parse and present DWARF type information

R=r
DELTA=940  (929 added, 1 deleted, 10 changed)
OCL=34679
CL=34686

src/pkg/Makefile

@@ -82,7 +82,6 @@ DIRS=\
 	utf8\
 
 NOTEST=\
-	debug/dwarf\
 	debug/proc\
 	go/ast\
 	go/doc\

src/pkg/debug/dwarf/Makefile

@@ -10,6 +10,7 @@ GOFILES=\
 	const.go\
 	entry.go\
 	open.go\
+	type.go\
 	unit.go\
 
 include $(GOROOT)/src/Make.pkg

src/pkg/debug/dwarf/buf.go

@@ -152,6 +152,6 @@ type DecodeError struct {
 }
 
 func (e DecodeError) String() string {
-	return "decoding dwarf section " + e.Name + " at offset " + strconv.Itoa64(int64(e.Offset)) + ": " + e.Error;
+	return "decoding dwarf section " + e.Name + " at offset 0x" + strconv.Itob64(int64(e.Offset), 16) + ": " + e.Error;
 }
 

src/pkg/debug/dwarf/const.go

@@ -350,3 +350,84 @@ func (t Tag) GoString() string {
 	return "dwarf.Tag(" + strconv.Itoa64(int64(t)) + ")";
 }
 
+// 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;
+	/* next four new in Dwarf v3 */
+	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 */
+	/* 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;
+	encImaginaryFloat = 0x09;
+)

src/pkg/debug/dwarf/entry.go

@@ -107,6 +107,22 @@ type Field struct {
 	Val interface{};
 }
 
+// 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{} {
+	for _, f := range e.Field {
+		if f.Attr == a {
+			return f.Val;
+		}
+	}
+	return nil;
+}
+
 // An Offset represents the location of an Entry within the DWARF info.
 // (See Reader.Seek.)
 type Offset uint32
@@ -157,17 +173,17 @@ func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
 
 		// constant
 		case formData1:
-			val = uint64(b.uint8());
+			val = int64(b.uint8());
 		case formData2:
-			val = uint64(b.uint16());
+			val = int64(b.uint16());
 		case formData4:
-			val = uint64(b.uint32());
+			val = int64(b.uint32());
 		case formData8:
-			val = uint64(b.uint64());
+			val = int64(b.uint64());
 		case formSdata:
 			val = int64(b.int());
 		case formUdata:
-			val = uint64(b.uint());
+			val = int64(b.uint());
 
 		// flag
 		case formFlag:
@@ -212,11 +228,17 @@ func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
 }
 
 // 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 os.Error;
 	unit int;
+	lastChildren bool;	// .Children of last entry returned by Next
+	lastSibling Offset;	// .Val(AttrSibling) of last entry returned by Next
 }
 
 // Reader returns a new Reader for Data.
@@ -232,6 +254,7 @@ func (d *Data) Reader() *Reader {
 func (r *Reader) Seek(off Offset) {
 	d := r.d;
 	r.err = nil;
+	r.lastChildren = false;
 	if off == 0 {
 		if len(d.unit) == 0 {
 			return;
@@ -258,7 +281,7 @@ func (r *Reader) Seek(off Offset) {
 
 // maybeNextUnit advances to the next unit if this one is finished.
 func (r *Reader) maybeNextUnit() {
-	for len(r.b.data) == 0 && r.unit < len(r.d.unit) {
+	for len(r.b.data) == 0 && r.unit+1 < len(r.d.unit) {
 		r.unit++;
 		u := &r.d.unit[r.unit];
 		r.b = makeBuf(r.d, "info", u.off, u.data, u.addrsize);
@@ -279,6 +302,46 @@ func (r *Reader) Next() (*Entry, os.Error) {
 	}
 	u := &r.d.unit[r.unit];
 	e := r.b.entry(u.atable, u.base);
-	r.err = r.b.err;
-	return e, r.err;
+	if r.b.err != nil {
+		r.err = r.b.err;
+		return nil, r.err;
+	}
+	if e != nil {
+		r.lastChildren = e.Children;
+		if r.lastChildren {
+			r.lastSibling, _ = e.Val(AttrSibling).(Offset);
+		}
+	} 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;
+	}
+
+	for {
+		e, err := r.Next();
+		if err != nil || e == nil || e.Tag == 0 {
+			break;
+		}
+		if e.Children {
+			r.SkipChildren();
+		}
+	}
+}
+

src/pkg/debug/dwarf/open.go

@@ -30,6 +30,7 @@ type Data struct {
 	abbrevCache map[uint32] abbrevTable;
 	addrsize int;
 	order binary.ByteOrder;
+	typeCache map[Offset] Type;
 	unit []unit;
 }
 
