1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Interface comparisons using types hidden
// inside reflected-on structs.
package main
import "reflect"
type T struct {
f float32
g float32
s string
t string
u uint32
v uint32
w uint32
x uint32
y uint32
z uint32
}
func add(s, t string) string {
return s + t
}
func assert(b bool) {
if !b {
panic("assert")
}
}
func main() {
var x T
x.f = 1.0
x.g = x.f
x.s = add("abc", "def")
x.t = add("abc", "def")
x.u = 1
x.v = 2
x.w = 1<<28
x.x = 2<<28
x.y = 0x12345678
x.z = x.y
// check mem and string
v := reflect.NewValue(x)
i := v.(*reflect.StructValue).Field(0)
j := v.(*reflect.StructValue).Field(1)
assert(i.Interface() == j.Interface())
s := v.(*reflect.StructValue).Field(2)
t := v.(*reflect.StructValue).Field(3)
assert(s.Interface() == t.Interface())
// make sure different values are different.
// make sure whole word is being compared,
// not just a single byte.
i = v.(*reflect.StructValue).Field(4)
j = v.(*reflect.StructValue).Field(5)
assert(i.Interface() != j.Interface())
i = v.(*reflect.StructValue).Field(6)
j = v.(*reflect.StructValue).Field(7)
assert(i.Interface() != j.Interface())
i = v.(*reflect.StructValue).Field(8)
j = v.(*reflect.StructValue).Field(9)
assert(i.Interface() == j.Interface())
}
/*
comparing uncomparable type float32
throw: interface compare
panic PC=0x28ceb8 [1]
throw+0x41 /Users/rsc/goX/src/runtime/runtime.c:54
throw(0x3014a, 0x0)
ifaceeq+0x15c /Users/rsc/goX/src/runtime/iface.c:501
ifaceeq(0x2aa7c0, 0x0, 0x0, 0x0, 0x2aa7c0, ...)
sys·ifaceeq+0x48 /Users/rsc/goX/src/runtime/iface.c:527
sys·ifaceeq(0x2aa7c0, 0x0, 0x0, 0x0, 0x2aa7c0, ...)
main·main+0x190 /Users/rsc/goX/src/cmd/gc/x.go:10
main·main()
mainstart+0xf /Users/rsc/goX/src/runtime/amd64/asm.s:53
mainstart()
sys·Goexit /Users/rsc/goX/src/runtime/proc.c:124
sys·Goexit()
*/
|
