coroutine segfaults

[Klaas-Jan Stol]

hi,

I was investigating a possible implementation of the "reset" method for 
coroutine.pmc, but I encountered the following:
if the coroutine is called more times than the coroutine ".yield()s", it 
segfaults

example:

.sub main :main
   .local int result
   .local pmc cor
   cor = global "_foo"

   result = cor()
   print result # prints 1
   print "\n"
  
   result = cor()
   print result # prints 2
   print "\n"
  
   result = cor()
   print result # prints 3
   print "\n"
  
   result = cor()
   print result # prints 4
   print "\n"
  
   result = cor()
   print result #prints 5
   print "\n"
  
   result = cor()
   print result # what should this do? start over again?
   print "\n"
   end
.end

.sub _foo
   .yield(1)
   .yield(2)
   .yield(3)
   .yield(4)
   .yield(5)
   #.yield(6)
.end

If the last .yield() is uncommented, it works, but otherwise, the last 
result (5, in this case), is printed twice. Can this be a bug?

regards,
klaas-jan