On Sun, 25 Aug 2024 18:29:47 GMT, Markus Grönlund <mgronlun@openjdk.org> wrote:

Greetings,

The name symbol for hidden (anonymous) classes has evolved. Initially, it consisted of only a base class name, e.g., "java/lang/invoke/LambdaForm$BMH", so JFR had to introduce a scheme for disambiguating one anonymous class from another.

The scheme (which still exists in JFR) appends the Java class mirror's hashcode to the base class name, e.g., "java/lang/invoke/LambdaForm$BMH/22626602".

With [JDK-8238358](https://bugs.openjdk.org/browse/JDK-8238358), the disambiguation of hidden class names is now intrinsic to the processing by the ClassFileParser. This is done by appending the InstanceKlass address to the base class name, e.g., "java/lang/invoke/LambdaForm$BMH+0x000000001d190000".

An argument can be made that JFR specialization for hidden (anonymous) classes may no longer be necessary. Indeed, the result now involves a "double" disambiguation: e.g., "java/lang/invoke/LambdaForm$BMH+0x000000001d190000/231202600".

It is now possible to simplify the handling of hidden (anonymous) class names, which avoids using the Java mirror oop. We might want to keep the "/" construct as that might be an implicit invariant on users' expectations (quickly done by replacing "+" with "/").

Testing: jdk_jfr

Thanks Markus

src/hotspot/share/jfr/support/jfrSymbolTable.cpp line 259:

257: const size_t len = static_cast<size_t>(name->utf8_length()); 258: char* hidden_klass_name = NEW_RESOURCE_ARRAY(char, len + 1); 259: strncpy(hidden_klass_name, name->as_klass_external_name(), len + 1);

Can't you use the `k->external_name()` which performs this plus to slash replacement already? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20708#discussion_r1730424838

Greetings,

The name symbol for hidden (anonymous) classes has evolved. Initially, it consisted of only a base class name, e.g., "java/lang/invoke/LambdaForm$BMH", so JFR had to introduce a scheme for disambiguating one anonymous class from another.

The scheme (which still exists in JFR) appends the Java class mirror's hashcode to the base class name, e.g., "java/lang/invoke/LambdaForm$BMH/22626602".

With [JDK-8238358](https://bugs.openjdk.org/browse/JDK-8238358), the disambiguation of hidden class names is now intrinsic to the processing by the ClassFileParser. This is done by appending the InstanceKlass address to the base class name, e.g., "java/lang/invoke/LambdaForm$BMH+0x000000001d190000".

An argument can be made that JFR specialization for hidden (anonymous) classes may no longer be necessary. Indeed, the result now involves a "double" disambiguation: e.g., "java/lang/invoke/LambdaForm$BMH+0x000000001d190000/231202600".

It is now possible to simplify the handling of hidden (anonymous) class names, which avoids using the Java mirror oop. We might want to keep the "/" construct as that might be an implicit invariant on users' expectations (quickly done by replacing "+" with "/").

Testing: jdk_jfr

Thanks Markus

Markus Grönlund has updated the pull request incrementally with two additional commits since the last revision: - cleanup - use existing k->external_name ------------- Changes: - all: https://git.openjdk.org/jdk/pull/20708/files - new: https://git.openjdk.org/jdk/pull/20708/files/805d78d5..cb10d174 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=20708&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20708&range=00-01 Stats: 25 lines in 1 file changed: 0 ins; 23 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/20708.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/20708/head:pull/20708 PR: https://git.openjdk.org/jdk/pull/20708

On Sun, 25 Aug 2024 18:29:47 GMT, Markus Grönlund <mgronlun@openjdk.org> wrote:

Greetings,

The name symbol for hidden (anonymous) classes has evolved. Initially, it consisted of only a base class name, e.g., "java/lang/invoke/LambdaForm$BMH", so JFR had to introduce a scheme for disambiguating one anonymous class from another.

The scheme (which still exists in JFR) appends the Java class mirror's hashcode to the base class name, e.g., "java/lang/invoke/LambdaForm$BMH/22626602".

With [JDK-8238358](https://bugs.openjdk.org/browse/JDK-8238358), the disambiguation of hidden class names is now intrinsic to the processing by the ClassFileParser. This is done by appending the InstanceKlass address to the base class name, e.g., "java/lang/invoke/LambdaForm$BMH+0x000000001d190000".

An argument can be made that JFR specialization for hidden (anonymous) classes may no longer be necessary. Indeed, the result now involves a "double" disambiguation: e.g., "java/lang/invoke/LambdaForm$BMH+0x000000001d190000/231202600".

It is now possible to simplify the handling of hidden (anonymous) class names, which avoids using the Java mirror oop. We might want to keep the "/" construct as that might be an implicit invariant on users' expectations (quickly done by replacing "+" with "/").

Testing: jdk_jfr

Thanks Markus

This pull request has now been integrated. Changeset: 0f667103 Author: Markus Grönlund <mgronlun@openjdk.org> URL: https://git.openjdk.org/jdk/commit/0f667103db7842fe9d3399f56baee0a5def4529e Stats: 59 lines in 2 files changed: 2 ins; 40 del; 17 mod 8338939: Simplify processing of hidden class names Reviewed-by: egahlin ------------- PR: https://git.openjdk.org/jdk/pull/20708