Only bug fixes left!

All changes of cpython have been implemented in PyPy, so all that's left to do now is fixing some bugs. Some minor changes had to be done, because not everything of cpython has to be implemented in PyPy. For example, in cpython slots are used to check the existence of a function and then call it. The type of an object has the information of valid functions, stored as elements inside structs. Here's an example of how the __await__ function get's called in cpython:
ot = Py_TYPE(o);
if (ot->tp_as_async != NULL) {
getter = ot→tp_as_async→am_await;
}
if (getter != NULL) {
PyObject *res = (*getter)(o);
if (res != NULL) { … }
return res;
}
PyErr_Format(PyExc_TypeError,
"object %.100s can't be used in 'await' expression",
ot→tp_name);
return NULL;

This 'getter' directs to the am_await slot in typeobject.c. There, a lookup is done having '__await__' as parameter. If it exists, it gets called, an error is raised otherwise.
In PyPy all of this is way more simple. Practically I just replace the getter with the lookup for __await__. All I want to do is call the method __await__ if it exists, so that's all to it. My code now looks like this:
w_await = space.lookup(self, “__await__”)
if w_await is None: …
res = space.get_and_call_function(w_await, self)
if is not None: …
return res


I also fixed the _set_sentinel problem I wrote about in the last post. All dependency problems of other (not yet covered) Python features have been fixed. I can already execute simple programs, but as soon as it gets a little more complex and uses certain asyncio features, I get an error about the GIL (global interpreter lock):
“Fatal RPython error: a thread is trying to wait for the GIL, but the GIL was not initialized”
First I have to read some descriptions of the GIL, because I am not sure where this problem could come up in my case.
There are also many minor bugs at the moment. I already fixed one of the bigger ones which didn't allow async or await to be the name of variables. I also just learned that something I implemented does not work with RPython which I wasn't aware of. My mentor is helping me out with that.
I also have to write more tests, because they are the safest and fastest way to check for errors. There are a few things I didn't test enough, so I need to catch up on writing tests a bit.


Things are not going forward as fast as I would love it to, because I often get to completely new things which I need to study first (like the GIL in this case, or the memoryview objects from the last blog entry). But there really shouldn't be much left to do now until everything works, so I am pretty optimistic with the time I have left. If I strive to complete this task soon, I am positive my proposal will be successful.