Shed Skin has issues running under PyPy and generating C++ extensions that work in PyPy. However, there is a patch against Shed Skin 0.7 that makes generating and using C++ extensions possible with PyPy (still requires copying setobject.h from CPython to PyPy's includes directory).
Official support for PyPy is being added, with a "-p" command line option to trigger compatibility code.
C++ extensions generated by Shed Skin may run much faster than the comparable Python code under PyPy. However, the overhead of running C-API extensions in PyPy is considerable, rendering many extensions slower. Performance is worst for repeated calls to extension code in a pure Python loop.
Given the setobject.h hack necessary for building Shed Skin extensions with
PyPy, code using built-ins set or frozenset will fail to run. This happens
because PyPy is missing
PySet_New, used in Shed Skin's
Other than that, all Shed Skin compatibility restrictions apply. Some code
(e.g. Shed Skin's own
nbody.py example) will segfault when run as a PyPy