RFR: 8311661: Resolve duplicate symbol of StringTable::StringTable with JDK static linking [v4]

[Ioi Lam]

On Wed, 12 Jul 2023 19:29:31 GMT, Jiangli Zhou <jiangli at openjdk.org> wrote:

>> Move StringTable to 'hotspot_jvm' namespace.
>
> Jiangli Zhou has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add hotspot_jvm:: to StringTable in javaClasses.hpp.

Hi Jiangli,

Putting the HotSpot code in a namespace is a fundamental change that should be done in a JEP. The idea of using namespaces for HotSpot has been around for a while, but so far there hasn't been a strong motivation for doing it. Perhaps static linking would finally give us a go-ahead reason.

The JEP should discuss the goals, design choices, risks and alternatives. For example:

- Other than static linking, what other problems can we solve with namespaces? Knowing the other goals may help us in choosing a design.
- Do we want a single namespace, or multiple namespaces (one for GC, one for JIT, etc)
- Do we want to change over incrementally (as in this PR), or in a single step
- Do we want to enable namespaces optionally (e.g., only for static linking)?
- With namespaces, the debug symbols will be much bigger, and we could also run into issues with debuggers and other tools. 
- There may be alternatives for static linking that may have less impact than namespaces.

The [hotspot-dev mailing list](https://mail.openjdk.org/mailman/listinfo/hotspot-dev) would be the best place to have such discussions. Also, at this time, many OpenJDK developers who are interested on this topic are on vacation, so we probably need to wait till the end of the summer so everyone has a chance to chime in.

JEP may feel like a lot of process, but for this change, I think it's the best avenue for exploration.

Thanks
Ioi

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PR Comment: https://git.openjdk.org/jdk/pull/14808#issuecomment-1634674049