fpsensor: Build fpsensor source file with C++

Note that this change also removes abs() since this change makes the
fingerprint firmware link against the toolchain's C standard library,
which already provides an implementation. abs() is not actually used by
the FPC matching algorithm even though it links against it.

BRANCH=none
BUG=b:236025198, b:234181908
TEST=On dragonclaw v0.2 with servo_micro and J-Trace attached:
     ./util/flash_jlink.py -b bloonchipper -i ./build/bloonchipper/ec.bin
     > fpenroll
     > fpmatch
TEST=On dragonclaw v0.2 with servo_micro and J-Trace attached:
     ./test/run_device_tests.py --board bloonchipper
     Test "aes": PASSED
     Test "cec": PASSED
     Test "cortexm_fpu": PASSED
     Test "crc": PASSED
     Test "flash_physical": PASSED
     Test "flash_write_protect": PASSED
     Test "fpsensor_hw": PASSED
     Test "fpsensor_spi_ro": PASSED
     Test "fpsensor_spi_rw": PASSED
     Test "fpsensor_uart_ro": PASSED
     Test "fpsensor_uart_rw": PASSED
     Test "mpu_ro": PASSED
     Test "mpu_rw": PASSED
     Test "mutex": PASSED
     Test "pingpong": PASSED
     Test "printf": PASSED
     Test "queue": PASSED
     Test "rollback_region0": PASSED
     Test "rollback_region1": PASSED
     Test "rollback_entropy": PASSED
     Test "rtc": PASSED
     Test "sha256": PASSED
     Test "sha256_unrolled": PASSED
     Test "static_if": PASSED
     Test "stdlib": PASSED
     Test "system_is_locked_wp_on": PASSED
     Test "system_is_locked_wp_off": PASSED
     Test "timer_dos": PASSED
     Test "utils": PASSED
     Test "utils_str": PASSED
     Test "stm32f_rtc": PASSED
     Test "panic_data_bloonchipper_v2.0.4277": PASSED
     Test "panic_data_bloonchipper_v2.0.5938": PASSED
TEST=On icetower v0.1 with servo_micro and J-Trace attached:
     ./util/flash_jlink.py -b dartmonkey -i ./build/dartmonkey/ec.bin
     > fpenroll
     > fpmatch
TEST=On icetower v0.1 with servo_micro and J-Trace attached:
     ./test/run_device_tests.py --board dartmonkey
     Test "aes": PASSED
     Test "cec": PASSED
     Test "cortexm_fpu": PASSED
     Test "crc": PASSED
     Test "flash_physical": PASSED
     Test "flash_write_protect": PASSED
     Test "fpsensor_hw": PASSED
     Test "fpsensor_spi_ro": PASSED
     Test "fpsensor_spi_rw": PASSED
     Test "fpsensor_uart_ro": PASSED
     Test "fpsensor_uart_rw": PASSED
     Test "mpu_ro": PASSED
     Test "mpu_rw": PASSED
     Test "mutex": PASSED
     Test "pingpong": PASSED
     Test "printf": PASSED
     Test "queue": PASSED
     Test "rollback_region0": PASSED
     Test "rollback_region1": PASSED
     Test "rollback_entropy": PASSED
     Test "rtc": PASSED
     Test "sha256": PASSED
     Test "sha256_unrolled": PASSED
     Test "static_if": PASSED
     Test "stdlib": PASSED
     Test "system_is_locked_wp_on": PASSED
     Test "system_is_locked_wp_off": PASSED
     Test "timer_dos": PASSED
     Test "utils": PASSED
     Test "utils_str": PASSED
     Test "panic_data_dartmonkey_v2.0.2887": PASSED
     Test "panic_data_nocturne_fp_v2.2.64": PASSED
     Test "panic_data_nami_fp_v2.2.144": PASSED

LOW_COVERAGE_REASON=legacy code
Force-Relevant-Builds: all
Cq-Depend: chromium:3894586
Signed-off-by: Tom Hughes <tomhughes@chromium.org>
Change-Id: I2c7947d21e7020b51f7b5b3d87ef64545de867c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3893045
Reviewed-by: Andrea Grandi <agrandi@google.com>
Reviewed-by: Bobby Casey <bobbycasey@google.com>
Code-Coverage: Zoss <zoss-cl-coverage@prod.google.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/Makefile.toolchain b/Makefile.toolchain
index b960fadb4f..a37e7cc100 100644
--- a/Makefile.toolchain
+++ b/Makefile.toolchain
@@ -29,6 +29,21 @@ endif
 # library.
 USE_BUILTIN_STDLIB:=1
 
+# Boards that compile with clang by default.
+# We can't use a config for this since the config generation uses the compiler.
+CLANG_BOARDS:= \
+	bloonchipper \
+	dartmonkey \
+	hatch_fp \
+	nami_fp \
+	nocturne_fp \
+	nucleo-dartmonkey \
+
+ifeq ($(filter $(BOARD), $(CLANG_BOARDS)), $(BOARD))
+CC=clang
+USE_BUILTIN_STDLIB:=0
+endif
+
 # Set the prefix for the compiler if specified (e.g., "x86_64-pc-linux-gnu-").
 ifeq ($(origin BUILDCC_PREFIX),undefined)
 # If building with Portage use the environment variable it provides.
@@ -170,9 +185,14 @@ ifneq ($(cc-name),clang)
 CFLAGS+= -ffat-lto-objects
 CFLAGS+= -fconserve-stack
 endif
+CXXFLAGS=$(CXXFLAGS_WARN)
 CXXFLAGS+=-DPROTOBUF_INLINE_NOT_IN_HEADERS=0
 ifeq ($(USE_BUILTIN_STDLIB), 1)
 CPPFLAGS+=-DUSE_BUILTIN_STDLIB
+else
+# TODO(https://issuetracker.google.com/234507656#comment19): C++ include path
+# should not be necessary.
+CXXFLAGS+=-I/usr/armv7m-cros-eabi/usr/include/c++/v1
 endif
 
 ifeq ($(LIBFTDI_NAME),)