Support for shared built Rubies

[kddnewton]

In order to support embedding Ruby inside other C projects.

[MSP-Greg]

Any platforms in particular?

[kddnewton]

Any and all really! Trying to support as many as I can, but at the moment if it's not shared it really be embedded.

[MSP-Greg]

I know of a commercial application that is using Window MinGW builds embedded, and I've hacked it to use an mswin build. Both work fine.

[kddnewton]

So it works if it's got --enable-shared as part of the config, but when it's not I run into this: https://github.com/prettier/plugin-ruby/pull/512/checks?check_run_id=539737773#step:9:68. Copied from there:

/usr/bin/ld: /home/runner/.rubies/ruby-2.6.5/lib/libruby-static.a(array.o): relocation R_X86_64_PC32 against symbol `rb_cFalseClass' can not be used when making a shared object; recompile with -fPIC

[eregon]

OK, I'll try to use --enable-shared for Rubies built by ruby-builder and ruby-dev-builder (Ubuntu and macOS).
I'll start with ruby-dev-builder, so we can verify it fixes your use-case and limit the risks.

[eregon]

ruby-head is now built with --enable-shared: https://github.com/ruby/ruby-dev-builder/releases

@kddeisz Could you try ruby-head in your PR/CI and see if that works?

[kddnewton]

Interesting - I've got a new error now: https://github.com/prettier/plugin-ruby/pull/512/checks?check_run_id=543575032#step:11:14. Error: libruby.so.2.8: cannot open shared object file: No such file or directory

[eregon]

I assume you're trying to require or process.dlopen() the node extension you built, and that links to libruby? Probably it doesn't find libruby.so.2.8 at runtime (because it only looks in /usr/lib, /usr/local/lib, etc).
You should be able to see if this is the issue with ldd path/to/extension.so which would show libruby.so.2.8 is unresolved.

To fix that I think you need to pass -rpath #{RbConfig::CONFIG['libdir']} in LDFLAGS when building the extension.

[eregon]

As of https://github.com/ruby/setup-ruby/releases/tag/v1.28.0 all Ruby builds use --enable-shared.
On Windows I believe this was already the case.

[kddnewton]

Thanks for this! It's compiling on everything now.

I still can't get it to actually find the .so file, but I'll keep trying configuration combinations.