValue
+}
+
+// An EnumValue represents a single enumeration value.
+type EnumValue struct {
+	Name string
+	Val  int64
+}
+
+func (t *EnumType) String() string {
+	s := "enum"
+	if t.EnumName != "" {
+		s += " " + t.EnumName
+	}
+	s += " {"
+	for i, v := range t.Val {
+		if i > 0 {
+			s += "; "
+		}
+		s += v.Name + "=" + strconv.FormatInt(v.Val, 10)
+	}
+	s += "}"
+	return s
+}
+
+// A FuncType represents a function type.
+type FuncType struct {
+	CommonType
+	ReturnType Type
+	ParamType  []Type
+}
+
+func (t *FuncType) String() string {
+	s := "func("
+	for i, t := range t.ParamType {
+		if i > 0 {
+			s += ", "
+		}
+		s += t.String()
+	}
+	s += ")"
+	if t.ReturnType != nil {
+		s += " " + t.ReturnType.String()
+	}
+	return s
+}
+
+// A DotDotDotType represents the variadic ... function parameter.
+type DotDotDotType struct {
+	CommonType
+}
+
+func (t *DotDotDotType) String() string { return "..." }
+
+// A TypedefType represents a named type.
+type TypedefType struct {
+	CommonType
+	Type Type
+}
+
+func (t *TypedefType) String() string { return t.Name }
+
+func (t *TypedefType) Size() int64 { return t.Type.Size() }
+
+// An UnsupportedType is a placeholder returned in situations where we
+// encounter a type that isn't supported.
+type UnsupportedType struct {
+	CommonType
+	Tag Tag
+}
+
+func (t *UnsupportedType) String() string {
+	if t.Name != "" {
+		return t.Name
+	}
+	return t.Name + "(unsupported type " + t.Tag.String() + ")"
+}
+
+// typeReader is used to read from either the info section or the
+// types section.
+type typeReader interface {
+	Seek(Offset)
+	Next() (*Entry, error)
+	clone() typeReader
+	offset() Offset
+	// AddressSize returns the size in bytes of addresses in the current
+	// compilation unit.
+	AddressSize() int
+}
+
+// Type reads the type at off in the DWARF ``info'' section.
+func (d *Data) Type(off Offset) (Type, error) {
+	return d.readType("info", d.Reader(), off, d.typeCache, nil)
+}
+
+// readType reads a type from r at off of name. It adds types to the
+// type cache, appends new typedef types to typedefs, and computes the
+// sizes of types. Callers should pass nil for typedefs; this is used
+// for internal recursion.
+func (d *Data) readType(name string, r typeReader, off Offset, typeCache map[Offset]Type, typedefs *[]*TypedefType) (Type, error) {
+	if t, ok := typeCache[off]; ok {
+		return t, nil
+	}
+	r.Seek(off)
+	e, err := r.Next()
+	if err != nil {
+		return nil, err
+	}
+	addressSize := r.AddressSize()
+	if e == nil || e.Offset != off {
+		return nil, DecodeError{name, off, "no type at offset"}
+	}
+
+	// If this is the root of the recursion, prepare to resolve
+	// typedef sizes once the recursion is done. This must be done
+	// after the type graph is constructed because it may need to
+	// resolve cycles in a different order than readType
+	// encounters them.
+	if typedefs == nil {
+		var typedefList []*TypedefType
+		defer func() {
+			for _, t := range typedefList {
+				t.Common().ByteSize = t.Type.Size()
+			}
+		}()
+		typedefs = &typedefList
+	}
+
+	// Parse type from Entry.
+	// Must always set typeCache[off] before calling
+	// d.readType recursively, to handle circular types correctly.
+	var typ Type
+
+	nextDepth := 0
+
+	// Get next child; set err if error happens.
+	next := func() *Entry {
+		if !e.Children {
+			return nil
+		}
+		// Only return direct children.
+		// Skip over composite entries that happen to be nested
+		// inside this one. Most DWARF generators wouldn't generate
+		// such a thing, but clang does.
+		// See golang.org/issue/6472.
