Eclipse Bug

This one had me puzzled for a while. I went to run some jSuneido code in Eclipse and I got a weird verifyError i.e. something wrong with the byte code. Probably just a glitch, a corrupted file or something. I recompiled the code. Same error. Meanwhile, all the jUnit tests (running all the time through Infinitest) were passing fine. And when I built the final jar, it worked fine as well.

Maybe my Eclipse or my configuration was messed up. I connected to my office machine and tried it there. And got the same error.

The problem was, I couldn't remember when this last worked. I've been mostly working in Go on gSuneido. I've made the occasional minor changes in jSuneido but probably didn't try to run anything inside Eclipse.

Maybe it was a Java 14 issue? Eclipse isn't very good at supporting the latest version of Java. Currently you have to install a patch to get Java 14 support. So I installed Java 13 and tried again with that. Same error.

I tried reinstalling Eclipse (2020-03). Didn't help. I tried installing the previous version of Eclipse (2019-12). Still no good.

I have to admit I was getting quite frustrated by this point. I'd had several computer issues in the last few days and I didn't need yet another one. I even considered switching IDE's. I installed JetBrains intelliJ (I have a license for all their products) and it had no problem running the code.  But I struggled just to get that far with intelliJ. It's quite an investment to learn an IDE and I didn't really want to start over. Especially when I'm not doing much Java development these days.

I narrowed it down to a problem with the Eclipse Java compiler (they have their own, separate from the JDK). If I compiled with the JDK it was fine, but if I compiled with Eclipse, it wouldn't work inside Eclipse or outside.

I vaguely remembered that I had fallen a bit behind with Eclipse and had jumped over the previous version (2019-12). So I installed 2019-09. And it worked! Finally!

By this point I was fairly sure it was an Eclipse Java compiler bug. I searched the Eclipse bug database (and the web) but couldn't find anything related.

I figured I should report a bug, but was, as usual, hesitant. There are lots of Eclipse users, why was I the only one to run into this? Was it something I was doing wrong? (Although in that case, why did the JDK work fine?) It sounds silly, but I was afraid of looking stupid in public.

I decided if I could create a simple example that reproduced the issue, then I'd file a bug. Luckily, by then I had a good idea of the issue and it wasn't hard to make the example.

Basically the bug came from the equivalent of:

MyFunc(condition ? derived1() : derived2())

derived1 and derived2 returned private classes with a common public parent (all from another package).

The type of the ?: expression should be the common public parent. But in the Eclipse bytecode it was Object (basically an unknown type). For some reason it wasn't looking past the private classes to see the common public parent. Curiously, if I assigned the ?: expression to a variable of the parent type, it handled that fine. Or if I rewrote the ?: as an if-else it was also fine. Using javap to look at the bytecode I could see the JDK stack map showed the correct parent type, but the Eclipse stack map showed Object.

I posted the bug and the next morning I saw:

I will investigate. Reproduced with your example.
Thanks! Great test case. This is really helpful

It was good to see it was valid. Later comments confirmed the bug and that the fix was trivial and would go into future versions.