JDK VS openjdk-jdk11

I felt out of the loop, thinking that Zero VM was some kind of new distro for OpenJDK but chasing <https://packages.debian.org/sid/openjdk-22-jre-zero#:~:text=...> to <https://sources.debian.org/src/openjdk-11/11.0.23%2B9-1/debi...> lead me to https://github.com/openjdk/jdk/tree/jdk-22-ga/src/hotspot/cp...

It seems that it's a specific CPU target for the Hotspot JIT for non-mainstream architectures (or for research purposes, as I saw mentioned once)

Completely gutted from the OpenJDK, last I checked. See here for the culprit PR: https://github.com/openjdk/jdk/pull/18688

> Yes, they're changing one aspect of signal handler use to work around this problem. They're not stopping the use of signal handlers in general. Hotspot continues to use signals for efficiency in general. See https://github.com/openjdk/jdk/blob/9059727df135dc90311bd476...

This whole thread is about SIGSEGV, and specifically their SIGSEGV handling. However, catching normal signals is not about efficiency.

Some of their exception handling is still odd: There is no reason for a program that receives SIGILL to ever attempt continuing. But others is fine, like catching SIGFPE to just forward an exception to the calling code.

(Sure, you could construct an argument to say that this is for efficiency if you considered the alternative to be implementing floating point in software so that all exceptions exist in user-space, but hardware floating point is the norm and such alternative would be wholly unreasonable.)

> The wonderful thing about choosing not to care about facts is having whatever opinions you want.

I appreciate the irony of you making such statement, proudly thinking that your opinion equals fact, and therefore any other opinion is not.

This discussion is nothing but subjective opinion vs. subjective opinion. Facts are (hopefully, as I can only speak for myself) inputs to both our opinions, but no opinion about "good" or "bad", "nasty" or not can ever be objective. Objective code quality does not exist.

I remember talking to Brendan about the PreserveFramePointer patch during my first months at Netflix in 2015. As of JDK 21, unfortunately it is no longer a general purpose solution for the JVM, because it prevents a fast path being taken for stack thawing for virtual threads: https://github.com/openjdk/jdk/blob/d32ce65781c1d7815a69ceac...

Also, you can read the source code for Double and other classes, which also contains the JavaDocs, as well as comments throughout the code.

So for example, the different implementations for java.awt.AWTEvent.java is written in:

It is not the memory address of the object. It is the hash code as can be seen from the source code (Java 11 version):

Code is here: https://github.com/AdoptOpenJDK/openjdk-jdk11/blob/master/src/java.base/share/classes/java/util/ImmutableCollections.java

In fact, ArrayList does it in exactly that way. The backing array gets dimensioned to a certain length and the number of actually stored elements is counted. If the backing array is filled to a certain point (not actually to full capacity), the backing array is resized. This is the way in which ArrayLists can grow. See: ArrayList source code - the size is declared in line 143.

Funny thing is, a HashSet in Java is just a facade for a HashMap

Good call. Files.lines() is doing what we were discussing here, with additional error handling to make sure the underlying BufferedReader is properly closed.

OpenJDK is on github, so the source for Optional in e.g. 11 is here.