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// 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 gosym implements access to the Go symbol
// and line number tables embedded in Go binaries generated
// by the gc compilers.
package gosym
 
// The table format is a variant of the format used in Plan 9's a.out
// format, documented at http://plan9.bell-labs.com/magic/man2html/6/a.out.
// The best reference for the differences between the Plan 9 format
// and the Go format is the runtime source, specifically ../../runtime/symtab.c.
 
import (
        "encoding/binary"
        "fmt"
        "strconv"
        "strings"
)
 
/*
 * Symbols
 */
 
// A Sym represents a single symbol table entry.
type Sym struct {
        Value  uint64
        Type   byte
        Name   string
        GoType uint64
        // If this symbol if a function symbol, the corresponding Func
        Func *Func
}
 
// Static returns whether this symbol is static (not visible outside its file).
func (s *Sym) Static() bool { return s.Type >= 'a' }
 
// PackageName returns the package part of the symbol name,
// or the empty string if there is none.
func (s *Sym) PackageName() string {
        if i := strings.Index(s.Name, "."); i != -1 {
                return s.Name[0:i]
        }
        return ""
}
 
// ReceiverName returns the receiver type name of this symbol,
// or the empty string if there is none.
func (s *Sym) ReceiverName() string {
        l := strings.Index(s.Name, ".")
        r := strings.LastIndex(s.Name, ".")
        if l == -1 || r == -1 || l == r {
                return ""
        }
        return s.Name[l+1 : r]
}
 
// BaseName returns the symbol name without the package or receiver name.
func (s *Sym) BaseName() string {
        if i := strings.LastIndex(s.Name, "."); i != -1 {
                return s.Name[i+1:]
        }
        return s.Name
}
 
// A Func collects information about a single function.
type Func struct {
        Entry uint64
        *Sym
        End       uint64
        Params    []*Sym
        Locals    []*Sym
        FrameSize int
        LineTable *LineTable
        Obj       *Obj
}
 
// An Obj represents a single object file.
type Obj struct {
        Funcs []Func
        Paths []Sym
}
 
/*
 * Symbol tables
 */
 
// Table represents a Go symbol table.  It stores all of the
// symbols decoded from the program and provides methods to translate
// between symbols, names, and addresses.
type Table struct {
        Syms  []Sym
        Funcs []Func
        Files map[string]*Obj
        Objs  []Obj
        //      textEnd uint64;
}
 
type sym struct {
        value  uint32
        gotype uint32
        typ    byte
        name   []byte
}
 
func walksymtab(data []byte, fn func(sym) error) error {
        var s sym
        p := data
        for len(p) >= 6 {
                s.value = binary.BigEndian.Uint32(p[0:4])
                typ := p[4]
                if typ&0x80 == 0 {
                        return &DecodingError{len(data) - len(p) + 4, "bad symbol type", typ}
                }
                typ &^= 0x80
                s.typ = typ
                p = p[5:]
                var i int
                var nnul int
                for i = 0; i < len(p); i++ {
                        if p[i] == 0 {
                                nnul = 1
                                break
                        }
                }
                switch typ {
                case 'z', 'Z':
                        p = p[i+nnul:]
                        for i = 0; i+2 <= len(p); i += 2 {
                                if p[i] == 0 && p[i+1] == 0 {
                                        nnul = 2
                                        break
                                }
                        }
                }
                if i+nnul+4 > len(p) {
                        return &DecodingError{len(data), "unexpected EOF", nil}
                }
                s.name = p[0:i]
                i += nnul
                s.gotype = binary.BigEndian.Uint32(p[i : i+4])
                p = p[i+4:]
                fn(s)
        }
        return nil
}
 
