openJDK-docker VS JDK

Install OpenJDK and Java Runtime Environment (JRE) 11

I hoped on to the OpenJDK docker repo and from there to the GitHub project.

https://openjdk.java.net

I know this because I'm one of OpenJDK's developers, and, like almost all OpenJDK developers, I work at Oracle, but you can just check for yourself, by, say, visiting OpenJDK's website.

What exactly is unsubstantiated here? Have you looked at OpenJDK's sources and/or licence and/or contributors? They're right here. And here's the project's homepage: https://openjdk.java.net.

Thanks! You are right, if Dockerfiles work for you, you probably don't need Modus. However, when the project grows, Dockerfiles may become rather complicated. For example, OpenJDK Dockerfile template uses AWK scripts and JQ filters to define build logic. This is when Modus becomes useful: an equivalent Modusfile is much more concise and runs faster.

Contrary to what vocal Kotlin advocates might believe, Kotlin only matters on Android, and that is thanks to Google pushing it no matter what.

https://spectrum.ieee.org/the-top-programming-languages-2023

https://snyk.io/reports/jvm-ecosystem-report-2021/

And even so, they had to conceed Android and Kotlin on their own, without the Java ecosystem aren't really much useful, thus ART is now updatable via Play Store, and currently supports OpenJDK 17 LTS on Android 12 and later devices.

As for your question regarding numbers, mostly Java 74.6%, C++ 13.7%, on the OpenJDK, other JVM implementations differ, e.g. GraalVM is mostly Java 91.8%, C 3.6%.

https://github.com/openjdk/jdk

https://github.com/oracle/graal

Two examples from many others, https://en.wikipedia.org/wiki/List_of_Java_virtual_machines

The actual text from https://bugs.java.com/bugdatabase/view_bug?bug_id=8327860 says this:

> We have been working on a patch that switches the jit protection mode to EXEC around these potential faulting memory accesses.

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...

The "safe fetch" code relies on a signal handler (either here https://github.com/openjdk/jdk/blob/48717d63cc58f693f0917e61... or here https://github.com/openjdk/jdk/blob/3c70f26b2f3fa9bc143e2506...), which is considered asynchronous delivery (i.e., delivered mid-execution, see `man 7 signal`) - which is why the `async-signal-safe` manpage simply states that it is functions that can safely be called within a signal handler.

This is opposed to calling `sigwait` or similar to actively suspend and wait for a signal, which is not possible to do here.

Granted, it may be that the stars align and their implementation works in practice, but that does not make it any less bizarre.

The signal comes from a safe fetch, which is just a read that allows ignoring the fault as if it never happened. Such a signal is deliver synchronously, so the usual restrictions for asynchronous signal handlers do not apply.

The code in question takes into account that the value read might be garbage. See the big comment here: https://github.com/openjdk/jdk/commit/29397d29baac3b29083b1b...

On current CPUs and operating systems, this is not an optimization, so the code was removed earlier this year: https://bugs.openjdk.org/browse/JDK-8320317

> 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...

Map doesn't implement the Collection interface.

https://github.com/openjdk/jdk/blob/master/src/java.base/sha...

C++ lets you write anything you can imagine, and the language features and standard library often facilitate that. The committee espouses the view that they want to provide many "zero [runtime] cost," abstractions. Anybody can contribute to the language, although the committee process is often slow and can be political, each release the surface area and capability of the language gets larger.

I believe Hazard Pointers are slated for C++26, and these will add a form "free later, but not quite garbage collection" to the language. There was a talk this year about using hazard pointers to implement a much faster std::shared_ptr.

It's a language with incredible depth because so many different paradigms have been implemented in it, but also has many pitfalls for new and old users because there are many different ways of solving the same problem.

I feel that in C++, more than any other language, you need to know the actual implementation under the hood to use it effectively. This means knowing not just what the language specifies, but can occaissionally require knowing what GCC or Clang generate on your particular hardware.

Many garbage collected languages are written in or have parts of their implementations in C++. See JS (https://github.com/v8/v8)and Java GC (https://github.com/openjdk/jdk/tree/36de19d4622e38b6c00644b0...)

I am not an expert on Java (or C++), so if someone knows better or can add more please correct me.

The JVM and Java the language have always been intertwined. The same people that develop the language, develop the VM. Lots of optimizations in the VM know specifically about Java the language idioms and implementation details. Check out this function which helps determine if instance fields are trusted: https://github.com/openjdk/jdk/blob/edd454b502b9bacde5549282...