+		for {
+			kid, err1 := r.Next()
+			if err1 != nil {
+				err = err1
+				return nil
+			}
+			if kid == nil {
+				err = DecodeError{name, r.offset(), "unexpected end of DWARF entries"}
+				return nil
+			}
+			if kid.Tag == 0 {
+				if nextDepth > 0 {
+					nextDepth--
+					continue
+				}
+				return nil
+			}
+			if kid.Children {
+				nextDepth++
+			}
+			if nextDepth > 0 {
+				continue
+			}
+			return kid
+		}
+	}
+
+	// Get Type referred to by Entry's AttrType field.
+	// Set err if error happens. Not having a type is an error.
+	typeOf := func(e *Entry) Type {
+		tval := e.Val(AttrType)
+		var t Type
+		switch toff := tval.(type) {
+		case Offset:
+			if t, err = d.readType(name, r.clone(), toff, typeCache, typedefs); err != nil {
+				return nil
+			}
+		case uint64:
+			if t, err = d.sigToType(toff); err != nil {
+				return nil
+			}
+		default:
+			// It appears that no Type means "void".
+			return new(VoidType)
+		}
+		return t
+	}
+
+	switch e.Tag {
+	case TagArrayType:
+		// Multi-dimensional array.  (DWARF v2 §5.4)
+		// Attributes:
+		//	AttrType:subtype [required]
+		//	AttrStrideSize: size in bits of each element of the array
+		//	AttrByteSize: size of entire array
+		// Children:
+		//	TagSubrangeType or TagEnumerationType giving one dimension.
+		//	dimensions are in left to right order.
+		t := new(ArrayType)
+		typ = t
+		typeCache[off] = t
+		if t.Type = typeOf(e); err != nil {
+			goto Error
+		}
+		t.StrideBitSize, _ = e.Val(AttrStrideSize).(int64)
+
+		// Accumulate dimensions,
+		var dims []int64
+		for kid := next(); kid != nil; kid = next() {
+			// TODO(rsc): Can also be TagEnumerationType
+			// but haven't seen that in the wild yet.
+			switch kid.Tag {
+			case TagSubrangeType:
+				count, ok := kid.Val(AttrCount).(int64)
+				if !ok {
+					// Old binaries may have an upper bound instead.
+					count, ok = kid.Val(AttrUpperBound).(int64)
+					if ok {
+						count++ // Length is one more than upper bound.
+					} else if len(dims) == 0 {
+						count = -1 // As in x[].
+					}
+				}
+				dims = append(dims, count)
+			case TagEnumerationType:
+				err = DecodeError{name, kid.Offset, "cannot handle enumeration type as array bound"}
+				goto Error
+			}
+		}
+		if len(dims) == 0 {
+			// LLVM generates this for x[].
+			dims = []int64{-1}
+		}
+
+		t.Count = dims[0]
+		for i := len(dims) - 1; i >= 1; i-- {
+			t.Type = &ArrayType{Type: t.Type, Count: dims[i]}
+		}
+
+	case TagBaseType:
+		// Basic type.  (DWARF v2 §5.1)
+		// Attributes:
+		//	AttrName: name of base type in programming language of the compilation unit [required]
+		//	AttrEncoding: encoding value for type (encFloat etc) [required]
+		//	AttrByteSize: size of type in bytes [required]
+		//	AttrBitOffset: for sub-byte types, size in bits
+		//	AttrBitSize: for sub-byte types, bit offset of high order bit in the AttrByteSize bytes
+		name, _ := e.Val(AttrName).(string)
+		enc, ok := e.Val(AttrEncoding).(int64)
+		if !ok {
+			err = DecodeError{name, e.Offset, "missing encoding attribute for " + name}
+			goto Error
+		}
+		switch enc {
+		default:
+			err = DecodeError{name, e.Offset, "unrecognized encoding attribute value"}
+			goto Error
+
+		case encAddress:
+			typ = new(AddrType)
+		case encBoolean:
+			typ = new(BoolType)
+		case encComplexFloat:
+			typ = new(ComplexType)
+			if name == "complex" {
+				// clang writes out 'complex' instead of 'complex float' or 'complex double'.
+				// clang also writes out a byte size that we can use to distinguish.
+				// See issue 8694.
