1// run
2
3// Copyright 2016 The Go Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style
5// license that can be found in the LICENSE file.
6
7// issue 17381: make sure leave function with non-empty frame
8// saves link register, so that traceback will work.
9
10package main
11
12import (
13	"runtime"
14	"unsafe"
15)
16
17func main() {
18	defer func() {
19		if recover() == nil {
20			panic("did not panic")
21		}
22		pcs := make([]uintptr, 20)
23		n := runtime.Callers(1, pcs)
24		for _, pc := range pcs[:n] {
25			if runtime.FuncForPC(pc).Name() == "main.main" {
26				return
27			}
28		}
29		panic("cannot find main.main in backtrace")
30	}()
31
32	prep()
33	f() // should panic
34}
35
36func funcPC(f interface{}) uintptr {
37	var ptr uintptr
38	return **(**uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&f)) + unsafe.Sizeof(ptr)))
39}
40
41//go:noinline
42func f() {
43	var t [1]int // non-empty frame
44	*(*int)(nil) = t[0]
45}
46
47var p = funcPC(runtime.GC) + 8
48
49//go:noinline
50func prep() {
51	// put some garbage on stack
52	var x = [20]uintptr{p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p}
53	_ = x
54}
55