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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.
// Annotate Ref in Prog with C types by parsing gcc debug output.
// Conversion of debug output to Go types.
package main
import (
"bytes"
"debug/dwarf"
"debug/elf"
"debug/macho"
"debug/pe"
"flag"
"fmt"
"go/ast"
"go/parser"
"go/token"
"os"
"runtime"
"strconv"
"strings"
"unicode"
)
var debugDefine = flag.Bool("debug-define", false, "print relevant #defines")
var debugGcc = flag.Bool("debug-gcc", false, "print gcc invocations")
var nameToC = map[string]string{
"schar": "signed char",
"uchar": "unsigned char",
"ushort": "unsigned short",
"uint": "unsigned int",
"ulong": "unsigned long",
"longlong": "long long",
"ulonglong": "unsigned long long",
"complexfloat": "float complex",
"complexdouble": "double complex",
}
// cname returns the C name to use for C.s.
// The expansions are listed in nameToC and also
// struct_foo becomes "struct foo", and similarly for
// union and enum.
func cname(s string) string {
if t, ok := nameToC[s]; ok {
return t
}
if strings.HasPrefix(s, "struct_") {
return "struct " + s[len("struct_"):]
}
if strings.HasPrefix(s, "union_") {
return "union " + s[len("union_"):]
}
if strings.HasPrefix(s, "enum_") {
return "enum " + s[len("enum_"):]
}
return s
}
// ParseFlags extracts #cgo CFLAGS and LDFLAGS options from the file
// preamble. Multiple occurrences are concatenated with a separating space,
// even across files.
func (p *Package) ParseFlags(f *File, srcfile string) {
linesIn := strings.Split(f.Preamble, "\n", -1)
linesOut := make([]string, 0, len(linesIn))
NextLine:
for _, line := range linesIn {
l := strings.TrimSpace(line)
if len(l) < 5 || l[:4] != "#cgo" || !unicode.IsSpace(int(l[4])) {
linesOut = append(linesOut, line)
continue
}
l = strings.TrimSpace(l[4:])
fields := strings.Split(l, ":", 2)
if len(fields) != 2 {
fatal("%s: bad #cgo line: %s", srcfile, line)
}
var k string
kf := strings.Fields(fields[0])
switch len(kf) {
case 1:
k = kf[0]
case 2:
k = kf[1]
switch kf[0] {
case runtime.GOOS:
case runtime.GOARCH:
case runtime.GOOS + "/" + runtime.GOARCH:
default:
continue NextLine
}
default:
fatal("%s: bad #cgo option: %s", srcfile, fields[0])
}
if k != "CFLAGS" && k != "LDFLAGS" {
fatal("%s: unsupported #cgo option %s", srcfile, k)
}
v := strings.TrimSpace(fields[1])
args, err := splitQuoted(v)
if err != nil {
fatal("%s: bad #cgo option %s: %s", srcfile, k, err.String())
}
if oldv, ok := p.CgoFlags[k]; ok {
p.CgoFlags[k] = oldv + " " + v
} else {
p.CgoFlags[k] = v
}
if k == "CFLAGS" {
p.GccOptions = append(p.GccOptions, args...)
}
}
f.Preamble = strings.Join(linesOut, "\n")
}
// splitQuoted splits the string s around each instance of one or more consecutive
// white space characters while taking into account quotes and escaping, and
// returns an array of substrings of s or an empty list if s contains only white space.
// Single quotes and double quotes are recognized to prevent splitting within the
// quoted region, and are removed from the resulting substrings. If a quote in s
// isn't closed err will be set and r will have the unclosed argument as the
// last element. The backslash is used for escaping.
//
// For example, the following string:
//
// `a b:"c d" 'e''f' "g\""`
//
// Would be parsed as:
//
// []string{"a", "b:c d", "ef", `g"`}
//
func splitQuoted(s string) (r []string, err os.Error) {
var args []string
arg := make([]int, len(s))
escaped := false
quoted := false
quote := 0
i := 0
for _, rune := range s {
switch {
case escaped:
escaped = false
case rune == '\\':
escaped = true
continue
case quote != 0:
if rune == quote {
quote = 0
continue
}
case rune == '"' || rune == '\'':
quoted = true
quote = rune
continue
case unicode.IsSpace(rune):
if quoted || i > 0 {
quoted = false
args = append(args, string(arg[:i]))
i = 0
}
continue
}
arg[i] = rune
i++
}
if quoted || i > 0 {
args = append(args, string(arg[:i]))
}
if quote != 0 {
err = os.ErrorString("unclosed quote")
} else if escaped {
err = os.ErrorString("unfinished escaping")
}
return args, err
}
// Translate rewrites f.AST, the original Go input, to remove
// references to the imported package C, replacing them with
// references to the equivalent Go types, functions, and variables.
