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