+				switch byteSize, _ := e.Val(AttrByteSize).(int64); byteSize {
+				case 8:
+					name = "complex float"
+				case 16:
+					name = "complex double"
+				}
+			}
+		case encFloat:
+			typ = new(FloatType)
+		case encSigned:
+			typ = new(IntType)
+		case encUnsigned:
+			typ = new(UintType)
+		case encSignedChar:
+			typ = new(CharType)
+		case encUnsignedChar:
+			typ = new(UcharType)
+		}
+		typeCache[off] = typ
+		t := typ.(interface {
+			Basic() *BasicType
+		}).Basic()
+		t.Name = name
+		t.BitSize, _ = e.Val(AttrBitSize).(int64)
+		t.BitOffset, _ = e.Val(AttrBitOffset).(int64)
+
+	case TagClassType, TagStructType, TagUnionType:
+		// Structure, union, or class type.  (DWARF v2 §5.5)
+		// Attributes:
+		//	AttrName: name of struct, union, or class
+		//	AttrByteSize: byte size [required]
+		//	AttrDeclaration: if true, struct/union/class is incomplete
+		// Children:
+		//	TagMember to describe one member.
+		//		AttrName: name of member [required]
+		//		AttrType: type of member [required]
+		//		AttrByteSize: size in bytes
+		//		AttrBitOffset: bit offset within bytes for bit fields
+		//		AttrBitSize: bit size for bit fields
+		//		AttrDataMemberLoc: location within struct [required for struct, class]
+		// There is much more to handle C++, all ignored for now.
+		t := new(StructType)
+		typ = t
+		typeCache[off] = t
+		switch e.Tag {
+		case TagClassType:
+			t.Kind = "class"
+		case TagStructType:
+			t.Kind = "struct"
+		case TagUnionType:
+			t.Kind = "union"
+		}
+		t.StructName, _ = e.Val(AttrName).(string)
+		t.Incomplete = e.Val(AttrDeclaration) != nil
+		t.Field = make([]*StructField, 0, 8)
+		var lastFieldType *Type
+		var lastFieldBitOffset int64
+		for kid := next(); kid != nil; kid = next() {
+			if kid.Tag != TagMember {
+				continue
+			}
+			f := new(StructField)
+			if f.Type = typeOf(kid); err != nil {
+				goto Error
+			}
+			switch loc := kid.Val(AttrDataMemberLoc).(type) {
+			case []byte:
+				// TODO: Should have original compilation
+				// unit here, not unknownFormat.
+				b := makeBuf(d, unknownFormat{}, "location", 0, loc)
+				if b.uint8() != opPlusUconst {
+					err = DecodeError{name, kid.Offset, "unexpected opcode"}
+					goto Error
+				}
+				f.ByteOffset = int64(b.uint())
+				if b.err != nil {
+					err = b.err
+					goto Error
+				}
+			case int64:
+				f.ByteOffset = loc
+			}
+
+			haveBitOffset := false
+			f.Name, _ = kid.Val(AttrName).(string)
+			f.ByteSize, _ = kid.Val(AttrByteSize).(int64)
+			f.BitOffset, haveBitOffset = kid.Val(AttrBitOffset).(int64)
+			f.BitSize, _ = kid.Val(AttrBitSize).(int64)
+			t.Field = append(t.Field, f)
+
+			bito := f.BitOffset
+			if !haveBitOffset {
+				bito = f.ByteOffset * 8
+			}
+			if bito == lastFieldBitOffset && t.Kind != "union" {
+				// Last field was zero width. Fix array length.
+				// (DWARF writes out 0-length arrays as if they were 1-length arrays.)
+				zeroArray(lastFieldType)
+			}
+			lastFieldType = &f.Type
+			lastFieldBitOffset = bito
+		}
+		if t.Kind != "union" {
+			b, ok := e.Val(AttrByteSize).(int64)
+			if ok && b*8 == lastFieldBitOffset {
+				// Final field must be zero width. Fix array length.
