| 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 cfg |
| 6 | |
| 7 | import ( |
| 8 | "bytes" |
| 9 | "fmt" |
| 10 | "go/ast" |
| 11 | "go/parser" |
| 12 | "go/token" |
| 13 | "testing" |
| 14 | ) |
| 15 | |
| 16 | const src = `package main |
| 17 | |
| 18 | import "log" |
| 19 | |
| 20 | func f1() { |
| 21 | live() |
| 22 | return |
| 23 | dead() |
| 24 | } |
| 25 | |
| 26 | func f2() { |
| 27 | for { |
| 28 | live() |
| 29 | } |
| 30 | dead() |
| 31 | } |
| 32 | |
| 33 | func f3() { |
| 34 | if true { // even known values are ignored |
| 35 | return |
| 36 | } |
| 37 | for true { // even known values are ignored |
| 38 | live() |
| 39 | } |
| 40 | for { |
| 41 | live() |
| 42 | } |
| 43 | dead() |
| 44 | } |
| 45 | |
| 46 | func f4(x int) { |
| 47 | switch x { |
| 48 | case 1: |
| 49 | live() |
| 50 | fallthrough |
| 51 | case 2: |
| 52 | live() |
| 53 | log.Fatal() |
| 54 | default: |
| 55 | panic("oops") |
| 56 | } |
| 57 | dead() |
| 58 | } |
| 59 | |
| 60 | func f4(ch chan int) { |
| 61 | select { |
| 62 | case <-ch: |
| 63 | live() |
| 64 | return |
| 65 | default: |
| 66 | live() |
| 67 | panic("oops") |
| 68 | } |
| 69 | dead() |
| 70 | } |
| 71 | |
| 72 | func f5(unknown bool) { |
| 73 | for { |
| 74 | if unknown { |
| 75 | break |
| 76 | } |
| 77 | continue |
| 78 | dead() |
| 79 | } |
| 80 | live() |
| 81 | } |
| 82 | |
| 83 | func f6(unknown bool) { |
| 84 | outer: |
| 85 | for { |
| 86 | for { |
| 87 | break outer |
| 88 | dead() |
| 89 | } |
| 90 | dead() |
| 91 | } |
| 92 | live() |
| 93 | } |
| 94 | |
| 95 | func f7() { |
| 96 | for { |
| 97 | break nosuchlabel |
| 98 | dead() |
| 99 | } |
| 100 | dead() |
| 101 | } |
| 102 | |
| 103 | func f8() { |
| 104 | select{} |
| 105 | dead() |
| 106 | } |
| 107 | |
| 108 | func f9(ch chan int) { |
| 109 | select { |
| 110 | case <-ch: |
| 111 | return |
| 112 | } |
| 113 | dead() |
| 114 | } |
| 115 | |
| 116 | func f10(ch chan int) { |
| 117 | select { |
| 118 | case <-ch: |
| 119 | return |
| 120 | dead() |
| 121 | default: |
| 122 | } |
| 123 | live() |
| 124 | } |
| 125 | |
| 126 | func f11() { |
| 127 | goto; // mustn't crash |
| 128 | dead() |
| 129 | } |
| 130 | |
| 131 | ` |
| 132 | |
| 133 | func TestDeadCode(t *testing.T) { |
| 134 | // We'll use dead code detection to verify the CFG. |
| 135 | |
| 136 | fset := token.NewFileSet() |
| 137 | f, err := parser.ParseFile(fset, "dummy.go", src, parser.Mode(0)) |
| 138 | if err != nil { |
| 139 | t.Fatal(err) |
| 140 | } |
| 141 | for _, decl := range f.Decls { |
| 142 | if decl, ok := decl.(*ast.FuncDecl); ok { |
| 143 | g := New(decl.Body, mayReturn) |
| 144 | |
| 145 | // Print statements in unreachable blocks |
| 146 | // (in order determined by builder). |
| 147 | var buf bytes.Buffer |
| 148 | for _, b := range g.Blocks { |
| 149 | if !b.Live { |
| 150 | for _, n := range b.Nodes { |
| 151 | fmt.Fprintf(&buf, "\t%s\n", formatNode(fset, n)) |
| 152 | } |
| 153 | } |
| 154 | } |
| 155 | |
| 156 | // Check that the result contains "dead" at least once but not "live". |
| 157 | if !bytes.Contains(buf.Bytes(), []byte("dead")) || |
| 158 | bytes.Contains(buf.Bytes(), []byte("live")) { |
| 159 | t.Errorf("unexpected dead statements in function %s:\n%s", |
| 160 | decl.Name.Name, |
| 161 | &buf) |
| 162 | t.Logf("control flow graph:\n%s", g.Format(fset)) |
| 163 | } |
| 164 | } |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | // A trivial mayReturn predicate that looks only at syntax, not types. |
| 169 | func mayReturn(call *ast.CallExpr) bool { |
| 170 | switch fun := call.Fun.(type) { |
| 171 | case *ast.Ident: |
| 172 | return fun.Name != "panic" |
| 173 | case *ast.SelectorExpr: |
| 174 | return fun.Sel.Name != "Fatal" |
| 175 | } |
| 176 | return true |
| 177 | } |
| 178 |
Members