atomic.go

Documentation: golang.org/x/tools/go/analysis/passes/atomic

     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  
     5  // Package atomic defines an Analyzer that checks for common mistakes
     6  // using the sync/atomic package.
     7  package atomic
     8  
     9  import (
    10  	"go/ast"
    11  	"go/token"
    12  	"go/types"
    13  
    14  	"golang.org/x/tools/go/analysis"
    15  	"golang.org/x/tools/go/analysis/passes/inspect"
    16  	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
    17  	"golang.org/x/tools/go/ast/inspector"
    18  )
    19  
    20  const Doc = `check for common mistakes using the sync/atomic package
    21  
    22  The atomic checker looks for assignment statements of the form:
    23  
    24  	x = atomic.AddUint64(&x, 1)
    25  
    26  which are not atomic.`
    27  
    28  var Analyzer = &analysis.Analyzer{
    29  	Name:             "atomic",
    30  	Doc:              Doc,
    31  	Requires:         []*analysis.Analyzer{inspect.Analyzer},
    32  	RunDespiteErrors: true,
    33  	Run:              run,
    34  }
    35  
    36  func run(pass *analysis.Pass) (interface{}, error) {
    37  	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
    38  
    39  	nodeFilter := []ast.Node{
    40  		(*ast.AssignStmt)(nil),
    41  	}
    42  	inspect.Preorder(nodeFilter, func(node ast.Node) {
    43  		n := node.(*ast.AssignStmt)
    44  		if len(n.Lhs) != len(n.Rhs) {
    45  			return
    46  		}
    47  		if len(n.Lhs) == 1 && n.Tok == token.DEFINE {
    48  			return
    49  		}
    50  
    51  		for i, right := range n.Rhs {
    52  			call, ok := right.(*ast.CallExpr)
    53  			if !ok {
    54  				continue
    55  			}
    56  			sel, ok := call.Fun.(*ast.SelectorExpr)
    57  			if !ok {
    58  				continue
    59  			}
    60  			pkgIdent, _ := sel.X.(*ast.Ident)
    61  			pkgName, ok := pass.TypesInfo.Uses[pkgIdent].(*types.PkgName)
    62  			if !ok || pkgName.Imported().Path() != "sync/atomic" {
    63  				continue
    64  			}
    65  
    66  			switch sel.Sel.Name {
    67  			case "AddInt32", "AddInt64", "AddUint32", "AddUint64", "AddUintptr":
    68  				checkAtomicAddAssignment(pass, n.Lhs[i], call)
    69  			}
    70  		}
    71  	})
    72  	return nil, nil
    73  }
    74  
    75  // checkAtomicAddAssignment walks the atomic.Add* method calls checking
    76  // for assigning the return value to the same variable being used in the
    77  // operation
    78  func checkAtomicAddAssignment(pass *analysis.Pass, left ast.Expr, call *ast.CallExpr) {
    79  	if len(call.Args) != 2 {
    80  		return
    81  	}
    82  	arg := call.Args[0]
    83  	broken := false
    84  
    85  	gofmt := func(e ast.Expr) string { return analysisutil.Format(pass.Fset, e) }
    86  
    87  	if uarg, ok := arg.(*ast.UnaryExpr); ok && uarg.Op == token.AND {
    88  		broken = gofmt(left) == gofmt(uarg.X)
    89  	} else if star, ok := left.(*ast.StarExpr); ok {
    90  		broken = gofmt(star.X) == gofmt(arg)
    91  	}
    92  
    93  	if broken {
    94  		pass.ReportRangef(left, "direct assignment to atomic value")
    95  	}
    96  }
    97
View as plain text