warnings compiling for CircuitPlayground Express

[jerryneedell]

Compiling for CPX yields some warnings. Does not happen on other boards.

jerryneedell@Ubuntu-Macmini:~/circuitpython/atmel-samd$ make BOARD=circuitplayground_express clean
Use make V=1, make V=2 or set BUILD_VERBOSE similarly in your environment to increase build verbosity.
rm -rf build-circuitplayground_express 
jerryneedell@Ubuntu-Macmini:~/circuitpython/atmel-samd$ make BOARD=circuitplayground_express 
Use make V=1, make V=2 or set BUILD_VERBOSE similarly in your environment to increase build verbosity.
Generating build-circuitplayground_express/genhdr/mpversion.h
GEN build-circuitplayground_express/genhdr/qstr.i.last
QSTR updated
GEN build-circuitplayground_express/genhdr/qstrdefs.generated.h
FREEZE ../frozen/Adafruit_CircuitPython_NeoPixel
arm-none-eabi-gcc -I. -I.. -I../lib/mp-readline -I../lib/timeutils -Iasf_conf/ -Iasf/common/boards/ -Iasf/common/services/sleepmgr/ -Iasf/common/services/storage/ctrl_access/ -Iasf/common/services/usb/ -Iasf/common/services/usb/class/cdc/ -Iasf/common/services/usb/class/cdc/device/ -Iasf/common/services/usb/class/hid/ -Iasf/common/services/usb/class/hid/device/ -Iasf/common/services/usb/class/hid/device/kbd/ -Iasf/common/services/usb/class/hid/device/mouse/ -Iasf/common/services/usb/class/msc/ -Iasf/common/services/usb/class/msc/device/ -Iasf/common/services/usb/udc/ -Iasf/common/utils -Iasf/common2/services/delay/ -Iasf/sam0/drivers/events -Iasf/sam0/drivers/extint -Iasf/sam0/drivers/port -Iasf/sam0/drivers/system -Iasf/sam0/drivers/adc/adc_sam_d_r -Iasf/sam0/drivers/dac -Iasf/sam0/drivers/dac/dac_sam_d_c -Iasf/sam0/drivers/sercom -Iasf/sam0/drivers/sercom/i2c -Iasf/sam0/drivers/system/clock -Iasf/sam0/drivers/system/clock/clock_samd21_r21_da -Iasf/sam0/drivers/system/interrupt -Iasf/sam0/drivers/system/interrupt/system_interrupt_samd21 -Iasf/sam0/drivers/system/pinmux -Iasf/sam0/drivers/system/power/power_sam_d_r -Iasf/sam0/drivers/system/reset/reset_sam_d_r -Iasf/sam0/drivers/tc -Iasf/sam0/drivers/usb -Iasf/sam0/utils -Iasf/sam0/utils/cmsis/samd21/include -Iasf/sam0/utils/cmsis/samd21/source -Iasf/sam0/utils/header_files -Iasf/sam0/utils/preprocessor -Iasf/thirdparty/CMSIS/Include -Iboards -Iboards/circuitplayground_express/ -Ifreetouch/ -Ibuild-circuitplayground_express -Wall -Werror -std=gnu11 -nostdlib -mthumb -mabi=aapcs-linux -mcpu=cortex-m0plus -msoft-float -mfloat-abi=soft -fsingle-precision-constant -fno-strict-aliasing -Wdouble-promotion -Wno-endif-labels -Wstrict-prototypes -Werror-implicit-function-declaration -Wpointer-arith -Wfloat-equal -Wundef -Wshadow -Wwrite-strings -Wsign-compare -Wmissing-format-attribute -Wno-deprecated-declarations -Wpacked -Wnested-externs -Wunreachable-code -Wcast-align -D__SAMD21G18A__ -DUSB_DEVICE_PRODUCT_ID=0x8019 -DUSB_DEVICE_VENDOR_ID=0x239A -DBOARD=USER_BOARD -ffunction-sections -fdata-sections -fshort-enums -D ARM_MATH_CM0PLUS=true -DSYSTICK_MODE -DEXTINT_CALLBACK_MODE=true -DUDD_ENABLE -DUSART_CALLBACK_MODE=false -DSPI_CALLBACK_MODE=false -DI2C_MASTER_CALLBACK_MODE=false -DDAC_CALLBACK_MODE=false -DTCC_ASYNC=false -DADC_CALLBACK_MODE=false -DEVENTS_INTERRUPT_HOOKS_MODE=false -DI2S_CALLBACK_MODE=false -DTC_ASYNC=true -DUSB_DEVICE_LPM_SUPPORT -DCIRCUITPY_CANARY_WORD=0xADAF00 -DCIRCUITPY_SAFE_RESTART_WORD=0xDEADBEEF --param max-inline-insns-single=500 -DFFCONF_H=\"lib/oofatfs/ffconf.h\"  -Os -DNDEBUG -flto -finline-limit=57 -DMICROPY_QSTR_EXTRA_POOL=mp_qstr_frozen_const_pool -DMICROPY_MODULE_FROZEN_MPY -Wno-error=lto-type-mismatch   -c -o build-circuitplayground_express/frozen_mpy.o build-circuitplayground_express/frozen_mpy.c
build-circuitplayground_express/frozen_mpy.c:53:26: warning: size of 'mp_qstr_const_pool' differ from the size of original declaration [-Wlto-type-mismatch]
 extern const qstr_pool_t mp_qstr_const_pool;
                          ^
../py/qstr.c:98:19: note: 'mp_qstr_const_pool' was previously declared here
 const qstr_pool_t mp_qstr_const_pool = {
                   ^
../py/qstr.c:113:26: warning: size of 'mp_qstr_frozen_const_pool' differ from the size of original declaration [-Wlto-type-mismatch]
 extern const qstr_pool_t MICROPY_QSTR_EXTRA_POOL;
                          ^
build-circuitplayground_express/frozen_mpy.c:54:19: note: 'mp_qstr_frozen_const_pool' was previously declared here
 const qstr_pool_t mp_qstr_frozen_const_pool = {
                   ^

29856 bytes free in flash out of 253440 bytes ( 247.5 kb ).
4812 bytes free in ram for stack out of 32768 bytes ( 32.0 kb ).

Create build-circuitplayground_express/firmware.bin
Create build-circuitplayground_express/firmware.uf2
python2 ../tools/uf2/utils/uf2conv.py -c -o build-circuitplayground_express/firmware.uf2 build-circuitplayground_express/firmware.bin
Converting to uf2, output size: 447488, start address: 0x2000
Wrote 447488 bytes to build-circuitplayground_express/firmware.uf2.

[dhalbert]

Those warnings are due to compiling the NeoPixel module as a frozen module for CPX. Frozen modules are not added to any other board build at the current time. There's an apparent bug in gcc when using LTO (link time optimization) that generates spurious warnings for a struct with a flexible array. Bug reported here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81440

Normally we treat all warnings as errors, and we've tried to fix anything that causes a warning. In this case we can't. We also can't suppress the warnings with a #pragma GCC diagnostic ignore, because the warnings happen at link time, way past the time the #pragma would be effective.