Description Andrey Kuznetsov 2019-08-21 04:40:55 EDT

Created attachment 279649 [details]
Gradle reproducer project

TypeSafeEnum instance can be used as part of HashMap key, for example, in org.aspectj.ajdt.internal.compiler.ast.AspectDeclaration#accessForInline. Since TypeSafeEnum does no override hashCode(), this may lead to inpredictable iteration order over HashMap entries.

I could not reproduce this by invoking ajc directly, but Gradle project attached demonstrates it good enough. From 2 to 4 repetitive builds are usually sufficient to get distinct class bytecode. E.g., under Windows it can be tested like this:

> gradle clean compileAspect && certutil -hashfile build/classes/java/main/Test.class sha1

While all versions of bytecode produced are correct, practical consequences of non-determinism are possible. For example, bnd tooling that builds OSGi bundles compares current class version to previously released version and insists on bundle version increasing when bytecode is changed (while it could change even without source modification due to issue being reported).

Please consider the following changes to fix the issue:
- Add "natural" hashCode() and equals() to TypeSafeEnum.
- Change the class of AspectDeclaration#accessForInline to LinkedHashMap, since HashMap per se does not guarantee fixed iteration order.