| // Copyright 2023 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 nilness inspects the control-flow graph of an SSA function |
| // and reports errors such as nil pointer dereferences and degenerate |
| // nil pointer comparisons. |
| // |
| // # Analyzer nilness |
| // |
| // nilness: check for redundant or impossible nil comparisons |
| // |
| // The nilness checker inspects the control-flow graph of each function in |
| // a package and reports nil pointer dereferences, degenerate nil |
| // pointers, and panics with nil values. A degenerate comparison is of the form |
| // x==nil or x!=nil where x is statically known to be nil or non-nil. These are |
| // often a mistake, especially in control flow related to errors. Panics with nil |
| // values are checked because they are not detectable by |
| // |
| // if r := recover(); r != nil { |
| // |
| // This check reports conditions such as: |
| // |
| // if f == nil { // impossible condition (f is a function) |
| // } |
| // |
| // and: |
| // |
| // p := &v |
| // ... |
| // if p != nil { // tautological condition |
| // } |
| // |
| // and: |
| // |
| // if p == nil { |
| // print(*p) // nil dereference |
| // } |
| // |
| // and: |
| // |
| // if p == nil { |
| // panic(p) |
| // } |
| // |
| // Sometimes the control flow may be quite complex, making bugs hard |
| // to spot. In the example below, the err.Error expression is |
| // guaranteed to panic because, after the first return, err must be |
| // nil. The intervening loop is just a distraction. |
| // |
| // ... |
| // err := g.Wait() |
| // if err != nil { |
| // return err |
| // } |
| // partialSuccess := false |
| // for _, err := range errs { |
| // if err == nil { |
| // partialSuccess = true |
| // break |
| // } |
| // } |
| // if partialSuccess { |
| // reportStatus(StatusMessage{ |
| // Code: code.ERROR, |
| // Detail: err.Error(), // "nil dereference in dynamic method call" |
| // }) |
| // return nil |
| // } |
| // |
| // ... |
| package nilness |
