This allows to define an abstract base class which would translate
C-level protocol to Python method calls, and any subclass inheriting
from it will support this feature. This in particular actually enables
recently introduced machine.PinBase class.
Allows to translate C-level pin API to Python-level pin API. In other
words, allows to implement a pin class and Python which will be usable
for efficient C-coded algorithms, like bitbanging SPI/I2C, time_pulse,
etc.
When built for Linux, libffi includes very bloated and workaround exec-alloc
implementation required to work around SELinux and other "sekuritee" features
which real people don't use. MicroPython has own alloc-exec implementation,
used to alloc memory for @micropython.native code. With this option enabled,
uPy's implementation will override libffi's. This saves 11K on x86_64 (and
that accounts for more than half of the libffi code size).
TODO: Possibly, we want to refactor this option to allow either use uPy's
implementation even for libffi, or allow to use libffi's implementation even
for uPy.
This actually saves "only" 6K for x86_64 build, as we're still more or less
careful to #ifdef unneeded code. But relying on --gc-sections in a "lazy"
manner would allow to make #ifdef'ing less pervasive (not suggested right
away, but an option for the future).
The time stamp is taken from the RTC for all newly generated
or changed files. RTC must be maintained separately.
The dummy time stamp of Jan 1, 2000 is set in vfs.stat() for the
root directory, avoiding invalid time values.
Paul Sokolovsky
Robert HH