RFR: 8304846: Provide a shared utility to dump generated classes defined via Lookup API [v6]

[Rémi Forax]

On Mon, 3 Apr 2023 20:24:56 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> This implements a shared utility to dump generated classes defined as normal/hidden classes via `Lookup` API.   This replaces the implementation in `LambdaMetaFactory` and method handle implementation that dumps the hidden class bytes on disk for debugging.   
>> 
>> For classes defined via `Lookup::defineClass`, `Lookup::defineHiddenClass` and `Lookup::defineHiddenClassWithClassData`, by default they will be dumped to the path specified in `-Djava.lang.invoke.Lookup.dumpClasses=<dumpDir>` 
>> 
>> The hidden classes generated for lambdas, `LambdaForms` and method handle implementation use non-default dumper so that they can be controlled via a separate system property and path as in the current implementation.
>> 
>> To dump lambda proxy classes, set this system property:
>>    -Djdk.internal.lambda.dumpProxyClasses=<dumpDir>
>> 
>> To dump LambdaForms and method handle implementation, set this system property:
>>    -Djava.lang.invoke.MethodHandle.DUMP_CLASS_FILES=true
>>    
>> P.S. `ProxyClassesDumper` is renamed to `ClassFileDumper` but for some reason, it's not shown as rename.
>
> Mandy Chung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   comments from Jorn Vernee

src/java.base/share/classes/jdk/internal/util/ClassFileDumper.java line 199:

> 197:                 @Override
> 198:                 public Path run() {
> 199:                     if (!Files.exists(path)) {

I do not think this is necessary, Files.createDirectories() already only create directories if they do not exist.
Moreover, someone can change the state of the files in between the two calls (Files.exists and Files.createDirectories) given that those two calls are not atomic from the filesystem POV.

src/java.base/share/classes/jdk/internal/util/ClassFileDumper.java line 216:

> 214:     }
> 215: 
> 216:     private static HexFormat HEX = HexFormat.of().withUpperCase();

'final' ?

src/java.base/share/classes/jdk/internal/util/ClassFileDumper.java line 226:

> 224:             // control characters
> 225:             if (c <= 31 || BAD_CHARS.contains(c)) {
> 226:                 sb.append("%");

sb.append('%')  // using a character instead of a String

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PR Review Comment: https://git.openjdk.org/jdk/pull/13182#discussion_r1156456578
PR Review Comment: https://git.openjdk.org/jdk/pull/13182#discussion_r1156456936
PR Review Comment: https://git.openjdk.org/jdk/pull/13182#discussion_r1156457481