From: "k0kubun (Takashi Kokubun) via ruby-core" <ruby-core@...>
Date: 2024-09-02T09:40:09+00:00
Subject: [ruby-core:119003] [Ruby master Bug#20653] Memory leak in String#start_with? when regexp times out

Issue #20653 has been updated by k0kubun (Takashi Kokubun).

Backport changed from 3.1: UNKNOWN, 3.2: WONTFIX, 3.3: REQUIRED to 3.1: UNKNOWN, 3.2: WONTFIX, 3.3: DONE

ruby_3_3 commit:ce565cd4b851977bf37a470bee54e441bb60486d.

----------------------------------------
Bug #20653: Memory leak in String#start_with? when regexp times out
https://bugs.ruby-lang.org/issues/20653#change-109578

* Author: peterzhu2118 (Peter Zhu)
* Status: Closed
* Backport: 3.1: UNKNOWN, 3.2: WONTFIX, 3.3: DONE
----------------------------------------
GitHub PR: https://github.com/ruby/ruby/pull/11247

This commit refactors how Onigmo handles timeout. Instead of raising a timeout error, onig_search will return a ONIGERR_TIMEOUT which the caller can free memory, and then raise a timeout error.

This fixes a memory leak in String#start_with when the regexp times out. For example:

```ruby
regex = Regexp.new("^#{"(a*)" * 10_000}x$", timeout: 0.000001)
str = "a" * 1000000 + "x"

10.times do
  100.times do
    str.start_with?(regex)
  rescue
  end

  puts `ps -o rss= -p #{$$}`
end
```

Before:

```
33216
51936
71152
81728
97152
103248
120384
133392
133520
133616
```

After:

```
14912
15376
15824
15824
16128
16128
16144
16144
16160
16160
```



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