On Thu, 2 Mar 2023 23:28:23 GMT, Paul Sandoz <[email protected]> wrote:
>> Adam Sotona has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> StackMapFrameInfo extracted to top level from StackMapTableAttribute
>
> src/java.base/share/classes/jdk/internal/classfile/CodeBuilder.java line 165:
>
>> 163: * @return this builder
>> 164: */
>> 165: default CodeBuilder transforming(CodeTransform transform,
>> Consumer<CodeBuilder> handler) {
>
> The functionality of this method, `transforming`, and
> `ClassfileBuilder::transform`, are in effect equivalent in their
> transforming: adding the results of transformed code to the builder. They
> differ in the source of code elements.
>
> The latter's behaviour can be implemented using the former, with a consumer
> that passes all elements of a code model to the builder e.g. `builder ->
> model.forEach(builder::with)`.
>
> The difference in naming initially confused me. To me this suggests the
> method names should be the same? (perhaps with the transformer being
> consistently the last argument?).
The `CodeBuilder::transforming` solves a bit different use cases than all the
other transform.
It is designed to be able to use code transformations on a code building
handler within a single pass.
Main reason is support of features like `StackTracker` in a form of code
transformation. `StackTracker` (or any other similar tool requiring to monitor
or affect code building) is passed as a transformation of a code fragment,
while it can immediately serve as a source of information necessary to generate
follow-up bytecode of the same method (in the same pass).
Example of such use case is here:
https://github.com/openjdk/jdk/blob/0e43af667ba6c6bda61461c260688bc46d3f3474/src/java.base/share/classes/jdk/internal/classfile/components/CodeStackTracker.java#L49
These code generation/transformation cases must be handled in a single pass and
`CodeBuilder::transforming` method has no similar peer in any other (method,
field or class) builder, because it is not necessary.
-------------
PR: https://git.openjdk.org/jdk/pull/10982