// NewTable decodes the Go symbol table in data,
// returning an in-memory representation.
func NewTable(symtab []byte, pcln *LineTable) (*Table, error) {
        var n int
        err := walksymtab(symtab, func(s sym) error {
                n++
                return nil
        })
        if err != nil {
                return nil, err
        }
 
        var t Table
        fname := make(map[uint16]string)
        t.Syms = make([]Sym, 0, n)
        nf := 0
        nz := 0
        lasttyp := uint8(0)
        err = walksymtab(symtab, func(s sym) error {
                n := len(t.Syms)
                t.Syms = t.Syms[0 : n+1]
                ts := &t.Syms[n]
                ts.Type = s.typ
                ts.Value = uint64(s.value)
                ts.GoType = uint64(s.gotype)
                switch s.typ {
                default:
                        // rewrite name to use . instead of · (c2 b7)
                        w := 0
                        b := s.name
                        for i := 0; i < len(b); i++ {
                                if b[i] == 0xc2 && i+1 < len(b) && b[i+1] == 0xb7 {
                                        i++
                                        b[i] = '.'
                                }
                                b[w] = b[i]
                                w++
                        }
                        ts.Name = string(s.name[0:w])
                case 'z', 'Z':
                        if lasttyp != 'z' && lasttyp != 'Z' {
                                nz++
                        }
                        for i := 0; i < len(s.name); i += 2 {
                                eltIdx := binary.BigEndian.Uint16(s.name[i : i+2])
                                elt, ok := fname[eltIdx]
                                if !ok {
                                        return &DecodingError{-1, "bad filename code", eltIdx}
                                }
                                if n := len(ts.Name); n > 0 && ts.Name[n-1] != '/' {
                                        ts.Name += "/"
                                }
                                ts.Name += elt
                        }
                }
                switch s.typ {
                case 'T', 't', 'L', 'l':
                        nf++
                case 'f':
                        fname[uint16(s.value)] = ts.Name
                }
                lasttyp = s.typ
                return nil
        })
        if err != nil {
                return nil, err
        }
 
        t.Funcs = make([]Func, 0, nf)
        t.Objs = make([]Obj, 0, nz)
        t.Files = make(map[string]*Obj)
 
        // Count text symbols and attach frame sizes, parameters, and
        // locals to them.  Also, find object file boundaries.
        var obj *Obj
        lastf := 0
        for i := 0; i < len(t.Syms); i++ {
                sym := &t.Syms[i]
                switch sym.Type {
                case 'Z', 'z': // path symbol
                        // Finish the current object
                        if obj != nil {
                                obj.Funcs = t.Funcs[lastf:]
                        }
                        lastf = len(t.Funcs)
 
                        // Start new object
                        n := len(t.Objs)
                        t.Objs = t.Objs[0 : n+1]
                        obj = &t.Objs[n]
 
                        // Count & copy path symbols
                        var end int
                        for end = i + 1; end < len(t.Syms); end++ {
                                if c := t.Syms[end].Type; c != 'Z' && c != 'z' {
                                        break
                                }
                        }
                        obj.Paths = t.Syms[i:end]
                        i = end - 1 // loop will i++
 
                        // Record file names
                        depth := 0
                        for j := range obj.Paths {
                                s := &obj.Paths[j]
                                if s.Name == "" {
                                        depth--
                                } else {
                                        if depth == 0 {
                                                t.Files[s.Name] = obj
                                        }
                                        depth++
                                }
                        }
 
                case 'T', 't', 'L', 'l': // text symbol
                        if n := len(t.Funcs); n > 0 {
                                t.Funcs[n-1].End = sym.Value
                        }
                        if sym.Name == "etext" {
                                continue
                        }
 
                        // Count parameter and local (auto) syms
                        var np, na int
                        var end int
                countloop:
                        for end = i + 1; end < len(t.Syms); end++ {
                                switch t.Syms[end].Type {
                                case 'T', 't', 'L', 'l', 'Z', 'z':
                                        break countloop
                                case 'p':
                                        np++
                                case 'a':
                                        na++
                                }
                        }
 
