Ruby Debugger API

Ruby Debugger API overview with

Transcript

1. Ruby Debugger API Dennis Ushakov or how I stopped worrying and wrote debugger core
2. Sample Program MAGIC_NUMBER = 10000000 ! def is_anybody_out_there? "Is anybody out there?" end ! def hardcore_action MAGIC_NUMBER.times { is_anybody_out_there? } end
3. Sample Program MAGIC_NUMBER = 10000000 ! def is_anybody_out_there? "Is anybody out there?" end ! def hardcore_action MAGIC_NUMBER.times { is_anybody_out_there? } end 3.45s
4. set_trace_func set_trace_func proc { 
 |event,file,line,id,binding,classname| 
 }
5. Event Types • line • call & return • c-call & c-return • class & end • raise • b-call & b-return — Ruby 2.0 • thread-begin & thread-end — Ruby 2.0
6. Binding • Kernel.binding • execution context (variables, methods)
7. Sample Output line debug_bench.rb:22 
 call debug_bench.rb:10 hardcore_action Object
 line debug_bench.rb:11 hardcore_action Object
 c-call debug_bench.rb:11 times Integer
 line debug_bench.rb:11 hardcore_action Object
 call debug_bench.rb:6 is_anybody_out_there? Object
 line debug_bench.rb:7 is_anybody_out_there? Object
 return debug_bench.rb:8 is_anybody_out_there? Object
 c-return debug_bench.rb:11 times Integer
 return debug_bench.rb:12 hardcore_action Object
 line debug_bench.rb:23
8. Sample Output line debug_bench.rb:22 
 call debug_bench.rb:10 hardcore_action Object
 line debug_bench.rb:11 hardcore_action Object
 c-call debug_bench.rb:11 times Integer
 line debug_bench.rb:11 hardcore_action Object
 call debug_bench.rb:6 is_anybody_out_there? Object
 line debug_bench.rb:7 is_anybody_out_there? Object
 return debug_bench.rb:8 is_anybody_out_there? Object
 c-return debug_bench.rb:11 times Integer
 return debug_bench.rb:12 hardcore_action Object
 line debug_bench.rb:23 61.73s
9. set_trace_func set_trace_func proc { 
 |event,file,line,id,binding,classname| 
 }
10. set_trace_func set_trace_func proc { 
 |event,file,line,id,binding,classname| 
 } 58.33s
11. rb_add_event_hook void rb_add_event_hook(
 rb_event_hook_func_t func,
 rb_event_flag_t events,
 VALUE data
 );
12. event_hook gem • If there’s a C API there should be a wrapper gem for it • Well, no
13. event_hook gem • With empty processing Ruby method 31.46s • With empty processing C method 6.48s
14. Ruby 2.0: moar API • TracePoint • debug_inspector
15. Ruby 2.0: TracePoint trace = TracePoint.new(*events) do |tp|
 end
 trace.enable
16. Ruby 2.0: TracePoint trace = TracePoint.new do |tp|
 end
 trace.enable 18.27s
17. Ruby 2.0: TracePoint trace = TracePoint.new do |tp| tp.binding
 end
 trace.enable 70.20s
18. Performance summary • run 3.45s • set_trace_func 61.73s • binding 58.33s • rb_add_event_hook • Ruby callback 31.46s • C callback 6.48s • TracePoint 18.27s
19. Under the hood • Everyone is using rb_add_event_hook
20. Ruby 2.0: debug_inspector VALUE rb_debug_inspector_open(
 rb_debug_inspector_func_t func,
 void *data
 );
21. debug_inspector gem • If there’s a C API there should be a wrapper gem for it that’s obsolete • Well, no
22. debug_inspector gem RubyVM::DebugInspector.open { |dc|
 locations = dc.backtrace_locations
 locations.size.times do |i|
 p dc.frame_binding(i)
 p dc.frame_iseq(i)
 p dc.frame_class(i)
 end
 }
23. Usages • set_trace_func • ruby -r debug.rb • rb_add_event_hook • ruby-debug-base/debugger • rcov
24. Usages • TracePoint + DebugInspector • debase • byebug • binding_of_caller
25. What seems to be the problem, officer?
26. line te.rb:9 call te.rb:5 m1
 9 if m1 line te.rb:5 m1
 10 1 return te.rb:5 m1 
 11 elsif m2 call te.rb:6 m2
 12 2 line te.rb:6 m2
 13 end return te.rb:6 m2
 line te.rb:12 Catch me if you can
27. That’s it
28. en_Dal dennis.ushakov@jetbrains.com denofevil
29. JRuby • org.jruby.runtime.EventHook • public boolean isInterestedInEvent(RubyEvent event) • public void eventHandler(
 ThreadContext tCtx, 
 String event, 
 String file, int line, 
 String methodName, 
 IRubyObject klass
 )