Issue #6649 has been updated by mame (Yusuke Endoh).

Status changed from Open to Assigned


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Feature #6649: Add new set_trace_func events "b-call", "b-return"
https://bugs.ruby-lang.org/issues/6649#change-28095

Author: ko1 (Koichi Sasada)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 


=begin
= Abstract

Add new events "b-call", "b-return" for set_trace_func().
When block is invoked, then "b-call" is called.
When block is finished, then "b-return" is called.

= Background

set_trace_func() has several events:

* "line"
* "call", "return"
* "c-call", "c-return"
* "class", "end"
* "raise"

With above events, we can trace execution.  However, we can't trace block invocation because there are no events related to block invocation and return from block.

For example, performance profiler using set_trace_func() has problem in such case:

  def m1
    yield
  end
  
  def m2
    m1 do
      # long time process
    end
  end

A method `m1' doesn't consume time, but `m2' consume long time (within block).
However, the profiler detects that the method `m1' consumes long time.


= Proposal

Add "b-call" and "b-return" events for set_trace_func.  "b-call" is for block invocation.  "b-return" is for returning from block.

Parameters:

* event: "b-call" or "b-return"
* file: filename of block
* line: start/end line number of block
* id: block owner method id
* binding: binding of block
* klass: block owner class

= Concerns

* This proposal breaks 100% compatibility.  It seems problem (*1).
* It will make some runtime overhead (slow down).
* parameters id and klass is appropriate?

(*1) Making an alternative API which can replace set_trace_func() (correctly speaking, set_trace_func() can be implemented with this new API) is another proposal.

  # as usual, the method name is temporary name
  set_trace_func2(lamda{|info|
    info.event
    ...
  }

=end



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