// 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"
"encoding/binary"
"errors"
"flag"
"fmt"
"go/ast"
"go/parser"
"go/token"
"os"
"strconv"
"strings"
"unicode"
"unicode/utf8"
)
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_"):]
}
if strings.HasPrefix(s, "sizeof_") {
return "sizeof(" + cname(s[len("sizeof_"):]) + ")"
}
return s
}
// DiscardCgoDirectives processes the import C preamble, and discards
// all #cgo CFLAGS and LDFLAGS directives, so they don't make their
// way into _cgo_export.h.
func (f *File) DiscardCgoDirectives() {
linesIn := strings.Split(f.Preamble, "\n")
linesOut := make([]string, 0, len(linesIn))
for _, line := range linesIn {
l := strings.TrimSpace(line)
if len(l) < 5 || l[:4] != "#cgo" || !unicode.IsSpace(rune(l[4])) {
linesOut = append(linesOut, line)
} else {
linesOut = append(linesOut, "")
}
}
f.Preamble = strings.Join(linesOut, "\n")
}
// addToFlag appends args to flag. All flags are later written out onto the
// _cgo_flags file for the build system to use.
func (p *Package) addToFlag(flag string, args []string) {
p.CgoFlags[flag] = append(p.CgoFlags[flag], args...)
if flag == "CFLAGS" {
// We'll also need these when preprocessing for dwarf information.
p.GccOptions = append(p.GccOptions, args...)
}
}
// 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 error) {
var args []string
arg := make([]rune, len(s))
escaped := false
quoted := false
quote := '\x00'
i := 0
for _, r := range s {
switch {
case escaped:
escaped = false
case r == '\\':
escaped = true
continue
case quote != 0:
if r == quote {
quote = 0
continue
}
case r == '"' || r == '\'':
quoted = true
quote = r
continue
case unicode.IsSpace(r):
if quoted || i > 0 {
quoted = false
args = append(args, string(arg[:i]))
i = 0
}
continue
}
arg[i] = r
i++
}
if quoted || i > 0 {
args = append(args, string(arg[:i]))
}
if quote != 0 {
err = errors.New("unclosed quote")
} else if escaped {
err = errors.New("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(f.Preamble)
b.WriteString(builtinProlog)
stdout := p.gccDefines(b.Bytes())
for _, line := range strings.Split(stdout, "\n") {
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 key == "__clang__" {
p.GccIsClang = true
}
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 {
// Determine kinds for names we already know about,
// like #defines or 'struct foo', before bothering with gcc.
var names, needType []*Name
for _, key := range nameKeys(f.Name) {
n := f.Name[key]
// If we've already found this name as a #define
// and we can translate it as a constant value, do so.
if n.Define != "" {
isConst := false
if _, err := strconv.Atoi(n.Define); err == nil {
isConst = true
} else if n.Define[0] == '"' || n.Define[0] == '\'' {
if _, err := parser.ParseExpr(n.Define); err == nil {
isConst = true
}
}
if isConst {
n.Kind = "const"
// Turn decimal into hex, just for consistency
// with enum-derived constants. Otherwise
// in the cgo -godefs output half the constants
// are in hex and half are in whatever the #define used.
i, err := strconv.ParseInt(n.Define, 0, 64)
if err == nil {
n.Const = fmt.Sprintf("%#x", i)
} else {
n.Const = n.Define
}
continue
}
if isName(n.Define) {
n.C = n.Define
}
}
needType = append(needType, n)
// If this is a struct, union, or enum type name, no need to guess the kind.
if strings.HasPrefix(n.C, "struct ") || strings.HasPrefix(n.C, "union ") || strings.HasPrefix(n.C, "enum ") {
n.Kind = "type"
continue
}
// Otherwise, we'll need to find out from gcc.
names = append(names, n)
}
// Bypass gcc if there's nothing left to find out.
if len(names) == 0 {
return needType
}
// Coerce gcc into telling us whether each name is a type, a value, or undeclared.
// For names, find out whether they are integer constants.
// We used to look at specific warning or error messages here, but that tied the
// behavior too closely to specific versions of the compilers.
// Instead, arrange that we can infer what we need from only the presence or absence
// of an error on a specific line.
//
// For each name, we generate these lines, where xxx is the index in toSniff plus one.
//
// #line xxx "not-declared"
// void __cgo_f_xxx_1(void) { __typeof__(name) *__cgo_undefined__; }
// #line xxx "not-type"
// void __cgo_f_xxx_2(void) { name *__cgo_undefined__; }
// #line xxx "not-const"
// void __cgo_f_xxx_3(void) { enum { __cgo_undefined__ = (name)*1 }; }
//
// If we see an error at not-declared:xxx, the corresponding name is not declared.
