[ruby-core:117027] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[ruby-core:117027] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[andrykonchin (Andrew Konchin) via ruby-core]

Issue #20319 has been reported by andrykonchin (Andrew Konchin).

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created singleton classes in an object singleton classes chain to become frozen immediately.




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[ruby-core:117028] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[Eregon (Benoit Daloze) via ruby-core]

Issue #20319 has been updated by Eregon (Benoit Daloze).


Alternatively, I think we could simplify `Kernel#freeze` to always only freeze the direct object and no other object, i.e. no singleton class would be frozen when freezing a singleton object.
State and methods are separate things, so IMO it doesn't gain anything to freeze singleton classes of a singleton object on `singleton_object.freeze`.
The methods can still be modified e.g. using `singleton_object.class.class_exec { def foo = 42 }`.

I think Kernel#freeze should only freeze the object itself, which means instance variables (and internal state if core/TypedStruct object) cannot be changed.
That would be both more consistent semantically and more efficient, while avoiding weird cases like the above.

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-107097

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




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[ruby-core:117054] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[jeremyevans0 (Jeremy Evans) via ruby-core]

Issue #20319 has been updated by jeremyevans0 (Jeremy Evans).


Eregon (Benoit Daloze) wrote in #note-3:
> I think Kernel#freeze should only freeze the object itself, which means instance variables (and internal state if core/TypedStruct object) cannot be changed.
> That would be both more consistent semantically and more efficient, while avoiding weird cases like the above.

I disagree.  If you do not freeze the object's singleton class, then you can define or undefine any method in the singleton class, which is almost the same as being able to modify the object (from a Ruby perspective, not a C perspective).

However, redefining methods in the singleton class of the singleton class of the object does not allow you to modify the object, it only allows you to modify the object's singleton class.  However, as the object's singleton class is frozen, we still should prevent it.

This bug should be fairly simple to fix by having `Kernel#freeze` go up the singleton class chain and freeze all currently instantiated singleton classes.

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-107128

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




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[ruby-core:117099] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[Eregon (Benoit Daloze) via ruby-core]

Issue #20319 has been updated by Eregon (Benoit Daloze).


jeremyevans0 (Jeremy Evans) wrote in #note-4:
> I disagree.  If you do not freeze the object's singleton class, then you can define or undefine any method in the singleton class, which is almost the same as being able to modify the object (from a Ruby perspective, not a C perspective).

One can still define or undefine any method in one of the ancestors (except the singleton class), or use `prepend`/`include` on any of these or even `refine` to change the behavior of that object.
Freezing the singleton class achieves very little IMO and is inconsistent with `Kernel#freeze` being a shallow freeze (that is, only freeze the immediate object, not other objects, which AFAIK holds for all other cases).

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-107172

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




-- 
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[ruby-core:117100] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[Eregon (Benoit Daloze) via ruby-core]

Issue #20319 has been updated by Eregon (Benoit Daloze).


> This bug should be fairly simple to fix by having `Kernel#freeze` go up the singleton class chain and freeze all currently instantiated singleton classes.

Yeah, that seems the smaller fix for now and at least it fixes a "should-be-idempotent method like singleton_class" dynamically freezing an existing singleton class.
Would you be able to make a PR for that?



----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-107173

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




-- 
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 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
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[ruby-core:117134] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[jeremyevans0 (Jeremy Evans) via ruby-core]

Issue #20319 has been updated by jeremyevans0 (Jeremy Evans).


I looked into this and the current behavior is deliberate, as there is a comment stating `should not propagate to meta-meta-class` (see `rb_freeze_singleton_class` definition in `class.c`). See related commit commit:d9a597408f0f192ff25ab51e1e6733fe6fefc01b.

Freezing the singleton class of the singleton class breaks `TestModule#test_frozen_singleton_class`. I came up with a solution that fixes this by walking down the attached object chain to make sure it ends in the object being frozen.  Not sure that is correct, but it does appear to pass CI: https://github.com/ruby/ruby/pull/10245

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-107210

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




-- 
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 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
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[ruby-core:117597] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[Eregon (Benoit Daloze) via ruby-core]

Issue #20319 has been updated by Eregon (Benoit Daloze).


@nobu WDYT? Could you review that PR?

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-108006

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




-- 
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 ______________________________________________
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 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
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[ruby-core:118208] [Ruby master Bug#20319] Singleton class is being frozen lazily in some cases

[mame (Yusuke Endoh) via ruby-core]

Issue #20319 has been updated by mame (Yusuke Endoh).


Discussed at the dev meeting, but no one had a deep understanding of Jeremy's patch, and matz was unable to make any decision.

----------------------------------------
Bug #20319: Singleton class is being frozen lazily in some cases
https://bugs.ruby-lang.org/issues/20319#change-108695

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* ruby -v: 3.2.2
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
I've noticed suspicious behaviour (it doesn't affect anything in practice for me though) when an object becomes frozen only its own singleton class becomes frozen immediately.

A singleton class of the object immediate singleton class becomes frozen lazily after `#singleton_class` method call:

```ruby
o = Object.new
klass = o.singleton_class.singleton_class

o.freeze

puts klass.frozen?                              # false <== here we expect true
puts o.singleton_class.singleton_class.frozen?  # true
puts klass.frozen?                              # true
```

I would expect all created (and visible to user) singleton classes in an object singleton classes chain to become frozen immediately when the object gets frozen.




-- 
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