[ruby-core:124839] [Ruby Bug#21880] The ultra_safe mode of pstore bundled with Ruby 4.0 is broken.

16 Feb 2026

      Issue #21880 has been updated by nobu (Nobuyoshi Nakada).

4.0 needs to backport gems/bundled_gems, and 3.2..3.4 need lib/pstore.rb.

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Bug #21880: The ultra_safe mode of pstore bundled with Ruby 4.0 is broken.
https://bugs.ruby-lang.org/issues/21880#change-116461

* Author: s3fxn (s3 fxn)
* Status: Open
* ruby -v: 4.0
* Backport: 3.2: REQUIRED, 3.3: REQUIRED, 3.4: REQUIRED, 4.0: REQUIRED
----------------------------------------
here is the reproduction code.

```console
$ ruby -v
ruby 4.0.1 (2026-01-13 revision e04267a14b) +PRISM [x86_64-linux]

$ cat pstore.rb 
```
```ruby
#!/usr/bin/env ruby
require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  if ENV['DEBUG']
    gem "pstore", "0.1.4"
  else
    gem "pstore"
  end
end

db = PStore.new("pstore.db")
db.ultra_safe = true
db.transaction do
  puts db["now"] = Time.now
end
```
```console
$ ruby pstore.rb
2026-02-15 04:49:31 +0000
/home/s3fxn/.rubies/ruby-4.0.1/lib/ruby/gems/4.0.0/gems/pstore-0.2.0/lib/pstore.rb:676:in 'Ractor.make_shareable': Proc's self is not shareable: #<Proc:0x0000749f688df078 /home/s3fxn/.rubies/ruby-4.0.1/lib/ruby/gems/4.0.0/gems/pstore-0.2.0/lib/pstore.rb:673> (Ractor::IsolationError)
	from /home/s3fxn/.rubies/ruby-4.0.1/lib/ruby/gems/4.0.0/gems/pstore-0.2.0/lib/pstore.rb:676:in 'PStore#on_windows?'
	from /home/s3fxn/.rubies/ruby-4.0.1/lib/ruby/gems/4.0.0/gems/pstore-0.2.0/lib/pstore.rb:685:in 'PStore#save_data'
	from /home/s3fxn/.rubies/ruby-4.0.1/lib/ruby/gems/4.0.0/gems/pstore-0.2.0/lib/pstore.rb:575:in 'PStore#transaction'
	from pstore.rb:14:in '<main>'

$ DEBUG=1 ruby pstore.rb
2026-02-15 04:49:53 +0000
```

-- 
https://bugs.ruby-lang.org/