From: "alanwu (Alan Wu)" <noreply@...>
Date: 2022-05-02T18:33:24+00:00
Subject: [ruby-core:108459] [Ruby master Bug#18730] Double `return` event handling with different tracepoints

Issue #18730 has been updated by alanwu (Alan Wu).


> Aren't both handlers same (global) in my first example?

They are, but the two invocations are coming from two
separate events while my script is concerned with handling
within one event. You can see this from a slightly modified
version of your script:

```ruby
def bar
  42 #bp here
end

def set_return_tp
  TracePoint.new(:return) do |tp|
    puts "Return hit #{tp.method_id}"
    tp.disable
    set_return_tp
  end.enable
end

set_return_tp
p :gap
bar
```

```
Return hit set_return_tp
:gap
Return hit bar
```


----------------------------------------
Bug #18730: Double `return` event handling with different tracepoints
https://bugs.ruby-lang.org/issues/18730#change-97497

* Author: hurricup (Alexandr Evstigneev)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
I'm not sure if this is a bug or intentional behavior, but feels a bit unexpected. Ruby 3.0.x, 3.1.x affected.

Here is the script demonstrating the issue:
```
def bar
  42 #bp here
end

tp_line = TracePoint.new(:line) do |tp0|
  puts "Got line event from #{tp0.path}:#{tp0.lineno}"

  tp_multi1 = TracePoint.new(:return, :b_return, :line) do |tp|
    if tp.lineno == 3
      puts "Got first return `#{tp.event}` from #{tp.path}:#{tp.lineno}"
      tp.disable
      # tp0.disable # uncommenting this line changes things to the more expected 


      tp_multi2 = TracePoint.new(:return, :b_return, :line) do |tps|
        puts "Got second return `#{tps.event}` from #{tps.path}:#{tps.lineno}"
      end
      tp_multi2.enable(target: RubyVM::InstructionSequence.of(method :bar))
    end
  end
  tp_multi1.enable
end

tp_line.enable(target: RubyVM::InstructionSequence.of(method :bar))

bar
```
1. We set a line TP to the `bar` method `iseq` (consider it a line breakpoint)
2. When line event is triggered we setting another untargeted tracepoint for the same method, to catch `line`, `return` and `b_return` events (consider it attempt to step into something)
3. When return event of the `bar` method is triggered, we disabling second tracepoint and setting another one, targeted to the same method and multiple events.

Output i get:
```
Got line event from /home/hurricup/test.rb:2
Got first return `return` from /home/hurricup/test.rb:3
Got second return `return` from /home/hurricup/test.rb:3
```
The questions are: 
1. why return triggered on the second tracepoint, when we already handeled it?
2. why disabling line tracepoint changes behavior?




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