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102 lines
3.3 KiB
102 lines
3.3 KiB
---
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title: "Eradicate"
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description: "The eradicate `@Nullable` checker for Java annotations."
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---
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The eradicate `@Nullable` checker for Java annotations.
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Activate with `--eradicate`.
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Supported languages:
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- C/C++/ObjC: No
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- Java: Yes
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> "I call it my billion-dollar mistake. It was the invention of the null
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> reference in 1965."
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>
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> [Tony Hoare](http://en.wikipedia.org/wiki/Tony_Hoare)
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### What is Infer:Eradicate?
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Infer:Eradicate is a type checker for `@Nullable` annotations for Java. It is part
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of the Infer static analysis suite of tools. The goal is to eradicate null
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pointer exceptions.
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<a href="https://developer.android.com/reference/android/support/annotation/Nullable.html">@Nullable</a>
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annotations denote that a parameter, field or the return value of a method can
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be null. When decorating a parameter, this denotes that the parameter can
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legitimately be null and the method will need to deal with it. When decorating a
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method, this denotes the method might legitimately return null.
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Starting from @Nullable-annotated programs, the checker performs a flow
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sensitive analysis to propagate the nullability through assignments and calls,
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and flags errors for unprotected accesses to nullable values or
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inconsistent/missing annotations. It can also be used to add annotations to a
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previously un-annotated program.
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### What is the @Nullable convention?
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If you say nothing, you're saying that the value cannot be null. This is the
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recommended option when possible:
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Program safely, annotate nothing!
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When this cannot be done, add a @Nullable annotation before the type to indicate
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that the value can be null.
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### What is annotated?
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Annotations are placed at the interface of method calls and field accesses:
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- Parameters and return type of a method declaration.
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- Field declarations.
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Local variable declarations are not annotated: their nullability is inferred.
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### How is Infer:Eradicate invoked?
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Eradicate can be invoked by adding the option `--eradicate` to the checkers mode
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as in this example:
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```bash
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infer run -a checkers --eradicate -- javac Test.java
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```
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The checker will report an error on the following program that accesses a
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nullable value without null check:
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```java
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class C {
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int getLength(@Nullable String s) {
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return s.length();
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}
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}
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```
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But it will not report an error on this guarded dereference:
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```java
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class C {
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int getLength(@Nullable String s) {
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if (s != null) {
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return s.length();
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} else {
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return -1;
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}
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}
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}
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```
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## List of Issue Types
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The following issue types are reported by this checker:
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- [ERADICATE_CONDITION_REDUNDANT](/docs/next/all-issue-types#eradicate_condition_redundant)
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- [ERADICATE_FIELD_NOT_INITIALIZED](/docs/next/all-issue-types#eradicate_field_not_initialized)
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- [ERADICATE_FIELD_NOT_NULLABLE](/docs/next/all-issue-types#eradicate_field_not_nullable)
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- [ERADICATE_INCONSISTENT_SUBCLASS_PARAMETER_ANNOTATION](/docs/next/all-issue-types#eradicate_inconsistent_subclass_parameter_annotation)
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- [ERADICATE_INCONSISTENT_SUBCLASS_RETURN_ANNOTATION](/docs/next/all-issue-types#eradicate_inconsistent_subclass_return_annotation)
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- [ERADICATE_PARAMETER_NOT_NULLABLE](/docs/next/all-issue-types#eradicate_parameter_not_nullable)
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- [ERADICATE_RETURN_NOT_NULLABLE](/docs/next/all-issue-types#eradicate_return_not_nullable)
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- [ERADICATE_RETURN_OVER_ANNOTATED](/docs/next/all-issue-types#eradicate_return_over_annotated)
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