// If we see an error at not-type:xxx, the corresponding name is a type.
// If we see an error at not-const:xxx, the corresponding name is not an integer constant.
// If we see no errors, we assume the name is an expression but not a constant
// (so a variable or a function).
//
// The specific input forms are chosen so that they are valid C syntax regardless of
// whether name denotes a type or an expression.
var b bytes.Buffer
b.WriteString(f.Preamble)
b.WriteString(builtinProlog)
for i, n := range names {
fmt.Fprintf(&b, "#line %d \"not-declared\"\n"+
"void __cgo_f_%d_1(void) { __typeof__(%s) *__cgo_undefined__; }\n"+
"#line %d \"not-type\"\n"+
"void __cgo_f_%d_2(void) { %s *__cgo_undefined__; }\n"+
"#line %d \"not-const\"\n"+
"void __cgo_f_%d_3(void) { enum { __cgo__undefined__ = (%s)*1 }; }\n",
i+1, i+1, n.C,
i+1, i+1, n.C,
i+1, i+1, n.C)
}
fmt.Fprintf(&b, "#line 1 \"completed\"\n"+
"int __cgo__1 = __cgo__2;\n")
stderr := p.gccErrors(b.Bytes())
if stderr == "" {
fatalf("%s produced no output\non input:\n%s", p.gccBaseCmd()[0], b.Bytes())
}
completed := false
sniff := make([]int, len(names))
const (
notType = 1 << iota
notConst
notDeclared
)
for _, line := range strings.Split(stderr, "\n") {
if !strings.Contains(line, ": error:") {
// we only care about errors.
// we tried to turn off warnings on the command line, but one never knows.
continue
}
c1 := strings.Index(line, ":")
if c1 < 0 {
continue
}
c2 := strings.Index(line[c1+1:], ":")
if c2 < 0 {
continue
}
c2 += c1 + 1
filename := line[:c1]
i, _ := strconv.Atoi(line[c1+1 : c2])
i--
if i < 0 || i >= len(names) {
continue
}
switch filename {
case "completed":
// Strictly speaking, there is no guarantee that seeing the error at completed:1
// (at the end of the file) means we've seen all the errors from earlier in the file,
// but usually it does. Certainly if we don't see the completed:1 error, we did
// not get all the errors we expected.
completed = true
case "not-declared":
sniff[i] |= notDeclared
case "not-type":
sniff[i] |= notType
case "not-const":
sniff[i] |= notConst
}
}
if !completed {
fatalf("%s did not produce error at completed:1\non input:\n%s\nfull error output:\n%s", p.gccBaseCmd()[0], b.Bytes(), stderr)
}
for i, n := range names {
switch sniff[i] {
default:
error_(token.NoPos, "could not determine kind of name for C.%s", fixGo(n.Go))
case notType:
n.Kind = "const"
case notConst:
n.Kind = "type"
case notConst | notType:
n.Kind = "not-type"
}
}
if nerrors > 0 {
// Check if compiling the preamble by itself causes any errors,
// because the messages we've printed out so far aren't helpful
// to users debugging preamble mistakes. See issue 8442.
preambleErrors := p.gccErrors([]byte(f.Preamble))
if len(preambleErrors) > 0 {
error_(token.NoPos, "\n%s errors for preamble:\n%s", p.gccBaseCmd()[0], preambleErrors)
}
fatalf("unresolved names")
}
needType = append(needType, 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(f.Preamble)
b.WriteString(builtinProlog)
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)
}
}
// Apple's LLVM-based gcc does not include the enumeration
// names and values in its DWARF debug output. In case we're
// using such a gcc, create a data block initialized with the values.
// We can read them out of the object file.
