Compile iseq_collector.c logic only on CRuby

[eregon]

Description

Compile iseq_collector.c logic only on CRuby

• iseq_collector.c relies on many CRuby internals, there is no point to compile it on other Rubies.
• It now fails to compile on TruffleRuby:

  ../../../../ext/debug/iseq_collector.c: In function ‘imemo_type’:
  ../../../../ext/debug/iseq_collector.c:18:13: error: implicit declaration of function ‘RBASIC’ [-Werror=implicit-function-declaration]
    18 |     return (RBASIC(imemo)->flags >> FL_USHIFT) & imemo_mask;
        |            ^~~~~~

See for example this GH action run: https://github.com/ruby/irb/actions/runs/7017641177/job/19091354167?pr=790#step:3:87

I also added a workflow to ensure the extension keeps building fine on TruffleRuby, and cleaned up a bit existing workflows.

[eregon]

Unfortunately there is a rubygems.org issue currently which means stringio 3.1.0 might not be picked up in CI: rubygems/rubygems.org#4247

[eregon]

I have pushed a small fix trying to get the gem to load on TruffleRuby, to figure out more CRuby-only code paths.
The error after this PR is:

$ ruby -rdebug -e 'p DEBUGGER__'                                
<internal:core> core/tracepoint.rb:24:in `block in initialize': unknown event: call (ArgumentError)
	from <internal:core> core/tracepoint.rb:19:in `each'
	from <internal:core> core/tracepoint.rb:19:in `initialize'
	from /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/debug-1.8.0/lib/debug/session.rb:1834:in `create_method_added_tracker'
	from /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/debug-1.8.0/lib/debug/session.rb:1854:in `<class:Session>'
	from /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/debug-1.8.0/lib/debug/session.rb:93:in `<module:DEBUGGER__>'
	from /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/debug-1.8.0/lib/debug/session.rb:87:in `<top (required)>'
	from <internal:core> core/kernel.rb:297:in `require_relative'
	from /home/eregon/.rubies/truffleruby-dev/lib/gems/gems/debug-1.8.0/lib/debug.rb:6:in `<top (required)>'
	from <internal:core> core/kernel.rb:234:in `gem_original_require'
	from <internal:/home/eregon/.rubies/truffleruby-dev/lib/mri/rubygems/core_ext/kernel_require.rb>:159:in `require'
	from <internal:core> core/unbound_method.rb:18:in `bind_call'
	from <internal:core> core/kernel.rb:272:in `require'
<internal:core> core/kernel.rb:236:in `gem_original_require': cannot load such file -- debug (LoadError)
	from <internal:/home/eregon/.rubies/truffleruby-dev/lib/mri/rubygems/core_ext/kernel_require.rb>:85:in `require'
	from <internal:core> core/unbound_method.rb:18:in `bind_call'
	from <internal:core> core/kernel.rb:272:in `require'

Which means TruffleRuby needs to implement more TracePoint events.

[eregon]

The Protocol workflow seems to randomly fail, already before:
https://github.com/ruby/debug/actions/workflows/protocol.yml?query=branch%3Amaster

[eregon]

Unfortunately there is a rubygems.org issue currently which means stringio 3.1.0 might not be picked up in CI: rubygems/rubygems.org#4247

That's fixed now, and the added truffleruby workflow passes.

[ko1]

BTW now debug.gem doesn't support TruffleRuby and why should we merge it?

[eregon]

BTW now debug.gem doesn't support TruffleRuby and why should we merge it?

Because it breaks irb's CI: https://github.com/ruby/irb/actions/runs/7017641177/job/19091354167?pr=790#step:3:87

[eregon]

And also it's important that Gemfile can just install the debug gem on TruffleRuby too.

[eregon]

@ko1 Let me give you some context.

• gem install debug works on TruffleRuby 23.1.1
• But it does not work on truffleruby master, because truffleruby no longer (and basically cannot) support RBASIC(obj)->flags since it changed its C extension implementation: Running C extensions natively oracle/truffleruby#3118 (comment).
• C extension should not use those flags anyway: https://bugs.ruby-lang.org/issues/18059
• https://github.com/ruby/debug/blob/master/ext/debug/iseq_collector.c is clearly CRuby-specific, it seems good to guard it anyway. It would probably segfault or other bad error on non-CRuby (if it compiled fine).
• https://github.com/ruby/debug/blob/master/ext/debug/debug.c OTOH is more portable and in fact TruffleRuby implements rb_debug_inspector_open().
• It's important the debug gem builds and gem-installs fine on TruffleRuby because it might be part of a Gemfile, or a gem dependency and also debug is a bundled gem since 3.1, so it is also built and shipped as part of truffleruby.
• require 'debug' fails (and on 23.1.1 too), that's fine for now, the debug gem does not support truffleruby yet. And in fact the next thing that breaks is TruffleRuby does not implement :call TracePoint yet (so up to TruffleRuby to implement that). + require 'debug' starts the debugger so it's only required when running the debugger not when loading the application.
• Also it means this code is now tested in CI.

[eregon]

@ko1 Could you take another look at this PR?
I don't think it's controversial to compile CRuby-specific code only on CRuby, is it?

[ko1]

Ok I'll merge it.

Note that, this is repeating, I don't provide TruffleRuby support yet and I'll remove .github/workflows/truffleruby.yml if new feature breaks the test and I don't have any idea to fix in future with informing you.

[eregon]

Thank you. Yes, that's fine.
I'm happy to help if you @-me on GitHub if there is any issue, but yes feel free to disable (e.g. if: false) or remove that workflow if not.