+				zeroArray(lastFieldType)
+			}
+		}
+
+	case TagConstType, TagVolatileType, TagRestrictType:
+		// Type modifier (DWARF v2 §5.2)
+		// Attributes:
+		//	AttrType: subtype
+		t := new(QualType)
+		typ = t
+		typeCache[off] = t
+		if t.Type = typeOf(e); err != nil {
+			goto Error
+		}
+		switch e.Tag {
+		case TagConstType:
+			t.Qual = "const"
+		case TagRestrictType:
+			t.Qual = "restrict"
+		case TagVolatileType:
+			t.Qual = "volatile"
+		}
+
+	case TagEnumerationType:
+		// Enumeration type (DWARF v2 §5.6)
+		// Attributes:
+		//	AttrName: enum name if any
+		//	AttrByteSize: bytes required to represent largest value
+		// Children:
+		//	TagEnumerator:
+		//		AttrName: name of constant
+		//		AttrConstValue: value of constant
+		t := new(EnumType)
+		typ = t
+		typeCache[off] = t
+		t.EnumName, _ = e.Val(AttrName).(string)
+		t.Val = make([]*EnumValue, 0, 8)
+		for kid := next(); kid != nil; kid = next() {
+			if kid.Tag == TagEnumerator {
+				f := new(EnumValue)
+				f.Name, _ = kid.Val(AttrName).(string)
+				f.Val, _ = kid.Val(AttrConstValue).(int64)
+				n := len(t.Val)
+				if n >= cap(t.Val) {
+					val := make([]*EnumValue, n, n*2)
+					copy(val, t.Val)
+					t.Val = val
+				}
+				t.Val = t.Val[0 : n+1]
+				t.Val[n] = f
+			}
+		}
+
+	case TagPointerType:
+		// Type modifier (DWARF v2 §5.2)
+		// Attributes:
+		//	AttrType: subtype [not required!  void* has no AttrType]
+		//	AttrAddrClass: address class [ignored]
+		t := new(PtrType)
+		typ = t
+		typeCache[off] = t
+		if e.Val(AttrType) == nil {
+			t.Type = &VoidType{}
+			break
+		}
+		t.Type = typeOf(e)
+
+	case TagSubroutineType:
+		// Subroutine type.  (DWARF v2 §5.7)
+		// Attributes:
+		//	AttrType: type of return value if any
+		//	AttrName: possible name of type [ignored]
+		//	AttrPrototyped: whether used ANSI C prototype [ignored]
+		// Children:
+		//	TagFormalParameter: typed parameter
+		//		AttrType: type of parameter
+		//	TagUnspecifiedParameter: final ...
+		t := new(FuncType)
+		typ = t
+		typeCache[off] = t
+		if t.ReturnType = typeOf(e); err != nil {
+			goto Error
+		}
+		t.ParamType = make([]Type, 0, 8)
+		for kid := next(); kid != nil; kid = next() {
+			var tkid Type
+			switch kid.Tag {
+			default:
+				continue
+			case TagFormalParameter:
+				if tkid = typeOf(kid); err != nil {
+					goto Error
+				}
+			case TagUnspecifiedParameters:
+				tkid = &DotDotDotType{}
+			}
+			t.ParamType = append(t.ParamType, tkid)
+		}
+
+	case TagTypedef:
+		// Typedef (DWARF v2 §5.3)
+		// Attributes:
+		//	AttrName: name [required]
+		//	AttrType: type definition [required]
+		t := new(TypedefType)
+		typ = t
+		typeCache[off] = t
+		t.Name, _ = e.Val(AttrName).(string)
+		t.Type = typeOf(e)
+
+	case TagUnspecifiedType:
+		// Unspecified type (DWARF v3 §5.2)
+		// Attributes:
+		//	AttrName: name
+		t := new(UnspecifiedType)
+		typ = t
+		typeCache[off] = t
+		t.Name, _ = e.Val(AttrName).(string)
+
+	default:
+		// This is some other type DIE that we're currently not
+		// equipped to handle. Return an abstract "unsupported type"
+		// object in such cases.
+		t := new(UnsupportedType)
+		typ = t
+		typeCache[off] = t
+		t.Tag = e.Tag
+		t.Name, _ = e.Val(AttrName).(string)
+	}
+
+	if err != nil {
+		goto Error
+	}
+
+	{
+		b, ok := e.Val(AttrByteSize).(int64)
+		if !ok {
+			b = -1
+			switch t := typ.(type) {
+			case *TypedefType:
+				// Record that we need to resolve this
+				// type's size once the type graph is
+				// constructed.
+				*typedefs = append(*typedefs, t)
+			case *PtrType:
+				b = int64(addressSize)
+			}
+		}
+		typ.Common().ByteSize = b
+	}
+	return typ, nil
+
+Error:
+	// If the parse fails, take the type out of the cache
+	// so that the next call with this offset doesn't hit
+	// the cache and return success.
