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Do not write T_PACKAGE header, if there are no packages. by krk · Pull Request #1075 · async-profiler/async-profiler · GitHub
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Do not write T_PACKAGE header, if there are no packages. #1075

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Do not write T_PACKAGE header, if there are no packages. #1075

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@krk krk commented Dec 6, 2024

This may happen while profiling non-java programs.

Description

jfr print broken while profiling non-jvm apps:

jfr print: unexpected internal error, Pool jdk.types.Package must contain at least one element
java.lang.InternalError: Pool jdk.types.Package must contain at least one element
        at jdk.jfr/jdk.jfr.internal.consumer.ChunkParser.fillConstantPools(ChunkParser.java:357)
        at jdk.jfr/jdk.jfr.internal.consumer.ChunkParser.<init>(ChunkParser.java:141)
        at jdk.jfr/jdk.jfr.internal.consumer.ChunkParser.<init>(ChunkParser.java:109)
        at jdk.jfr/jdk.jfr.internal.consumer.ChunkParser.<init>(ChunkParser.java:105)
        at jdk.jfr/jdk.jfr.consumer.RecordingFile.createChunkParser(RecordingFile.java:318)
        at jdk.jfr/jdk.jfr.consumer.RecordingFile.findNext(RecordingFile.java:294)
        at jdk.jfr/jdk.jfr.consumer.RecordingFile.<init>(RecordingFile.java:89)
        at jdk.jfr/jdk.jfr.internal.tool.EventPrintWriter.print(EventPrintWriter.java:74)
        at jdk.jfr/jdk.jfr.internal.tool.Print.execute(Print.java:165)
        at jdk.jfr/jdk.jfr.internal.tool.Main.main(Main.java:92)

Do not write the T_PACKAGE prelude in the constant pool, if there are no packages.

How has this been tested?

LD_PRELOAD async-profiler into a native app, jfr print the resulting jfr file.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

@krk
Do not write T_PACKAGE header, if there are no packages.
9e2d816 
This may happen while profiling non-java programs.
apangin
apangin reviewed Dec 6, 2024
View reviewed changes
src/flightRecorder.cpp
writeLogLevels(buf);

// Patch pool count.
buf->put8(poolCountOffset, poolCount);
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It's not that trivial.
Buffer can be flushed while dumping other constant pools.

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Also, the problem is relevant to other dictionaries, too - for example, when a recording contains no samples.
An alternative workaround that I thought of is to populate dictionary with a dummy element if it is empty.

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krk commented Dec 6, 2024

Closing for now.

@krk krk closed this Dec 6, 2024
@apangin apangin mentioned this pull request Dec 30, 2024
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