fmt.Fprintf(&b, "long long __cgodebug_data[] = {\n")
for _, n := range names {
if n.Kind == "const" {
fmt.Fprintf(&b, "\t%s,\n", n.C)
} else {
fmt.Fprintf(&b, "\t0,\n")
}
}
// for the last entry, we can not use 0, otherwise
// in case all __cgodebug_data is zero initialized,
// LLVM-based gcc will place the it in the __DATA.__common
// zero-filled section (our debug/macho doesn't support
// this)
fmt.Fprintf(&b, "\t1\n")
fmt.Fprintf(&b, "};\n")
d, bo, debugData := p.gccDebug(b.Bytes())
enumVal := make([]int64, len(debugData)/8)
for i := range enumVal {
enumVal[i] = int64(bo.Uint64(debugData[i*8:]))
}
// 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
}
nameToRef := make(map[*Name]*Ref)
for _, ref := range f.Ref {
nameToRef[ref.Name] = ref
}
r := d.Reader()
for {
e, err := r.Next()
if err != nil {
fatalf("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 {
fatalf("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 {
fatalf("malformed DWARF TagVariable entry")
}
if !strings.HasPrefix(name, "__cgo__") {
break
}
typ, err := d.Type(typOff)
if err != nil {
fatalf("loading DWARF type: %s", err)
}
t, ok := typ.(*dwarf.PtrType)
if !ok || t == nil {
fatalf("internal error: %s has non-pointer type", name)
}
i, err := strconv.Atoi(name[7:])
if err != nil {
fatalf("malformed __cgo__ name: %s", name)
}
if enums[i] != 0 {
t, err := d.Type(enums[i])
if err != nil {
fatalf("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, p.IntSize)
for i, n := range names {
if types[i] == nil {
continue
}
pos := token.NoPos
if ref, ok := nameToRef[n]; ok {
pos = ref.Pos()
}
f, fok := types[i].(*dwarf.FuncType)
if n.Kind != "type" && fok {
n.Kind = "func"
n.FuncType = conv.FuncType(f, pos)
} else {
n.Type = conv.Type(types[i], pos)
if enums[i] != 0 && n.Type.EnumValues != nil {
k := fmt.Sprintf("__cgo_enum__%d", i)
n.Kind = "const"
n.Const = fmt.Sprintf("%#x", n.Type.EnumValues[k])
// Remove injected enum to ensure the value will deep-compare
// equally in future loads of the same constant.
delete(n.Type.EnumValues, k)
}
// Prefer debug data over DWARF debug output, if we have it.
if n.Kind == "const" && i < len(enumVal) {
n.Const = fmt.Sprintf("%#x", enumVal[i])
}
}
conv.FinishType(pos)
}
}
// mangleName does name mangling to translate names
// from the original Go source files to the names
// used in the final Go files generated by cgo.
func (p *Package) mangleName(n *Name) {
// When using gccgo variables have to be
// exported so that they become global symbols
// that the C code can refer to.
prefix := "_C"
if *gccgo && n.IsVar() {
prefix = "C"
}
n.Mangle = prefix + n.Kind + "_" + n.Go
}
// 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. In *godefs mode, rewriteRef replaces the names
// with full definitions instead of mangled names.
func (p *Package) rewriteRef(f *File) {
// Keep a list of all the functions, to remove the ones
// only used as expressions and avoid generating bridge
// code for them.
functions := make(map[string]bool)
// Assign mangled names.
for _, n := range f.Name {
if n.Kind == "not-type" {
n.Kind = "var"
}
if n.Mangle == "" {
p.mangleName(n)
}
if n.Kind == "func" {
functions[n.Go] = false
}
}
// 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 {
if r.Name.Kind == "const" && r.Name.Const == "" {
error_(r.Pos(), "unable to find value of constant C.%s", fixGo(r.Name.Go))
}
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", fixGo(r.Name.Go))
break
}
functions[r.Name.Go] = true
if r.Context == "call2" {
if r.Name.Go == "_CMalloc" {
error_(r.Pos(), "no two-result form for C.malloc")
break
}
// 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" {
// Function is being used in an expression, to e.g. pass around a C function pointer.
// Create a new Name for this Ref which causes the variable to be declared in Go land.
fpName := "fp_" + r.Name.Go
name := f.Name[fpName]
if name == nil {
name = &Name{
Go: fpName,
C: r.Name.C,
Kind: "fpvar",
Type: &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("void*"), Go: ast.NewIdent("unsafe.Pointer")},
}
p.mangleName(name)
f.Name[fpName] = name
}
r.Name = name
// Rewrite into call to _Cgo_ptr to prevent assignments. The _Cgo_ptr
// function is defined in out.go and simply returns its argument. See
// issue 7757.
expr = &ast.CallExpr{
Fun: &ast.Ident{NamePos: (*r.Expr).Pos(), Name: "_Cgo_ptr"},
Args: []ast.Expr{ast.NewIdent(name.Mangle)},
}
} else if r.Name.Kind == "type" {
// Okay - might be new(T)
expr = r.Name.Type.Go
} else if r.Name.Kind == "var" {
expr = &ast.StarExpr{Star: (*r.Expr).Pos(), X: expr}
}
case "selector":
if r.Name.Kind == "var" {
expr = &ast.StarExpr{Star: (*r.Expr).Pos(), X: expr}
} else {
error_(r.Pos(), "only C variables allowed in selector expression", fixGo(r.Name.Go))
}
case "type":
if r.Name.Kind != "type" {
error_(r.Pos(), "expression C.%s used as type", fixGo(r.Name.Go))
} else if r.Name.Type == nil {
// Use of C.enum_x, C.struct_x or C.union_x without C definition.
