[ruby-core:125397] [Ruby Bug#22021] Array#delete_if may delete wrong object if array has been altered already

4 May 2026


      Issue #22021 has been reported by chucke (Tiago Cardoso).

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Bug #22021: Array#delete_if may delete wrong object if array has been altered already
https://bugs.ruby-lang.org/issues/22021

* Author: chucke (Tiago Cardoso)
* Status: Open
* ruby -v: 4.0.2
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
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The simplest example I can come up with:

```ruby
$ar = ar = [1, 2, 3, 4, 5]

def delete_at(i)
  $ar.delete(i)
end

ar.delete_if { |i| i == 2 ? (delete_ar(i) && true) : false }

ar #=> [1, 4, 5], and it should be [1, 3, 4, 5]
```


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