This new config option allows to control whether MicroPython uses its own
internal printf or not (if not, an external one should be linked in).
Accompanying this new option is the inclusion of lib/utils/printf.c in the
core list of source files, so that ports no longer need to include it
themselves.
Minimal support code for a Cortex-M CPU is added, along with set-up
code for an STM32F4xx MCU, including a UART for a REPL. Tested on
a pyboard. Code size is 77592 bytes.
Scenario: module1 depends on some common file from lib/, so specifies it
in its SRC_MOD, and the same situation with module2, then common file
from lib/ eventually ends up listed twice in $(OBJ), which leads to link
errors.
Make is equipped to deal with such situation easily, quoting the manual:
"The value of $^ omits duplicate prerequisites, while $+ retains them and
preserves their order." So, just use $^ consistently in all link targets.
Unlike bare-arm, which is mostly intended to show raw interpreter size,
without library and support code dependencies. This port is intended to
be a better base to start new ports, and also will include emulation
build to allow debug some aspects of embedded targets on POSIX systems.
This initial commit is verbatim copy of bare-arm code.
