Add new C APIs used by the new json release

[chrisseaton]

Without these fixes essentially the entire Ruby ecosystem seems to stop working!

Shopify#1

[eregon]

Minor: this could be RUBY_INVOKE_NO_WRAP() to avoid wrapping the return value.

[chrisseaton]

Done.

[chrisseaton]

You mean RUBY_CEXT_INVOKE_NO_WRAP I think.

[eregon]

Yes, indeed.

[eregon]

Thanks!
@aardvark179 Could you review too?

Without these fixes essentially the entire Ruby ecosystem seems to stop working!

I wonder what depends on the json gem and doesn't use the bundled json, maybe we should figure this out if it doesn't work as expected.

We could also ask for a new json release that checks if those C functions are available before using them, that way TruffleRuby 19.3.0 would still work with latest json.

[ggrossetie]

We could also ask for a new json release that checks if those C functions are available before using them, that way TruffleRuby 19.3.0 would still work with latest json.

That would be great 👍

[eregon]

We could also ask for a new json release that checks if those C functions are available before using them, that way TruffleRuby 19.3.0 would still work with latest json.

That's unfortunately not so easy because we actually declare and define the function.
I'll check if we can avoid defining functions we don't implement, but I think we can't (i.e., C extensions don't compile anymore) last time I tried.
Maybe we need something like #ifdef GCCOMPACT or so.

[chrisseaton]

I wonder what depends on the json gem and doesn't use the bundled json

i18n is a concrete example at the bottom of many stacks. Non-standard-library json is everywhere.