+	delete(typeCache, off)
+	return nil, err
+}
+
+func zeroArray(t *Type) {
+	if t == nil {
+		return
+	}
+	at, ok := (*t).(*ArrayType)
+	if !ok || at.Type.Size() == 0 {
+		return
+	}
+	// Make a copy to avoid invalidating typeCache.
+	tt := *at
+	tt.Count = 0
+	*t = &tt
+}
diff --git a/src/debug/dwarf/type_test.go b/src/debug/dwarf/type_test.go
new file mode 100644
index 0000000..fda03fd
--- /dev/null
+++ b/src/debug/dwarf/type_test.go
@@ -0,0 +1,230 @@
+// 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.
+
+package dwarf_test
+
+import (
+	. "debug/dwarf"
+	"debug/elf"
+	"debug/macho"
+	"debug/pe"
+	"fmt"
+	"strconv"
+	"testing"
+)
+
+var typedefTests = map[string]string{
+	"t_ptr_volatile_int":                    "*volatile int",
+	"t_ptr_const_char":                      "*const char",
+	"t_long":                                "long int",
+	"t_ushort":                              "short unsigned int",
+	"t_func_int_of_float_double":            "func(float, double) int",
+	"t_ptr_func_int_of_float_double":        "*func(float, double) int",
+	"t_ptr_func_int_of_float_complex":       "*func(complex float) int",
+	"t_ptr_func_int_of_double_complex":      "*func(complex double) int",
+	"t_ptr_func_int_of_long_double_complex": "*func(complex long double) int",
+	"t_func_ptr_int_of_char_schar_uchar":    "func(char, signed char, unsigned char) *int",
+	"t_func_void_of_char":                   "func(char) void",
+	"t_func_void_of_void":                   "func() void",
+	"t_func_void_of_ptr_char_dots":          "func(*char, ...) void",
+	"t_my_struct":                           "struct my_struct {vi volatile int@0; x char@4 : 1@7; y int@4 : 4@27; z [0]int@8; array [40]long long int@8; zz [0]int@328}",
+	"t_my_struct1":                          "struct my_struct1 {zz [1]int@0}",
+	"t_my_union":                            "union my_union {vi volatile int@0; x char@0 : 1@7; y int@0 : 4@28; array [40]long long int@0}",
+	"t_my_enum":                             "enum my_enum {e1=1; e2=2; e3=-5; e4=1000000000000000}",
+	"t_my_list":                             "struct list {val short int@0; next *t_my_list@8}",
+	"t_my_tree":                             "struct tree {left *struct tree@0; right *struct tree@8; val long long unsigned int@16}",
+}
+
+// As Apple converts gcc to a clang-based front end
+// they keep breaking the DWARF output. This map lists the
+// conversion from real answer to Apple answer.
+var machoBug = map[string]string{
+	"func(*char, ...) void":                                 "func(*char) void",
+	"enum my_enum {e1=1; e2=2; e3=-5; e4=1000000000000000}": "enum my_enum {e1=1; e2=2; e3=-5; e4=-1530494976}",
+}
+
+func elfData(t *testing.T, name string) *Data {
+	f, err := elf.Open(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	d, err := f.DWARF()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return d
+}
+
+func machoData(t *testing.T, name string) *Data {
+	f, err := macho.Open(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	d, err := f.DWARF()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return d
+}
+
+func peData(t *testing.T, name string) *Data {
+	f, err := pe.Open(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	d, err := f.DWARF()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return d
+}
+
+func TestTypedefsELF(t *testing.T) { testTypedefs(t, elfData(t, "testdata/typedef.elf"), "elf") }
+
+func TestTypedefsMachO(t *testing.T) {
+	testTypedefs(t, machoData(t, "testdata/typedef.macho"), "macho")
+}
+
+func TestTypedefsELFDwarf4(t *testing.T) { testTypedefs(t, elfData(t, "testdata/typedef.elf4"), "elf") }
+
