Parametric-vm spec / unused CONSTANT_Parameter is illegal

Remi Forax forax at
Wed Mar 10 21:59:49 UTC 2021

Hi all,
slowly reading the Parametric-vm spec.

With my ASM hat,
"As a structural constraint, it is illegal for a CONSTANT_Parameter constant to be unused."

This is different of all other CONSTANTs and doesn't work well with the idea that you can patch a classfile by copying the existing constant pool and replace only the method(s) you want, because if i replace a parametric method by a non parametric one, the existing CONSTANT_Parameter will stay in the constant pool with no reference to it anymore.

Being able to patch a classfile like this is very important in term of speed for some transformers / agents.

If the VM is able to find that a CONSTANT_Parameter is unused, instead of throwing an error, why not ignoring it ?


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