Feature #17863: rewrite lib/debug.rb with latest API

• Status: Closed
• Assignee: ko1 (Koichi Sasada)
• Target version: -

[ko1 (Koichi Sasada)]

I rewrite lib/debug.rb (called old debug.rb) with recent TracePoint APIs (called new debug.rb).

It has several incompatibility but maybe nobody uses lib/debug.rb so there is no compatible issues. In fact I tried several features of lib/debug.rb and it doesn't work nowaday.

You can see the doc on https://github.com/ruby/debug

Compare with existing other debuggers, it has several advantages:

• Fast: No performance penalty on non-stepping mode and non-breakpoints.
• Remote debugging: Support remote debugging natively.
  • UNIX domain socket
  • TCP/IP
  • VSCode/DAP integration (TODO)
• Extensible: application can introduce debugging support with several methods
  • By rdbg command
  • By loading libraries with -r command line option
  • By calling Ruby's method explicitly
• Misc
  • Support threads (almost done) and ractors (TODO).
  • Support suspending and entering to the console debugging with Ctrl-C at most of timing.
  • Show parameters on backtrace command.

And do not need to write it on Gemfile because it will be a default gem from Ruby 3.1.

Important differences:

• require 'debug' is only a way to enable old debug.rb, but new debug.rb can be enabled with:
  • require
  • rdbg command (like bybug)
  • binding.bp method like binding.irb
• Support remote debugging
• Support several options like non-stop mode and so on
• old debug.rb evaluate unrecognized command as Ruby script, but new debug.rb doesn't allow this spec.
  • obj.foo will be evaluated as Ruby script on old debug.rb (and byebug)
  • new debug.rb shows unknown command because it is typo safe and extension safe.
  • To see the result, you need to use p command like p obj.foo.

Now you can try on 2.6-master with gem install debug --pre.

[byroot (Jean Boussier)]

I tried it with our app, and it crashes weirdly, maybe because of Thread.report_on_exception = true?

(rdbg) c
#<Thread:0x00007fa3421f4630 ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:78 run> terminated with exception (report_on_exception is true):
~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/source_repository.rb:13:in `read': No such file or directory @ rb_sysopen - eval (Errno::ENOENT)
	from ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/source_repository.rb:13:in `add'
	from ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:825:in `on_load'
	from ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:88:in `block in initialize'
["~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/thread_client.rb",
 599,
 #<Errno::ENOENT: No such file or directory @ rb_sysopen - eval>,
 ["~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/source_repository.rb:13:in `read'",
  "~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/source_repository.rb:13:in `add'",
  "~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:825:in `on_load'",
  "~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:88:in `block in initialize'"]]
~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/source_repository.rb:13:in `read': No such file or directory @ rb_sysopen - eval (Errno::ENOENT)
	from ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/source_repository.rb:13:in `add'
	from ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:825:in `on_load'
	from ~/.gem/ruby/3.0.1/gems/debug-1.0.0.beta3/lib/debug/session.rb:88:in `block in initialize'

[Eregon (Benoit Daloze)]

binding.bp

What does bp mean? It seems hard to guess. Why not binding.debugger or binding.debug ?

[byroot (Jean Boussier)]

"Break Point" I presume. But yes, my 2 cents of feedback is the same. Might just be habit, but I had a hard time remembering it just during my 10 minutes session of trying the gem.

I'm very used to Kernel#debugger / Kernel#byebug.

Also on another note I figured the bug above: https://github.com/ruby/debug/pull/10

[ko1 (Koichi Sasada)]

I want to avoid Kernel#... for compatibility.
If binding.debug makes sense, I prefer it.

[ko1 (Koichi Sasada)]

ko1 (Koichi Sasada) wrote in #note-4:

I want to avoid Kernel#... for compatibility.
If binding.debug makes sense, I prefer it.

or both? (#bp and #debug). mame-san said binding is too long and he doesn't want to write it :p

[Eregon (Benoit Daloze)]

I think binding.debug is best. It's not that long to type, and people are already used to e.g. binding.irb/pry.
Too short feels cryptic and easier to get accidentally committed.

[hsbt (Hiroshi SHIBATA)]

• Status changed from Open to Closed
• Assignee set to ko1 (Koichi Sasada)

debug.rb was replaced debug gem at https://github.com/ruby/ruby/pull/4804