func (p *Package) Translate(f *File) {
for _, cref := range f.Ref {
// Convert C.ulong to C.unsigned long, etc.
cref.Name.C = cname(cref.Name.Go)
}
p.loadDefines(f)
needType := p.guessKinds(f)
if len(needType) > 0 {
p.loadDWARF(f, needType)
}
p.rewriteRef(f)
}
// loadDefines coerces gcc into spitting out the #defines in use
// in the file f and saves relevant renamings in f.Name[name].Define.
func (p *Package) loadDefines(f *File) {
var b bytes.Buffer
b.WriteString(builtinProlog)
b.WriteString(f.Preamble)
stdout := p.gccDefines(b.Bytes())
for _, line := range strings.Split(stdout, "\n", -1) {
if len(line) < 9 || line[0:7] != "#define" {
continue
}
line = strings.TrimSpace(line[8:])
var key, val string
spaceIndex := strings.Index(line, " ")
tabIndex := strings.Index(line, "\t")
if spaceIndex == -1 && tabIndex == -1 {
continue
} else if tabIndex == -1 || (spaceIndex != -1 && spaceIndex < tabIndex) {
key = line[0:spaceIndex]
val = strings.TrimSpace(line[spaceIndex:])
} else {
key = line[0:tabIndex]
val = strings.TrimSpace(line[tabIndex:])
}
if n := f.Name[key]; n != nil {
if *debugDefine {
fmt.Fprintf(os.Stderr, "#define %s %s\n", key, val)
}
n.Define = val
}
}
}
// guessKinds tricks gcc into revealing the kind of each
// name xxx for the references C.xxx in the Go input.
// The kind is either a constant, type, or variable.
func (p *Package) guessKinds(f *File) []*Name {
// Coerce gcc into telling us whether each name is
// a type, a value, or undeclared. We compile a function
// containing the line:
// name;
// If name is a type, gcc will print:
// cgo-test:2: warning: useless type name in empty declaration
// If name is a value, gcc will print
// cgo-test:2: warning: statement with no effect
// If name is undeclared, gcc will print
// cgo-test:2: error: 'name' undeclared (first use in this function)
// A line number directive causes the line number to
// correspond to the index in the names array.
//
// The line also has an enum declaration:
// name; enum { _cgo_enum_1 = name };
// If name is not a constant, gcc will print:
// cgo-test:4: error: enumerator value for '_cgo_enum_4' is not an integer constant
// we assume lines without that error are constants.
// Make list of names that need sniffing, type lookup.
toSniff := make([]*Name, 0, len(f.Name))
needType := make([]*Name, 0, len(f.Name))
for _, n := range f.Name {
// If we've already found this name as a #define
// and we can translate it as a constant value, do so.
if n.Define != "" {
ok := false
if _, err := strconv.Atoi(n.Define); err == nil {
ok = true
} else if n.Define[0] == '"' || n.Define[0] == '\'' {
_, err := parser.ParseExpr(fset, "", n.Define)
if err == nil {
ok = true
}
}
if ok {
n.Kind = "const"
n.Const = n.Define
continue
}
if isName(n.Define) {
n.C = n.Define
}
}
// If this is a struct, union, or enum type name,
// record the kind but also that we need type information.
if strings.HasPrefix(n.C, "struct ") || strings.HasPrefix(n.C, "union ") || strings.HasPrefix(n.C, "enum ") {
n.Kind = "type"
i := len(needType)
needType = needType[0 : i+1]
needType[i] = n
continue
}
i := len(toSniff)
toSniff = toSniff[0 : i+1]
toSniff[i] = n
}
if len(toSniff) == 0 {
return needType
}
var b bytes.Buffer
b.WriteString(builtinProlog)
b.WriteString(f.Preamble)
b.WriteString("void __cgo__f__(void) {\n")
b.WriteString("#line 0 \"cgo-test\"\n")
for i, n := range toSniff {
fmt.Fprintf(&b, "%s; enum { _cgo_enum_%d = %s }; /* cgo-test:%d */\n", n.C, i, n.C, i)
}
b.WriteString("}\n")
stderr := p.gccErrors(b.Bytes())
if stderr == "" {
fatal("gcc produced no output\non input:\n%s", b.Bytes())
}
names := make([]*Name, len(toSniff))
copy(names, toSniff)
isConst := make([]bool, len(toSniff))
for i := range isConst {
isConst[i] = true // until proven otherwise
}
for _, line := range strings.Split(stderr, "\n", -1) {
if len(line) < 9 || line[0:9] != "cgo-test:" {
// the user will see any compiler errors when the code is compiled later.
