fiddle test_qsort fails

[ahorek]

Environment jruby 9.2.10.0-SNAPSHOT (2.5.7) 2019-11-08 c56caa3 Java HotSpot(TM) 64-Bit Server VM 11.0.2+9-LTS on 11.0.2+9-LTS +jit [linux-x86_64] Linux DESKTOP-2POPPQP 4.4.0-17763-Microsoft #864-Microsoft Thu Nov 07 15:22:00 PST 2019 x86_64 x86_64 x86_64 GNU/Linux

I fixed a bunch of bugs in https://github.com/jruby/jruby/pull/5960

but in order to support https://github.com/ankane/lightgbm/tree/fiddle there's one blocker which I don't know how to fix

a simple test case https://github.com/jruby/jruby/blob/4e8bb2666a7257f0f5986800f96bb88efdd6acbd/test/mri/fiddle/test_func.rb#L73

Expected Behavior test passes

Actual Behavior

Fiddle::TestFunc#test_qsort1:
TypeError: cannot convert parameter to native pointer

this code tries to convert the class into a pointer https://github.com/jruby/jruby/blob/42ae3ed3dad8a272464c215346b182a1b5e8cb56/core/src/main/java/org/jruby/ext/ffi/jffi/JITRuntime.java#L530

[ahorek]

• the same issue as https://github.com/jruby/jruby/issues/7307