                        // Fill in the function symbol
                        n := len(t.Funcs)
                        t.Funcs = t.Funcs[0 : n+1]
                        fn := &t.Funcs[n]
                        sym.Func = fn
                        fn.Params = make([]*Sym, 0, np)
                        fn.Locals = make([]*Sym, 0, na)
                        fn.Sym = sym
                        fn.Entry = sym.Value
                        fn.Obj = obj
                        if pcln != nil {
                                fn.LineTable = pcln.slice(fn.Entry)
                                pcln = fn.LineTable
                        }
                        for j := i; j < end; j++ {
                                s := &t.Syms[j]
                                switch s.Type {
                                case 'm':
                                        fn.FrameSize = int(s.Value)
                                case 'p':
                                        n := len(fn.Params)
                                        fn.Params = fn.Params[0 : n+1]
                                        fn.Params[n] = s
                                case 'a':
                                        n := len(fn.Locals)
                                        fn.Locals = fn.Locals[0 : n+1]
                                        fn.Locals[n] = s
                                }
                        }
                        i = end - 1 // loop will i++
                }
        }
        if obj != nil {
                obj.Funcs = t.Funcs[lastf:]
        }
        return &t, nil
}
 
// PCToFunc returns the function containing the program counter pc,
// or nil if there is no such function.
func (t *Table) PCToFunc(pc uint64) *Func {
        funcs := t.Funcs
        for len(funcs) > 0 {
                m := len(funcs) / 2
                fn := &funcs[m]
                switch {
                case pc < fn.Entry:
                        funcs = funcs[0:m]
                case fn.Entry <= pc && pc < fn.End:
                        return fn
                default:
                        funcs = funcs[m+1:]
                }
        }
        return nil
}
 
// PCToLine looks up line number information for a program counter.
// If there is no information, it returns fn == nil.
func (t *Table) PCToLine(pc uint64) (file string, line int, fn *Func) {
        if fn = t.PCToFunc(pc); fn == nil {
                return
        }
        file, line = fn.Obj.lineFromAline(fn.LineTable.PCToLine(pc))
        return
}
 
// LineToPC looks up the first program counter on the given line in
// the named file.  Returns UnknownPathError or UnknownLineError if
// there is an error looking up this line.
func (t *Table) LineToPC(file string, line int) (pc uint64, fn *Func, err error) {
        obj, ok := t.Files[file]
        if !ok {
                return 0, nil, UnknownFileError(file)
        }
        abs, err := obj.alineFromLine(file, line)
        if err != nil {
                return
        }
        for i := range obj.Funcs {
                f := &obj.Funcs[i]
                pc := f.LineTable.LineToPC(abs, f.End)
                if pc != 0 {
                        return pc, f, nil
                }
        }
        return 0, nil, &UnknownLineError{file, line}
}
 
// LookupSym returns the text, data, or bss symbol with the given name,
// or nil if no such symbol is found.
func (t *Table) LookupSym(name string) *Sym {
        // TODO(austin) Maybe make a map
        for i := range t.Syms {
                s := &t.Syms[i]
                switch s.Type {
                case 'T', 't', 'L', 'l', 'D', 'd', 'B', 'b':
                        if s.Name == name {
                                return s
                        }
                }
        }
        return nil
}
 
// LookupFunc returns the text, data, or bss symbol with the given name,
// or nil if no such symbol is found.
func (t *Table) LookupFunc(name string) *Func {
        for i := range t.Funcs {
                f := &t.Funcs[i]
                if f.Sym.Name == name {
                        return f
                }
        }
        return nil
}
 
// SymByAddr returns the text, data, or bss symbol starting at the given address.
// TODO(rsc): Allow lookup by any address within the symbol.
func (t *Table) SymByAddr(addr uint64) *Sym {
        // TODO(austin) Maybe make a map
        for i := range t.Syms {
                s := &t.Syms[i]
                switch s.Type {
                case 'T', 't', 'L', 'l', 'D', 'd', 'B', 'b':
                        if s.Value == addr {
                                return s
                        }
                }
        }
        return nil
}
 
/*
 * Object files
 */
 
func (o *Obj) lineFromAline(aline int) (string, int) {
        type stackEnt struct {
                path   string
                start  int
                offset int
                prev   *stackEnt
        }
 
        noPath := &stackEnt{"", 0, 0, nil}
        tos := noPath
 
        // TODO(austin) I have no idea how 'Z' symbols work, except
        // that they pop the stack.
pathloop:
        for _, s := range o.Paths {
                val := int(s.Value)
                switch {
                case val > aline:
                        break pathloop
 
                case val == 1:
                        // Start a new stack
                        tos = &stackEnt{s.Name, val, 0, noPath}
 
