Issue #7678 has been reported by nobu (Nobuyoshi Nakada).

----------------------------------------
Bug #7678: $_ and $~ are shared across Fibers halfway
https://bugs.ruby-lang.org/issues/7678

Author: nobu (Nobuyoshi Nakada)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 
ruby -v: r38748


$_ and $~ have thread local method scope, but are shared across fibers in same thread.

  $ ./ruby -v -e '/a/ =~ "a"; p $~; Fiber.new{/b/=~"b"; p $~}.resume; p $~'
  ruby 2.0.0dev (2013-01-09 trunk 38748) [x86_64-darwin11]
  #<MatchData "a">
  #<MatchData "b">
  #<MatchData "b">

But, it is cleared at Fiber.start.

  $ ./ruby -v -e '/a/ =~ "a"; p $~; Fiber.new{p $~}.resume; p $~'
  ruby 2.0.0dev (2013-01-09 trunk 38748) [x86_64-darwin11]
  #<MatchData "a">
  nil
  nil

These two behaviors seem mismatched.  I think:

* If they should be shared, then the latter example should show same
  MatchData 3 times.

* If they should be cleared at starting fibers, those variables in the
  original fiber should be unchanged.



-- 
http://bugs.ruby-lang.org/