Leaning Technologies•4mo ago

How to debug class loading

Hi, I'm dropping in here from github (https://github.com/leaningtech/cheerpj-meta/issues/195). I'm trying to run the kotlin compiler in a browser (https://github.com/F43nd1r/kotlin-compiler-cheerpj) - however this leads to "Bad class file cj3.js:1:420827" on the console with no further info. How can I debug here to see where the issue might be?

GitHub

Issues · leaningtech/cheerpj-meta

Run Java 8 applications, libraries, applets, Java Web Start, and Oracle Forms on the web without legacy plugins. - Issues · leaningtech/cheerpj-meta

GitHub

GitHub - F43nd1r/kotlin-compiler-cheerpj

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16 Replies

apignotti•4mo ago

The bad class file message is most likely caused by an internal bug where non-class data is being parsed as a class. What version of CJ are your using?

F43nd1r•4mo ago

https://cjrtnc.leaningtech.com/3_20240416_465/cj3loader.js

apignotti•4mo ago

We had success running kotlin code, including the kotlin compiler in the past For a specific version, but it's a codebase that tends to do extremely complicated manipulations It's quite possible the fix will be easy, just upload test complete HTML test case to a publicly accessible URL so that we can take a look For reference: https://discord.com/channels/988743885121548329/1178768677479403671/1178781364561129612 about our previous experiments with kotlin

F43nd1r•4mo ago

I linked it in the OP - the html would be here https://github.com/F43nd1r/kotlin-compiler-cheerpj/blob/master/src/main/serve/index.html

GitHub

kotlin-compiler-cheerpj/src/main/serve/index.html at master · F43nd...

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apignotti•4mo ago

Can you deploy a ready-made page already integrated with CJ? For us is time consuming to get sources to build, and we never need the source anyway

F43nd1r•4mo ago

Oh, that is an interesting approach - I was trying to get the embedded compiler running instead of the standalone I'll set up gh pages, give me a minute https://f43nd1r.github.io/kotlin-compiler-cheerpj/ there you go Note that currently everything happens only on the console, nothing visible on the page

apignotti•4mo ago

apignotti•4mo ago

That's what I get, it does not seem to be what you previously mentioned

F43nd1r•4mo ago

Oh, typical web development fun: only happens in firefox, chrome shows what you posted Continuing with chrome, I got to a stacktrace:

Stacktrace: java.lang.Error: java.lang.ArrayIndexOutOfBoundsException
    at java.lang.Error.<init>(Unknown Source)
    at org.jetbrains.kotlin.com.intellij.util.containers.ConcurrentLongObjectHashMap.<clinit>(Unknown Source)
    at org.jetbrains.kotlin.com.intellij.util.containers.ContainerUtil.createConcurrentLongObjectMap(Unknown Source)
        [...]
    at kotlin.script.experimental.host.BasicScriptingHost.eval(Unknown Source)
    at com.faendir.KotlinCompiler.eval(Unknown Source)
Caused by: java.lang.ArrayIndexOutOfBoundsException
    at .(Unknown Source)
    at java.lang.invoke.LambdaForm$DMH.invokeVirtual_LL_J(Unknown Source)
    at .(Unknown Source)
    ... 31 more

Stacktrace: java.lang.Error: java.lang.ArrayIndexOutOfBoundsException
    at java.lang.Error.<init>(Unknown Source)
    at org.jetbrains.kotlin.com.intellij.util.containers.ConcurrentLongObjectHashMap.<clinit>(Unknown Source)
    at org.jetbrains.kotlin.com.intellij.util.containers.ContainerUtil.createConcurrentLongObjectMap(Unknown Source)
        [...]
    at kotlin.script.experimental.host.BasicScriptingHost.eval(Unknown Source)
    at com.faendir.KotlinCompiler.eval(Unknown Source)
Caused by: java.lang.ArrayIndexOutOfBoundsException
    at .(Unknown Source)
    at java.lang.invoke.LambdaForm$DMH.invokeVirtual_LL_J(Unknown Source)
    at .(Unknown Source)
    ... 31 more

Looking at the source of ConcurrentLongObjectHashMap, the kotlin compiler seems to be accessing com.sun.misc.Unsafe using reflection here. Hard to tell which call exactly with no line numbers. I assume I can't turn on line numbers in cheerpj somewhere?

apignotti•4mo ago

Debugging information is not supported at this time

F43nd1r•4mo ago

Alright, I thought evaluating some kotlin would've been an impressive demo of cheerpj. Probably a bit too ambitious - at least I'm out of my depth here. I can see the kotlin compiler tries to figure out the memory layout of certain classes, I assume that's the part which is just different enough on cheerpj to not work out, but I have no idea how to debug or fix any of it. Thanks for the help either way 🙂

apignotti•4mo ago

Give me a few hours before giving up As a matter of fact, the Firefox issue is already fixed locally

F43nd1r•4mo ago

oh, that's cool. Sure if you continue on your side I'll happily follow along!

apignotti•4mo ago

I've fixed a few minor issues and this is the output I get right now, which is the same I see when running with native Java 8

apignotti•4mo ago

Please try again with the following build: https://cjrtnc.leaningtech.com/3_20240425_466/cj3loader.js

F43nd1r•4mo ago

yeah that's because my hello world isn't actually valid kotlin code 😂 I updated the demo with the new build and a bit of UI - https://f43nd1r.github.io/kotlin-compiler-cheerpj/ Not the fastest in the world, but it works! Impressive how you got that fixed so fast

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How to debug class loading