// GCC won't raise an error when using pointers to such unknown types.
error_(r.Pos(), "type C.%s: undefined C type '%s'", fixGo(r.Name.Go), r.Name.C)
} else {
expr = r.Name.Type.Go
}
default:
if r.Name.Kind == "func" {
error_(r.Pos(), "must call C.%s", fixGo(r.Name.Go))
}
}
if *godefs {
// Substitute definition for mangled type name.
if id, ok := expr.(*ast.Ident); ok {
if t := typedef[id.Name]; t != nil {
expr = t.Go
}
if id.Name == r.Name.Mangle && r.Name.Const != "" {
expr = ast.NewIdent(r.Name.Const)
}
}
}
// Copy position information from old expr into new expr,
// in case expression being replaced is first on line.
// See golang.org/issue/6563.
pos := (*r.Expr).Pos()
switch x := expr.(type) {
case *ast.Ident:
expr = &ast.Ident{NamePos: pos, Name: x.Name}
}
*r.Expr = expr
}
// Remove functions only used as expressions, so their respective
// bridge functions are not generated.
for name, used := range functions {
if !used {
delete(f.Name, name)
}
}
}
// gccBaseCmd returns the start of the compiler command line.
// It uses $CC if set, or else $GCC, or else the compiler recorded
// during the initial build as defaultCC.
// defaultCC is defined in zdefaultcc.go, written by cmd/dist.
func (p *Package) gccBaseCmd() []string {
// Use $CC if set, since that's what the build uses.
if ret := strings.Fields(os.Getenv("CC")); len(ret) > 0 {
return ret
}
// Try $GCC if set, since that's what we used to use.
if ret := strings.Fields(os.Getenv("GCC")); len(ret) > 0 {
return ret
}
return strings.Fields(defaultCC)
}
// gccMachine returns the gcc -m flag to use, either "-m32", "-m64" or "-marm".
func (p *Package) gccMachine() []string {
switch goarch {
case "amd64":
return []string{"-m64"}
case "386":
return []string{"-m32"}
case "arm":
return []string{"-marm"} // not thumb
case "s390":
return []string{"-m31"}
case "s390x":
return []string{"-m64"}
}
return nil
}
func gccTmp() string {
return *objDir + "_cgo_.o"
}
// gccCmd returns the gcc command line to use for compiling
// the input.
func (p *Package) gccCmd() []string {
c := append(p.gccBaseCmd(),
"-w", // no warnings
"-Wno-error", // warnings are not errors
"-o"+gccTmp(), // write object to tmp
"-gdwarf-2", // generate DWARF v2 debugging symbols
"-c", // do not link
"-xc", // input language is C
)
if p.GccIsClang {
c = append(c,
"-ferror-limit=0",
// Apple clang version 1.7 (tags/Apple/clang-77) (based on LLVM 2.9svn)
// doesn't have -Wno-unneeded-internal-declaration, so we need yet another
// flag to disable the warning. Yes, really good diagnostics, clang.
"-Wno-unknown-warning-option",
"-Wno-unneeded-internal-declaration",
"-Wno-unused-function",
"-Qunused-arguments",
// Clang embeds prototypes for some builtin functions,
// like malloc and calloc, but all size_t parameters are
// incorrectly typed unsigned long. We work around that
// by disabling the builtin functions (this is safe as
// it won't affect the actual compilation of the C code).
// See: https://golang.org/issue/6506.
"-fno-builtin",
)
}
c = append(c, p.GccOptions...)
c = append(c, p.gccMachine()...)
c = append(c, "-") //read input from standard input
return c
}
// gccDebug runs gcc -gdwarf-2 over the C program stdin and
// returns the corresponding DWARF data and, if present, debug data block.
func (p *Package) gccDebug(stdin []byte) (*dwarf.Data, binary.ByteOrder, []byte) {
runGcc(stdin, p.gccCmd())
isDebugData := func(s string) bool {
// Some systems use leading _ to denote non-assembly symbols.
