Issue #20924 has been updated by javanthropus (Jeremy Bopp). Note that replacing `#readline` with `#gets` in the examples causes the issue to be seen in all Ruby versions, including 3.3.6. ---------------------------------------- Bug #20924: IO#readline ignores the limit argument when the encoding is UTF-32LE and the limit would split a character https://bugs.ruby-lang.org/issues/20924#change-110797 * Author: javanthropus (Jeremy Bopp) * Status: Open * ruby -v: ruby 3.4.0dev (2024-11-28T12:38:16Z master 3af1a04741) +PRISM [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- ```ruby require 'tempfile' Tempfile.open(binmode: true, encoding: 'utf-32le') do |f| f.write('0123456789') f.rewind # A limit that would truncate a character becomes completely ignored f.readline(3).bytesize # => 40; should be 4 end Tempfile.open(binmode: true, encoding: 'utf-32le') do |f| f.write('0123456789') f.rewind # A limit on character boundaries is respected f.readline(4).bytesize # => 4 end Tempfile.open(encoding: 'utf-8:utf-32le') do |f| f.write('0123456789') f.rewind # A limit that would truncate a character becomes completely ignored f.readline(3).bytesize # => 40; should be 4 end Tempfile.open(encoding: 'utf-8:utf-32le') do |f| f.write('0123456789') f.rewind # A limit on character boundaries is respected f.readline(4).bytesize # => 4 end ``` This doesn't happen with UTF-32BE. This also doesn't happen in Ruby 3.3, but it does happen in 3.4-dev and Ruby 3.0 - 3.2. -- https://bugs.ruby-lang.org/