75 lines
2.1 KiB
Go
75 lines
2.1 KiB
Go
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package sa5002
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import (
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"go/ast"
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"go/constant"
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"go/types"
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"honnef.co/go/tools/analysis/code"
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"honnef.co/go/tools/analysis/lint"
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"honnef.co/go/tools/analysis/report"
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"golang.org/x/tools/go/analysis"
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"golang.org/x/tools/go/analysis/passes/inspect"
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)
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var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
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Analyzer: &analysis.Analyzer{
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Name: "SA5002",
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Run: run,
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Requires: []*analysis.Analyzer{inspect.Analyzer},
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},
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Doc: &lint.RawDocumentation{
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Title: `The empty for loop (\"for {}\") spins and can block the scheduler`,
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Since: "2017.1",
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Severity: lint.SeverityWarning,
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MergeIf: lint.MergeIfAny,
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},
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})
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var Analyzer = SCAnalyzer.Analyzer
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func run(pass *analysis.Pass) (any, error) {
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fn := func(node ast.Node) {
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loop := node.(*ast.ForStmt)
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if len(loop.Body.List) != 0 || loop.Post != nil {
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return
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}
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if loop.Init != nil {
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// TODO(dh): this isn't strictly necessary, it just makes
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// the check easier.
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return
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}
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// An empty loop is bad news in two cases: 1) The loop has no
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// condition. In that case, it's just a loop that spins
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// forever and as fast as it can, keeping a core busy. 2) The
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// loop condition only consists of variable or field reads and
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// operators on those. The only way those could change their
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// value is with unsynchronised access, which constitutes a
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// data race.
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//
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// If the condition contains any function calls, its behaviour
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// is dynamic and the loop might terminate. Similarly for
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// channel receives.
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if loop.Cond != nil {
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if code.MayHaveSideEffects(pass, loop.Cond, nil) {
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return
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}
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if ident, ok := loop.Cond.(*ast.Ident); ok {
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if k, ok := pass.TypesInfo.ObjectOf(ident).(*types.Const); ok {
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if !constant.BoolVal(k.Val()) {
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// don't flag `for false {}` loops. They're a debug aid.
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return
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}
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}
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}
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report.Report(pass, loop, "loop condition never changes or has a race condition")
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}
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report.Report(pass, loop, "this loop will spin, using 100% CPU", report.ShortRange())
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}
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code.Preorder(pass, fn, (*ast.ForStmt)(nil))
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return nil, nil
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}
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