[metapost] some question about pens

[Taco Hoekwater]

Hartmut Henkel wrote:
>> the attached code compares six variants of a stroked half circle drawn
>> with a circled and squared pen (left and right column) and with
>> linecap set to {rounded, squared, butt} (top to bottom).
> 
> i just get here with 1.003:
> 
> hahe at hahepc1:~$ mpost pens
> This is MetaPost, Version 1.003 (Web2C 7.5.5)
> (pens.mp
> 
> it freezes!

Same here. It never exits from offset_prep.