[ruby-core:107323] [Ruby master Bug#18518] NoMemoryError + [FATAL] failed to allocate memory for twice 1 << large

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


From this log it's clear this issue happens on 3.1.0 macOS:
https://github.com/eregon/rubyspec/runs/4981235909?check_suite_focus=true
```
2022-01-28T13:37:48.1570860Z Integer#<< (with n << m) when m is a bignum or larger than int
2022-01-28T13:37:48.1659830Z - returns -1 when m < 0 and n < 0
2022-01-28T13:37:48.1755940Z - returns 0 when m < 0 and n >= 0
2022-01-28T13:37:48.1856250Z - returns 0 when m > 0 bignum and n == 0
2022-01-28T13:40:01.6596730Z /Users/runner/work/_temp/353a7019-b804-42ad-941b-7043b8a7804b.sh: line 1:  1391 Killed: 9               ../mspec/bin/mspec -fs --timeout 90
2022-01-28T13:40:01.6597290Z - raises NoMemoryError when m > 0 and n != 0
2022-01-28T13:40:01.6671710Z ##[error]Process completed with exit code 137.
```

----------------------------------------
Bug #18518: NoMemoryError + [FATAL] failed to allocate memory for twice 1 << large
https://bugs.ruby-lang.org/issues/18518#change-96221

* 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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