1// Copyright 2013 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
5package main
6
7import (
8	"go/ast"
9	"go/token"
10)
11
12func init() {
13	register("atomic",
14		"check for common mistaken usages of the sync/atomic package",
15		checkAtomicAssignment,
16		assignStmt)
17}
18
19// checkAtomicAssignment walks the assignment statement checking for common
20// mistaken usage of atomic package, such as: x = atomic.AddUint64(&x, 1)
21func checkAtomicAssignment(f *File, node ast.Node) {
22	n := node.(*ast.AssignStmt)
23	if len(n.Lhs) != len(n.Rhs) {
24		return
25	}
26	if len(n.Lhs) == 1 && n.Tok == token.DEFINE {
27		return
28	}
29
30	for i, right := range n.Rhs {
31		call, ok := right.(*ast.CallExpr)
32		if !ok {
33			continue
34		}
35		sel, ok := call.Fun.(*ast.SelectorExpr)
36		if !ok {
37			continue
38		}
39		pkg, ok := sel.X.(*ast.Ident)
40		if !ok || pkg.Name != "atomic" {
41			continue
42		}
43
44		switch sel.Sel.Name {
45		case "AddInt32", "AddInt64", "AddUint32", "AddUint64", "AddUintptr":
46			f.checkAtomicAddAssignment(n.Lhs[i], call)
47		}
48	}
49}
50
51// checkAtomicAddAssignment walks the atomic.Add* method calls checking for assigning the return value
52// to the same variable being used in the operation
53func (f *File) checkAtomicAddAssignment(left ast.Expr, call *ast.CallExpr) {
54	if len(call.Args) != 2 {
55		return
56	}
57	arg := call.Args[0]
58	broken := false
59
60	if uarg, ok := arg.(*ast.UnaryExpr); ok && uarg.Op == token.AND {
61		broken = f.gofmt(left) == f.gofmt(uarg.X)
62	} else if star, ok := left.(*ast.StarExpr); ok {
63		broken = f.gofmt(star.X) == f.gofmt(arg)
64	}
65
66	if broken {
67		f.Bad(left.Pos(), "direct assignment to atomic value")
68	}
69}
70