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There's not really a second C# runtime. Java has several, some based on the Openjdk, but a few that are completely new like OpenJ9 and Graal. The closest C# h

There's not really a second C# runtime. Java has several, some based on the Openjdk, but a few that are completely new like OpenJ9 and Graal. The closest C# has is mono. This sort of thing is bound to happen with that situation. Heck, it happens with C++ whenever a new C++ version comes out. Some C++11 features took years to make their way into all the compilers.

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vlovich123 19d ago
Graal is based on OpenJDK. OpenJ9 while using a separate JVM and JIT leverage the openjdk class path as well as the build environment and various other things. I don’t think there’s a single alternate implementation that doesn’t leverage a good chunk of openjdk somehow
- samus 18d ago
  For the simple reason that class files with JVM bytecode are the standardized intermediate representation. Therefore, duplicating the frontend is wasted effort.
  - pjmlp 18d ago
    Up to a point. Embedded systems versions tend to have their own ways, which is why despite everything Android using Dex isn't a first in the Java ecosystem.
    - samus 18d ago
      IMHO, Dex is a historical artifact. In the past it was thought that the format provides benefits for JIT compilation because it's register based, which turned out to not be case.
      - pjmlp 18d ago
        Lots of "improvements" on Dalvik over J2ME was Google's marketing to sidestep Sun, speaking as ex-Nokia, coupled with the experience of Java on Symbian devices and Sony Ericson. All these years afterwards it quite clear that there is just similar fragmentation, and implementation differences between all OEMs selling every kind of devices, and as you say the format doesn't really provide that much benefits. What ART has going for it, are all the improvements they started on Android 7 and later, by having a mix of handwritten interpreter in Assembly, JIT compiler with cache, AOT compilation with the device on idle, and sharing of PGO metadata via the PlayStore across devices. Ironically Windows Phone did it first, with MDIL on Windows Phone 8 followed by .NET Native on Windows Phone 10, using compilation via the Windows Store, but Microsoft fumbled the delivery.
        deleted 18d ago
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- pjmlp 18d ago
  PTC and Aicas for example.

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vlovich123 19d ago

Graal is based on OpenJDK. OpenJ9 while using a separate JVM and JIT leverage the openjdk class path as well as the build environment and various other things. I don’t think there’s a single alternate implementation that doesn’t leverage a good chunk of openjdk somehow

samus 18d ago
For the simple reason that class files with JVM bytecode are the standardized intermediate representation. Therefore, duplicating the frontend is wasted effort.
- pjmlp 18d ago
  Up to a point. Embedded systems versions tend to have their own ways, which is why despite everything Android using Dex isn't a first in the Java ecosystem.
  - samus 18d ago
    IMHO, Dex is a historical artifact. In the past it was thought that the format provides benefits for JIT compilation because it's register based, which turned out to not be case.
    - pjmlp 18d ago
      Lots of "improvements" on Dalvik over J2ME was Google's marketing to sidestep Sun, speaking as ex-Nokia, coupled with the experience of Java on Symbian devices and Sony Ericson. All these years afterwards it quite clear that there is just similar fragmentation, and implementation differences between all OEMs selling every kind of devices, and as you say the format doesn't really provide that much benefits. What ART has going for it, are all the improvements they started on Android 7 and later, by having a mix of handwritten interpreter in Assembly, JIT compiler with cache, AOT compilation with the device on idle, and sharing of PGO metadata via the PlayStore across devices. Ironically Windows Phone did it first, with MDIL on Windows Phone 8 followed by .NET Native on Windows Phone 10, using compilation via the Windows Store, but Microsoft fumbled the delivery.
      - deleted 18d ago
        [deleted]
pjmlp 18d ago
PTC and Aicas for example.