RFR: 8333268: Fixes for static build

[Magnus Ihse Bursie]

On Thu, 30 May 2024 13:00:21 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> This patch contains a set of changes to improve static builds. They will pave the way for implementing a full static-only java launcher. The changes here will:
> 
> 1) Make sure non-exported symbols are made local in the static libraries. This means that the risk of symbol conflict is the same for static libraries as for dynamic libraries (i.e. in practice zero, as long as a consistent naming scheme is used for exported functions).
> 
> 2) Remove the work-arounds to exclude duplicated symbols.
> 
> 3) Fix some code in hotspot and the JDK libraries that did not work properly with a static java launcher.
> 
> The latter fixes are copied from or inspired by the work done by @jianglizhou and her team as part of the Project Leyden [Hermetic Java](https://github.com/openjdk/leyden/tree/hermetic-java-runtime).

Some open questions:

* Do `os::lookup_function` need to be implemented on Windows too, for symmetry, even if it is only used on Unix platforms?

* Many of the changes in Hotspot boils down to `os::dll_load` doing the wrong thing when running with a static build. Perhaps we should provide a better function that knows how to find and load a symbol for both static and dynamic builds, and use that instead of making a lot of tests for static/dynamic on each location we need to look up a symbol from some other JDK library.

* I managed to replace most of the #ifdef STATIC_BUILD with runtime checks. There are some places remaining though. Apart from the #ifdefs needed for JNI/JVMTI, which will need spec changes to address, there are code in java_md_macosx.m, jio.c and awt_Mlib.c that I did not manage to turn into runtime checks. They will need some more thorough work than just changing an `#ifdef` to an `if () {`.

* And of course, the code in the build system to share all .o files except the two linktype files is still under development...

I moved this away from Draft state, since I think it needs some visibility, especially since it touches several different parts of the code base, and such reviews tend to take time.

I think the code here is good and basically okay to integrate. This patch will not on it's own solve the entire problem of building a proper static launcher, but it takes several important steps along the way. I think the changes here are reasonable to integrate into mainline at this point.

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PR Comment: https://git.openjdk.org/jdk/pull/19478#issuecomment-2140743300
PR Comment: https://git.openjdk.org/jdk/pull/19478#issuecomment-2168635393