1// run
2
3// Copyright 2021 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// This tickles a stack-allocation bug when the register ABI is enabled.
8// The original report was from cue, internal/core/adt/equality.go,
9// function equalVertex.
10
11// In the failing case, something bad gets passed to equalTerminal.
12
13package main
14
15import "fmt"
16
17type Kind uint16
18type Flag uint16
19
20const (
21	allKinds Kind = 1
22	TopKind  Kind = (allKinds - 1)
23)
24type Value interface {
25	Kind() Kind
26}
27type Vertex struct {
28	BaseValue Value
29	name string
30}
31func (v *Vertex) Kind() Kind {
32	return TopKind
33}
34
35func main() {
36	vA := &Vertex{name:"vA",}
37	vB := &Vertex{name:"vB",}
38	vX := &Vertex{name:"vX",}
39	vA.BaseValue = vX
40	vB.BaseValue = vX
41	_ = equalVertex(vA, vB, Flag(1))
42}
43
44var foo string
45
46//go:noinline
47func (v *Vertex) IsClosedStruct() bool {
48	return true
49}
50
51func equalVertex(x *Vertex, v Value, flags Flag) bool {
52	y, ok := v.(*Vertex)
53	if !ok {
54		return false
55	}
56	v, ok1 := x.BaseValue.(Value)
57	w, ok2 := y.BaseValue.(Value)
58	if !ok1 && !ok2 {
59		return true // both are struct or list.
60	}
61	return equalTerminal(v, w, flags)
62}
63
64//go:noinline
65func equalTerminal(x Value, y Value, flags Flag) bool {
66	foo = fmt.Sprintf("EQclosed %s %s %d\n", x.(*Vertex).name, y.(*Vertex).name, flags)
67	return true
68}
69