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Source file src/cmd/vet/atomic.go

Documentation: cmd/vet

  // Copyright 2013 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 main
  
  import (
  	"go/ast"
  	"go/token"
  )
  
  func init() {
  	register("atomic",
  		"check for common mistaken usages of the sync/atomic package",
  		checkAtomicAssignment,
  		assignStmt)
  }
  
  // checkAtomicAssignment walks the assignment statement checking for common
  // mistaken usage of atomic package, such as: x = atomic.AddUint64(&x, 1)
  func checkAtomicAssignment(f *File, node ast.Node) {
  	n := node.(*ast.AssignStmt)
  	if len(n.Lhs) != len(n.Rhs) {
  		return
  	}
  	if len(n.Lhs) == 1 && n.Tok == token.DEFINE {
  		return
  	}
  
  	for i, right := range n.Rhs {
  		call, ok := right.(*ast.CallExpr)
  		if !ok {
  			continue
  		}
  		sel, ok := call.Fun.(*ast.SelectorExpr)
  		if !ok {
  			continue
  		}
  		pkg, ok := sel.X.(*ast.Ident)
  		if !ok || pkg.Name != "atomic" {
  			continue
  		}
  
  		switch sel.Sel.Name {
  		case "AddInt32", "AddInt64", "AddUint32", "AddUint64", "AddUintptr":
  			f.checkAtomicAddAssignment(n.Lhs[i], call)
  		}
  	}
  }
  
  // checkAtomicAddAssignment walks the atomic.Add* method calls checking for assigning the return value
  // to the same variable being used in the operation
  func (f *File) checkAtomicAddAssignment(left ast.Expr, call *ast.CallExpr) {
  	if len(call.Args) != 2 {
  		return
  	}
  	arg := call.Args[0]
  	broken := false
  
  	if uarg, ok := arg.(*ast.UnaryExpr); ok && uarg.Op == token.AND {
  		broken = f.gofmt(left) == f.gofmt(uarg.X)
  	} else if star, ok := left.(*ast.StarExpr); ok {
  		broken = f.gofmt(star.X) == f.gofmt(arg)
  	}
  
  	if broken {
  		f.Bad(left.Pos(), "direct assignment to atomic value")
  	}
  }
  

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