diff --git a/go/ast/scope.go b/go/ast/scope.go
index 8e32912..681e853 100644
--- a/go/ast/scope.go
+++ b/go/ast/scope.go
@@ -83,6 +83,7 @@ type Object struct {
 	Decl interface{} // corresponding Field, XxxSpec, FuncDecl, or LabeledStmt; or nil
 	Data interface{} // object-specific data; or nil
 	Type interface{} // place holder for type information; may be nil
+	Next *Object     // corresponding platform dependent implement; or nil
 }
 
 // NewObj creates a new object of a given kind and name.
diff --git a/go/parser/parser.go b/go/parser/parser.go
index a69f185..bfda935 100644
--- a/go/parser/parser.go
+++ b/go/parser/parser.go
@@ -16,6 +16,7 @@ import (
 	"fmt"
 	"regexp"
 	"strconv"
+	"strings"
 )
 
 // The mode parameter to the Parse* functions is a set of flags (or 0).
@@ -216,6 +217,11 @@ func (p *parser) declare1(decl ast.Node, scope *ast.Scope, kind ast.ObjKind, ide
 }
 
 func (p *parser) redeclared(ident *ast.Ident, prev *ast.Object, reason string) {
+	if f := p.fset.File(ident.Pos()); f.IsPlatformDependent() {
+		ident.Obj.Next = prev.Next
+		prev.Next = ident.Obj
+		return
+	}
 	if p.mode&DeclarationErrors == 0 {
 		return
 	}
@@ -2215,6 +2221,9 @@ func (p *parser) parseFile() *ast.File {
 	}
 	initialScope := p.topScope
 
+	// get platform dependent info from file name or build tag
+	platformDependent(p.file, p.comments)
+
 	// package clause
 	doc := p.leadComment
 	pos := p.expect(token.PACKAGE)
@@ -2248,3 +2257,65 @@ func (p *parser) parseFile() *ast.File {
 
 	return &ast.File{doc, pos, ident, decls, p.fileScope, nil, nil, p.comments}
 }
+
+var (
+	goosSuffixes = []string{
+		"_dragonfly.go",
+		"_netbsd.go",
+		"_openbsd.go",
+		"_solaris.go",
+		"_freebsd.go",
+		"_nacl.go",
+		"_android.go",
+		"_plan9.go",
+		"_darwin.go",
+		"_linux.go",
+		"_windows.go",
+	}
+	goarchSuffixes = []string{
+		"_amd64.go",
+		"_amd64p32.go",
+		"_arm.go",
+		"_ppc64.go",
+		"_ppc64le.go",
+		"_386.go",
+	}
+	buildPrefix = "// +build"
+)
+
+// platformDependent sets file is platform dependent or not
+func platformDependent(f *token.File, cgs []*ast.CommentGroup) {
+	if f == nil {
+		return
+	}
+
+	//TODO: if file already has platform dependent info, return
+
+	// get from file name
+	fn := f.Name()
+	for _, os := range goosSuffixes {
+		if strings.HasSuffix(fn, os) {
+			f.PlatformDependent()
+			return
+		}
+	}
+	for _, arch := range goarchSuffixes {
+		if strings.HasSuffix(fn, arch) {
+			f.PlatformDependent()
+			return
+		}
+	}
+
+	// get from build constraint
+	if cgs == nil {
+		return
+	}
+	for _, cg := range cgs {
+		for _, c := range cg.List {
+			if strings.HasPrefix(c.Text, buildPrefix) {
+				f.PlatformDependent()
+				return
+			}
+		}
+	}
+}
diff --git a/go/token/position.go b/go/token/position.go
index fbe1763..464599a 100644
--- a/go/token/position.go
+++ b/go/token/position.go
@@ -166,6 +166,8 @@ type File struct {
 	// lines and infos are protected by set.mutex
 	lines []int
 	infos []lineInfo
+
+	platformDep bool // platformDep indicate whether this file is platform dependent
 }
 
