libgo/go/cmd/vet/testdata/unsafeptr.go

   1 // Copyright 2014 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package testdata
   6
   7 import (
   8         "reflect"
   9         "unsafe"
  10 )
  11
  12 func f() {
  13         var x unsafe.Pointer
  14         var y uintptr
  15         x = unsafe.Pointer(y) // ERROR "possible misuse of unsafe.Pointer"
  16         y = uintptr(x)
  17
  18         // only allowed pointer arithmetic is ptr +/-/&^ num.
  19         // num+ptr is technically okay but still flagged: write ptr+num instead.
  20         x = unsafe.Pointer(uintptr(x) + 1)
  21         x = unsafe.Pointer(1 + uintptr(x))          // ERROR "possible misuse of unsafe.Pointer"
  22         x = unsafe.Pointer(uintptr(x) + uintptr(x)) // ERROR "possible misuse of unsafe.Pointer"
  23         x = unsafe.Pointer(uintptr(x) - 1)
  24         x = unsafe.Pointer(1 - uintptr(x)) // ERROR "possible misuse of unsafe.Pointer"
  25         x = unsafe.Pointer(uintptr(x) &^ 3)
  26         x = unsafe.Pointer(1 &^ uintptr(x)) // ERROR "possible misuse of unsafe.Pointer"
  27
  28         // certain uses of reflect are okay
  29         var v reflect.Value
  30         x = unsafe.Pointer(v.Pointer())
  31         x = unsafe.Pointer(v.UnsafeAddr())
  32         var s1 *reflect.StringHeader
  33         x = unsafe.Pointer(s1.Data)
  34         var s2 *reflect.SliceHeader
  35         x = unsafe.Pointer(s2.Data)
  36         var s3 reflect.StringHeader
  37         x = unsafe.Pointer(s3.Data) // ERROR "possible misuse of unsafe.Pointer"
  38         var s4 reflect.SliceHeader
  39         x = unsafe.Pointer(s4.Data) // ERROR "possible misuse of unsafe.Pointer"
  40
  41         // but only in reflect
  42         var vv V
  43         x = unsafe.Pointer(vv.Pointer())    // ERROR "possible misuse of unsafe.Pointer"
  44         x = unsafe.Pointer(vv.UnsafeAddr()) // ERROR "possible misuse of unsafe.Pointer"
  45         var ss1 *StringHeader
  46         x = unsafe.Pointer(ss1.Data) // ERROR "possible misuse of unsafe.Pointer"
  47         var ss2 *SliceHeader
  48         x = unsafe.Pointer(ss2.Data) // ERROR "possible misuse of unsafe.Pointer"
  49
  50 }
  51
  52 type V interface {
  53         Pointer() uintptr
  54         UnsafeAddr() uintptr
  55 }
  56
  57 type StringHeader struct {
  58         Data uintptr
  59 }
  60
  61 type SliceHeader struct {
  62         Data uintptr
  63 }