[diffoscope] javap exits with 1 on .classdata

[Aman Sharma]

Hi,


I am computing the difference between two Java classfiles that have an extension classdata, but diffoscope 302 does not process them using javap and falls back to hexdump. Running file over them also returns "compiled Java class data, version 52.0 (Java 1.8)" which seems to be a valid criteria to start comparing with Java comparators<https://salsa.debian.org/reproducible-builds/diffoscope/-/blob/master/diffoscope/comparators/java.py?ref_type=heads#L78>.


These classes are reference and rebuild versions of `inst/io/opentelemetry/javaagent/instrumentation/rmi/context/jpms/ExposeRmiModuleInstrumentation$2.classdata` from this jar<https://repo1.maven.org/maven2/io/opentelemetry/javaagent/opentelemetry-javaagent/2.4.0/opentelemetry-javaagent-2.4.0.jar>.


If we simply rename their extensions to `.class` and then compare, there is a valid diff by javap.


Regards,
Aman Sharma

PhD Student
KTH Royal Institute of Technology
School of Electrical Engineering and Computer Science (EECS)
Department of Theoretical Computer Science (TCS)
<http://www.kth.se><https://www.kth.se/profile/amansha><https://www.kth.se/profile/amansha>
<https://www.kth.se/profile/amansha>https://algomaster99.github.io/
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