This patch against HEAD provides the inverse operations to all the
ast2obj_* functions in Python/Python-ast.c: effectively, this allows
conversion to & from a PyObject representation of a Python AST.

Additionally, it updates the compile() builtin to allow it to compile
Python ASTs to bytecode.

The patch seems to work for most simple cases, but crashes out with a
segfault when trying to compile functions for some reason.

Attaching a sample program to demonstrate the crash.

Georg is working on the AST front.

This is great work!

The problem is that ast2obj_object translates NULL values to Py_None,
but obj2ast_object doesn't translate that back. This definition fixes
your testcase:

static int obj2ast_object(PyObject* obj, PyObject** out, PyArena* arena)
{
    if (obj == Py_None)
        obj = NULL;
    Py_XINCREF(obj);
    *out = obj;
    return 0;
}

I knew it would be a simple one for somebody who knew what to look for
:) Thanks Georg! r02 is the updated patch. Changing the title of the
tracker issue to reflect that this *should* be a complete patch now.

Any further recommendations?

Updating the patch to apply cleanly against HEAD.

I'll try to handle it this weekend.

Georg, just a ping: still waiting on a review for this.

So I finally got to this one :)
I had to fix a few things, mainly error handling, and a refleak.
And I found a refleak in the compiler :)
Reviewed and committed in r62004.