Expose fstring related APIs to C-extensions
As discussed with @tenderlove here: https://github.com/ruby/ruby/pull/2287#issuecomment-513865160
We'd like to update various data format parsers (JSON, MessagePack, etc) to add the possibility to deduplicate strings while parsing.
But unfortunately the
rb_fstring_* family of functions isn't available to C-extensions, so the only available fallback is
rb_funcall(str, rb_intern("-@")) which most parsers will likely consider too slow. So the various
rb_fstring_* functions would need to be public.
Proposed patch: https://github.com/ruby/ruby/pull/2299