From: "hurricup (Alexandr Evstigneev)" <noreply@...>
Date: 2022-03-28T14:16:44+00:00
Subject: [ruby-core:108100] [Ruby master Feature#18660] Line event flags on instruction in method/block signature

Issue #18660 has been updated by hurricup (Alexandr Evstigneev).


ko1 (Koichi Sasada) wrote in #note-2:
> I understand the request, but current specification is because of the current implementation (I don't have good idea to implement it without performance penalty).

And one more question. If I want my debugger to be able to stop on the signature code, would it be enough to find `insn_info`s for the signature instructions and set `RUBY_EVENT_LINE` for them? Or do I need to do something else?




----------------------------------------
Feature #18660: Line event flags on instruction in method/block signature
https://bugs.ruby-lang.org/issues/18660#change-97064

* Author: hurricup (Alexandr Evstigneev)
* Status: Closed
* Priority: Normal
----------------------------------------
Ruby in question is 3.0.3. Not sure what behavior is on different versions, but presume the same.

It's unclear why operations in signatures are not marked with `Li`, despite they may be a valid and meaningful code. Consider example:

```
class A
  def foo(some = BasicObject.new)
    yield
  end
end

A.new.foo {|a = BasicObject.new| 1 + a}
```

And here is the disasm of method iseq:
```
local table (size: 1, argc: 0 [opts: 1, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] some@0<Opt=0>
0000 opt_getinlinecache                     9, <is:0>                 (   2)
0003 putobject                              true
0005 getconstant                            :BasicObject
0007 opt_setinlinecache                     <is:0>
0009 opt_send_without_block                 <calldata!mid:new, argc:0, ARGS_SIMPLE>
0011 setlocal_WC_0                          some@0
0013 invokeblock                            <calldata!argc:0, ARGS_SIMPLE>(   3)[LiCa]
0015 leave                                                            (   4)[Re]

```

Here is the block iseq:
```
local table (size: 1, argc: 0 [opts: 1, rest: -1, post: 0, block: -1, kw: -1@-1, kwrest: -1])
[ 1] a@0<Opt=0>
0000 opt_getinlinecache                     9, <is:0>                 (   7)
0003 putobject                              true
0005 getconstant                            :BasicObject
0007 opt_setinlinecache                     <is:0>
0009 opt_send_without_block                 <calldata!mid:new, argc:0, ARGS_SIMPLE>
0011 setlocal_WC_0                          a@0
0013 nop                                    [Bc]
0014 putobject_INT2FIX_1_                   [Li]
0015 getlocal_WC_0                          a@0
0017 opt_plus                               <calldata!mid:+, argc:1, ARGS_SIMPLE>
0019 nop
0020 leave                                                            (   7)[Br]
```

And this is a bit confusing. 
1. I would expect `Ca`/`Bc` events to be fired on the first instruction, not in the middle of `iseq`
2. I would expect `Li` to exist on pc=0 for the both method and block



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