[10] RFR 8186046 Minimal ConstantDynamic support

[Paul Sandoz]

> On 7 Nov 2017, at 12:04, Karen Kinnear <karen.kinnear at oracle.com> wrote:
> 
> Paul,
> 
> Thank you for the explanations. Asking for your help in some test case construction at the end here:
> 
>>> 3. java/lang/invoke/package-info.java 128-134
>>> Error handling could be clearer.
>>> My understanding is that if a LinkageError or subclass is thrown, this will be rethrown
>>> for all subsequent attempts. Other errors, e.g. VMError may retry resolution
> I was WRONG here - this does match the JVMS. Apologies for the confusion.
>>> 
>>> 9. test/jdk/java/lang/invoke/common/test/java/lang/invoke/lib/InstructionHelper.java
>>> How would I write an ldc CONSTANT_Dynamic which referred to a bootstrap method that
>>> was not ACC_STATIC?
>> 
>> https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.23
>> 
>> See the note under bootstrap_method_ref. The kind of method handle is constrained because of the arguments that are pushed on the stack before invocation. I believe it’s possible to have a constructor, but the declaring class would need to be a subtype of CallSite in the case of indy, and a subtype of the constant value type in the case of condy.
>> 
>> 
>>> Or was not ACC_PUBLIC?
>> 
>> That’s dependent on the accessibility between the lookup class the the BSM declaring class.
>> 
>> 
>>> Or was 
>>> Or did I read the invoke dynamic method incorrectly?
>>> 
>> 
>> By default, and for convenience, the InstructionHelper assumes the BSM is declared by the lookup class. I recently modified that to support the BSM being declared on another class, to test the minimal set of BSMs for condy (separate issue [1]). Note it’s always possible to use the bytecode API more directly.
>> 
>> So we can easily add more -ve tests for non-accessible or non-static BSMs.

I am wrong, i forgot i updated the API to remove the declaration of the BSM kind, and it only supports static BSMs.


> Thank you - that is what we were trying to do - test BSM declared in another class, test in-accessible
> BSM and test non static method.
> 

The latter (access to a BSM in another class) is easy now using the high-level construct of InstructionHelper.ldcDynamicConstant (see patch for the condy BSMs, which is also in the amber repo in the condy branch).


> Could you help us figure out how to
> 1) invoke a constructor? 
> 2) invoke a virtual method? How do you pass the receiver? 
> 

I think for these you will need to use ASM tools to massage the MH for the BSM e.g. develop for a class with a static BSM then adjust the constant pool entry for the associated MH.

Paul.