test/unsafebuiltins.go

   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 package main
   8
   9 import (
  10         "math"
  11         "unsafe"
  12 )
  13
  14 const maxUintptr = 1 << (8 * unsafe.Sizeof(uintptr(0)))
  15
  16 func main() {
  17         var p [10]byte
  18
  19         // unsafe.Add
  20         {
  21                 p1 := unsafe.Pointer(&p[1])
  22                 assert(unsafe.Add(p1, 1) == unsafe.Pointer(&p[2]))
  23                 assert(unsafe.Add(p1, -1) == unsafe.Pointer(&p[0]))
  24         }
  25
  26         // unsafe.Slice
  27         {
  28                 s := unsafe.Slice(&p[0], len(p))
  29                 assert(&s[0] == &p[0])
  30                 assert(len(s) == len(p))
  31                 assert(cap(s) == len(p))
  32
  33                 // nil pointer
  34                 mustPanic(func() { _ = unsafe.Slice((*int)(nil), 0) })
  35
  36                 // negative length
  37                 var neg int = -1
  38                 mustPanic(func() { _ = unsafe.Slice(new(byte), neg) })
  39
  40                 // length too large
  41                 var tooBig uint64 = math.MaxUint64
  42                 mustPanic(func() { _ = unsafe.Slice(new(byte), tooBig) })
  43
  44                 // size overflows address space
  45                 mustPanic(func() { _ = unsafe.Slice(new(uint64), maxUintptr/8) })
  46                 mustPanic(func() { _ = unsafe.Slice(new(uint64), maxUintptr/8+1) })
  47         }
  48 }
  49
  50 func assert(ok bool) {
  51         if !ok {
  52                 panic("FAIL")
  53         }
  54 }
  55
  56 func mustPanic(f func()) {
  57         defer func() {
  58                 assert(recover() != nil)
  59         }()
  60         f()
  61 }