continue
}
line = line[9:]
colon := strings.Index(line, ":")
if colon < 0 {
continue
}
i, err := strconv.Atoi(line[0:colon])
if err != nil {
continue
}
what := ""
switch {
default:
continue
case strings.Contains(line, ": useless type name in empty declaration"):
what = "type"
isConst[i] = false
case strings.Contains(line, ": statement with no effect"):
what = "not-type" // const or func or var
case strings.Contains(line, "undeclared"):
error(token.NoPos, "%s", strings.TrimSpace(line[colon+1:]))
case strings.Contains(line, "is not an integer constant"):
isConst[i] = false
continue
}
n := toSniff[i]
if n == nil {
continue
}
toSniff[i] = nil
n.Kind = what
j := len(needType)
needType = needType[0 : j+1]
needType[j] = n
}
for i, b := range isConst {
if b {
names[i].Kind = "const"
}
}
for _, n := range toSniff {
if n == nil {
continue
}
if n.Kind != "" {
continue
}
error(token.NoPos, "could not determine kind of name for C.%s", n.Go)
}
if nerrors > 0 {
fatal("unresolved names")
}
return needType
}
// loadDWARF parses the DWARF debug information generated
// by gcc to learn the details of the constants, variables, and types
// being referred to as C.xxx.
func (p *Package) loadDWARF(f *File, names []*Name) {
// Extract the types from the DWARF section of an object
// from a well-formed C program. Gcc only generates DWARF info
// for symbols in the object file, so it is not enough to print the
// preamble and hope the symbols we care about will be there.
// Instead, emit
// typeof(names[i]) *__cgo__i;
// for each entry in names and then dereference the type we
// learn for __cgo__i.
var b bytes.Buffer
b.WriteString(builtinProlog)
b.WriteString(f.Preamble)
for i, n := range names {
fmt.Fprintf(&b, "typeof(%s) *__cgo__%d;\n", n.C, i)
if n.Kind == "const" {
fmt.Fprintf(&b, "enum { __cgo_enum__%d = %s };\n", i, n.C)
}
}
d := p.gccDebug(b.Bytes())
// Scan DWARF info for top-level TagVariable entries with AttrName __cgo__i.
types := make([]dwarf.Type, len(names))
enums := make([]dwarf.Offset, len(names))
nameToIndex := make(map[*Name]int)
for i, n := range names {
nameToIndex[n] = i
}
r := d.Reader()
for {
e, err := r.Next()
if err != nil {
fatal("reading DWARF entry: %s", err)
}
if e == nil {
break
}
switch e.Tag {
case dwarf.TagEnumerationType:
offset := e.Offset
for {
e, err := r.Next()
if err != nil {
fatal("reading DWARF entry: %s", err)
}
if e.Tag == 0 {
break
}
if e.Tag == dwarf.TagEnumerator {
entryName := e.Val(dwarf.AttrName).(string)
if strings.HasPrefix(entryName, "__cgo_enum__") {
n, _ := strconv.Atoi(entryName[len("__cgo_enum__"):])
if 0 <= n && n < len(names) {
enums[n] = offset
}
}
}
}
case dwarf.TagVariable:
name, _ := e.Val(dwarf.AttrName).(string)
typOff, _ := e.Val(dwarf.AttrType).(dwarf.Offset)
if name == "" || typOff == 0 {
fatal("malformed DWARF TagVariable entry")
}
if !strings.HasPrefix(name, "__cgo__") {
break
}
typ, err := d.Type(typOff)
if err != nil {
fatal("loading DWARF type: %s", err)
}
t, ok := typ.(*dwarf.PtrType)
if !ok || t == nil {
fatal("internal error: %s has non-pointer type", name)
}
i, err := strconv.Atoi(name[7:])
if err != nil {
fatal("malformed __cgo__ name: %s", name)
}
if enums[i] != 0 {
t, err := d.Type(enums[i])
if err != nil {
fatal("loading DWARF type: %s", err)
}
types[i] = t
} else {
types[i] = t.Type
}
}
if e.Tag != dwarf.TagCompileUnit {
r.SkipChildren()
}
}
// Record types and typedef information.