+func testTypedefs(t *testing.T, d *Data, kind string) {
+	r := d.Reader()
+	seen := make(map[string]bool)
+	for {
+		e, err := r.Next()
+		if err != nil {
+			t.Fatal("r.Next:", err)
+		}
+		if e == nil {
+			break
+		}
+		if e.Tag == TagTypedef {
+			typ, err := d.Type(e.Offset)
+			if err != nil {
+				t.Fatal("d.Type:", err)
+			}
+			t1 := typ.(*TypedefType)
+			var typstr string
+			if ts, ok := t1.Type.(*StructType); ok {
+				typstr = ts.Defn()
+			} else {
+				typstr = t1.Type.String()
+			}
+
+			if want, ok := typedefTests[t1.Name]; ok {
+				if seen[t1.Name] {
+					t.Errorf("multiple definitions for %s", t1.Name)
+				}
+				seen[t1.Name] = true
+				if typstr != want && (kind != "macho" || typstr != machoBug[want]) {
+					t.Errorf("%s:\n\thave %s\n\twant %s", t1.Name, typstr, want)
+				}
+			}
+		}
+		if e.Tag != TagCompileUnit {
+			r.SkipChildren()
+		}
+	}
+
+	for k := range typedefTests {
+		if !seen[k] {
+			t.Errorf("missing %s", k)
+		}
+	}
+}
+
+func TestTypedefCycle(t *testing.T) {
+	// See issue #13039: reading a typedef cycle starting from a
+	// different place than the size needed to be computed from
+	// used to crash.
+	//
+	// cycle.elf built with GCC 4.8.4:
+	//    gcc -g -c -o cycle.elf cycle.c
+	d := elfData(t, "testdata/cycle.elf")
+	r := d.Reader()
+	offsets := []Offset{}
+	for {
+		e, err := r.Next()
+		if err != nil {
+			t.Fatal("r.Next:", err)
+		}
+		if e == nil {
+			break
+		}
+		switch e.Tag {
+		case TagBaseType, TagTypedef, TagPointerType, TagStructType:
+			offsets = append(offsets, e.Offset)
+		}
+	}
+
+	// Parse each type with a fresh type cache.
+	for _, offset := range offsets {
+		d := elfData(t, "testdata/cycle.elf")
+		_, err := d.Type(offset)
+		if err != nil {
+			t.Fatalf("d.Type(0x%x): %s", offset, err)
+		}
+	}
+}
+
+var unsupportedTypeTests = []string{
+	// varname:typename:string:size
+	"culprit::(unsupported type ReferenceType):8",
+	"pdm::(unsupported type PtrToMemberType):-1",
+}
+
+func TestUnsupportedTypes(t *testing.T) {
+	// Issue 29601:
+	// When reading DWARF from C++ load modules, we can encounter
+	// oddball type DIEs. These will be returned as "UnsupportedType"
+	// objects; check to make sure this works properly.
+	d := elfData(t, "testdata/cppunsuptypes.elf")
+	r := d.Reader()
+	seen := make(map[string]bool)
+	for {
+		e, err := r.Next()
+		if err != nil {
+			t.Fatal("r.Next:", err)
+		}
+		if e == nil {
+			break
+		}
+		if e.Tag == TagVariable {
+			vname, _ := e.Val(AttrName).(string)
+			tAttr := e.Val(AttrType)
+			typOff, ok := tAttr.(Offset)
+			if !ok {
+				t.Errorf("variable at offset %v has no type", e.Offset)
+				continue
+			}
+			typ, err := d.Type(typOff)
+			if err != nil {
+				t.Errorf("err in type decode: %v\n", err)
+				continue
+			}
+			unsup, isok := typ.(*UnsupportedType)
+			if !isok {
+				continue
+			}
+			tag := vname + ":" + unsup.Name + ":" + unsup.String() +
+				":" + strconv.FormatInt(unsup.Size(), 10)
+			seen[tag] = true
+		}
+	}
+	dumpseen := false
+	for _, v := range unsupportedTypeTests {
+		if !seen[v] {
+			t.Errorf("missing %s", v)
+			dumpseen = true
+		}
+	}
+	if dumpseen {
+		for k := range seen {
+			fmt.Printf("seen: %s\n", k)
+		}
+	}
+}
diff --git a/src/debug/dwarf/typeunit.go b/src/debug/dwarf/typeunit.go
new file mode 100644
index 0000000..27aa078
--- /dev/null
+++ b/src/debug/dwarf/typeunit.go
@@ -0,0 +1,160 @@
+// Copyright 2012 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 dwarf
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// Parse the type units stored in a DWARF4 .debug_types section. Each
+// type unit defines a single primary type and an 8-byte signature.
