From: "byroot (Jean Boussier) via ruby-core" Date: 2026-10-17T12:21:44+00:00 Subject: [ruby-core:127158] [Ruby Bug#22452] `rb_equal` returns true for `NaN == NaN` Issue #22452 has been updated by byroot (Jean Boussier). Possibly a duplicate of [Bug #1720] where it was established that `Float::NaN == Float::NaN` is "undefined" therefore OK. It seems that the motivation was to not prevent optimization of `rb_equal`. ---------------------------------------- Bug #22452: `rb_equal` returns true for `NaN == NaN` https://bugs.ruby-lang.org/issues/22452#change-119564 * Author: byroot (Jean Boussier) * Status: Open * Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- I noticed this while trying to cleanup and simplify `rb_equal`. ```ruby >> Float::NAN == Float::NAN => false >> [Float::NAN].index(Float::NAN) => 0 ``` I would expect it to return `nil`. `Array#index` is just an example, any core method, and even C extension relying on `rb_equal` is similarly impacted. This bug is present on all Ruby versions, except for versions between 2.1 and 2.4. The bug seem to have been re-introduced in 2.5 by [6e0e067de31511cebec01d176f628442371db879](https://github.com/ruby/ruby/commit/6e0e067de31511cebec01d176f628442371db879) JRuby seem to have the same behavior, but TruffleRuby correctly returns`nil`. -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/