godefs: delete, replaced by cgo -godefs

Godefs was a C program that ran gcc and then parsed the
stabs debugging information in the resulting object file to
generate C or Go code for bootstrapping as part of
package runtime or package syscall.

Cgo does the same work, but using the dwarf debugging
information.  Add -godefs and -cdefs options to cgo that
mimic godefs's output, albeit with different input
(a Go program, not a C program).

This has been a "nice to have" for a while but was forced
by Apple removing stabs debugging output from their
latest compilers.

Fixes #835.
Fixes #2338.

R=golang-dev, bradfitz, r, dave, iant
CC=golang-dev
https://golang.org/cl/5367043

src/cmd/cgo/gcc.go

@@ -24,6 +24,7 @@ import (
 	"strconv"
 	"strings"
 	"unicode"
+	"unicode/utf8"
 )
 
 var debugDefine = flag.Bool("debug-define", false, "print relevant #defines")
@@ -59,6 +60,9 @@ func cname(s string) string {
 	if strings.HasPrefix(s, "enum_") {
 		return "enum " + s[len("enum_"):]
 	}
+	if strings.HasPrefix(s, "sizeof_") {
+		return "sizeof(" + cname(s[len("sizeof_"):]) + ")"
+	}
 	return s
 }
 
@@ -347,7 +351,16 @@ func (p *Package) guessKinds(f *File) []*Name {
 			}
 			if ok {
 				n.Kind = "const"
-				n.Const = n.Define
+				// 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.Btoi64(n.Define, 0)
+				if err == nil {
+					n.Const = fmt.Sprintf("%#x", i)
+				} else {
+					n.Const = n.Define
+				}
 				continue
 			}
 
@@ -589,12 +602,12 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 			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])
+				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)
 			} else if n.Kind == "const" && i < len(enumVal) {
-				n.Const = strconv.Itoa64(enumVal[i])
+				n.Const = fmt.Sprintf("%#x", enumVal[i])
 			}
 		}
 	}
@@ -603,7 +616,8 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 
 // 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.
+// the xxx.  In *godefs or *cdefs mode, rewriteRef replaces the names
+// with full definitions instead of mangled names.
 func (p *Package) rewriteRef(f *File) {
 	// Assign mangled names.
 	for _, n := range f.Name {
@@ -679,6 +693,17 @@ func (p *Package) rewriteRef(f *File) {
 				error_(r.Pos(), "must call C.%s", r.Name.Go)
 			}
 		}
+		if *godefs || *cdefs {
+			// Substitute definition for mangled type name.
+			if id, ok := expr.(*ast.Ident); ok {
+				if t := typedef[id.Name]; t != nil {
+					expr = t
+				}
+				if id.Name == r.Name.Mangle && r.Name.Const != "" {
+					expr = ast.NewIdent(r.Name.Const)
+				}
+			}
+		}
 		*r.Expr = expr
 	}
 }
@@ -856,6 +881,7 @@ type typeConv struct {
 
 var tagGen int
 var typedef = make(map[string]ast.Expr)
+var goIdent = make(map[string]*ast.Ident)
 
 func (c *typeConv) Init(ptrSize int64) {
 	c.ptrSize = ptrSize
@@ -1121,6 +1147,7 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 		}
 		name := c.Ident("_Ctype_" + dt.Kind + "_" + tag)
 		t.Go = name // publish before recursive calls
+		goIdent[name.Name] = name
 		switch dt.Kind {
 		case "union", "class":
 			typedef[name.Name] = c.Opaque(t.Size)
@@ -1155,7 +1182,8 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 			t.Align = c.ptrSize
 			break
 		}
-		name := c.Ident("_Ctypedef_" + dt.Name)
+		name := c.Ident("_Ctype_" + dt.Name)
+		goIdent[name.Name] = name
 		t.Go = name // publish before recursive call
 		sub := c.Type(dt.Type)
 		t.Size = sub.Size
@@ -1163,6 +1191,9 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 		if _, ok := typedef[name.Name]; !ok {
 			typedef[name.Name] = sub.Go
 		}
+		if *godefs || *cdefs {
+			t.Go = sub.Go
+		}
 
 	case *dwarf.UcharType:
 		if t.Size != 1 {
@@ -1206,7 +1237,9 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
 			s = strings.Join(strings.Split(s, " "), "") // strip spaces
 			name := c.Ident("_Ctype_" + s)
 			typedef[name.Name] = t.Go
-			t.Go = name
+			if !*godefs && !*cdefs {
+				t.Go = name
+			}
 		}
 	}
 
@@ -1331,38 +1364,61 @@ func (c *typeConv) Struct(dt *dwarf.StructType) (expr *ast.StructType, csyntax s
 		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] {
+	if !*godefs && !*cdefs {
+		for cid, goid := range ident {
+			if token.Lookup([]byte(goid)).IsKeyword() {
+				// Avoid keyword
 				goid = "_" + goid
-			}
 
-			used[goid] = true
-			ident[cid] = 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.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)
+		tgo := t.Go
+		size := t.Size
+
+		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))
+		}
+
 		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
+		name := f.Name
+		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}
+		off += size
 		buf.WriteString(t.C.String())
 		buf.WriteString(" ")
-		buf.WriteString(f.Name)
+		buf.WriteString(name)
 		buf.WriteString("; ")
 		if t.Align > align {
 			align = t.Align
@@ -1377,6 +1433,96 @@ func (c *typeConv) Struct(dt *dwarf.StructType) (expr *ast.StructType, csyntax s
 	}
 	buf.WriteString("}")
 	csyntax = buf.String()
+
+	if *godefs || *cdefs {
+		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 strings.HasPrefix(n.Name, prefix) && n.Name != prefix {
+				n.Name = n.Name[len(prefix):]
+			}
+			if n.Name == "_" {
+				// Use exported name instead.
+				n.Name = "Pad_cgo_" + strconv.Itoa(npad)
+				npad++
+			}
+			if !*cdefs {
+				n.Name = upper(n.Name)
+			}
+		}
+		p := &f.Type
+		t := *p
+		if star, ok := t.(*ast.StarExpr); ok {
+			star = &ast.StarExpr{X: star.X}
+			*p = star
+			p = &star.X
+			t = *p
+		}
+		if id, ok := t.(*ast.Ident); ok {
+			if id.Name == "unsafe.Pointer" {
+				*p = ast.NewIdent("*byte")
+			}
+		}
+	}
+}
+
+// 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 {
+	if *cdefs {
+		return ""
+	}
+	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
+}