From: os97673@...
Date: 2015-02-24T15:32:47+00:00
Subject: [ruby-core:68284] [Ruby trunk - Feature #10844] TracePoint API needs an event to inform about creating/removing a new frame without calling something

Issue #10844 has been updated by Oleg Sukhodolsky.


David Rodr��guez wrote:
> Both of those issues arised from several bugs in the TracePoint API that led to unbalanced counts of call/return events in some cases. Once all those bugs are fixed, the calculated stack size should be reliable enough so that a single notion of stack size is need.

As for counting: could you please refer those bugs?

> Furthermore, I don't think Byebug is actually using the "real stack size" anymore.

Yes, byebug doesn't use real stack size but it means it does not provide complete information about the stack :(


----------------------------------------
Feature #10844: TracePoint API needs an event to inform about creating/removing a new frame without calling something
https://bugs.ruby-lang.org/issues/10844#change-51641

* Author: Oleg Sukhodolsky
* Status: Feedback
* Priority: Normal
* Assignee: Koichi Sasada
----------------------------------------
There are some situations when Ruby VM creates a new frame even if there is no calls
E.g. ensure create a new block.
Here is a simple program which shows that the frame is added but no event is reported.
It is important to known about such situations to correctly implement stepping in debugger.
It would be nice if the api reports about such situations with something like :start_frame/:end events.
What do you think?

~~~ruby
def actual_stack_size(frames_to_skip=3)
  bt = Thread.current.backtrace_locations(frames_to_skip)
  bt.size
end
TracePoint.new do |tp|
  printf "%8s %s:%-2d %13s %d\n", tp.event, tp.path, tp.lineno, tp.method_id, actual_stack_size
end.enable

begin
  raise
rescue
  'error'
end
1
~~~

~~~ruby
c_return ruby/debugger/ruby-16236.rb:7         enable 1
    line ruby/debugger/ruby-16236.rb:9                1
    line ruby/debugger/ruby-16236.rb:10               1
  c_call ruby/debugger/ruby-16236.rb:10         raise 1
c_return ruby/debugger/ruby-16236.rb:10         raise 1
  c_call ruby/debugger/ruby-16236.rb:10           new 1
  c_call ruby/debugger/ruby-16236.rb:10    initialize 2
c_return ruby/debugger/ruby-16236.rb:10    initialize 2
c_return ruby/debugger/ruby-16236.rb:10           new 1
  c_call ruby/debugger/ruby-16236.rb:10     backtrace 1
c_return ruby/debugger/ruby-16236.rb:10     backtrace 1
   raise ruby/debugger/ruby-16236.rb:10               1
  c_call ruby/debugger/ruby-16236.rb:12           === 2
c_return ruby/debugger/ruby-16236.rb:12           === 2
    line ruby/debugger/ruby-16236.rb:12               2
    line ruby/debugger/ruby-16236.rb:14               1
~~~



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