var conv typeConv
conv.Init(p.PtrSize)
for i, n := range names {
f, fok := types[i].(*dwarf.FuncType)
if n.Kind != "type" && fok {
n.Kind = "func"
n.FuncType = conv.FuncType(f)
} else {
n.Type = conv.Type(types[i])
if enums[i] != 0 && n.Type.EnumValues != nil {
k := fmt.Sprintf("__cgo_enum__%d", i)
n.Kind = "const"
n.Const = strconv.Itoa64(n.Type.EnumValues[k])
// Remove injected enum to ensure the value will deep-compare
// equally in future loads of the same constant.
n.Type.EnumValues[k] = 0, false
}
}
}
}
// rewriteRef rewrites all the C.xxx references in f.AST to refer to the
// Go equivalents, now that we have figured out the meaning of all
// the xxx.
func (p *Package) rewriteRef(f *File) {
// Assign mangled names.
for _, n := range f.Name {
if n.Kind == "not-type" {
n.Kind = "var"
}
if n.Mangle == "" {
n.Mangle = "_C" + n.Kind + "_" + n.Go
}
}
// Now that we have all the name types filled in,
// scan through the Refs to identify the ones that
// are trying to do a ,err call. Also check that
// functions are only used in calls.
for _, r := range f.Ref {
var expr ast.Expr = ast.NewIdent(r.Name.Mangle) // default
switch r.Context {
case "call", "call2":
if r.Name.Kind != "func" {
if r.Name.Kind == "type" {
r.Context = "type"
expr = r.Name.Type.Go
break
}
error(r.Pos(), "call of non-function C.%s", r.Name.Go)
break
}
if r.Context == "call2" {
if r.Name.FuncType.Result == nil {
error(r.Pos(), "assignment count mismatch: 2 = 0")
}
// Invent new Name for the two-result function.
n := f.Name["2"+r.Name.Go]
if n == nil {
n = new(Name)
*n = *r.Name
n.AddError = true
n.Mangle = "_C2func_" + n.Go
f.Name["2"+r.Name.Go] = n
}
expr = ast.NewIdent(n.Mangle)
r.Name = n
break
}
case "expr":
if r.Name.Kind == "func" {
error(r.Pos(), "must call C.%s", r.Name.Go)
}
if r.Name.Kind == "type" {
// Okay - might be new(T)
expr = r.Name.Type.Go
}
if r.Name.Kind == "var" {
expr = &ast.StarExpr{X: expr}
}
case "type":
if r.Name.Kind != "type" {
error(r.Pos(), "expression C.%s used as type", r.Name.Go)
} else {
expr = r.Name.Type.Go
}
default:
if r.Name.Kind == "func" {
error(r.Pos(), "must call C.%s", r.Name.Go)
}
}
*r.Expr = expr
}
}
// gccName returns the name of the compiler to run. Use $GCC if set in
// the environment, otherwise just "gcc".
func (p *Package) gccName() (ret string) {
if ret = os.Getenv("GCC"); ret == "" {
ret = "gcc"
}
return
}
// gccMachine returns the gcc -m flag to use, either "-m32" or "-m64".
func (p *Package) gccMachine() string {
if p.PtrSize == 8 {
return "-m64"
}
return "-m32"
}
const gccTmp = "_obj/_cgo_.o"
// gccCmd returns the gcc command line to use for compiling
// the input.
func (p *Package) gccCmd() []string {
return []string{
p.gccName(),
p.gccMachine(),
"-Wall", // many warnings
"-Werror", // warnings are errors
"-o" + gccTmp, // write object to tmp
"-gdwarf-2", // generate DWARF v2 debugging symbols
"-fno-eliminate-unused-debug-types", // gets rid of e.g. untyped enum otherwise
"-c", // do not link
"-xc", // input language is C
"-", // read input from standard input
}
}
// gccDebug runs gcc -gdwarf-2 over the C program stdin and
// returns the corresponding DWARF data and any messages
// printed to standard error.
func (p *Package) gccDebug(stdin []byte) *dwarf.Data {
runGcc(stdin, append(p.gccCmd(), p.GccOptions...))
