Source file
test/slicecap.go
1
2
3
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5
6
7 package main
8
9 import "unsafe"
10
11 var (
12 hello = "hello"
13 bytes = []byte{1, 2, 3, 4, 5}
14 ints = []int32{1, 2, 3, 4, 5}
15
16 five = 5
17
18 ok = true
19 )
20
21 func notOK() {
22 if ok {
23 println("BUG:")
24 ok = false
25 }
26 }
27
28 func checkString(desc, s string) {
29 p1 := *(*uintptr)(unsafe.Pointer(&s))
30 p2 := *(*uintptr)(unsafe.Pointer(&hello))
31 if p1-p2 >= 5 {
32 notOK()
33 println("string", desc, "has invalid base")
34 }
35 }
36
37 func checkBytes(desc string, s []byte) {
38 p1 := *(*uintptr)(unsafe.Pointer(&s))
39 p2 := *(*uintptr)(unsafe.Pointer(&bytes))
40 if p1-p2 >= 5 {
41 println("byte slice", desc, "has invalid base")
42 }
43 }
44
45 func checkInts(desc string, s []int32) {
46 p1 := *(*uintptr)(unsafe.Pointer(&s))
47 p2 := *(*uintptr)(unsafe.Pointer(&ints))
48 if p1-p2 >= 5*4 {
49 println("int slice", desc, "has invalid base")
50 }
51 }
52
53 func main() {
54 {
55 x := hello
56 checkString("x", x)
57 checkString("x[5:]", x[5:])
58 checkString("x[five:]", x[five:])
59 checkString("x[5:five]", x[5:five])
60 checkString("x[five:5]", x[five:5])
61 checkString("x[five:five]", x[five:five])
62 checkString("x[1:][2:][2:]", x[1:][2:][2:])
63 y := x[4:]
64 checkString("y[1:]", y[1:])
65 }
66 {
67 x := bytes
68 checkBytes("x", x)
69 checkBytes("x[5:]", x[5:])
70 checkBytes("x[five:]", x[five:])
71 checkBytes("x[5:five]", x[5:five])
72 checkBytes("x[five:5]", x[five:5])
73 checkBytes("x[five:five]", x[five:five])
74 checkBytes("x[1:][2:][2:]", x[1:][2:][2:])
75 y := x[4:]
76 checkBytes("y[1:]", y[1:])
77 }
78 {
79 x := ints
80 checkInts("x", x)
81 checkInts("x[5:]", x[5:])
82 checkInts("x[five:]", x[five:])
83 checkInts("x[5:five]", x[5:five])
84 checkInts("x[five:5]", x[five:5])
85 checkInts("x[five:five]", x[five:five])
86 checkInts("x[1:][2:][2:]", x[1:][2:][2:])
87 y := x[4:]
88 checkInts("y[1:]", y[1:])
89 }
90 }
91
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