[ruby-core:125692] [Ruby Bug#22103] Constant-folded /o regexp crashes with dupstring of a Regexp

11 Jun 2026

      Issue #22103 has been reported by shugo (Shugo Maeda).

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Bug #22103: Constant-folded /o regexp crashes with dupstring of a Regexp
https://bugs.ruby-lang.org/issues/22103

* Author: shugo (Shugo Maeda)
* Status: Open
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
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A `/o` (once) regexp whose interpolation folds to a constant crashes at runtime:

```ruby
def m; /#{"a"}/o; end
m   #=> [BUG] heap_idx_for_size: allocation size too large
```

A plain `/#{"a"}/` (no `/o`) is fine.

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