1// run
2
3// Copyright 2020 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// Test conversion from slice to array pointer.
8
9package main
10
11func wantPanic(fn func(), s string) {
12	defer func() {
13		err := recover()
14		if err == nil {
15			panic("expected panic")
16		}
17		if got := err.(error).Error(); got != s {
18			panic("expected panic " + s + " got " + got)
19		}
20	}()
21	fn()
22}
23
24func main() {
25	s := make([]byte, 8, 10)
26	for i := range s {
27		s[i] = byte(i)
28	}
29	if p := (*[8]byte)(s); &p[0] != &s[0] {
30		panic("*[8]byte conversion failed")
31	}
32	if [8]byte(s) != *(*[8]byte)(s) {
33		panic("[8]byte conversion failed")
34	}
35	wantPanic(
36		func() {
37			_ = (*[9]byte)(s)
38		},
39		"runtime error: cannot convert slice with length 8 to array or pointer to array with length 9",
40	)
41	wantPanic(
42		func() {
43			_ = [9]byte(s)
44		},
45		"runtime error: cannot convert slice with length 8 to array or pointer to array with length 9",
46	)
47
48	var n []byte
49	if p := (*[0]byte)(n); p != nil {
50		panic("nil slice converted to *[0]byte should be nil")
51	}
52	_ = [0]byte(n)
53
54	z := make([]byte, 0)
55	if p := (*[0]byte)(z); p == nil {
56		panic("empty slice converted to *[0]byte should be non-nil")
57	}
58	_ = [0]byte(z)
59
60	var p *[]byte
61	wantPanic(
62		func() {
63			_ = [0]byte(*p) // evaluating *p should still panic
64		},
65		"runtime error: invalid memory address or nil pointer dereference",
66	)
67
68	// Test with named types
69	type Slice []int
70	type Int4 [4]int
71	type PInt4 *[4]int
72	ii := make(Slice, 4)
73	if p := (*Int4)(ii); &p[0] != &ii[0] {
74		panic("*Int4 conversion failed")
75	}
76	if p := PInt4(ii); &p[0] != &ii[0] {
77		panic("PInt4 conversion failed")
78	}
79}
80
81// test static variable conversion
82
83var (
84	ss  = make([]string, 10)
85	s5  = (*[5]string)(ss)
86	s10 = (*[10]string)(ss)
87
88	ns  []string
89	ns0 = (*[0]string)(ns)
90
91	zs  = make([]string, 0)
92	zs0 = (*[0]string)(zs)
93)
94
95func init() {
96	if &ss[0] != &s5[0] {
97		panic("s5 conversion failed")
98	}
99	if &ss[0] != &s10[0] {
100		panic("s5 conversion failed")
101	}
102	if ns0 != nil {
103		panic("ns0 should be nil")
104	}
105	if zs0 == nil {
106		panic("zs0 should not be nil")
107	}
108}
109