From: "ko1 (Koichi Sasada)" <redmine@...>
Date: 2012-11-15T21:31:04+09:00
Subject: [ruby-core:49369] [ruby-trunk - Bug #7214] Ruby 2.0 breaks support for some debugging tools


Issue #7214 has been updated by ko1 (Koichi Sasada).


=begin
[PLEASE REVIEW!!]

= Abstract

I made debugger support interface.
https://github.com/ko1/ruby/compare/debugger_api

Currently, no docs, no tests.

Sorry for my laziness.

Please review it.

= Background

Generally, debugger needs two features.

(1) Flow (execution) control API
(2) Inpsection API

For (1), inserting breakpoints, watch points and so on.
However, I don't touch these features because of no time to discuss.
(set_trace_func and TracePoint will help it)

For (2), (2-1) inspecting current thread's frames, (2-2) thread frames and (2-3) global environment.
We can access (2-3) using Ruby's powerful reflecting features (such as global_variables and so on).
We lacks (2-1) and (2-2). Currently, we don't have flow control features ((1)'s feature) to stop other threads.
So I decide to support only (2-1) "inspecting current thread's frames".

To make (2-1), `Binding.of_caller' (which is supported by 'binding_of_caller') gem is almost enough for debugger.
However, `Binding.of_caller' is too powerful and it can break Ruby's semantics.
I feel that we need to restrict for debugging purpose.

= API

With above consideration, I made a new C/Ruby API.

https://github.com/ko1/ruby/compare/debugger_api

== C-Level APIs

Types:
* typedef struct rb_debug_inspector_struct rb_debug_inspector_t;
* typedef VALUE (*rb_debug_inspector_func_t)(const rb_debug_inspector_t *, void *);

Functions:
* VALUE rb_debug_inspector_open(rb_debug_inspector_func_t func, void *data);
* VALUE rb_debug_inspector_frame_binding_get(const rb_debug_inspector_t *dc, int index);
* VALUE rb_debug_inspector_frame_class_get(const rb_debug_inspector_t *dc, int index);
* VALUE rb_debug_inspector_backtrace_locations(const rb_debug_inspector_t *dc);

== Ruby-level APIs (RubVM::DebugInspector)

You can use the following APIs after "require 'rubyvm/debug_inspector'".

* RubVM::DebugInspector.open{|inspector| ...}
* RubVM::DebugInspector#backtrace_locations #=> locations array
* RubVM::DebugInspector#frame_binding(i) #=> i-th binding.
  Generated bindings can be `broken' outside of `RubVM::DebugInspector.open' block
  to avoid abusing this powerful feature (now, they are not broken)
* RubVM::DebugInspector#frame_class(i) #=> i-th method class

Ruby level API is sample code of C-level APIs.

== Sample code

The following sample code is very simple debugger (breakpoint).

  require 'rubyvm/debug_inspector'
  
  def breakpoint
    RubyVM::DebugInspector.open{|inspector|
      $inspector = inspector
      inspector.backtrace_locations.each_with_index{|location, i|
        b = inspector.frame_binding(i) # binding is nil if it is for when C's context
        vars = b ? b.eval('local_variables') : []
        puts [i, location.to_s, vars, b, inspector.frame_class(i)].inspect
      }
    }
  end
  
  def foo
    foo_a = foo_b = nil
    breakpoint
  end
  
  hello = 1
  foo
  
  begin
    # DebugInspector object is not active outside block of
    # RubyVM::DebugInspector.open
    p $inspector.backtrace_locations
  rescue ArgumentError => e
    p [:ok, e]
  end

= Consideration

== Satisfaction

I'm sorry I don't make surveys about debugger APIs for current CRuby's debugger
and debuggers for alternative Ruby implementations.
Please point out that it is enough or not enough, misunderstood and so on.

== Toward Ruby 2.0.0

Ruby 2.0.0 spec was already frozen :(
Make debug_inspector gem for 2.0.0?

=end

----------------------------------------
Bug #7214: Ruby 2.0 breaks support for some debugging tools
https://bugs.ruby-lang.org/issues/7214#change-32925

Author: banister (john mair)
Status: Open
Priority: Normal
Assignee: ko1 (Koichi Sasada)
Category: core
Target version: 2.0.0
ruby -v: ruby 2.0.0dev (2012-10-18 trunk 37260) [x86_64-linux] 


Notably the "Pry" debugger breaks, and (though i haven't checked) I'm assuming the 'debugger' project as well. The reason for the breakages (as far as i can see) is that the `rb_vm_make_env_object` function is now hidden. In the comments for 1.9.3's vm.c it was stated an alternative API for `rb_vm_make_env_object` (see https://github.com/ruby/ruby/blob/ruby_1_9_3/vm.c#L53-60) would be provided, but I have been unable to find one.

Can you please inform me of where I can find the new API (if it exists), or alternatively, provide a work-around so we can get the debuggers working on Ruby 2.0

Thanks






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