[GROOVY-8579] No bytecode level check is done before producing JDK8+ bytecodes

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.5.0-rc-3
• Assignee: Paul King
• Reporter: Paul King
• Created: 14/May/18 03:20
• Updated: 17/Nov/19 07:35
• Resolved: 19/May/18 15:22

Description

Create a file using a JDK8 static interface method, e.g. MyScript.groovy:

import groovy.transform.CompileStatic

@CompileStatic
Comparator myMethod() {
    Map.Entry.comparingByKey()
}

Compile using JDK8. On Groovy 3.0, use -Dgroovy.target.bytecode=1.7 (not required for 2.5/6).

Note from javap -v that the bytecode version is:

 major version: 51

and that an InterfaceMethodref to the Map.Entry static interface method exists:

   #48 = InterfaceMethodref #45.#47       // java/util/Map$Entry.comparingByKey:()Ljava/util/Comparator;

Now try to use that class in another script, e.g.:

println new MyScript().myMethod()

You will note this error:

java.lang.VerifyError: Illegal type at constant pool entry 48 in class MyScript
Exception Details:
  Location:
    MyScript.myMethod()Ljava/util/Comparator; @0: invokestatic
  Reason:
    Constant pool index 48 is invalid

For Groovy 2.5/6 you can just run groovy MyScript.groovy to see the VerifyError, though using groovyc will let you see the generated bytecode.

So there are two problems:

• we should not set bytecode level to be the minimum level for the Groovy version (7 is default for 2.5/6) when producing bytecode requiring JDK8+.
• we should probably just complain if groovy.target.bytecode is ever set below the minimum value for the particular Groovy version.

Issue Links

• links to: GitHub Pull Request #709
• links to: GitHub Pull Request #1087