// Try to parse f as ELF and Mach-O and hope one works.
var f interface {
DWARF() (*dwarf.Data, os.Error)
}
var err os.Error
if f, err = elf.Open(gccTmp); err != nil {
if f, err = macho.Open(gccTmp); err != nil {
if f, err = pe.Open(gccTmp); err != nil {
fatal("cannot parse gcc output %s as ELF or Mach-O or PE object", gccTmp)
}
}
}
d, err := f.DWARF()
if err != nil {
fatal("cannot load DWARF debug information from %s: %s", gccTmp, err)
}
return d
}
// gccDefines runs gcc -E -dM -xc - over the C program stdin
// and returns the corresponding standard output, which is the
// #defines that gcc encountered while processing the input
// and its included files.
func (p *Package) gccDefines(stdin []byte) string {
base := []string{p.gccName(), p.gccMachine(), "-E", "-dM", "-xc", "-"}
stdout, _ := runGcc(stdin, append(base, p.GccOptions...))
return stdout
}
// gccErrors runs gcc over the C program stdin and returns
// the errors that gcc prints. That is, this function expects
// gcc to fail.
func (p *Package) gccErrors(stdin []byte) string {
// TODO(rsc): require failure
args := append(p.gccCmd(), p.GccOptions...)
if *debugGcc {
fmt.Fprintf(os.Stderr, "$ %s <<EOF\n", strings.Join(args, " "))
os.Stderr.Write(stdin)
fmt.Fprint(os.Stderr, "EOF\n")
}
stdout, stderr, _ := run(stdin, args)
if *debugGcc {
os.Stderr.Write(stdout)
os.Stderr.Write(stderr)
}
return string(stderr)
}
// runGcc runs the gcc command line args with stdin on standard input.
// If the command exits with a non-zero exit status, runGcc prints
// details about what was run and exits.
// Otherwise runGcc returns the data written to standard output and standard error.
// Note that for some of the uses we expect useful data back
// on standard error, but for those uses gcc must still exit 0.
func runGcc(stdin []byte, args []string) (string, string) {
if *debugGcc {
fmt.Fprintf(os.Stderr, "$ %s <<EOF\n", strings.Join(args, " "))
os.Stderr.Write(stdin)
fmt.Fprint(os.Stderr, "EOF\n")
}
stdout, stderr, ok := run(stdin, args)
if *debugGcc {
os.Stderr.Write(stdout)
os.Stderr.Write(stderr)
}
if !ok {
os.Stderr.Write(stderr)
os.Exit(2)
}
return string(stdout), string(stderr)
}
// A typeConv is a translator from dwarf types to Go types
// with equivalent memory layout.
type typeConv struct {
// Cache of already-translated or in-progress types.
m map[dwarf.Type]*Type
typedef map[string]ast.Expr
// Predeclared types.
bool ast.Expr
byte ast.Expr // denotes padding
int8, int16, int32, int64 ast.Expr
uint8, uint16, uint32, uint64, uintptr ast.Expr
float32, float64 ast.Expr
complex64, complex128 ast.Expr
void ast.Expr
unsafePointer ast.Expr
string ast.Expr
ptrSize int64
}
var tagGen int
var typedef = make(map[string]ast.Expr)
func (c *typeConv) Init(ptrSize int64) {
c.ptrSize = ptrSize
c.m = make(map[dwarf.Type]*Type)
c.bool = c.Ident("bool")
c.byte = c.Ident("byte")
c.int8 = c.Ident("int8")
c.int16 = c.Ident("int16")
c.int32 = c.Ident("int32")
c.int64 = c.Ident("int64")
c.uint8 = c.Ident("uint8")
c.uint16 = c.Ident("uint16")
c.uint32 = c.Ident("uint32")
c.uint64 = c.Ident("uint64")
c.uintptr = c.Ident("uintptr")
c.float32 = c.Ident("float32")
c.float64 = c.Ident("float64")
c.complex64 = c.Ident("complex64")
c.complex128 = c.Ident("complex128")
c.unsafePointer = c.Ident("unsafe.Pointer")
c.void = c.Ident("void")
c.string = c.Ident("string")
}
// base strips away qualifiers and typedefs to get the underlying type
func base(dt dwarf.Type) dwarf.Type {
for {
if d, ok := dt.(*dwarf.QualType); ok {
dt = d.Type
continue
}
if d, ok := dt.(*dwarf.TypedefType); ok {
dt = d.Type
continue
}
break
}
return dt
}
// Map from dwarf text names to aliases we use in package "C".
var dwarfToName = map[string]string{
"long int": "long",
"long unsigned int": "ulong",
"unsigned int": "uint",
"short unsigned int": "ushort",
"short int": "short",
"long long int": "longlong",
"long long unsigned int": "ulonglong",
"signed char": "schar",
"float complex": "complexfloat",
"double complex": "complexdouble",
}
const signedDelta = 64
// String returns the current type representation. Format arguments
// are assembled within this method so that any changes in mutable
// values are taken into account.
func (tr *TypeRepr) String() string {
if len(tr.Repr) == 0 {
return ""
}
if len(tr.FormatArgs) == 0 {
return tr.Repr
}
return fmt.Sprintf(tr.Repr, tr.FormatArgs...)
