[ruby-core:111138] [Ruby master Bug#19169] Kernel#freeze doesn't propagate to singleton class when the singleton class has prepended modules

[ruby-core:111138] [Ruby master Bug#19169] Kernel#freeze doesn't propagate to singleton class when the singleton class has prepended modules

[alanwu (Alan Wu)]

Issue #19169 has been reported by alanwu (Alan Wu).

----------------------------------------
Bug #19169: Kernel#freeze doesn't propagate to singleton class when the singleton class has prepended modules
https://bugs.ruby-lang.org/issues/19169

* Author: alanwu (Alan Wu)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0dev (2022-12-01T16:50:48Z master 9da2a5204f) [arm64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
```ruby
a = []
singleton = a.singleton_class
a.freeze
p singleton.frozen? # => true

a = []
singleton = a.singleton_class.tap { |klass| klass.prepend(Module.new) }
a.freeze
p singleton.frozen? # => false
```

It's because of this function:

```c
void
rb_freeze_singleton_class(VALUE x)
{
    /* should not propagate to meta-meta-class, and so on */
    if (!(RBASIC(x)->flags & FL_SINGLETON)) {
        VALUE klass = RBASIC_CLASS(x);
        if (klass && (klass = RCLASS_ORIGIN(klass)) != 0 &&
            FL_TEST(klass, (FL_SINGLETON|FL_FREEZE)) == FL_SINGLETON) {
            OBJ_FREEZE_RAW(klass);
        }
    }
}
```
It freezes the origin class of the singleton class, but I'm not sure why.
When there is no prepended modules `RCLASS_ORIGIN(klass)` just returns `klass`.
It's old code, so maybe the meaning of `RCLASS_ORIGIN` has changed?

Practically speaking not a big deal because each time one calls `.singleton_class`
it copies the frozen bit of the attached object to the singleton class.



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[ruby-core:111145] [Ruby master Bug#19169] Kernel#freeze doesn't propagate to singleton class when the singleton class has prepended modules

[byroot (Jean Boussier)]

Issue #19169 has been updated by byroot (Jean Boussier).


I ran it against older rubies, and it seems like it has been behaving like this since `prepend` was introduced.

It seem to work on TruffleRuby, but not JRuby.

----------------------------------------
Bug #19169: Kernel#freeze doesn't propagate to singleton class when the singleton class has prepended modules
https://bugs.ruby-lang.org/issues/19169#change-100428

* Author: alanwu (Alan Wu)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.0dev (2022-12-01T16:50:48Z master 9da2a5204f) [arm64-darwin22]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
```ruby
a = []
singleton = a.singleton_class
a.freeze
p singleton.frozen? # => true

a = []
singleton = a.singleton_class.tap { |klass| klass.prepend(Module.new) }
a.freeze
p singleton.frozen? # => false
```

It's because of this function:

```c
void
rb_freeze_singleton_class(VALUE x)
{
    /* should not propagate to meta-meta-class, and so on */
    if (!(RBASIC(x)->flags & FL_SINGLETON)) {
        VALUE klass = RBASIC_CLASS(x);
        if (klass && (klass = RCLASS_ORIGIN(klass)) != 0 &&
            FL_TEST(klass, (FL_SINGLETON|FL_FREEZE)) == FL_SINGLETON) {
            OBJ_FREEZE_RAW(klass);
        }
    }
}
```
It freezes the origin class of the singleton class, but I'm not sure why.
When there is no prepended modules `RCLASS_ORIGIN(klass)` just returns `klass`.
It's old code, so maybe the meaning of `RCLASS_ORIGIN` has changed?

Practically speaking not a big deal because each time one calls `.singleton_class`
it copies the frozen bit of the attached object to the singleton class.



-- 
https://bugs.ruby-lang.org/
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 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
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