github.com/likebike/go--@v0.0.0-20190911215757-0bd925d16e96/go/src/cmd/vet/atomic.go (about)

     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 main
     6  
     7  import (
     8  	"go/ast"
     9  	"go/token"
    10  )
    11  
    12  func 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)
    21  func 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
    53  func (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  }