                case s.Name == "":
                        // Pop
                        if tos == noPath {
                                return "", 0
                        }
                        tos.prev.offset += val - tos.start
                        tos = tos.prev
 
                default:
                        // Push
                        tos = &stackEnt{s.Name, val, 0, tos}
                }
        }
 
        if tos == noPath {
                return "", 0
        }
        return tos.path, aline - tos.start - tos.offset + 1
}
 
func (o *Obj) alineFromLine(path string, line int) (int, error) {
        if line < 1 {
                return 0, &UnknownLineError{path, line}
        }
 
        for i, s := range o.Paths {
                // Find this path
                if s.Name != path {
                        continue
                }
 
                // Find this line at this stack level
                depth := 0
                var incstart int
                line += int(s.Value)
        pathloop:
                for _, s := range o.Paths[i:] {
                        val := int(s.Value)
                        switch {
                        case depth == 1 && val >= line:
                                return line - 1, nil
 
                        case s.Name == "":
                                depth--
                                if depth == 0 {
                                        break pathloop
                                } else if depth == 1 {
                                        line += val - incstart
                                }
 
                        default:
                                if depth == 1 {
                                        incstart = val
                                }
                                depth++
                        }
                }
                return 0, &UnknownLineError{path, line}
        }
        return 0, UnknownFileError(path)
}
 
/*
 * Errors
 */
 
// UnknownFileError represents a failure to find the specific file in
// the symbol table.
type UnknownFileError string
 
func (e UnknownFileError) Error() string { return "unknown file: " + string(e) }
 
// UnknownLineError represents a failure to map a line to a program
// counter, either because the line is beyond the bounds of the file
// or because there is no code on the given line.
type UnknownLineError struct {
        File string
        Line int
}
 
func (e *UnknownLineError) Error() string {
        return "no code at " + e.File + ":" + strconv.Itoa(e.Line)
}
 
// DecodingError represents an error during the decoding of
// the symbol table.
type DecodingError struct {
        off int
        msg string
        val interface{}
}
 
func (e *DecodingError) Error() string {
        msg := e.msg
        if e.val != nil {
                msg += fmt.Sprintf(" '%v'", e.val)
        }
        msg += fmt.Sprintf(" at byte %#x", e.off)
        return msg
}

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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [debug/] [gosym/] [symtab.go] - Blame information for rev 749

