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x/tools/go/analysis/passes/ctrlflow: encode more knowledge about standard library in ctrlflow analyzer #497

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x/tools/go/analysis/passes/ctrlflow: encode more knowledge about standard library in ctrlflow analyzer #497

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24 changes: 23 additions & 1 deletion go/analysis/passes/ctrlflow/ctrlflow.go
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Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,21 @@ func (c *CFGs) callMayReturn(call *ast.CallExpr) (r bool) {
return false // panic never returns
}

// "Some driver implementations (such as those based on Bazel and Blaze) do not
// currently apply analyzers to packages of the standard library. Therefore, for
// best results, analyzer authors should not rely on analysis facts being available
// for standard packages." [1].
// This means that we cannot rely on the noReturn fact being available for standard
// library functions.
// Therefore, here we check if the function is an intrinsic no-return function.
//
// [1]: https://pkg.go.dev/golang.org/x/tools/go/analysis
if sel, ok := call.Fun.(*ast.SelectorExpr); ok {
if fn, ok := c.pass.TypesInfo.ObjectOf(sel.Sel).(*types.Func); ok && isIntrinsicNoReturn(fn) {
return false // intrinsic no-return functions
}
}

// Is this a static call? Also includes static functions
// parameterized by a type. Such functions may or may not
// return depending on the parameter type, but in some
Expand Down Expand Up @@ -227,5 +242,12 @@ func isIntrinsicNoReturn(fn *types.Func) bool {
// Add functions here as the need arises, but don't allocate memory.
path, name := fn.Pkg().Path(), fn.Name()
return path == "syscall" && (name == "Exit" || name == "ExitProcess" || name == "ExitThread") ||
path == "runtime" && name == "Goexit"
(path == "runtime" && name == "Goexit") ||
// Ideally we should not need to list the following functions since they
// internally call the functions above. However, we will only know that _if_
// we also analyze the standard library. For some driver implementations like
// Bazel it would not do so currently. Therefore, we list them here.
(path == "log" && (name == "Fatal" || name == "Fatalf")) ||
(path == "os" && (name == "Exit")) ||
(path == "testing" && (name == "FailNow" || name == "Skip" || name == "Skipf" || name == "SkipNow"))
}