runtime/pprof: don't print extraneous 0 after goexit

This fixes erroneous handling of the more result parameter of
runtime.Frames.Next.

Fixes #16349.

Change-Id: I4f1c0263dafbb883294b31dbb8922b9d3e650200
Reviewed-on: https://go-review.googlesource.com/24911
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/pprof/pprof.go

@@ -353,12 +353,9 @@ func printStackRecord(w io.Writer, stk []uintptr, allFrames bool) {
 		if name == "" {
 			show = true
 			fmt.Fprintf(w, "#\t%#x\n", frame.PC)
-		} else {
+		} else if name != "runtime.goexit" && (show || !strings.HasPrefix(name, "runtime.")) {
 			// Hide runtime.goexit and any runtime functions at the beginning.
 			// This is useful mainly for allocation traces.
-			if name == "runtime.goexit" || !show && strings.HasPrefix(name, "runtime.") {
-				continue
-			}
 			show = true
 			fmt.Fprintf(w, "#\t%#x\t%s+%#x\t%s:%d\n", frame.PC, name, frame.PC-frame.Entry, frame.File, frame.Line)
 		}

src/runtime/pprof/pprof_test.go

@@ -497,6 +497,10 @@ func TestBlockProfile(t *testing.T) {
 		t.Fatalf("Bad profile header:\n%v", prof)
 	}
 
+	if strings.HasSuffix(prof, "#\t0x0\n\n") {
+		t.Errorf("Useless 0 suffix:\n%v", prof)
+	}
+
 	for _, test := range tests {
 		if !regexp.MustCompile(strings.Replace(test.re, "\t", "\t+", -1)).MatchString(prof) {
 			t.Fatalf("Bad %v entry, expect:\n%v\ngot:\n%v", test.name, test.re, prof)