Issue #20104 has been updated by luke-gru (Luke Gruber). So I looked into this and it's this commit that introduces that behavior: 7193b404a1a56e50f8046d0382914907020c1559 ---------------------------------------- Bug #20104: Regexp#match returns nil but allocates T_MATCH objects https://bugs.ruby-lang.org/issues/20104#change-105942 * Author: jeremyevans0 (Jeremy Evans) * Status: Open * Priority: Normal * ruby -v: ruby 3.4.0dev (2023-12-30T03:14:38Z master 8e32c01742) [x86_64-openbsd7.4] * Backport: 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONTNEED, 3.3: REQUIRED ---------------------------------------- Between Ruby 3.2 and 3.3, behavior changed so that Regexp#match will allocate a T_MATCH object even when there is no match. Example code: ```ruby h = {} GC.start GC.disable ObjectSpace.count_objects(h) matches = h[:T_MATCH] || 0 md = /\A[A-Z]+\Z/.match('1') ObjectSpace.count_objects(h) new_matches = h[:T_MATCH] || 0 puts "/\\A[A-Z]+\\Z/.match('1') => #{md.inspect} generates #{new_matches - matches} T_MATCH objects" ``` Result with Ruby 1.9-3.2: ``` /\A[A-Z]+\Z/.match('1') => nil generates 0 T_MATCH objects ``` Results with Ruby 3.3.0 and current master branch: ``` /\A[A-Z]+\Z/.match('1') => nil generates 1 T_MATCH objects ``` This results in a measurable performance decrease for both Sinatra and Roda web applications, as reported at: https://old.reddit.com/r/ruby/comments/18sxtv9/ruby_330_performance_ups_and_... Thanks to GitHub users kiskoza and tagliala for producing a minimal example showing this issue: https://github.com/caxlsx/caxlsx/issues/336 -- https://bugs.ruby-lang.org/