@@ -51,6 +52,7 @@ func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Dat
 		ranges: ranges,
 		str: str,
 		abbrevCache: make(map[uint32]abbrevTable),
+		typeCache: make(map[uint32]Type),
 	};
 
 	// Sniff .debug_info to figure out byte order.

src/pkg/debug/dwarf/testdata/typedef.c

+// 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.
+
+/*
+gcc -gdwarf-2 -c typedef.c && gcc -gdwarf-2 -o typedef.elf typedef.o
+*/
+
+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_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;
+	long long array[40];
+} t_my_struct;
+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_union *a12a;
+t_my_enum *a13;
+t_my_list *a14;
+t_my_tree *a15;
+
+int main()
+{
+	return 0;
+}

src/pkg/debug/dwarf/type.go

+// 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 (
+	"os";
+	"strconv";
+)
+
+// 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;
+}
+
+// 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;
+}
+
+// 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();
+}
+
+// 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;
+}
+
+func (t *ArrayType) String() string {
+	return "[" + strconv.Itoa64(t.Count) + "]" + t.Type.String();
+}
+
+// A VoidType represents the C void type.
+// It is only used as the subtype for a pointer:
+// a FuncType that returns no value has a nil ReturnType.
+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;
+	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.Itoa64(f.ByteOffset);
+		if f.BitSize > 0 {
+			s += " : " + strconv.Itoa64(f.BitSize);
+			s += "@" + strconv.Itoa64(f.BitOffset);
+		}
+	}
+	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.Itoa64(v.Val);
+	}
+	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;
+}
+
+// A Type conventionally represents a pointer to any of the
+// specific Type structures (CharType, StructType, etc.).
+type Type interface {
+	Common() *CommonType;
+	String() string;
+}
+
+func (d *Data) Type(off Offset) (Type, os.Error) {
+	if t, ok := d.typeCache[off]; ok {
+		return t, nil;
+	}
+
+	r := d.Reader();
+	r.Seek(off);
+	e, err := r.Next();
+	if err != nil {
+		return nil, err;
+	}
+	if e == nil || e.Offset != off {
+		return nil, DecodeError{"info", off, "no type at offset"};
+	}
+
+	// Parse type from Entry.
+	// Must always set d.typeCache[off] before calling
+	// d.Type recursively, to handle circular types correctly.
+	var typ Type;
+
+	// Get next child; set err if error happens.
+	next := func() *Entry {
+		if !e.Children {
+			return nil;
+		}
+		kid, err1 := r.Next();
+		if err1 != nil {
+			err = err1;
+			return nil;
+		}
+		if kid == nil {
+			err = DecodeError{"info", r.b.off, "unexpected end of DWARF entries"};
+			return nil;
+		}
+		if kid.Tag == 0 {
+			return nil;
+		}
+		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 {
+		toff, ok := e.Val(AttrType).(Offset);
+		if !ok {
+			err = DecodeError{"info", e.Offset, "missing type attribute"};
+			return nil;
+		}
+		var t Type;
+		if t, err = d.Type(toff); err != nil {
+			return nil;
+		}
+		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;
+		d.typeCache[off] = t;
+		if t.Type = typeOf(e); err != nil {
+			goto Error;
+		}
+		t.StrideBitSize, _ = e.Val(AttrStrideSize).(int64);
+
+		// Accumulate dimensions,
+		ndim := 0;
+		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:
+				max, ok := kid.Val(AttrUpperBound).(int64);
+				if !ok {
+					err = DecodeError{"info", kid.Offset, "missing upper bound"};
+					goto Error;
+				}
+				if ndim == 0 {
+					t.Count = max+1;
+				} else {
+					// Multidimensional array.
+					// Create new array type underneath this one.
+					t.Type = &ArrayType{Type: t.Type, Count: max+1};
+				}
+				ndim++;
+			case TagEnumerationType:
+				err = DecodeError{"info", kid.Offset, "cannot handle enumeration type as array bound"};
+				goto Error;
+			}
+		}
+		if ndim == 0 {
+			err = DecodeError{"info", e.Offset, "missing dimension for array"};
+			goto Error;
+		}
+
+	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{"info", e.Offset, "missing encoding attribute for " + name};
+			goto Error;
+		}
+		switch enc {
+		default:
+			err = DecodeError{"info", e.Offset, "unrecognized encoding attribute value"};
+			goto Error;
+
+		case encAddress:
+			typ = new(AddrType);
+		case encBoolean:
+			typ = new(BoolType);
+		case encComplexFloat:
+			typ = new(ComplexType);
+		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);
+		}
+		d.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;
+		d.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);
+		for kid := next(); kid != nil; kid = next() {
+			if kid.Tag == TagMember {
+				f := new(StructField);
+				if f.Type = typeOf(kid); err != nil {
+					goto Error;
+				}
+				if loc, ok := kid.Val(AttrDataMemberLoc).([]byte); ok {
+					b := makeBuf(d, "location", 0, loc, d.addrsize);
+					if b.uint8() != opPlusUconst {
+						err = DecodeError{"info", kid.Offset, "unexpected opcode"};
+						goto Error;
+					}
+					f.ByteOffset = int64(b.uint());
+					if b.err != nil {
+						err = b.err;
+						goto Error;
+					}
+				}
+				f.Name, _ = kid.Val(AttrName).(string);
+				f.ByteSize, _ = kid.Val(AttrByteSize).(int64);
+				f.BitOffset, _ = kid.Val(AttrBitOffset).(int64);
+				f.BitSize, _ = kid.Val(AttrBitSize).(int64);
+				n := len(t.Field);
+				if n >= cap(t.Field) {
+					fld := make([]*StructField, n, n*2);
+					for i, f := range t.Field {
+						fld[i] = f;
+					}
+					t.Field = fld;
+				}
+				t.Field = t.Field[0:n+1];
+				t.Field[n] = f;
+			}
+		}
+
+	case TagConstType, TagVolatileType, TagRestrictType:
+		// Type modifier (DWARF v2 §5.2)
+		// Attributes:
+		//	AttrType: subtype
+		t := new(QualType);
+		typ = t;
+		d.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;
+		d.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);
+					for i, f := range t.Val {
+						val[i] = f;
+					}
+					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;
+		d.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 prototye [ignored]
+		// Children:
+		//	TagFormalParameter: typed parameter
+		//		AttrType: type of parameter
+		//	TagUnspecifiedParameter: final ...
+		t := new(FuncType);
+		typ = t;
+		d.typeCache[off] = t;
+		if e.Val(AttrType) != nil {
+			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{};
+			}
+			n := len(t.ParamType);
+			if n >= cap(t.ParamType) {
+				param := make([]Type, n, n*2);
+				for i, t := range t.ParamType {
+					param[i] = t;
+				}
+				t.ParamType = param;
+			}
+			t.ParamType = t.ParamType[0:n+1];
+			t.ParamType[n] = tkid;
+		}
+
+	case TagTypedef:
+		// Typedef (DWARF v2 §5.3)
+		// Attributes:
+		//	AttrName: name [required]
+		//	AttrType: type definition [required]
+		t := new(TypedefType);
+		typ = t;
+		d.typeCache[off] = t;
+		t.Name, _ = e.Val(AttrName).(string);
+		t.Type = typeOf(e);
+	}
+
+	if err != nil {
+		goto Error;
+	}
+
+	typ.Common().ByteSize, _ = e.Val(AttrByteSize).(int64);
+
+	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.
+	d.typeCache[off] = nil, false;
+	return nil, err;
+}

