Oracle Contributing GraalVM Community Edition Java Code to OpenJDK

Post by Macha » Wed, Oct 26, 2022, 3:18 PM UTC

stonemetal12 wrote: post #20

simias wrote: post #5

Earlier quoted context omitted.

Maybe it's my ignorance of the Java ecosystem or a lack of imagination but how could a language that requires a heavy runtime be written in itself? Wouldn't you need a runtime for the runtime, and then a runtime for the runtime for the runtime and then...? I can't quite imagine how you'd bootstrap something like that.

You can write a C compiler in Java. The output of the C compiler doesn't depend on the JVM, it would be a regular old program written in C. Writing a Java runtime would be similar, the output would be an executable that doesn't depend on the JVM.

Post by chrisseaton » Wed, Oct 26, 2022, 3:19 PM UTC

Taywee wrote: post #22

crustycoder wrote: post #12

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It's no different to writing any other compiler for Language X in Language X, and that's a really common thing to do. The Java compiler emits files containing Java Bytecode which are subsequently run by a different invocation of the JVM.

It's different in that the JVM is not a compiler. It's a bit like suggesting writing CPython in Python. It's possible only if the interpreter's Python source can be compiled ahead of time, like PyPy.

Post by chrisseaton » Wed, Oct 26, 2022, 3:21 PM UTC

Macha wrote: post #21

stonemetal12 wrote: post #20

Earlier quoted context omitted.

You can write a C compiler in Java. The output of the C compiler doesn't depend on the JVM, it would be a regular old program written in C. Writing a Java runtime would be similar, the output would be an executable that doesn't depend on the JVM.

A runtime is not a compiler. The process of bootstrapping a compiler is understood, but if the runtime itself requires a runtime at runtime, that is much more of a turtles all the way down problem than with a runtime less language. It's like how PyPy is Python but with the asterisk that it's bootstrapped with RPython which is an almost-subset of python so that it doesn't require a runtime. You could define a statical…

Post by chrisseaton » Wed, Oct 26, 2022, 3:22 PM UTC

treffer wrote: post #26

pulse7 wrote: post #2

Maybe we will soon see the Java Virtual Machine implemented wholly in (a subset of) Java...

There was a java implementation of a JVM, jikes rvm. I haven't looked at it for ages and looking at Wikipedia it seems dead, so curious if there is any newer attempts....

Post by Macha » Wed, Oct 26, 2022, 3:28 PM UTC

chrisseaton wrote: post #25

Macha wrote: post #21

Earlier quoted context omitted.

A runtime is not a compiler. The process of bootstrapping a compiler is understood, but if the runtime itself requires a runtime at runtime, that is much more of a turtles all the way down problem than with a runtime less language. It's like how PyPy is Python but with the asterisk that it's bootstrapped with RPython which is an almost-subset of python so that it doesn't require a runtime. You could define a statical…

> You could define a statically compilable Java subset (like that which gcj used to accept) and build a runtime in that which would mean omitting features such as reflection but a lot of defacto standard java tooling like Spring Framework would not be compatible. But the JVM you build using your statically compilable Java subset can then run the Spring Framework or whatever.