From: "byroot (Jean Boussier) via ruby-core" <ruby-core@...>
Date: 2024-02-09T16:59:38+00:00
Subject: [ruby-core:116657] [Ruby master Bug#20253] `Proc.dup` and `Proc#clone` don't preserve finalizers

Issue #20253 has been updated by byroot (Jean Boussier).


While looking at this, it appears that instance variables are also not copied over in `Proc#dup`, but somehow are in `Proc#clone`:

```ruby
def ivar_dup(obj)
  obj.instance_variable_set(:@foo, 1)
  p [:dup, obj.dup.instance_variable_get(:@foo)]
  p [:clone, obj.clone.instance_variable_get(:@foo)]
end

ivar_dup(Object.new)
ivar_dup(Proc.new { })
```

```
[:dup, 1]
[:clone, 1]
[:dup, nil]
[:clone, 1]
```

Which really raise the question of why Proc has a completely different codepath for duping/cloning, AFAIK no other core type does this.

----------------------------------------
Bug #20253: `Proc.dup` and `Proc#clone` don't preserve finalizers
https://bugs.ruby-lang.org/issues/20253#change-106667

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* Backport: 3.0: WONTFIX, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
While reviewing the fix for [Bug #20250] @peterzhu2118 pointed that `FL_FINALIZE` should probably also be cleared.

However after some extra testing, it appears `Object#dup` and `Object#clone` do copy over the finalizer (which makes sense).

But for some reason `Proc` has its own `dup/clone` implementation, which does copy the `FL_FINALIZE` flag, but doesn't copy the finalizer:

Test script:

```ruby
def fin(sym)
  ->(_) { p sym }
end

obj = Object.new
ObjectSpace.define_finalizer(obj, fin(:obj))
obj.dup
obj.clone

proc = Proc.new { }
ObjectSpace.define_finalizer(proc, fin(:proc))
proc.dup
proc.clone
```

Expected output:

```
:proc
:proc
:proc
:obj
:obj
:obj
```

Actual output:

```
:proc
:obj
:obj
:obj
```

This discrepancy is present all the way back to Ruby 1.9.

It's so niche I'm not sure it's worth a backport though...



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