Issue #16900 has been reported by jeremyevans0 (Jeremy Evans).

----------------------------------------
Bug #16900: Disposable call-cache introduced memory leak
https://bugs.ruby-lang.org/issues/16900

* Author: jeremyevans0 (Jeremy Evans)
* Status: Open
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* Backport: 2.5: DONTNEED, 2.6: DONTNEED, 2.7: DONTNEED
----------------------------------------
commit:b9007b6c548f91e88fd3f2ffa23de740431fa969 (Introduce disposable call-cache) introduced a memory leak for classes that include or prepend modules.  Taking the example memory leak script used in the commit message for commit:5922c954614e5947a548780bb3b894626affe6dd:

```ruby
    module M; def bar; end; end
    loop{
      Class.new do
        def foo; end
        prepend M
      end
    }
```

There is unbounded growth:

```
jeremy   56984  0.0  0.1 59540 14940 p2  S+      5:15PM    0:00.19 ruby example.rb
jeremy   56984  0.0  0.1 61852 18640 p2  S+      5:15PM    0:00.40 ruby example.rb
jeremy   56984  0.0  0.1 62700 19940 p2  S+      5:15PM    0:00.62 ruby example.rb
jeremy   56984  0.0  0.1 63696 21364 p2  S+      5:15PM    0:00.83 ruby example.rb
jeremy   56984  4.1  0.1 64632 22748 p2  S+      5:15PM    0:01.05 ruby example.rb
jeremy   56984  4.1  0.1 65664 24188 p2  S+      5:15PM    0:01.26 ruby example.rb
jeremy   56984  4.1  0.2 66632 25432 p2  S+      5:15PM    0:01.47 ruby example.rb
jeremy   56984  4.1  0.2 67484 26552 p2  S+      5:15PM    0:01.70 ruby example.rb
jeremy   56984  8.5  0.2 68456 27772 p2  S+      5:15PM    0:01.92 ruby example.rb
jeremy   56984  8.5  0.2 69536 29164 p2  S+      5:15PM    0:02.14 ruby example.rb
jeremy   56984  8.5  0.2 70424 30252 p2  S+      5:15PM    0:02.36 ruby example.rb
```

This issue appears to be limited to classes that include or prepend modules.

* Same memory leak when switching from `prepend` to `include`
* No memory leak when switching from `Class.new` to `Module.new`
* No memory leak when removing the `prepend`
* No memory leak when removing the `prepend` and subclassing the class.



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