RFR: 8294972: Convert jdk.jlink internal plugins to use the Classfile API [v8]

[Adam Sotona]

On Thu, 16 Mar 2023 02:43:39 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> Adam Sotona has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fixed SystemModulesPlugin
>
> src/jdk.jlink/share/classes/jdk/tools/jlink/internal/plugins/IncludeLocalesPlugin.java line 160:
> 
>> 158:                     resource.type().equals(ResourcePoolEntry.Type.CLASS_OR_RESOURCE)) {
>> 159:                     byte[] bytes = resource.contentBytes();
>> 160:                     if (newClassReader(path, bytes).interfaces().stream()
> 
> `IncludeLocalesPluginTest.java` test is failing.   Adding `-J-Djlink.debug=true` will get the stack trace:
>  
> 
> Failed to parse class file: /jdk.localedata/sun/text/resources/ext/LineBreakIteratorData_th
> java.lang.IllegalStateException: Bad magic number
> 	at java.base/jdk.internal.classfile.impl.ClassReaderImpl.<init>(ClassReaderImpl.java:94)
> 	at java.base/jdk.internal.classfile.impl.ClassImpl.<init>(ClassImpl.java:68)
> 	at java.base/jdk.internal.classfile.Classfile.parse(Classfile.java:165)
> 	at jdk.jlink/jdk.tools.jlink.internal.plugins.AbstractPlugin.newClassReader(AbstractPlugin.java:105)
> 	at jdk.jlink/jdk.tools.jlink.internal.plugins.IncludeLocalesPlugin.lambda$transform$5(IncludeLocalesPlugin.java:161)
> 	at jdk.jlink/jdk.tools.jlink.plugin.ResourcePool.lambda$transformAndCopy$0(ResourcePool.java:112)
> 	at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
> 	at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1924)
> 	at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:762)
> 	at jdk.jlink/jdk.tools.jlink.plugin.ResourcePool.transformAndCopy(ResourcePool.java:111)
> 	at jdk.jlink/jdk.tools.jlink.internal.plugins.IncludeLocalesPlugin.transform(IncludeLocalesPlugin.java:154)
> 	at jdk.jlink/jdk.tools.jlink.internal.ImagePluginStack.visitResources(ImagePluginStack.java:262)
> 	at jdk.jlink/jdk.tools.jlink.internal.ImageFileCreator.generateJImage(ImageFileCreator.java:184)
> 	at jdk.jlink/jdk.tools.jlink.internal.ImageFileCreator.writeImage(ImageFileCreator.java:163)
> 	at jdk.jlink/jdk.tools.jlink.internal.ImageFileCreator.create(ImageFileCreator.java:100)
> 	at jdk.jlink/jdk.tools.jlink.internal.JlinkTask$ImageHelper.retrieve(JlinkTask.java:889)
> 	at jdk.jlink/jdk.tools.jlink.internal.ImagePluginStack.operate(ImagePluginStack.java:194)
> 	at jdk.jlink/jdk.tools.jlink.internal.JlinkTask.createImage(JlinkTask.java:452)
> 	at jdk.jlink/jdk.tools.jlink.internal.JlinkTask.run(JlinkTask.java:292)
> 	at jdk.jlink/jdk.tools.jlink.internal.Main.run(Main.java:56)
> 	at jdk.jlink/jdk.tools.jlink.internal.Main.main(Main.java:34)
> Dumping class file 26549-include-locales//jdk.localedata/sun/text/resources/ext/LineBreakIteratorData_th
> ```	
> 
> Apparently `/jdk.localedata/sun/text/resources/ext/LineBreakIteratorData_th` is not a valid class file.  Using ASM `ClassReader` to parse this resource file succeeds because it does not do much of the class file validation.    Instead the ClassFile API throws `IllegalStateException` as it has a bad magic number.
> 
> @naotoj what is the file format of this `LineBreakIteratorData_th` file?

This plugin does not fit to the Classfile API use cases portfolio at all. Here it is only needed to get interfaces list out of the constant pool and then the Utf8 CP entries are in-place modified. That is out of the Classfile API or ASM capabilities. Bad magic number is not the only difference, both libraries fail whenever touching even headers of any other standard classfile elements, only constant pool and interfaces seem to be "safe". 
I can prepare very simple standalone helper class dealing with this case to remove ASM dependency. 
However knowing more about the file format is always useful :)

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PR: https://git.openjdk.org/jdk/pull/12944