}
// Empty returns true if the result of String would be "".
func (tr *TypeRepr) Empty() bool {
return len(tr.Repr) == 0
}
// Set modifies the type representation.
// If fargs are provided, repr is used as a format for fmt.Sprintf.
// Otherwise, repr is used unprocessed as the type representation.
func (tr *TypeRepr) Set(repr string, fargs ...interface{}) {
tr.Repr = repr
tr.FormatArgs = fargs
}
// Type returns a *Type with the same memory layout as
// dtype when used as the type of a variable or a struct field.
func (c *typeConv) Type(dtype dwarf.Type) *Type {
if t, ok := c.m[dtype]; ok {
if t.Go == nil {
fatal("type conversion loop at %s", dtype)
}
return t
}
t := new(Type)
t.Size = dtype.Size()
t.Align = -1
t.C = &TypeRepr{Repr: dtype.Common().Name}
c.m[dtype] = t
if t.Size < 0 {
// Unsized types are [0]byte
t.Size = 0
t.Go = c.Opaque(0)
if t.C.Empty() {
t.C.Set("void")
}
return t
}
switch dt := dtype.(type) {
default:
fatal("unexpected type: %s", dtype)
case *dwarf.AddrType:
if t.Size != c.ptrSize {
fatal("unexpected: %d-byte address type - %s", t.Size, dtype)
}
t.Go = c.uintptr
t.Align = t.Size
case *dwarf.ArrayType:
if dt.StrideBitSize > 0 {
// Cannot represent bit-sized elements in Go.
t.Go = c.Opaque(t.Size)
break
}
gt := &ast.ArrayType{
Len: c.intExpr(dt.Count),
}
t.Go = gt // publish before recursive call
sub := c.Type(dt.Type)
t.Align = sub.Align
gt.Elt = sub.Go
t.C.Set("typeof(%s[%d])", sub.C, dt.Count)
case *dwarf.BoolType:
t.Go = c.bool
t.Align = c.ptrSize
case *dwarf.CharType:
if t.Size != 1 {
fatal("unexpected: %d-byte char type - %s", t.Size, dtype)
}
t.Go = c.int8
t.Align = 1
case *dwarf.EnumType:
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
t.C.Set("enum " + dt.EnumName)
signed := 0
t.EnumValues = make(map[string]int64)
for _, ev := range dt.Val {
t.EnumValues[ev.Name] = ev.Val
if ev.Val < 0 {
signed = signedDelta
}
}
switch t.Size + int64(signed) {
default:
fatal("unexpected: %d-byte enum type - %s", t.Size, dtype)
case 1:
t.Go = c.uint8
case 2:
t.Go = c.uint16
case 4:
t.Go = c.uint32
case 8:
t.Go = c.uint64
case 1 + signedDelta:
t.Go = c.int8
case 2 + signedDelta:
t.Go = c.int16
case 4 + signedDelta:
t.Go = c.int32
case 8 + signedDelta:
t.Go = c.int64
}
case *dwarf.FloatType:
switch t.Size {
default:
fatal("unexpected: %d-byte float type - %s", t.Size, dtype)
case 4:
t.Go = c.float32
case 8:
t.Go = c.float64
}
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
case *dwarf.ComplexType:
switch t.Size {
default:
fatal("unexpected: %d-byte complex type - %s", t.Size, dtype)
case 8:
t.Go = c.complex64
case 16:
t.Go = c.complex128
}
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
case *dwarf.FuncType:
// No attempt at translation: would enable calls
// directly between worlds, but we need to moderate those.
