[ruby-core:104475] [Ruby master Bug#17048] Calling initialize_copy on live modules leads to crashes
From:
merch-redmine@...
Date:
2021-07-02 17:11:39 UTC
List:
ruby-core #104475
Issue #17048 has been updated by jeremyevans0 (Jeremy Evans).
This example in the original post has been fixed recently in the master branch. I bisected the fixing commit to commit:3dd3ea092acead6179033f2c95525ffc5b8bb6ff. However, as that changes constant lookup order, I'm guessing we aren't going to want to backport it.
Ruby still allows calling `Module.allocate` and calling `Module#initialize_copy` on modules with subclasses. And the example in #note-9 still can cause an occasional hang in my environment. So I'm going to leave this open.
----------------------------------------
Bug #17048: Calling initialize_copy on live modules leads to crashes
https://bugs.ruby-lang.org/issues/17048#change-92735
* Author: alanwu (Alan Wu)
* Status: Open
* Priority: Normal
* ruby -v: ruby 2.8.0dev (2020-07-23T14:44:25Z master 098e8c2873) [x86_64-linux]
* Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN
----------------------------------------
Here's a repro script
```ruby
loop do
m = Module.new do
prepend Module.new
def hello
end
end
klass = Class.new { include m }
m.send(:initialize_copy, Module.new)
GC.start
klass.new.hello rescue nil
end
```
Here's a script that shows that it has broken semantics even
when it happens to not crash.
```ruby
module A
end
class B
include A
end
module C
Const = :C
end
module D
Const = :D
end
A.send(:initialize_copy, C)
p B::Const # :C, makes sense
A.send(:initialize_copy, D)
p B::Const # :D, makes sense
A.send(:initialize_copy, Module.new)
p (begin B::Const rescue NameError; 'NameError' end) # NameError, makes sense
A.send(:initialize_copy, C)
p B::Const # still NameErorr. Weird
```
This example shows that the problem exists [as far back as 2.0.0](https://wandbox.org/permlink/4dVDY9sNXJ803jh8).
I think the easiest way to fix this is to forbid calling `:initialize_copy`
on modules that have children. Another option is to try to decide on
the semantics of this. Though I don't think it's worth the effort as this
has been broken for a long time and people don't seem to to be using it.
Thoughts?
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