return s == "__cgodebug_data" || s == "___cgodebug_data"
}
if f, err := macho.Open(gccTmp()); err == nil {
defer f.Close()
d, err := f.DWARF()
if err != nil {
fatalf("cannot load DWARF output from %s: %v", gccTmp(), err)
}
var data []byte
if f.Symtab != nil {
for i := range f.Symtab.Syms {
s := &f.Symtab.Syms[i]
if isDebugData(s.Name) {
// Found it. Now find data section.
if i := int(s.Sect) - 1; 0 <= i && i < len(f.Sections) {
sect := f.Sections[i]
if sect.Addr <= s.Value && s.Value < sect.Addr+sect.Size {
if sdat, err := sect.Data(); err == nil {
data = sdat[s.Value-sect.Addr:]
}
}
}
}
}
}
return d, f.ByteOrder, data
}
if f, err := elf.Open(gccTmp()); err == nil {
defer f.Close()
d, err := f.DWARF()
if err != nil {
fatalf("cannot load DWARF output from %s: %v", gccTmp(), err)
}
var data []byte
symtab, err := f.Symbols()
if err == nil {
for i := range symtab {
s := &symtab[i]
if isDebugData(s.Name) {
// Found it. Now find data section.
if i := int(s.Section); 0 <= i && i < len(f.Sections) {
sect := f.Sections[i]
if sect.Addr <= s.Value && s.Value < sect.Addr+sect.Size {
if sdat, err := sect.Data(); err == nil {
data = sdat[s.Value-sect.Addr:]
}
}
}
}
}
}
return d, f.ByteOrder, data
}
if f, err := pe.Open(gccTmp()); err == nil {
defer f.Close()
d, err := f.DWARF()
if err != nil {
fatalf("cannot load DWARF output from %s: %v", gccTmp(), err)
}
var data []byte
for _, s := range f.Symbols {
if isDebugData(s.Name) {
if i := int(s.SectionNumber) - 1; 0 <= i && i < len(f.Sections) {
sect := f.Sections[i]
if s.Value < sect.Size {
if sdat, err := sect.Data(); err == nil {
data = sdat[s.Value:]
}
}
}
}
}
return d, binary.LittleEndian, data
}
fatalf("cannot parse gcc output %s as ELF, Mach-O, PE object", gccTmp())
panic("not reached")
}
// 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 := append(p.gccBaseCmd(), "-E", "-dM", "-xc")
base = append(base, p.gccMachine()...)
stdout, _ := runGcc(stdin, append(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 := p.gccCmd()
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
// Map from types to incomplete pointers to those types.
ptrs map[dwarf.Type][]*Type
// Keys of ptrs in insertion order (deterministic worklist)
ptrKeys []dwarf.Type
// 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
string ast.Expr
goVoid ast.Expr // _Ctype_void, denotes C's void
goVoidPtr ast.Expr // unsafe.Pointer or *byte
ptrSize int64
intSize int64
}
var tagGen int
var typedef = make(map[string]*Type)
var goIdent = make(map[string]*ast.Ident)
func (c *typeConv) Init(ptrSize, intSize int64) {
c.ptrSize = ptrSize
c.intSize = intSize
c.m = make(map[dwarf.Type]*Type)
c.ptrs = 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.void = c.Ident("void")
c.string = c.Ident("string")
c.goVoid = c.Ident("_Ctype_void")
// Normally cgo translates void* to unsafe.Pointer,
// but for historical reasons -godefs uses *byte instead.
if *godefs {
c.goVoidPtr = &ast.StarExpr{X: c.byte}
} else {
c.goVoidPtr = c.Ident("unsafe.Pointer")
}
}
// 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 reports whether 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
}
// FinishType completes any outstanding type mapping work.
// In particular, it resolves incomplete pointer types.
func (c *typeConv) FinishType(pos token.Pos) {
// Completing one pointer type might produce more to complete.
// Keep looping until they're all done.
for len(c.ptrKeys) > 0 {
dtype := c.ptrKeys[0]
c.ptrKeys = c.ptrKeys[1:]
// Note Type might invalidate c.ptrs[dtype].
t := c.Type(dtype, pos)
for _, ptr := range c.ptrs[dtype] {
ptr.Go.(*ast.StarExpr).X = t.Go
ptr.C.Set("%s*", t.C)
}
c.ptrs[dtype] = nil // retain the map key
}
}
// 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, pos token.Pos) *Type {
if t, ok := c.m[dtype]; ok {
if t.Go == nil {
fatalf("%s: type conversion loop at %s", lineno(pos), dtype)
}
return t
}
t := new(Type)
t.Size = dtype.Size() // note: wrong for array of pointers, corrected below
t.Align = -1
t.C = &TypeRepr{Repr: dtype.Common().Name}
c.m[dtype] = t
switch dt := dtype.(type) {
default:
fatalf("%s: unexpected type: %s", lineno(pos), dtype)
case *dwarf.AddrType:
if t.Size != c.ptrSize {
fatalf("%s: unexpected: %d-byte address type - %s", lineno(pos), 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
}
count := dt.Count
if count == -1 {
// Indicates flexible array member, which Go doesn't support.
