cmd/internal/obj: change linkgetline from C to Go func style

Passes toolstash -cmp.

Change-Id: I8725dee490778be9c1fd31990a6b27df9713c3c9
Reviewed-on: https://go-review.googlesource.com/20957Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/obj/line_test.go

@@ -40,9 +40,7 @@ func TestLineHist(t *testing.T) {
 	}
 
 	for i, want := range expect {
-		var f *LSym
-		var l int32
-		linkgetline(ctxt, int32(i), &f, &l)
+		f, l := linkgetline(ctxt, int32(i))
 		have := fmt.Sprintf("%s:%d", f.Name, l)
 		if have != want {
 			t.Errorf("linkgetline(%d) = %q, want %q", i, have, want)

src/cmd/internal/obj/obj.go

@@ -273,18 +273,15 @@ func (h *LineHist) AbsFileLine(lineno int) (file string, line int) {
 // This is a simplified copy of linklinefmt above.
 // It doesn't allow printing the full stack, and it returns the file name and line number separately.
 // TODO: Unify with linklinefmt somehow.
-func linkgetline(ctxt *Link, lineno int32, f **LSym, l *int32) {
+func linkgetline(ctxt *Link, lineno int32) (f *LSym, l int32) {
 	stk := ctxt.LineHist.At(int(lineno))
 	if stk == nil || stk.AbsFile == "" {
-		*f = Linklookup(ctxt, "??", HistVersion)
-		*l = 0
-		return
+		return Linklookup(ctxt, "??", HistVersion), 0
 	}
 	if stk.Sym == nil {
 		stk.Sym = Linklookup(ctxt, stk.AbsFile, HistVersion)
 	}
-	*f = stk.Sym
-	*l = int32(stk.fileLineAt(int(lineno)))
+	return stk.Sym, int32(stk.fileLineAt(int(lineno)))
 }
 
 func Linkprfile(ctxt *Link, line int) {

src/cmd/internal/obj/pcln.go

@@ -143,9 +143,7 @@ func pctofileline(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg
 	if p.As == ATEXT || p.As == ANOP || p.As == AUSEFIELD || p.Lineno == 0 || phase == 1 {
 		return oldval
 	}
-	var l int32
-	var f *LSym
-	linkgetline(ctxt, p.Lineno, &f, &l)
+	f, l := linkgetline(ctxt, p.Lineno)
 	if f == nil {
 		//	print("getline failed for %s %v\n", ctxt->cursym->name, p);
 		return oldval