libgo/go/cmd/vet/testdata/lostcancel.go

   1 // Copyright 2016 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         "context"
   9         "log"
  10         "os"
  11         "testing"
  12 )
  13
  14 // Check the three functions and assignment forms (var, :=, =) we look for.
  15 // (Do these early: line numbers are fragile.)
  16 func _() {
  17         var ctx, cancel = context.WithCancel() // ERROR "the cancel function is not used on all paths \(possible context leak\)"
  18 } // ERROR "this return statement may be reached without using the cancel var defined on line 17"
  19
  20 func _() {
  21         ctx, cancel2 := context.WithDeadline() // ERROR "the cancel2 function is not used..."
  22 } // ERROR "may be reached without using the cancel2 var defined on line 21"
  23
  24 func _() {
  25         var ctx context.Context
  26         var cancel3 func()
  27         ctx, cancel3 = context.WithTimeout() // ERROR "function is not used..."
  28 } // ERROR "this return statement may be reached without using the cancel3 var defined on line 27"
  29
  30 func _() {
  31         ctx, _ := context.WithCancel()  // ERROR "the cancel function returned by context.WithCancel should be called, not discarded, to avoid a context leak"
  32         ctx, _ = context.WithTimeout()  // ERROR "the cancel function returned by context.WithTimeout should be called, not discarded, to avoid a context leak"
  33         ctx, _ = context.WithDeadline() // ERROR "the cancel function returned by context.WithDeadline should be called, not discarded, to avoid a context leak"
  34 }
  35
  36 func _() {
  37         ctx, cancel := context.WithCancel()
  38         defer cancel() // ok
  39 }
  40
  41 func _() {
  42         ctx, cancel := context.WithCancel() // ERROR "not used on all paths"
  43         if condition {
  44                 cancel()
  45         }
  46         return // ERROR "this return statement may be reached without using the cancel var"
  47 }
  48
  49 func _() {
  50         ctx, cancel := context.WithCancel()
  51         if condition {
  52                 cancel()
  53         } else {
  54                 // ok: infinite loop
  55                 for {
  56                         print(0)
  57                 }
  58         }
  59 }
  60
  61 func _() {
  62         ctx, cancel := context.WithCancel() // ERROR "not used on all paths"
  63         if condition {
  64                 cancel()
  65         } else {
  66                 for i := 0; i < 10; i++ {
  67                         print(0)
  68                 }
  69         }
  70 } // ERROR "this return statement may be reached without using the cancel var"
  71
  72 func _() {
  73         ctx, cancel := context.WithCancel()
  74         // ok: used on all paths
  75         switch someInt {
  76         case 0:
  77                 new(testing.T).FailNow()
  78         case 1:
  79                 log.Fatal()
  80         case 2:
  81                 cancel()
  82         case 3:
  83                 print("hi")
  84                 fallthrough
  85         default:
  86                 os.Exit(1)
  87         }
  88 }
  89
  90 func _() {
  91         ctx, cancel := context.WithCancel() // ERROR "not used on all paths"
  92         switch someInt {
  93         case 0:
  94                 new(testing.T).FailNow()
  95         case 1:
  96                 log.Fatal()
  97         case 2:
  98                 cancel()
  99         case 3:
 100                 print("hi") // falls through to implicit return
 101         default:
 102                 os.Exit(1)
 103         }
 104 } // ERROR "this return statement may be reached without using the cancel var"
 105
 106 func _(ch chan int) int {
 107         ctx, cancel := context.WithCancel() // ERROR "not used on all paths"
 108         select {
 109         case <-ch:
 110                 new(testing.T).FailNow()
 111         case y <- ch:
 112                 print("hi") // falls through to implicit return
 113         case ch <- 1:
 114                 cancel()
 115         default:
 116                 os.Exit(1)
 117         }
 118 } // ERROR "this return statement may be reached without using the cancel var"
 119
 120 func _(ch chan int) int {
 121         ctx, cancel := context.WithCancel()
 122         // A blocking select must execute one of its cases.
 123         select {
 124         case <-ch:
 125                 panic()
 126         }
 127 }
 128
 129 func _() {
 130         go func() {
 131                 ctx, cancel := context.WithCancel() // ERROR "not used on all paths"
 132                 print(ctx)
 133         }() // ERROR "may be reached without using the cancel var"
 134 }
 135
 136 var condition bool
 137 var someInt int
 138
 139 // Regression test for Go issue 16143.
 140 func _() {
 141         var x struct{ f func() }
 142         x.f()
 143 }
 144
 145 // Regression test for Go issue 16230.
 146 func _() (ctx context.Context, cancel func()) {
 147         ctx, cancel = context.WithCancel()
 148         return // a naked return counts as a load of the named result values
 149 }
 150
 151 // Same as above, but for literal function.
 152 var _ = func() (ctx context.Context, cancel func()) {
 153         ctx, cancel = context.WithCancel()
 154         return
 155 }