RFR: 8356548: Use ClassFile API instead of ASM to transform classes in tests [v7]

[Serguei Spitsyn]

On Tue, 14 Oct 2025 23:12:34 GMT, Chen Liang <liach at openjdk.org> wrote:

>> One of the goals of ClassFile API is to avoid updating the copy of ASM in the JDK (now moved to the test library) to support future class file formats.
>> 
>> However, some tests in hotspot turn out to parse latest class files, usually produced by the javac in the JDK under test, to transform them to inject desired bytecode patterns. If we keep these tests, we must keep maintaining the ASM library to accept all current class files, which will be costly with the upcoming project Valhalla.
>> 
>> To avoid maintaining ASM down the road, we can either:
>> 1. Migrate the transformation to ClassFile API
>> 2. Set source and release version in javac flags to produce stable bytecode
>> 
>> I recommend migrating to ClassFile API; javac has a deprecation policy, that in the future, old source and target versions will no longer be supported, and we would still need another port at that time.
>
> Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 16 additional commits since the last revision:
> 
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/asm-test-upgrade
>  - Ioi review
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/asm-test-upgrade
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/asm-test-upgrade
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/asm-test-upgrade
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/asm-test-upgrade
>  - Merge branch 'fix/asm-test-upgrade' of github.com:liachmodded/jdk into fix/asm-test-upgrade
>  - Update test/hotspot/jtreg/compiler/calls/common/InvokeDynamicPatcher.java
>    
>    Co-authored-by: Andrew Haley <aph-open at littlepinkcloud.com>
>  - Variable name improvements
>  - Merge branch 'master' of https://github.com/openjdk/jdk into fix/asm-test-upgrade
>  - ... and 6 more: https://git.openjdk.org/jdk/compare/e7527539...25972f2d

test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/RedefineAnnotations.java line 94:

> 92:                 public void accept(ClassBuilder builder, ClassElement element) {
> 93:                     if (element instanceof FieldModel field && field.fieldName().stringValue().startsWith("dummy")) {
> 94:                         // Remove dummy field

Q: Is this dummy field removed or added? Seems to be a mismatch between the comment and the real action.

test/hotspot/jtreg/serviceability/jvmti/RedefineClasses/RedefineRetransform/RedefineRetransform.java line 102:

> 100:     // Extracts ClassVersion values from the provided class bytes.
> 101:     private static int getClassBytesVersion(byte[] classBytes) {
> 102:         ClassModel clazz = ClassFile.of().parse(classBytes);

Nit: Better to make it consistent with the case below and call it `classModel` instead of `clazz`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25124#discussion_r2431212827
PR Review Comment: https://git.openjdk.org/jdk/pull/25124#discussion_r2431217408