gcc/testsuite/go.test/test/recover1.go

   1 // run
   2
   3 // Copyright 2010 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 // Test of recover during recursive panics.
   8 // Here be dragons.
   9
  10 package main
  11
  12 import "runtime"
  13
  14 func main() {
  15         test1()
  16         test2()
  17         test3()
  18         test4()
  19         test5()
  20         test6()
  21         test7()
  22 }
  23
  24 func die() {
  25         runtime.Breakpoint()    // can't depend on panic
  26 }
  27
  28 func mustRecover(x interface{}) {
  29         mustNotRecover()        // because it's not a defer call
  30         v := recover()
  31         if v == nil {
  32                 println("missing recover")
  33                 die()   // panic is useless here
  34         }
  35         if v != x {
  36                 println("wrong value", v, x)
  37                 die()
  38         }
  39
  40         // the value should be gone now regardless
  41         v = recover()
  42         if v != nil {
  43                 println("recover didn't recover")
  44                 die()
  45         }
  46 }
  47
  48 func mustNotRecover() {
  49         v := recover()
  50         if v != nil {
  51                 println("spurious recover")
  52                 die()
  53         }
  54 }
  55
  56 func withoutRecover() {
  57         mustNotRecover()        // because it's a sub-call
  58 }
  59
  60 func test1() {
  61         // Easy nested recursive panic.
  62         defer mustRecover(1)
  63         defer func() {
  64                 defer mustRecover(2)
  65                 panic(2)
  66         }()
  67         panic(1)
  68 }
  69
  70 func test2() {
  71         // Sequential panic.
  72         defer mustNotRecover()
  73         defer func() {
  74                 v := recover()
  75                 if v == nil || v.(int) != 2 {
  76                         println("wrong value", v, 2)
  77                         die()
  78                 }
  79                 defer mustRecover(3)
  80                 panic(3)
  81         }()
  82         panic(2)
  83 }
  84
  85 func test3() {
  86         // Sequential panic - like test2 but less picky.
  87         defer mustNotRecover()
  88         defer func() {
  89                 recover()
  90                 defer mustRecover(3)
  91                 panic(3)
  92         }()
  93         panic(2)
  94 }
  95
  96 func test4() {
  97         // Single panic.
  98         defer mustNotRecover()
  99         defer func() {
 100                 recover()
 101         }()
 102         panic(4)
 103 }
 104
 105 func test5() {
 106         // Single panic but recover called via defer
 107         defer mustNotRecover()
 108         defer func() {
 109                 defer recover()
 110         }()
 111         panic(5)
 112 }
 113
 114 func test6() {
 115         // Sequential panic.
 116         // Like test3, but changed recover to defer (same change as test4 → test5).
 117         defer mustNotRecover()
 118         defer func() {
 119                 defer recover() // like a normal call from this func; runs because mustRecover stops the panic
 120                 defer mustRecover(3)
 121                 panic(3)
 122         }()
 123         panic(2)
 124 }
 125
 126 func test7() {
 127         // Like test6, but swapped defer order.
 128         // The recover in "defer recover()" is now a no-op,
 129         // because it runs called from panic, not from the func,
 130         // and therefore cannot see the panic of 2.
 131         // (Alternately, it cannot see the panic of 2 because
 132         // there is an active panic of 3.  And it cannot see the
 133         // panic of 3 because it is at the wrong level (too high on the stack).)
 134         defer mustRecover(2)
 135         defer func() {
 136                 defer mustRecover(3)
 137                 defer recover() // now a no-op, unlike in test6.
 138                 panic(3)
 139         }()
 140         panic(2)
 141 }