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What language is the JVM written in? All safe code in existence running on von Neumann architectures is built on a foundation of unsafe code. The goal of all m

What language is the JVM written in? All safe code in existence running on von Neumann architectures is built on a foundation of unsafe code. The goal of all memory-safe languages is to provide safe abstractions on top of an unsafe core.

throwaway2037 2y ago
> What language is the JVM written in? I am pretty sure it is C++. I like your second paragraph. It is well written.
- pjmlp 2y ago
  Depends on which JVM you are talking about, some are 100% Java, some are a mix of Java and C, others are a mix of Java and C++, in all cases a bit of Assembly as well.
  - throwaway2037 2y ago
    You are right. I should have been more clear. I am talking about the bog standard one that most people use from Oracle/OpenJDK. A long time back it was called "HotSpot JVM". That one has source code available on GitHub. It is mostly C++ with a little bit of C and assembly.
    - pjmlp 2y ago
      Define mostly, https://github.com/openjdk/jdk 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.
      - saagarjha 2y ago
        JDK≠JVM
        pjmlp 2y ago
        If you are only talking about libjvm.so you would be right, then again that alone won't do much help for Java developers.
        saagarjha 2y ago
        That is what most people are talking about when they are discussing the JVM, yes
rat87 2y ago
I don't think what something was written in should count. Baring bugs it should still be memory safe. But I believe JVM has ffi and as soon as you use ffi you risk messing up that memory safety.
- sunshowers 2y ago
  Does it help to think of "safe Rust" as a language that's written in "unsafe Rust"? That's basically what it is.
pjmlp 2y ago
Depends on which JVM you are talking about, some are 100% Java, some are a mix of Java and C, others are a mix of Java and C++, in all cases a bit of Assembly as well.

throwaway2037 2y ago

> What language is the JVM written in? I am pretty sure it is C++. I like your second paragraph. It is well written.

pjmlp 2y ago
Depends on which JVM you are talking about, some are 100% Java, some are a mix of Java and C, others are a mix of Java and C++, in all cases a bit of Assembly as well.
- throwaway2037 2y ago
  You are right. I should have been more clear. I am talking about the bog standard one that most people use from Oracle/OpenJDK. A long time back it was called "HotSpot JVM". That one has source code available on GitHub. It is mostly C++ with a little bit of C and assembly.
  - pjmlp 2y ago
    Define mostly, https://github.com/openjdk/jdk 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.
    - saagarjha 2y ago
      JDK≠JVM
      - pjmlp 2y ago
        If you are only talking about libjvm.so you would be right, then again that alone won't do much help for Java developers.
        saagarjha 2y ago
        That is what most people are talking about when they are discussing the JVM, yes

rat87 2y ago

I don't think what something was written in should count. Baring bugs it should still be memory safe. But I believe JVM has ffi and as soon as you use ffi you risk messing up that memory safety.

sunshowers 2y ago
Does it help to think of "safe Rust" as a language that's written in "unsafe Rust"? That's basically what it is.

pjmlp 2y ago

Depends on which JVM you are talking about, some are 100% Java, some are a mix of Java and C, others are a mix of Java and C++, in all cases a bit of Assembly as well.