* No weak link for modules. It only impacts _os and _time and is
already disabled for non-full builds.
* Turn off PA00 and PA01 because they are the crystal on the Metro
M0 Express.
* Change ejected default to false to move it to BSS. It is set on
USB connection anyway.
* Set sinc_filter to const. Doesn't help flash but keeps it out of
RAM.
This gets a further speedup of about 2s (12s -> 9.5s elapsed build time)
for stm32f405_feather
For what are probably historical reasons, the qstr process involves
preprocessing a large number of source files into a single "qstr.i.last"
file, then reading this and splitting it into one "qstr" file for each
original source ("*.c") file.
By eliminating the step of writing qstr.i.last as well as making the
regular-expression-matching part be parallelized, build speed is further
improved.
Because the step to build QSTR_DEFS_COLLECTED does not access
qstr.i.last, the path is replaced with "-" in the Makefile.
Rather than simply invoking gcc in preprocessor mode with a list of files, use
a Python script with the (python3) ThreadPoolExecutor to invoke the
preprocessor in parallel.
The amount of concurrency is the number of system CPUs, not the makefile "-j"
parallelism setting, because there is no simple and correct way for a Python
program to correctly work together with make's idea of parallelism.
This reduces the build time of stm32f405 feather (a non-LTO build) from 16s to
12s on my 16-thread Ryzen machine.
Some examples of improved compliance with CPython that currently
have divergent behavior in CircuitPython are listed below:
* yield from is not allowed in async methods
```
>>> async def f():
... yield from 'abc'
...
Traceback (most recent call last):
File "<stdin>", line 2, in f
SyntaxError: 'yield from' inside async function
```
* await only works on awaitable expressions
```
>>> async def f():
... await 'not awaitable'
...
>>> f().send(None)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 2, in f
AttributeError: 'str' object has no attribute '__await__'
```
* only __await__()able expressions are awaitable
Okay this one actually does not work in circuitpython at all today.
This is how CPython works though and pretending __await__ does not
exist will only bite users who write both.
```
>>> class c:
... pass
...
>>> def f(self):
... yield
... yield
... return 'f to pay respects'
...
>>> c.__await__ = f # could just as easily have put it on the class but this shows how it's wired
>>> async def g():
... awaitable_thing = c()
... partial = await awaitable_thing
... return 'press ' + partial
...
>>> q = g()
>>> q.send(None)
>>> q.send(None)
>>> q.send(None)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
StopIteration: press f to pay respects
```
This adds the `async def` and `await` verbs to valid CircuitPython syntax using the Micropython implementation.
Consider:
```
>>> class Awaitable:
... def __iter__(self):
... for i in range(3):
... print('awaiting', i)
... yield
... return 42
...
>>> async def wait_for_it():
... a = Awaitable()
... result = await a
... return result
...
>>> task = wait_for_it()
>>> next(task)
awaiting 0
>>> next(task)
awaiting 1
>>> next(task)
awaiting 2
>>> next(task)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
StopIteration: 42
>>>
```
and more excitingly:
```
>>> async def it_awaits_a_subtask():
... value = await wait_for_it()
... print('twice as good', value * 2)
...
>>> task = it_awaits_a_subtask()
>>> next(task)
awaiting 0
>>> next(task)
awaiting 1
>>> next(task)
awaiting 2
>>> next(task)
twice as good 84
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
StopIteration:
```
Note that this is just syntax plumbing, not an all-encompassing implementation of an asynchronous task scheduler or asynchronous hardware apis.
uasyncio might be a good module to bring in, or something else - but the standard Python syntax does not _strictly require_ deeper hardware
support.
Micropython implements the await verb via the __iter__ function rather than __await__. It's okay.
The syntax being present will enable users to write clean and expressive multi-step state machines that are written serially and interleaved
according to the rules provided by those users.
Given that this does not include an all-encompassing C scheduler, this is expected to be an advanced functionality until the community settles
on the future of deep hardware support for async/await in CircuitPython. Users will implement yield-based schedulers and tasks wrapping
synchronous hardware APIs with polling to avoid blocking, while their application business logic gets simple `await` statements.
This already begins obscuring things, because now there are two sets of
shared-module functions for manipulating the same structure, e.g.,
common_hal_canio_remote_transmission_request_get_id and
common_hal_canio_message_get_id
New contributor @mdroberts1243 encountered an interesting problem in
which the argument they had named "column_underscore_and_page_addressing"
simply couldn't be used; I discovered that internally this had been
transformed into "column_underscore∧page_addressing", because QSTR
makes _ENTITY_ stand for the same thing as &ENTITY; does in HTML.
This might be nice for some things, but we don't want it here!
I was unable to find a sensible way to "escape" and prevent this entity
coding, so instead I ripped out support for the _and_ and _or_ escapes.
Tested & working:
* Send standard packets
* Receive standard packets (1 FIFO, no filter)
Interoperation between SAM E54 Xplained running this tree and
MicroPython running on STM32F405 Feather with an external
transceiver was also tested.
Many other aspects of a full implementation are not yet present,
such as error detection and recovery.
Discord user Folknology encountered a problem building with Python 3.6.9,
`TypeError: ord() expected a character, but string of length 0 found`.
I was able to reproduce the problem using Python3.5*, and discovered that
the meaning of the regular expression `"|."` had changed in 3.7. Before,
```
>>> [m.group(0) for m in re.finditer("|.", "hello")]
['', '', '', '', '', '']
```
After:
```
>>> [m.group(0) for m in re.finditer("|.", "hello")]
['', 'h', '', 'e', '', 'l', '', 'l', '', 'o', '']
```
Check if `words` is empty and if so use `"."` as the regular expression
instead. This gives the same result on both versions:
```
['h', 'e', 'l', 'l', 'o']
```
and fixes the generation of the huffman dictionary.
Folknology verified that this fix worked for them.
* I could easily install 3.5 but not 3.6. 3.5 reproduced the same problem
This construct (which I added without sufficient testing,
apparently) is only supported in Python 3.7 and newer. Make it
optional so that this script works on other Python versions. This
means that if you have a system with non-UTF-8 encoding you will
need to use Python 3.7.
In particular, this affects a problem building circuitpython in
github's ubuntu-18.04 virtual environment when Python 3.7 is not
explicitly installed. cookie-cuttered libraries call for Python
3.6:
```
- name: Set up Python 3.6
uses: actions/setup-python@v1
with:
python-version: 3.6
```
Since CircuitPython's own build calls for 3.8, this problem was not
detected.
This problem was also encountered by discord user mdroberts1243.
The failure I encountered was here:
https://github.com/jepler/Jepler_CircuitPython_udecimal/runs/1138045020?check_suite_focus=true
.. while my step of "clone and build circuitpython unix port" is
unusual, I think the same problem would have affected "build assets"
if that step had been reached.
