jdk

This is calling up dim old memories of Java (which I haven't used in years) and boxing primitive float values into Float objects which provide their own implementation of equals() and hashCode(). AFAICT the pre-hash values come from this method [0] which returns an integer which is a 1:1 representation of the float bytes except that NaNs are all collapsed to one canonical form. So at least at this phase, it doesn't quantize any virtually-equal floats together. Skimming an implementation of HashMap [1], I didn't notice any obvious "do something special for Floats" code. [0] https://docs.oracle.com/en/java/javase/17/docs/api/java.base... [1] https://github.com/openjdk/jdk/blob/master/src/java.base/sha...

The JVM is of course just software. In this case it's mostly software written in C++ and that software allocates "its own heap" using uh... malloc https://github.com/openjdk/jdk/blob/master/src/hotspot/share...

I believe, Oracle JVM uses polling? This is the class responsible for safepoints: https://github.com/openjdk/jdk/blob/4b544f93ad0e2beae4c80e06... And this is one of the implementations: https://github.com/openjdk/jdk/blob/4b544f93ad0e2beae4c80e06... The arming code: https://github.com/openjdk/jdk/blob/4b544f93ad0e2beae4c80e06... I might be missing something, but I'd be terribly surprised if VM games are worth it.

Java has a bunch of code which looks like it's trying to do the right kind of escaping for msvcrt vs cmd.exe: https://github.com/openjdk/jdk/blob/jdk-26%2B1/src/java.base... But i would be lying if i said i understood what was going on there. Some googling suggests this was added around 1.7, ie in the early 2010s. But then, that Rust CVE seems to originate in this work, and this guy claims Java said "won't fix", which suggests it is vulnerable: https://flatt.tech/research/posts/batbadbut-you-cant-securel... But there's no link, and i can't find any discussion about it, so i don't know what the actual situation is.

To be more precise, Java initially uses a linked list for nodes within a bin. If the number of items inside the bin crosses TREEIFY_THRESHOLD (which is 8), then that specific bin is converted into a RB tree. This is detailed in implementation notes comment here: https://github.com/openjdk/jdk/blob/56468c42bef8524e53a929dc...

Map.of() promises to return an immutable map. new HashMap<>() does not. https://docs.oracle.com/en/java/javase/17/docs/api/java.base... How it tells the JVM this? It uses the internal annotation @jdk.internal.ValueBased https://github.com/openjdk/jdk/blob/jdk-17-ga/src/java.base/...

Define mostly, https://github.com/openjdk/jdk - Java 74.1% - C++ 14.0% - C 7.9% - Assembly 2.7% And those values have been increasing for Java with each OpenJDK release.

> if javac involves IR, SSA based analysis and transformation (which I assume it does) https://github.com/openjdk/jdk/blob/master/src/jdk.compiler/... I am fairly certain that it does not. The JVM is a stack-machine. I wrote a compiler for a simple programming language that compiled down to JVM bytecode for a project in the early 2010s. Its output for test programs was as fast as the comparative Java ones because they were fairly similar at the bytecode level. The HotSpot JVM is where all the optimization effort is applied.

This is similar to how java.util.concurrent.atomic.LongAdder works: https://github.com/openjdk/jdk/blob/master/src/java.base/sha...

Java https://github.com/openjdk/jdk/blob/master/Makefile Rust https://github.com/rust-lang/rust/blob/master/tests/run-make... Go https://github.com/golang/go/blob/master/src/runtime/Makefil... NodeJS https://github.com/nodejs/node/blob/main/Makefile OCaml https://github.com/ocaml/ocaml/blob/trunk/Makefile Python https://github.com/python/cpython/blob/main/Makefile.pre.in Haskell https://github.com/ghc/ghc/blob/master/ghc/Makefile R https://github.com/wch/r-source/blob/trunk/Makefile.in CLR https://github.com/mono/mono/blob/main/Makefile.am Ruby https://github.com/ruby/ruby/blob/master/enc/Makefile.in