Issue #21092 has been reported by jeremyd2019 (Jeremy Drake). ---------------------------------------- Bug #21092: error building ruby 3.4.1 on cygwin https://bugs.ruby-lang.org/issues/21092 * Author: jeremyd2019 (Jeremy Drake) * Status: Open * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- While building from the release tarball ruby-3.4.1.tar.xz (also confirmed in snapshot-master.tar.gz from Jan 27, 2025), I get the following error: ../ruby-3.4.1/ext/extmk.rb:279:in 'Array#-': no implicit conversion of nil into Array (TypeError) from ../ruby-3.4.1/ext/extmk.rb:279:in 'Object#extmake' from ../ruby-3.4.1/ext/extmk.rb:659:in 'block in <main>' from ../ruby-3.4.1/ext/extmk.rb:653:in 'Array#each' from ../ruby-3.4.1/ext/extmk.rb:653:in '<main>' I have tracked this down to happening when an ext writes a dummy makefile. In this case, that ext is .bundle/gems/syslog-0.2.0. See https://github.com/ruby/syslog/pull/16 for fixing why it is writing a dummy makefile to begin with, but still, it seems like extmk.rb should handle this case gracefully rather than breaking the build. -- https://bugs.ruby-lang.org/