Issue #3231 has been updated by Akinori MUSHA. Thanks so much for the detailed explanation. Can I ask you something? Does VC++ search directories in random order, or does it work under any specific rules that changed in VC++ 2010? In Unix, there is a spec in SUS that the order of specifying -I/-L options is significant for the compiler commands, and they shall search directories named in those options in the order specified. ---------------------------------------- http://redmine.ruby-lang.org/issues/show/3231 ---------------------------------------- http://redmine.ruby-lang.org