// Translate to zero-length array instead.
count = 0
}
sub := c.Type(dt.Type, pos)
t.Align = sub.Align
t.Go = &ast.ArrayType{
Len: c.intExpr(count),
Elt: sub.Go,
}
// Recalculate t.Size now that we know sub.Size.
t.Size = count * sub.Size
t.C.Set("__typeof__(%s[%d])", sub.C, dt.Count)
case *dwarf.BoolType:
t.Go = c.bool
t.Align = 1
case *dwarf.CharType:
if t.Size != 1 {
fatalf("%s: unexpected: %d-byte char type - %s", lineno(pos), 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:
fatalf("%s: unexpected: %d-byte enum type - %s", lineno(pos), 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:
fatalf("%s: unexpected: %d-byte float type - %s", lineno(pos), 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:
fatalf("%s: unexpected: %d-byte complex type - %s", lineno(pos), 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 {
fatalf("%s: unexpected: %d-bit int type - %s", lineno(pos), dt.BitSize, dtype)
}
switch t.Size {
default:
fatalf("%s: unexpected: %d-byte int type - %s", lineno(pos), 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:
// Clang doesn't emit DW_AT_byte_size for pointer types.
if t.Size != c.ptrSize && t.Size != -1 {
fatalf("%s: unexpected: %d-byte pointer type - %s", lineno(pos), t.Size, dtype)
}
t.Size = c.ptrSize
t.Align = c.ptrSize
if _, ok := base(dt.Type).(*dwarf.VoidType); ok {
t.Go = c.goVoidPtr
t.C.Set("void*")
break
}
// Placeholder initialization; completed in FinishType.
t.Go = &ast.StarExpr{}
t.C.Set("<incomplete>*")
if _, ok := c.ptrs[dt.Type]; !ok {
c.ptrKeys = append(c.ptrKeys, dt.Type)
}
c.ptrs[dt.Type] = append(c.ptrs[dt.Type], t)
case *dwarf.QualType:
// Ignore qualifier.
t = c.Type(dt.Type, pos)
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 dt.ByteSize < 0 && tag == "" { // opaque unnamed struct - should not be possible
break
}
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
goIdent[name.Name] = name
if dt.ByteSize < 0 {
// Size calculation in c.Struct/c.Opaque will die with size=-1 (unknown),
// so execute the basic things that the struct case would do
// other than try to determine a Go representation.
tt := *t
tt.C = &TypeRepr{"%s %s", []interface{}{dt.Kind, tag}}
tt.Go = c.Ident("struct{}")
typedef[name.Name] = &tt
break
}
switch dt.Kind {
case "class", "union":
t.Go = c.Opaque(t.Size)
if t.C.Empty() {
t.C.Set("__typeof__(unsigned char[%d])", t.Size)
}
t.Align = 1 // TODO: should probably base this on field alignment.
typedef[name.Name] = t
case "struct":
g, csyntax, align := c.Struct(dt, pos)
if t.C.Empty() {
t.C.Set(csyntax)
}
t.Align = align
tt := *t
if tag != "" {
tt.C = &TypeRepr{"struct %s", []interface{}{tag}}
}
tt.Go = g
typedef[name.Name] = &tt
}
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
}
if dt.Name == "_GoBytes_" {
// Special C name for Go []byte type.
// Knows slice layout used by compilers: pointer, length, cap.
t.Go = c.Ident("[]byte")
t.Size = c.ptrSize + 4 + 4
t.Align = c.ptrSize
break
}
name := c.Ident("_Ctype_" + dt.Name)
goIdent[name.Name] = name
sub := c.Type(dt.Type, pos)
t.Go = name
t.Size = sub.Size
t.Align = sub.Align
oldType := typedef[name.Name]
if oldType == nil {
tt := *t
tt.Go = sub.Go
typedef[name.Name] = &tt
}
// If sub.Go.Name is "_Ctype_struct_foo" or "_Ctype_union_foo" or "_Ctype_class_foo",
// use that as the Go form for this typedef too, so that the typedef will be interchangeable
// with the base type.
