[pypy-dev] C interpreter written in Python, and running CPython on top of PyPy

[Armin Rigo]

Hi Celil,

On Fri, Jan 6, 2012 at 15:59, Celil <celil.kj at gmail.com> wrote:
> Is anybody already working on that? With PyPy this would presumably be quite
> easy to do. The interpreter will load the C code, create an AST (presumably
> using pyparsing and the EBNF spec of the C-language), and then populate the
> Flow Object Space with all the C objects, and create a control flow graph of
> the application logic.

I think you are confusing several levels.  I don't see what you would
gain by this exercise.  Interoperability problems between C and PyPy
are not going to be magically solved just because we turn C code into
lltyped flow graphs.  That seems rather pointless: from lltyped flow
graphs, what we do is mostly turn them into C code again.

For an example of the confusion:

> Interpreting C code would greatly help
> CPython developers by freeing them from the task of having to repeatedly
> compile their code.

No: flow graphs need to be created (a Python process that is slower
than gcc), then turned into more C code (more time), and finally
compiled... by gcc itself.

Unless you really have in mind an interpreter-with-JIT for the C
language, fully written in PyPy; but in this case there are no flow
graphs around.  Our JIT would give bad results anyway, because C is a
low-level language, not a dynamic language.


A bientôt,

Armin.