Line No.	Rev	Author	Line
1	747	jeremybenn	`// Copyright 2009 The Go Authors. All rights reserved.`
2			`// Use of this source code is governed by a BSD-style`
3			`// license that can be found in the LICENSE file.`
4
5			`// Package gosym implements access to the Go symbol`
6			`// and line number tables embedded in Go binaries generated`
7			`// by the gc compilers.`
8			`package gosym`
9
10			`// The table format is a variant of the format used in Plan 9's a.out`
11			`// format, documented at http://plan9.bell-labs.com/magic/man2html/6/a.out.`
12			`// The best reference for the differences between the Plan 9 format`
13			`// and the Go format is the runtime source, specifically ../../runtime/symtab.c.`
14
15			`import (`
16			`"encoding/binary"`
17			`"fmt"`
18			`"strconv"`
19			`"strings"`
20			`)`
21
22			`/*`
23			`* Symbols`
24			`*/`
25
26			`// A Sym represents a single symbol table entry.`
27			`type Sym struct {`
28			`Value uint64`
29			`Type byte`
30			`Name string`
31			`GoType uint64`
32			`// If this symbol if a function symbol, the corresponding Func`
33			`Func *Func`
34			`}`
35
36			`// Static returns whether this symbol is static (not visible outside its file).`
37			`func (s *Sym) Static() bool { return s.Type >= 'a' }`
38
39			`// PackageName returns the package part of the symbol name,`
40			`// or the empty string if there is none.`
41			`func (s *Sym) PackageName() string {`
42			`if i := strings.Index(s.Name, "."); i != -1 {`
43			`return s.Name[0:i]`
44			`}`
45			`return ""`
46			`}`
47
48			`// ReceiverName returns the receiver type name of this symbol,`
49			`// or the empty string if there is none.`
50			`func (s *Sym) ReceiverName() string {`
51			`l := strings.Index(s.Name, ".")`
52			`r := strings.LastIndex(s.Name, ".")`
53			`if l == -1 \|\| r == -1 \|\| l == r {`
54			`return ""`
55			`}`
56			`return s.Name[l+1 : r]`
57			`}`
58
59			`// BaseName returns the symbol name without the package or receiver name.`
60			`func (s *Sym) BaseName() string {`
61			`if i := strings.LastIndex(s.Name, "."); i != -1 {`
62			`return s.Name[i+1:]`
63			`}`
64			`return s.Name`
65			`}`
66
67			`// A Func collects information about a single function.`
68			`type Func struct {`
69			`Entry uint64`
70			`*Sym`
71			`End uint64`
72			`Params []*Sym`
73			`Locals []*Sym`
74			`FrameSize int`
75			`LineTable *LineTable`
76			`Obj *Obj`
77			`}`
78
79			`// An Obj represents a single object file.`
80			`type Obj struct {`
81			`Funcs []Func`
82			`Paths []Sym`
83			`}`
84
85			`/*`
86			`* Symbol tables`
87			`*/`
88
89			`// Table represents a Go symbol table. It stores all of the`
90			`// symbols decoded from the program and provides methods to translate`
91			`// between symbols, names, and addresses.`
92			`type Table struct {`
93			`Syms []Sym`
94			`Funcs []Func`
95			`Files map[string]*Obj`
96			`Objs []Obj`
97			`// textEnd uint64;`
98			`}`
99
100			`type sym struct {`
101			`value uint32`
102			`gotype uint32`
103			`typ byte`
104			`name []byte`
105			`}`
106
107			`func walksymtab(data []byte, fn func(sym) error) error {`
108			`var s sym`
109			`p := data`
110			`for len(p) >= 6 {`
111			`s.value = binary.BigEndian.Uint32(p[0:4])`
112			`typ := p[4]`
113			`if typ&0x80 == 0 {`
114			`return &DecodingError{len(data) - len(p) + 4, "bad symbol type", typ}`
115			`}`
116			`typ &^= 0x80`
117			`s.typ = typ`
118			`p = p[5:]`
119			`var i int`
120			`var nnul int`
121			`for i = 0; i < len(p); i++ {`
122			`if p[i] == 0 {`
123			`nnul = 1`
124			`break`
125			`}`
126			`}`
127			`switch typ {`
128			`case 'z', 'Z':`
129			`p = p[i+nnul:]`
130			`for i = 0; i+2 <= len(p); i += 2 {`
