For make v3.81, using "make -B" can set $? to empty and in this case the
auto-qstr generation needs to pass all args (ie $^) to cpp. The previous
fix for this (which was removed in 23a693ec2d)
used if statements in the shell command, which gave very long lines that
didn't work on certain systems (eg cygwin).
The fix in this patch is to use an $if(...) expression, which will evaluate
to $? (only newer prerequisites) if it's non empty, otherwise it will use
$^ (all prerequisites).
This ensures that mpy-cross is automatically built (and is up-to-date) for
ports that use frozen bytecode. It also makes sure that .mpy files are
re-built if mpy-cross is changed.
Build happens in 3 stages:
1. Zephyr config header and make vars are generated from prj.conf.
2. libmicropython is built using them.
3. Zephyr is built and final link happens.
When make is passed "-B" it seems that everything is considered out-of-date
and so $? expands to all prerequisites. Thus there is no need for a
special check to see if $? is emtpy.
With this patch one can now do "make FROZEN_MPY_DIR=../../frozen" to
specify a directory containing scripts to be frozen (as well as absolute
paths).
The compiled .mpy files are now stored in $(BUILD)/frozen_mpy/.
Now, to use frozen bytecode all a port needs to do is define
FROZEN_MPY_DIR to the directory containing the .py files to freeze, and
define MICROPY_MODULE_FROZEN_MPY and MICROPY_QSTR_EXTRA_POOL.
E.g. for stmhal, accumulated preprocessed output may grow large due to
bloated vendor headers, and then reprocessing tens of megabytes on each
build make take couple of seconds on fast hardware (=> potentially dozens
of seconds on slow hardware). So instead, split once after each change,
and only cat repetitively (guaranteed to be fast, as there're thousands
of lines involved at most).
Damien George
Paul Sokolovsky
Alexander Steffen
Dave Hylands