// In -godefs mode, do this for all typedefs.
if isStructUnionClass(sub.Go) || *godefs {
t.Go = sub.Go
if isStructUnionClass(sub.Go) {
// Use the typedef name for C code.
typedef[sub.Go.(*ast.Ident).Name].C = t.C
}
// If we've seen this typedef before, and it
// was an anonymous struct/union/class before
// too, use the old definition.
// TODO: it would be safer to only do this if
// we verify that the types are the same.
if oldType != nil && isStructUnionClass(oldType.Go) {
t.Go = oldType.Go
}
}
case *dwarf.UcharType:
if t.Size != 1 {
fatalf("%s: unexpected: %d-byte uchar type - %s", lineno(pos), t.Size, dtype)
}
t.Go = c.uint8
t.Align = 1
case *dwarf.UintType:
if dt.BitSize > 0 {
fatalf("%s: unexpected: %d-bit uint type - %s", lineno(pos), dt.BitSize, dtype)
}
switch t.Size {
default:
fatalf("%s: unexpected: %d-byte uint type - %s", lineno(pos), 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.goVoid
t.C.Set("void")
t.Align = 1
}
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, " "), "") // strip spaces
name := c.Ident("_Ctype_" + s)
tt := *t
typedef[name.Name] = &tt
if !*godefs {
t.Go = name
}
}
}
if t.Size < 0 {
// Unsized types are [0]byte, unless they're typedefs of other types
// or structs with tags.
// if so, use the name we've already defined.
t.Size = 0
switch dt := dtype.(type) {
case *dwarf.TypedefType:
// ok
case *dwarf.StructType:
if dt.StructName != "" {
break
}
t.Go = c.Opaque(0)
default:
t.Go = c.Opaque(0)
}
if t.C.Empty() {
t.C.Set("void")
}
}
if t.C.Empty() {
fatalf("%s: internal error: did not create C name for %s", lineno(pos), dtype)
}
return t
}
// isStructUnionClass reports whether the type described by the Go syntax x
// is a struct, union, or class with a tag.
func isStructUnionClass(x ast.Expr) bool {
id, ok := x.(*ast.Ident)
if !ok {
return false
}
name := id.Name
return strings.HasPrefix(name, "_Ctype_struct_") ||
strings.HasPrefix(name, "_Ctype_union_") ||
strings.HasPrefix(name, "_Ctype_class_")
}
// 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, pos token.Pos) *Type {
t := c.Type(dtype, pos)
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 {
break
}
t = c.Type(ptr, pos)
if t == nil {
return nil
}
// Remember the C spelling, in case the struct
// has __attribute__((unavailable)) on it. See issue 2888.
t.Typedef = dt.Name
}
}
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, pos token.Pos) *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, pos)
gp[i] = &ast.Field{Type: p[i].Go}
}
var r *Type
var gr []*ast.Field
if _, ok := dtype.ReturnType.(*dwarf.VoidType); ok {
gr = []*ast.Field{{Type: c.goVoid}}
} else if dtype.ReturnType != nil {
r = c.Type(dtype.ReturnType, pos)
gr = []*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: strconv.FormatInt(n, 10),
}
}
// Add padding of given size to fld.
func (c *typeConv) pad(fld []*ast.Field, sizes []int64, size int64) ([]*ast.Field, []int64) {
n := len(fld)
fld = fld[0 : n+1]
fld[n] = &ast.Field{Names: []*ast.Ident{c.Ident("_")}, Type: c.Opaque(size)}
sizes = sizes[0 : n+1]
sizes[n] = size
return fld, sizes
}
// Struct conversion: return Go and (gc) C syntax for type.
func (c *typeConv) Struct(dt *dwarf.StructType, pos token.Pos) (expr *ast.StructType, csyntax string, align int64) {
// Minimum alignment for a struct is 1 byte.
align = 1
var buf bytes.Buffer
buf.WriteString("struct {")
fld := make([]*ast.Field, 0, 2*len(dt.Field)+1) // enough for padding around every field
sizes := make([]int64, 0, 2*len(dt.Field)+1)
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
}
if !*godefs {
for cid, goid := range ident {
if token.Lookup(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
}
}
}
anon := 0
for _, f := range dt.Field {
if f.ByteOffset > off {
fld, sizes = c.pad(fld, sizes, f.ByteOffset-off)
off = f.ByteOffset
}
name := f.Name
ft := f.Type
// In godefs mode, if this field is a C11
// anonymous union then treat the first field in the
// union as the field in the struct. This handles
// cases like the glibc <sys/resource.h> file; see
// issue 6677.