t.Go = c.uintptr
t.Align = c.ptrSize
case *dwarf.IntType:
if dt.BitSize > 0 {
fatal("unexpected: %d-bit int type - %s", dt.BitSize, dtype)
}
switch t.Size {
default:
fatal("unexpected: %d-byte int type - %s", t.Size, dtype)
case 1:
t.Go = c.int8
case 2:
t.Go = c.int16
case 4:
t.Go = c.int32
case 8:
t.Go = c.int64
}
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
case *dwarf.PtrType:
t.Align = c.ptrSize
// Translate void* as unsafe.Pointer
if _, ok := base(dt.Type).(*dwarf.VoidType); ok {
t.Go = c.unsafePointer
t.C.Set("void*")
break
}
gt := &ast.StarExpr{}
t.Go = gt // publish before recursive call
sub := c.Type(dt.Type)
gt.X = sub.Go
t.C.Set("%s*", sub.C)
case *dwarf.QualType:
// Ignore qualifier.
t = c.Type(dt.Type)
c.m[dtype] = t
return t
case *dwarf.StructType:
// Convert to Go struct, being careful about alignment.
// Have to give it a name to simulate C "struct foo" references.
tag := dt.StructName
if tag == "" {
tag = "__" + strconv.Itoa(tagGen)
tagGen++
} else if t.C.Empty() {
t.C.Set(dt.Kind + " " + tag)
}
name := c.Ident("_Ctype_" + dt.Kind + "_" + tag)
t.Go = name // publish before recursive calls
switch dt.Kind {
case "union", "class":
typedef[name.Name] = c.Opaque(t.Size)
if t.C.Empty() {
t.C.Set("typeof(unsigned char[%d])", t.Size)
}
case "struct":
g, csyntax, align := c.Struct(dt)
if t.C.Empty() {
t.C.Set(csyntax)
}
t.Align = align
typedef[name.Name] = g
}
case *dwarf.TypedefType:
// Record typedef for printing.
if dt.Name == "_GoString_" {
// Special C name for Go string type.
// Knows string layout used by compilers: pointer plus length,
// which rounds up to 2 pointers after alignment.
t.Go = c.string
t.Size = c.ptrSize * 2
t.Align = c.ptrSize
break
}
name := c.Ident("_Ctypedef_" + dt.Name)
t.Go = name // publish before recursive call
sub := c.Type(dt.Type)
t.Size = sub.Size
t.Align = sub.Align
if _, ok := typedef[name.Name]; !ok {
typedef[name.Name] = sub.Go
}
case *dwarf.UcharType:
if t.Size != 1 {
fatal("unexpected: %d-byte uchar type - %s", t.Size, dtype)
}
t.Go = c.uint8
t.Align = 1
case *dwarf.UintType:
if dt.BitSize > 0 {
fatal("unexpected: %d-bit uint type - %s", dt.BitSize, dtype)
}
switch t.Size {
default:
fatal("unexpected: %d-byte uint type - %s", t.Size, dtype)
case 1:
t.Go = c.uint8
case 2:
t.Go = c.uint16
case 4:
t.Go = c.uint32
case 8:
t.Go = c.uint64
}
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
case *dwarf.VoidType:
t.Go = c.void
t.C.Set("void")
}
switch dtype.(type) {
case *dwarf.AddrType, *dwarf.BoolType, *dwarf.CharType, *dwarf.IntType, *dwarf.FloatType, *dwarf.UcharType, *dwarf.UintType:
s := dtype.Common().Name
if s != "" {
if ss, ok := dwarfToName[s]; ok {
s = ss
}
s = strings.Join(strings.Split(s, " ", -1), "") // strip spaces
name := c.Ident("_Ctype_" + s)
typedef[name.Name] = t.Go
t.Go = name
}
}
if t.C.Empty() {
fatal("internal error: did not create C name for %s", dtype)
}
return t
}
// FuncArg returns a Go type with the same memory layout as
// dtype when used as the type of a C function argument.
func (c *typeConv) FuncArg(dtype dwarf.Type) *Type {
t := c.Type(dtype)
switch dt := dtype.(type) {
case *dwarf.ArrayType:
// Arrays are passed implicitly as pointers in C.
// In Go, we must be explicit.
tr := &TypeRepr{}
tr.Set("%s*", t.C)
return &Type{
Size: c.ptrSize,
Align: c.ptrSize,
Go: &ast.StarExpr{X: t.Go},
C: tr,
}
case *dwarf.TypedefType:
// C has much more relaxed rules than Go for
// implicit type conversions. When the parameter
// is type T defined as *X, simulate a little of the
// laxness of C by making the argument *X instead of T.
if ptr, ok := base(dt.Type).(*dwarf.PtrType); ok {
// Unless the typedef happens to point to void* since
// Go has special rules around using unsafe.Pointer.
if _, void := base(ptr.Type).(*dwarf.VoidType); !void {
return c.Type(ptr)
}
}
}
return t
}
// FuncType returns the Go type analogous to dtype.