+// Other sections may then use formRefSig8 to refer to the type.
+
+// The typeUnit format is a single type with a signature. It holds
+// the same data as a compilation unit.
+type typeUnit struct {
+	unit
+	toff  Offset // Offset to signature type within data.
+	name  string // Name of .debug_type section.
+	cache Type   // Cache the type, nil to start.
+}
+
+// Parse a .debug_types section.
+func (d *Data) parseTypes(name string, types []byte) error {
+	b := makeBuf(d, unknownFormat{}, name, 0, types)
+	for len(b.data) > 0 {
+		base := b.off
+		n, dwarf64 := b.unitLength()
+		if n != Offset(uint32(n)) {
+			b.error("type unit length overflow")
+			return b.err
+		}
+		hdroff := b.off
+		vers := int(b.uint16())
+		if vers != 4 {
+			b.error("unsupported DWARF version " + strconv.Itoa(vers))
+			return b.err
+		}
+		var ao uint64
+		if !dwarf64 {
+			ao = uint64(b.uint32())
+		} else {
+			ao = b.uint64()
+		}
+		atable, err := d.parseAbbrev(ao, vers)
+		if err != nil {
+			return err
+		}
+		asize := b.uint8()
+		sig := b.uint64()
+
+		var toff uint32
+		if !dwarf64 {
+			toff = b.uint32()
+		} else {
+			to64 := b.uint64()
+			if to64 != uint64(uint32(to64)) {
+				b.error("type unit type offset overflow")
+				return b.err
+			}
+			toff = uint32(to64)
+		}
+
+		boff := b.off
+		d.typeSigs[sig] = &typeUnit{
+			unit: unit{
+				base:   base,
+				off:    boff,
+				data:   b.bytes(int(n - (b.off - hdroff))),
+				atable: atable,
+				asize:  int(asize),
+				vers:   vers,
+				is64:   dwarf64,
+			},
+			toff: Offset(toff),
+			name: name,
+		}
+		if b.err != nil {
+			return b.err
+		}
+	}
+	return nil
+}
+
+// Return the type for a type signature.
+func (d *Data) sigToType(sig uint64) (Type, error) {
+	tu := d.typeSigs[sig]
+	if tu == nil {
+		return nil, fmt.Errorf("no type unit with signature %v", sig)
+	}
+	if tu.cache != nil {
+		return tu.cache, nil
+	}
+
+	b := makeBuf(d, tu, tu.name, tu.off, tu.data)
+	r := &typeUnitReader{d: d, tu: tu, b: b}
+	t, err := d.readType(tu.name, r, tu.toff, make(map[Offset]Type), nil)
+	if err != nil {
+		return nil, err
+	}
+
+	tu.cache = t
+	return t, nil
+}
+
+// typeUnitReader is a typeReader for a tagTypeUnit.
+type typeUnitReader struct {
+	d   *Data
+	tu  *typeUnit
+	b   buf
+	err error
+}
+
+// Seek to a new position in the type unit.
+func (tur *typeUnitReader) Seek(off Offset) {
+	tur.err = nil
+	doff := off - tur.tu.off
+	if doff < 0 || doff >= Offset(len(tur.tu.data)) {
+		tur.err = fmt.Errorf("%s: offset %d out of range; max %d", tur.tu.name, doff, len(tur.tu.data))
+		return
+	}
+	tur.b = makeBuf(tur.d, tur.tu, tur.tu.name, off, tur.tu.data[doff:])
+}
+
+// AddressSize returns the size in bytes of addresses in the current type unit.
+func (tur *typeUnitReader) AddressSize() int {
+	return tur.tu.unit.asize
+}
+
+// Next reads the next Entry from the type unit.
+func (tur *typeUnitReader) Next() (*Entry, error) {
+	if tur.err != nil {
+		return nil, tur.err
+	}
+	if len(tur.tu.data) == 0 {
+		return nil, nil
+	}
+	e := tur.b.entry(nil, tur.tu.atable, tur.tu.base, tur.tu.vers)
+	if tur.b.err != nil {
+		tur.err = tur.b.err
+		return nil, tur.err
+	}
+	return e, nil
+}
+
+// clone returns a new reader for the type unit.
