From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2023-01-05T19:56:41+00:00
Subject: [ruby-core:111665] [Ruby master Bug#18518] NoMemoryError + [FATAL] failed to allocate memory for twice 1 << large

Issue #18518 has been updated by Eregon (Benoit Daloze).


This is still not fixed.
I think CRuby should check if RHS is bigger than 2**31 and if so raise an exception immediately instead of taking a lot of time and run into OOM:
https://github.com/ruby/ruby/commit/5df711844586312891bb466dbc72265490488d94#commitcomment-95187725

----------------------------------------
Bug #18518: NoMemoryError + [FATAL] failed to allocate memory for twice 1 << large
https://bugs.ruby-lang.org/issues/18518#change-101055

* Author: Eregon (Benoit Daloze)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.0.2p107 (2021-07-07 revision 0db68f0233) [x86_64-linux]
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Repro:
```ruby
exp = 2**40 # also fails with bignum e.g. 2**64

def exc
  begin
    yield
  rescue NoMemoryError => e
    p :NoMemoryError
  end
end

p exp
exc { (1 << exp) }
exc { (-1 << exp) }
exc { (bignum_value << exp) }
exc { (-bignum_value << exp) }
```

Output:
```
$ ruby -v mri_oom.rb
ruby 3.0.2p107 (2021-07-07 revision 0db68f0233) [x86_64-linux]
mri_oom.rb:7: warning: assigned but unused variable - e
1099511627776
:NoMemoryError
[FATAL] failed to allocate memory
```

3.1.0 seems fine:
```
$ ruby -v mri_oom.rb
ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-linux]
mri_oom.rb:7: warning: assigned but unused variable - e
1099511627776
:NoMemoryError
:NoMemoryError
:NoMemoryError
:NoMemoryError
```



-- 
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