// There is no guarantee about matching memory layout.
func (c *typeConv) FuncType(dtype *dwarf.FuncType) *FuncType {
p := make([]*Type, len(dtype.ParamType))
gp := make([]*ast.Field, len(dtype.ParamType))
for i, f := range dtype.ParamType {
// gcc's DWARF generator outputs a single DotDotDotType parameter for
// function pointers that specify no parameters (e.g. void
// (*__cgo_0)()). Treat this special case as void. This case is
// invalid according to ISO C anyway (i.e. void (*__cgo_1)(...) is not
// legal).
if _, ok := f.(*dwarf.DotDotDotType); ok && i == 0 {
p, gp = nil, nil
break
}
p[i] = c.FuncArg(f)
gp[i] = &ast.Field{Type: p[i].Go}
}
var r *Type
var gr []*ast.Field
if _, ok := dtype.ReturnType.(*dwarf.VoidType); !ok && dtype.ReturnType != nil {
r = c.Type(dtype.ReturnType)
gr = []*ast.Field{&ast.Field{Type: r.Go}}
}
return &FuncType{
Params: p,
Result: r,
Go: &ast.FuncType{
Params: &ast.FieldList{List: gp},
Results: &ast.FieldList{List: gr},
},
}
}
// Identifier
func (c *typeConv) Ident(s string) *ast.Ident {
return ast.NewIdent(s)
}
// Opaque type of n bytes.
func (c *typeConv) Opaque(n int64) ast.Expr {
return &ast.ArrayType{
Len: c.intExpr(n),
Elt: c.byte,
}
}
// Expr for integer n.
func (c *typeConv) intExpr(n int64) ast.Expr {
return &ast.BasicLit{
Kind: token.INT,
Value: []byte(strconv.Itoa64(n)),
}
}
// Add padding of given size to fld.
func (c *typeConv) pad(fld []*ast.Field, size int64) []*ast.Field {
n := len(fld)
fld = fld[0 : n+1]
fld[n] = &ast.Field{Names: []*ast.Ident{c.Ident("_")}, Type: c.Opaque(size)}
return fld
}
// Struct conversion: return Go and (6g) C syntax for type.
func (c *typeConv) Struct(dt *dwarf.StructType) (expr *ast.StructType, csyntax string, align int64) {
var buf bytes.Buffer
buf.WriteString("struct {")
fld := make([]*ast.Field, 0, 2*len(dt.Field)+1) // enough for padding around every field
off := int64(0)
// Rename struct fields that happen to be named Go keywords into
// _{keyword}. Create a map from C ident -> Go ident. The Go ident will
// be mangled. Any existing identifier that already has the same name on
// the C-side will cause the Go-mangled version to be prefixed with _.
// (e.g. in a struct with fields '_type' and 'type', the latter would be
// rendered as '__type' in Go).
ident := make(map[string]string)
used := make(map[string]bool)
for _, f := range dt.Field {
ident[f.Name] = f.Name
used[f.Name] = true
}
for cid, goid := range ident {
if token.Lookup([]byte(goid)).IsKeyword() {
// Avoid keyword
goid = "_" + goid
// Also avoid existing fields
for _, exist := used[goid]; exist; _, exist = used[goid] {
goid = "_" + goid
}
used[goid] = true
ident[cid] = goid
}
}
for _, f := range dt.Field {
if f.BitSize > 0 && f.BitSize != f.ByteSize*8 {
continue
}
if f.ByteOffset > off {
fld = c.pad(fld, f.ByteOffset-off)
off = f.ByteOffset
}
t := c.Type(f.Type)
n := len(fld)
fld = fld[0 : n+1]
fld[n] = &ast.Field{Names: []*ast.Ident{c.Ident(ident[f.Name])}, Type: t.Go}
off += t.Size
buf.WriteString(t.C.String())
buf.WriteString(" ")
buf.WriteString(f.Name)
buf.WriteString("; ")
if t.Align > align {
align = t.Align
}
}
if off < dt.ByteSize {
fld = c.pad(fld, dt.ByteSize-off)
off = dt.ByteSize
}
if off != dt.ByteSize {
fatal("struct size calculation error")
}
buf.WriteString("}")
csyntax = buf.String()
expr = &ast.StructType{Fields: &ast.FieldList{List: fld}}
return
}