131			`if p[i] == 0 && p[i+1] == 0 {`
132			`nnul = 2`
133			`break`
134			`}`
135			`}`
136			`}`
137			`if i+nnul+4 > len(p) {`
138			`return &DecodingError{len(data), "unexpected EOF", nil}`
139			`}`
140			`s.name = p[0:i]`
141			`i += nnul`
142			`s.gotype = binary.BigEndian.Uint32(p[i : i+4])`
143			`p = p[i+4:]`
144			`fn(s)`
145			`}`
146			`return nil`
147			`}`
148
149			`// NewTable decodes the Go symbol table in data,`
150			`// returning an in-memory representation.`
151			`func NewTable(symtab []byte, pcln LineTable) (Table, error) {`
152			`var n int`
153			`err := walksymtab(symtab, func(s sym) error {`
154			`n++`
155			`return nil`
156			`})`
157			`if err != nil {`
158			`return nil, err`
159			`}`
160
161			`var t Table`
162			`fname := make(map[uint16]string)`
163			`t.Syms = make([]Sym, 0, n)`
164			`nf := 0`
165			`nz := 0`
166			`lasttyp := uint8(0)`
167			`err = walksymtab(symtab, func(s sym) error {`
168			`n := len(t.Syms)`
169			`t.Syms = t.Syms[0 : n+1]`
170			`ts := &t.Syms[n]`
171			`ts.Type = s.typ`
172			`ts.Value = uint64(s.value)`
173			`ts.GoType = uint64(s.gotype)`
174			`switch s.typ {`
175			`default:`
176			`// rewrite name to use . instead of · (c2 b7)`
177			`w := 0`
178			`b := s.name`
179			`for i := 0; i < len(b); i++ {`
180			`if b[i] == 0xc2 && i+1 < len(b) && b[i+1] == 0xb7 {`
181			`i++`
182			`b[i] = '.'`
183			`}`
184			`b[w] = b[i]`
185			`w++`
186			`}`
187			`ts.Name = string(s.name[0:w])`
188			`case 'z', 'Z':`
189			`if lasttyp != 'z' && lasttyp != 'Z' {`
190			`nz++`
191			`}`
192			`for i := 0; i < len(s.name); i += 2 {`
193			`eltIdx := binary.BigEndian.Uint16(s.name[i : i+2])`
194			`elt, ok := fname[eltIdx]`
195			`if !ok {`
196			`return &DecodingError{-1, "bad filename code", eltIdx}`
197			`}`
198			`if n := len(ts.Name); n > 0 && ts.Name[n-1] != '/' {`
199			`ts.Name += "/"`
200			`}`
201			`ts.Name += elt`
202			`}`
203			`}`
204			`switch s.typ {`
205			`case 'T', 't', 'L', 'l':`
206			`nf++`
207			`case 'f':`
208			`fname[uint16(s.value)] = ts.Name`
209			`}`
210			`lasttyp = s.typ`
211			`return nil`
212			`})`
213			`if err != nil {`
214			`return nil, err`
215			`}`
216
217			`t.Funcs = make([]Func, 0, nf)`
218			`t.Objs = make([]Obj, 0, nz)`
219			`t.Files = make(map[string]*Obj)`
220
221			`// Count text symbols and attach frame sizes, parameters, and`
222			`// locals to them. Also, find object file boundaries.`
223			`var obj *Obj`
224			`lastf := 0`
225			`for i := 0; i < len(t.Syms); i++ {`
226			`sym := &t.Syms[i]`
227			`switch sym.Type {`
228			`case 'Z', 'z': // path symbol`
229			`// Finish the current object`
230			`if obj != nil {`
231			`obj.Funcs = t.Funcs[lastf:]`
232			`}`
233			`lastf = len(t.Funcs)`
234
235			`// Start new object`
236			`n := len(t.Objs)`
237			`t.Objs = t.Objs[0 : n+1]`
238			`obj = &t.Objs[n]`
239
240			`// Count & copy path symbols`
241			`var end int`
242			`for end = i + 1; end < len(t.Syms); end++ {`
243			`if c := t.Syms[end].Type; c != 'Z' && c != 'z' {`
244			`break`
245			`}`
246			`}`
247			`obj.Paths = t.Syms[i:end]`
248			`i = end - 1 // loop will i++`
249
250			`// Record file names`
251			`depth := 0`
252			`for j := range obj.Paths {`
253			`s := &obj.Paths[j]`
254			`if s.Name == "" {`
255			`depth--`
256			`} else {`
257			`if depth == 0 {`
258			`t.Files[s.Name] = obj`
259			`}`
260			`depth++`
261			`}`
262			`}`
263
264			`case 'T', 't', 'L', 'l': // text symbol`
265			`if n := len(t.Funcs); n > 0 {`
266			`t.Funcs[n-1].End = sym.Value`
267			`}`
268			`if sym.Name == "etext" {`
269			`continue`
270			`}`
271
272			`// Count parameter and local (auto) syms`
273			`var np, na int`
