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Copy pathcfg_test.go
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177 lines (155 loc) · 2.41 KB
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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cfg
import (
"bytes"
"fmt"
"go/ast"
"go/parser"
"go/token"
"testing"
)
const src = `package main
import "log"
func f1() {
live()
return
dead()
}
func f2() {
for {
live()
}
dead()
}
func f3() {
if true { // even known values are ignored
return
}
for true { // even known values are ignored
live()
}
for {
live()
}
dead()
}
func f4(x int) {
switch x {
case 1:
live()
fallthrough
case 2:
live()
log.Fatal()
default:
panic("oops")
}
dead()
}
func f4(ch chan int) {
select {
case <-ch:
live()
return
default:
live()
panic("oops")
}
dead()
}
func f5(unknown bool) {
for {
if unknown {
break
}
continue
dead()
}
live()
}
func f6(unknown bool) {
outer:
for {
for {
break outer
dead()
}
dead()
}
live()
}
func f7() {
for {
break nosuchlabel
dead()
}
dead()
}
func f8() {
select{}
dead()
}
func f9(ch chan int) {
select {
case <-ch:
return
}
dead()
}
func f10(ch chan int) {
select {
case <-ch:
return
dead()
default:
}
live()
}
func f11() {
goto; // mustn't crash
dead()
}
`
func TestDeadCode(t *testing.T) {
// We'll use dead code detection to verify the CFG.
fset := token.NewFileSet()
f, err := parser.ParseFile(fset, "dummy.go", src, parser.Mode(0))
if err != nil {
t.Fatal(err)
}
for _, decl := range f.Decls {
if decl, ok := decl.(*ast.FuncDecl); ok {
g := New(decl.Body, mayReturn)
// Print statements in unreachable blocks
// (in order determined by builder).
var buf bytes.Buffer
for _, b := range g.Blocks {
if !b.Live {
for _, n := range b.Nodes {
fmt.Fprintf(&buf, "\t%s\n", formatNode(fset, n))
}
}
}
// Check that the result contains "dead" at least once but not "live".
if !bytes.Contains(buf.Bytes(), []byte("dead")) ||
bytes.Contains(buf.Bytes(), []byte("live")) {
t.Errorf("unexpected dead statements in function %s:\n%s",
decl.Name.Name,
&buf)
t.Logf("control flow graph:\n%s", g.Format(fset))
}
}
}
}
// A trivial mayReturn predicate that looks only at syntax, not types.
func mayReturn(call *ast.CallExpr) bool {
switch fun := call.Fun.(type) {
case *ast.Ident:
return fun.Name != "panic"
case *ast.SelectorExpr:
return fun.Sel.Name != "Fatal"
}
return true
}