Continuation in fiber dumps core

e$B1sF#$H?=$7$^$9!#e(B

thunk e$B$,0J2<$N%3!<%I$Ge(B segv e$B$7$^$9!#e(B

c = nil
f = Fiber.new do
callcc {|c2| c = c2 }
end
f.yield
c.call