274			`var end int`
275			`countloop:`
276			`for end = i + 1; end < len(t.Syms); end++ {`
277			`switch t.Syms[end].Type {`
278			`case 'T', 't', 'L', 'l', 'Z', 'z':`
279			`break countloop`
280			`case 'p':`
281			`np++`
282			`case 'a':`
283			`na++`
284			`}`
285			`}`
286
287			`// Fill in the function symbol`
288			`n := len(t.Funcs)`
289			`t.Funcs = t.Funcs[0 : n+1]`
290			`fn := &t.Funcs[n]`
291			`sym.Func = fn`
292			`fn.Params = make([]*Sym, 0, np)`
293			`fn.Locals = make([]*Sym, 0, na)`
294			`fn.Sym = sym`
295			`fn.Entry = sym.Value`
296			`fn.Obj = obj`
297			`if pcln != nil {`
298			`fn.LineTable = pcln.slice(fn.Entry)`
299			`pcln = fn.LineTable`
300			`}`
301			`for j := i; j < end; j++ {`
302			`s := &t.Syms[j]`
303			`switch s.Type {`
304			`case 'm':`
305			`fn.FrameSize = int(s.Value)`
306			`case 'p':`
307			`n := len(fn.Params)`
308			`fn.Params = fn.Params[0 : n+1]`
309			`fn.Params[n] = s`
310			`case 'a':`
311			`n := len(fn.Locals)`
312			`fn.Locals = fn.Locals[0 : n+1]`
313			`fn.Locals[n] = s`
314			`}`
315			`}`
316			`i = end - 1 // loop will i++`
317			`}`
318			`}`
319			`if obj != nil {`
320			`obj.Funcs = t.Funcs[lastf:]`
321			`}`
322			`return &t, nil`
323			`}`
324
325			`// PCToFunc returns the function containing the program counter pc,`
326			`// or nil if there is no such function.`
327			`func (t Table) PCToFunc(pc uint64) Func {`
328			`funcs := t.Funcs`
329			`for len(funcs) > 0 {`
330			`m := len(funcs) / 2`
331			`fn := &funcs[m]`
332			`switch {`
333			`case pc < fn.Entry:`
334			`funcs = funcs[0:m]`
335			`case fn.Entry <= pc && pc < fn.End:`
336			`return fn`
337			`default:`
338			`funcs = funcs[m+1:]`
339			`}`
340			`}`
341			`return nil`
342			`}`
343
344			`// PCToLine looks up line number information for a program counter.`
345			`// If there is no information, it returns fn == nil.`
346			`func (t Table) PCToLine(pc uint64) (file string, line int, fn Func) {`
347			`if fn = t.PCToFunc(pc); fn == nil {`
348			`return`
349			`}`
350			`file, line = fn.Obj.lineFromAline(fn.LineTable.PCToLine(pc))`
351			`return`
352			`}`
353
354			`// LineToPC looks up the first program counter on the given line in`
355			`// the named file. Returns UnknownPathError or UnknownLineError if`
356			`// there is an error looking up this line.`
357			`func (t Table) LineToPC(file string, line int) (pc uint64, fn Func, err error) {`
358			`obj, ok := t.Files[file]`
359			`if !ok {`
360			`return 0, nil, UnknownFileError(file)`
361			`}`
362			`abs, err := obj.alineFromLine(file, line)`
363			`if err != nil {`
364			`return`
365			`}`
366			`for i := range obj.Funcs {`
367			`f := &obj.Funcs[i]`
368			`pc := f.LineTable.LineToPC(abs, f.End)`
369			`if pc != 0 {`
370			`return pc, f, nil`
371			`}`
372			`}`
373			`return 0, nil, &UnknownLineError{file, line}`
374			`}`
375
376			`// LookupSym returns the text, data, or bss symbol with the given name,`
377			`// or nil if no such symbol is found.`
378			`func (t Table) LookupSym(name string) Sym {`
379			`// TODO(austin) Maybe make a map`
380			`for i := range t.Syms {`
381			`s := &t.Syms[i]`
382			`switch s.Type {`
383			`case 'T', 't', 'L', 'l', 'D', 'd', 'B', 'b':`
384			`if s.Name == name {`
385			`return s`
386			`}`
387			`}`
388			`}`
389			`return nil`
390			`}`
391
392			`// LookupFunc returns the text, data, or bss symbol with the given name,`
393			`// or nil if no such symbol is found.`
394			`func (t Table) LookupFunc(name string) Func {`
395			`for i := range t.Funcs {`
396			`f := &t.Funcs[i]`
397			`if f.Sym.Name == name {`
398			`return f`
399			`}`
400			`}`
401			`return nil`
402			`}`
403
