Russ Cox | 57eb06f | 2012-02-16 23:51:04 -0500 | [diff] [blame] | 1 | // run |
Russ Cox | b6ad074 | 2010-03-31 11:47:09 -0700 | [diff] [blame] | 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 | } |