if *godefs {
if st, ok := f.Type.(*dwarf.StructType); ok && name == "" && st.Kind == "union" && len(st.Field) > 0 && !used[st.Field[0].Name] {
name = st.Field[0].Name
ident[name] = name
ft = st.Field[0].Type
}
}
// TODO: Handle fields that are anonymous structs by
// promoting the fields of the inner struct.
t := c.Type(ft, pos)
tgo := t.Go
size := t.Size
talign := t.Align
if f.BitSize > 0 {
if f.BitSize%8 != 0 {
continue
}
size = f.BitSize / 8
name := tgo.(*ast.Ident).String()
if strings.HasPrefix(name, "int") {
name = "int"
} else {
name = "uint"
}
tgo = ast.NewIdent(name + fmt.Sprint(f.BitSize))
talign = size
}
if talign > 0 && f.ByteOffset%talign != 0 {
// Drop misaligned fields, the same way we drop integer bit fields.
// The goal is to make available what can be made available.
// Otherwise one bad and unneeded field in an otherwise okay struct
// makes the whole program not compile. Much of the time these
// structs are in system headers that cannot be corrected.
continue
}
n := len(fld)
fld = fld[0 : n+1]
if name == "" {
name = fmt.Sprintf("anon%d", anon)
anon++
ident[name] = name
}
fld[n] = &ast.Field{Names: []*ast.Ident{c.Ident(ident[name])}, Type: tgo}
sizes = sizes[0 : n+1]
sizes[n] = size
off += size
buf.WriteString(t.C.String())
buf.WriteString(" ")
buf.WriteString(name)
buf.WriteString("; ")
if talign > align {
align = talign
}
}
if off < dt.ByteSize {
fld, sizes = c.pad(fld, sizes, dt.ByteSize-off)
off = dt.ByteSize
}
// If the last field in a non-zero-sized struct is zero-sized
// the compiler is going to pad it by one (see issue 9401).
// We can't permit that, because then the size of the Go
// struct will not be the same as the size of the C struct.
// Our only option in such a case is to remove the field,
// which means that it can not be referenced from Go.
for off > 0 && sizes[len(sizes)-1] == 0 {
n := len(sizes)
fld = fld[0 : n-1]
sizes = sizes[0 : n-1]
}
if off != dt.ByteSize {
fatalf("%s: struct size calculation error off=%d bytesize=%d", lineno(pos), off, dt.ByteSize)
}
buf.WriteString("}")
csyntax = buf.String()
if *godefs {
godefsFields(fld)
}
expr = &ast.StructType{Fields: &ast.FieldList{List: fld}}
return
}
func upper(s string) string {
if s == "" {
return ""
}
r, size := utf8.DecodeRuneInString(s)
if r == '_' {
return "X" + s
}
return string(unicode.ToUpper(r)) + s[size:]
}
// godefsFields rewrites field names for use in Go or C definitions.
// It strips leading common prefixes (like tv_ in tv_sec, tv_usec)
// converts names to upper case, and rewrites _ into Pad_godefs_n,
// so that all fields are exported.
func godefsFields(fld []*ast.Field) {
prefix := fieldPrefix(fld)
npad := 0
for _, f := range fld {
for _, n := range f.Names {
if n.Name != prefix {
n.Name = strings.TrimPrefix(n.Name, prefix)
}
if n.Name == "_" {
// Use exported name instead.
n.Name = "Pad_cgo_" + strconv.Itoa(npad)
npad++
}
n.Name = upper(n.Name)
}
}
}
// fieldPrefix returns the prefix that should be removed from all the
// field names when generating the C or Go code. For generated
// C, we leave the names as is (tv_sec, tv_usec), since that's what
// people are used to seeing in C. For generated Go code, such as
// package syscall's data structures, we drop a common prefix
// (so sec, usec, which will get turned into Sec, Usec for exporting).
func fieldPrefix(fld []*ast.Field) string {
prefix := ""
for _, f := range fld {
for _, n := range f.Names {
// Ignore field names that don't have the prefix we're
// looking for. It is common in C headers to have fields
// named, say, _pad in an otherwise prefixed header.
// If the struct has 3 fields tv_sec, tv_usec, _pad1, then we
// still want to remove the tv_ prefix.
// The check for "orig_" here handles orig_eax in the
// x86 ptrace register sets, which otherwise have all fields
// with reg_ prefixes.
if strings.HasPrefix(n.Name, "orig_") || strings.HasPrefix(n.Name, "_") {
continue
}
i := strings.Index(n.Name, "_")
if i < 0 {
continue
}
if prefix == "" {
prefix = n.Name[:i+1]
} else if prefix != n.Name[:i+1] {
return ""
}
}
}
return prefix
}