404			`// SymByAddr returns the text, data, or bss symbol starting at the given address.`
405			`// TODO(rsc): Allow lookup by any address within the symbol.`
406			`func (t Table) SymByAddr(addr uint64) Sym {`
407			`// TODO(austin) Maybe make a map`
408			`for i := range t.Syms {`
409			`s := &t.Syms[i]`
410			`switch s.Type {`
411			`case 'T', 't', 'L', 'l', 'D', 'd', 'B', 'b':`
412			`if s.Value == addr {`
413			`return s`
414			`}`
415			`}`
416			`}`
417			`return nil`
418			`}`
419
420			`/*`
421			`* Object files`
422			`*/`
423
424			`func (o *Obj) lineFromAline(aline int) (string, int) {`
425			`type stackEnt struct {`
426			`path string`
427			`start int`
428			`offset int`
429			`prev *stackEnt`
430			`}`
431
432			`noPath := &stackEnt{"", 0, 0, nil}`
433			`tos := noPath`
434
435			`// TODO(austin) I have no idea how 'Z' symbols work, except`
436			`// that they pop the stack.`
437			`pathloop:`
438			`for _, s := range o.Paths {`
439			`val := int(s.Value)`
440			`switch {`
441			`case val > aline:`
442			`break pathloop`
443
444			`case val == 1:`
445			`// Start a new stack`
446			`tos = &stackEnt{s.Name, val, 0, noPath}`
447
448			`case s.Name == "":`
449			`// Pop`
450			`if tos == noPath {`
451			`return "", 0`
452			`}`
453			`tos.prev.offset += val - tos.start`
454			`tos = tos.prev`
455
456			`default:`
457			`// Push`
458			`tos = &stackEnt{s.Name, val, 0, tos}`
459			`}`
460			`}`
461
462			`if tos == noPath {`
463			`return "", 0`
464			`}`
465			`return tos.path, aline - tos.start - tos.offset + 1`
466			`}`
467
468			`func (o *Obj) alineFromLine(path string, line int) (int, error) {`
469			`if line < 1 {`
470			`return 0, &UnknownLineError{path, line}`
471			`}`
472
473			`for i, s := range o.Paths {`
474			`// Find this path`
475			`if s.Name != path {`
476			`continue`
477			`}`
478
479			`// Find this line at this stack level`
480			`depth := 0`
481			`var incstart int`
482			`line += int(s.Value)`
483			`pathloop:`
484			`for _, s := range o.Paths[i:] {`
485			`val := int(s.Value)`
486			`switch {`
487			`case depth == 1 && val >= line:`
488			`return line - 1, nil`
489
490			`case s.Name == "":`
491			`depth--`
492			`if depth == 0 {`
493			`break pathloop`
494			`} else if depth == 1 {`
495			`line += val - incstart`
496			`}`
497
498			`default:`
499			`if depth == 1 {`
500			`incstart = val`
501			`}`
502			`depth++`
503			`}`
504			`}`
505			`return 0, &UnknownLineError{path, line}`
506			`}`
507			`return 0, UnknownFileError(path)`
508			`}`
509
510			`/*`
511			`* Errors`
512			`*/`
513
514			`// UnknownFileError represents a failure to find the specific file in`
515			`// the symbol table.`
516			`type UnknownFileError string`
517
518			`func (e UnknownFileError) Error() string { return "unknown file: " + string(e) }`
519
520			`// UnknownLineError represents a failure to map a line to a program`
521			`// counter, either because the line is beyond the bounds of the file`
522			`// or because there is no code on the given line.`
523			`type UnknownLineError struct {`
524			`File string`
525			`Line int`
526			`}`
527
528			`func (e *UnknownLineError) Error() string {`
529			`return "no code at " + e.File + ":" + strconv.Itoa(e.Line)`
530			`}`
531
532			`// DecodingError represents an error during the decoding of`
533			`// the symbol table.`
534			`type DecodingError struct {`
535			`off int`
536			`msg string`
537			`val interface{}`
538			`}`
539
540			`func (e *DecodingError) Error() string {`
541			`msg := e.msg`
542			`if e.val != nil {`
543			`msg += fmt.Sprintf(" '%v'", e.val)`
544			`}`
545			`msg += fmt.Sprintf(" at byte %#x", e.off)`
546			`return msg`
547			`}`