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When make is passed "-B" it seems that everything is considered out-of-date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).
If make -B is run, the rule is run with $? empty. Extract fron all file in
this case. But this gets fragile, really "make clean" should be used instead
with such build complexity.
When there're C files to be (re)compiled, they're all passed first to
preprocessor. QSTR references are extracted from preprocessed output and
split per original C file. Then all available qstr files (including those
generated previously) are catenated together. Only if the resulting content
has changed, the output file is written (causing almost global rebuild
to pick up potentially renumbered qstr's). Otherwise, it's not updated
to not cause spurious rebuilds. Related make rules are split to minimize
amount of commands executed in the interim case (when some C files were
updated, but no qstrs were changed).
Damien George
Paul Sokolovsky
Dave Hylands
Jan Čapek