Issue #20182 has been reported by k0kubun (Takashi Kokubun). ---------------------------------------- Feature #20182: Rewrite Array#each in Ruby https://bugs.ruby-lang.org/issues/20182 * Author: k0kubun (Takashi Kokubun) * Status: Open * Priority: Normal ---------------------------------------- ## Proposal Rewrite Array#each in Ruby https://github.com/ruby/ruby/pull/6687. ```rb class Array def each unless block_given? return to_enum(:each) { self.length } end i = 0 while i < self.length yield self[i] i = i.succ end self end end ``` ## Purpose Make it possible for YJIT to optimize ISEQs across `Array#each`. ## Background Whether JIT-compiled or not, calling Ruby from C is more expensive than calling Ruby from Ruby. It also prevents YJIT from making cross-ISEQ optimizations. This is problematic especially for loop methods written in C like `Array#each` since the overhead is repeated at every iteration. ## Discussions There are a couple of things I'd like to discuss in this ticket: 1. @Eregon has pointed out that there's a race condition in the above implementation. `self[i]` would yield `nil` if the element was removed by another thread or TracePoint after `i < self.length`. Is it `Array#each`'s responsibility to atomically operate on elements, or are users supposed to avoid mutating the array in the middle of its loop? 2. If `Integer#<`, `Integer#length`, `Integer#succ`, or `Array#[]` is overridden in an incompatible way, the Ruby implementation may not work correctly. May I assume it's acceptable? -- https://bugs.ruby-lang.org/