 // Name returns the file name of file f as registered with AddFile.
@@ -314,6 +316,16 @@ func (f *File) info(offset int) (filename string, line, column int) {
 	return
 }
 
+// IsPlatformDependent returns whether this file platform dependent
+func (f *File) IsPlatformDependent() bool {
+	return f.platformDep
+}
+
+// PlatformDependent sets this file is platform dependent (default is false)
+func (f *File) PlatformDependent() {
+	f.platformDep = true
+}
+
 // A FileSet represents a set of source files.
 // Methods of file sets are synchronized; multiple goroutines
 // may invoke them concurrently.
@@ -366,7 +378,7 @@ func (s *FileSet) AddFile(filename string, base, size int) *File {
 		panic("illegal base or size")
 	}
 	// base >= s.base && size >= 0
-	f := &File{s, filename, base, size, []int{0}, nil}
+	f := &File{s, filename, base, size, []int{0}, nil, false}
 	base += size + 1 // +1 because EOF also has a position
 	if base < 0 {
 		panic("token.Pos offset overflow (> 2G of source code in file set)")
diff --git a/godef.go b/godef.go
index a9198a3..2f98868 100644
--- a/godef.go
+++ b/godef.go
@@ -28,6 +28,7 @@ var aflag = flag.Bool("a", false, "print public type and member information")
 var Aflag = flag.Bool("A", false, "print all type and members information")
 var fflag = flag.String("f", "", "Go source filename")
 var acmeFlag = flag.Bool("acme", false, "use current acme window")
+var pflag = flag.Bool("p", false, "print all platform-dependent definitions")
 
 func fail(s string, a ...interface{}) {
 	fmt.Fprint(os.Stderr, "godef: "+fmt.Sprintf(s, a...)+"\n")
@@ -86,7 +87,12 @@ func main() {
 		src = b
 	}
 	pkgScope := ast.NewScope(parser.Universe)
-	f, err := parser.ParseFile(types.FileSet, filename, src, 0, pkgScope)
+	var mode uint
+	if *pflag {
+		// parse comments to get build constraint
+		mode |= parser.ParseComments
+	}
+	f, err := parser.ParseFile(types.FileSet, filename, src, mode, pkgScope)
 	if f == nil {
 		fail("cannot parse %s: %v", filename, err)
 	}
@@ -218,8 +224,15 @@ func (o orderedObjects) Swap(i, j int)      { o[i], o[j] = o[j], o[i] }
 
 func done(obj *ast.Object, typ types.Type) {
 	defer os.Exit(0)
-	pos := types.FileSet.Position(types.DeclPos(obj))
-	fmt.Printf("%v\n", pos)
+	if *pflag {
+		for o := obj; o != nil; o = o.Next {
+			pos := types.FileSet.Position(types.DeclPos(o))
+			fmt.Printf("%v\n", pos)
+		}
+	} else {
+		pos := types.FileSet.Position(types.DeclPos(obj))
+		fmt.Printf("%v\n", pos)
+	}
 	if typ.Kind == ast.Bad || !*tflag {
 		return
 	}
@@ -310,6 +323,12 @@ func parseLocalPackage(filename string, src *ast.File, pkgScope *ast.Scope) (*as
 		return nil, errNoPkgFiles
 	}
 
+	var mode uint
+	if *pflag {
+		// parse comments to get build constraint
+		mode |= parser.ParseComments
+	}
+
 	for _, pf := range list {
 		file := filepath.Join(d, pf)
 		if !strings.HasSuffix(pf, ".go") ||
@@ -317,7 +336,7 @@ func parseLocalPackage(filename string, src *ast.File, pkgScope *ast.Scope) (*as
 			pkgName(file) != pkg.Name {
 			continue
 		}
-		src, err := parser.ParseFile(types.FileSet, file, nil, 0, pkg.Scope)
+		src, err := parser.ParseFile(types.FileSet, file, nil, mode, pkg.Scope)
 		if err == nil {
 			pkg.Files[file] = src
 		}