+func (tur *typeUnitReader) clone() typeReader {
+	return &typeUnitReader{
+		d:  tur.d,
+		tu: tur.tu,
+		b:  makeBuf(tur.d, tur.tu, tur.tu.name, tur.tu.off, tur.tu.data),
+	}
+}
+
+// offset returns the current offset.
+func (tur *typeUnitReader) offset() Offset {
+	return tur.b.off
+}
diff --git a/src/debug/dwarf/unit.go b/src/debug/dwarf/unit.go
new file mode 100644
index 0000000..29a744f
--- /dev/null
+++ b/src/debug/dwarf/unit.go
@@ -0,0 +1,130 @@
+// 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.
+
+package dwarf
+
+import (
+	"sort"
+	"strconv"
+)
+
+// DWARF debug info is split into a sequence of compilation units.
+// Each unit has its own abbreviation table and address size.
+
+type unit struct {
+	base   Offset // byte offset of header within the aggregate info
+	off    Offset // byte offset of data within the aggregate info
+	data   []byte
+	atable abbrevTable
+	asize  int
+	vers   int
+	utype  uint8 // DWARF 5 unit type
+	is64   bool  // True for 64-bit DWARF format
+}
+
+// Implement the dataFormat interface.
+
+func (u *unit) version() int {
+	return u.vers
+}
+
+func (u *unit) dwarf64() (bool, bool) {
+	return u.is64, true
+}
+
+func (u *unit) addrsize() int {
+	return u.asize
+}
+
+func (d *Data) parseUnits() ([]unit, error) {
+	// Count units.
+	nunit := 0
+	b := makeBuf(d, unknownFormat{}, "info", 0, d.info)
+	for len(b.data) > 0 {
+		len, _ := b.unitLength()
+		if len != Offset(uint32(len)) {
+			b.error("unit length overflow")
+			break
+		}
+		b.skip(int(len))
+		nunit++
+	}
+	if b.err != nil {
+		return nil, b.err
+	}
+
+	// Again, this time writing them down.
+	b = makeBuf(d, unknownFormat{}, "info", 0, d.info)
+	units := make([]unit, nunit)
+	for i := range units {
+		u := &units[i]
+		u.base = b.off
+		var n Offset
+		n, u.is64 = b.unitLength()
+		dataOff := b.off
+		vers := b.uint16()
+		if vers < 2 || vers > 5 {
+			b.error("unsupported DWARF version " + strconv.Itoa(int(vers)))
+			break
+		}
+		u.vers = int(vers)
+		if vers >= 5 {
+			u.utype = b.uint8()
+			u.asize = int(b.uint8())
+		}
+		var abbrevOff uint64
+		if u.is64 {
+			abbrevOff = b.uint64()
+		} else {
+			abbrevOff = uint64(b.uint32())
+		}
+		atable, err := d.parseAbbrev(abbrevOff, u.vers)
+		if err != nil {
+			if b.err == nil {
+				b.err = err
+			}
+			break
+		}
+		u.atable = atable
+		if vers < 5 {
+			u.asize = int(b.uint8())
+		}
+
+		switch u.utype {
+		case utSkeleton, utSplitCompile:
+			b.uint64() // unit ID
+		case utType, utSplitType:
+			b.uint64()  // type signature
+			if u.is64 { // type offset
+				b.uint64()
+			} else {
+				b.uint32()
+			}
+		}
+
+		u.off = b.off
+		u.data = b.bytes(int(n - (b.off - dataOff)))
+	}
+	if b.err != nil {
+		return nil, b.err
+	}
+	return units, nil
+}
+
+// offsetToUnit returns the index of the unit containing offset off.
+// It returns -1 if no unit contains this offset.
+func (d *Data) offsetToUnit(off Offset) int {
+	// Find the unit after off
+	next := sort.Search(len(d.unit), func(i int) bool {
+		return d.unit[i].off > off
+	})
+	if next == 0 {
+		return -1
+	}
+	u := &d.unit[next-1]
+	if u.off <= off && off < u.off+Offset(len(u.data)) {
+		return next - 1
+	}
+	return -1
+}