src/pkg/debug/dwarf/type_test.go

+// 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 (
+	"debug/elf";
+	"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_func_ptr_int_of_char_schar_uchar": "func(char, signed char, unsigned char) *int",
+	"t_func_void_of_char": "func(char)",
+	"t_func_void_of_void": "func()",
+	"t_func_void_of_ptr_char_dots": "func(*char, ...)",
+	"t_my_struct": "struct my_struct {vi volatile int@0; x char@4 : 1@7; y int@4 : 4@27; array [40]long long int@8}",
+	"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}"
+};
+
+func elfData(t *testing.T, name string) *Data {
+	f, err := elf.Open(name);
+	if err != nil {
+		t.Fatal(err);
+	}
+	
+	dat := func(name string) []byte {
+		s := f.Section(".debug_" + name);
+		if s == nil {
+			return nil
+		}
+		b, err := s.Data();
+		if err != nil {
+			t.Fatal(".debug_"+name+":", err);
+		}
+		return b;
+	};
+	
+	d, err := New(dat("abbrev"), nil, nil, dat("info"), nil, nil, nil, dat("str"));
+	if err != nil {
+		t.Fatal("New:", err);
+	}
+	
+	return d;
+}
+
+
+func TestTypedefs(t *testing.T) {
+	d := elfData(t, "testdata/typedef.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 == 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 _, ok := seen[t1.Name]; ok {
+					t.Errorf("multiple definitions for %s", t1.Name);
+				}
+				seen[t1.Name] = true;
+				if typstr != 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 _, ok := seen[k]; !ok {
+			t.Errorf("missing %s", k);
+		}
+	}
+}