[ruby-core:113027] [Ruby master Bug#19550] Memory leak in iclass for 32 bit systems

27 Mar 2023

      Issue #19550 has been updated by peterzhu2118 (Peter Zhu).

Fix: https://github.com/ruby/ruby/pull/7597

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Bug #19550: Memory leak in iclass for 32 bit systems
https://bugs.ruby-lang.org/issues/19550#change-102561

* Author: peterzhu2118 (Peter Zhu)
* Status: Open
* Priority: Normal
* Backport: 2.7: DONTNEED, 3.0: DONTNEED, 3.1: DONTNEED, 3.2: REQUIRED
----------------------------------------
If !RCLASS_EXT_EMBEDDED (e.g. 32 bit systems) then the rb_classext_t is allocated throug malloc so it must be freed.

The issue can be seen in the following script:

```ruby
20.times do
  100_000.times do
    mod = Module.new
    Class.new do
      include mod
    end
  end

  # Output the Resident Set Size (memory usage, in KB) of the current Ruby process
  puts `ps -o rss= -p #{$$}`
end
```

Before this fix, the max RSS is 280MB, while after this change, it's 30MB.

-- 
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