[pypy-dev] fiber support

Armin Rigo armin.rigo at gmail.com
Wed Oct 18 06:59:17 EDT 2017

Hi David,

On 16 October 2017 at 21:18, David Callahan <dcallahan at fb.com> wrote:
> folly:fibers  (https://github.com/facebook/folly/tree/master/folly/fibers )
> is a C++ package for lightweight, cooperatively scheduled threads.  We have
> an application which extends this to CPython by adding the following
> save/restore code around task function invocation:

This will never work inside PyPy, even using cpyext, because cpyext's
notion of exceptions is different from the internal one inside PyPy.

Instead, you should look at the ``_continuation`` module or more
likely the ``greenlet`` module, which is built-in in PyPy (and
available as a CPython extension module, too, if you like).  It should
give you a replacement, though of course you need to adapt the

If you really want to use folly:fibers or a specific package manipulating
the C stack, then I'm afraid it's quite hard.  The ``greenlet``
module in PyPy is based on ``stacklet``, which is an internal part of
PyPy doing the same thing using the necessary bookkeeping for PyPy,
which is different than the one for CPython you included in your
e-mail.  If you really want to look there, you'd need to replicate that
logic around folly:fibres (search for all "stacklet" file names in
several places in the PyPy source code).

A bientôt,


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