Comment by simoncion
6 months ago
> I always hear about it, but never encountered it myself in 25 years of commercial Java development.
Lucky you, I guess?
> Is it “sharing” or having every version of runtime used by at least one app?
I'm not sure what you're asking here? As I'm sure you're aware, software that links against dependent libraries can choose to not care which version it links against, or link against a major, minor, or patch version, depending on how much it does care, and how careful the maintainers of the dependent software are.
So, the number of SOs you end up with depends on how picky your installed software is, and how reasonable the maintainers of the libraries they use are.
> So, the number of SOs you end up with depends on how picky your installed software is, and how reasonable the maintainers of the libraries they use are.
And that is the hard problem, because it’s people problem, not technical one, and it’s platform independent. When some Java app was requiring a specific build of JRE, it wasn’t limitation or requirement of the platform, but rather the choice of developers based on their expectations and level of trust. Windows still dominates desktop space and it’s not uncommon for C++ programs to install or require a specific version of runtime, so you eventually have lots of them installed.
I don't see how Microsoft's and Sun's/Oracle's decision to encourage bundling all dependent software (including what would ordinarily be considered to be system libraries) with your program has to do with long-established practices in the *nix world.
I do agree that the world becomes much easier for a language/runtime maintainer if you get to ignore backwards-compatibility concerns because you've convinced your users to just pack in the entire system they built against with their program.
First of all, *nix is not synonymous with C++ programming, so focusing on it specifically is bringing apples to discussion about oranges. When Java is brought to the discussion about C++ I do expect that variety of platforms is taken into account.
Second, you can have shared libraries/runtimes on Windows or in Java world. There exists versioning and *nix is not unique in that. Both are rather agnostic to the way you ship your app. In server Java unless you ship a container, you usually do not ship the JRE. On a desktop - it depends, shared JREs were always possible.
Third, DLL hell does exist in *nix environments too. The versioning mechanism you mention is a technical solution to a people problem and it doesn't work perfectly. Things do break if you relax your dependency constraints too much. How much - it depends on developers and the amount of trust they put in maintainers. So you inevitably end up with multiple versions of the same library or runtime on the same machine, no matter what OS or cross-platform solution do you use. It is not much different from shipping a bundle.
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