Compiler preprocessor output available?

Is it possible to view the output of the preprocessor, when compiling a program?
I would like to see the result of #if, #elif, #define and such statements to understand what is going
to be compiled. I am guessing the logic is evaluated before compiling starts, but maybe everything
happens on the fly.
I didn’t find a command for the CLI, maybe Workbench?

If it’s not available in the mainline compiler, check out neopo. You might be able to define a special make target and run it as shown here: https://neopo.xyz/docs/quick-docs

@nrobinson2000

2 Likes

When developing in Workbench, Intellisense can do a decent job to give hints for what code will be included when compiling by reducing the brightness of code that won’t be included.

It might be possible to obtain the true preprocessor output using the -E flag for g++, but since there are several different makefiles at play when building Particle firmware, it could be quite a challenge.

Looking at the verbose compiler output might be useful: (Empty project compiled for argon.)

make[3]: Entering directory '/home/nrobinson/.particle/toolchains/deviceOS/2.0.0/user'
Building cpp file: /home/nrobinson/code/neopo/test//src/test.cpp
Invoking: ARM GCC CPP Compiler
mkdir -p ../build/target/user/platform-12-m/test/src/
arm-none-eabi-gcc -DSTM32_DEVICE -DnRF52840 -DNRF52840_XXAA -DPLATFORM_THREADING=1 -DPLATFORM_ID=12 -DPLATFORM_NAME=argon -DPLATFORM_GEN=3 -DUSBD_VID_SPARK=0x2B04 -DUSBD_PID_DFU=0xD00C -DUSBD_PID_CDC=0xC00C -DSPARK_PLATFORM -g3 -gdwarf-2 -Os -mcpu=cortex-m4 -mthumb -mabi=aapcs -mfloat-abi=hard -mfpu=fpv4-sp-d16 --specs=nano.specs -DINCLUDE_PLATFORM=1 -DSOFTDEVICE_PRESENT=1 -DS140 -DPRODUCT_ID=12 -DPRODUCT_FIRMWARE_VERSION=65535 -D_WIZCHIP_=W5500 -DUSE_STDPERIPH_DRIVER -DDFU_BUILD_ENABLE -DLFS_CONFIG=lfs_config.h -DSYSTEM_VERSION_STRING=2.0.0 -DRELEASE_BUILD -I./inc -I../wiring/inc -I../system/inc -I../services/inc -I../third_party/nanopb/nanopb -I../communication/inc -I../hal/inc -I../hal/shared -I../hal/src/argon -I../hal/network/lwip/esp32 -I../hal/src/nRF52840 -I../hal/src/armv7 -I../hal/src/nRF52840 -I../hal/src/nRF52840/lwip -I../hal/src/nRF52840/freertos -I../hal/src/nRF52840/mbedtls -I../hal/src/nRF52840/littlefs -I../hal -I../hal/src/nRF52840/posix -I../hal/network -I../hal/network/api -I../hal/network/lwip -I../hal/network/lwip/posix -I../hal/network/lwip/wiznet -I../hal/network/ncp -I../hal/network/ncp/at_parser -I../hal/network/util -I../third_party/lwip/lwip/src/include -I../third_party/freertos/freertos/FreeRTOS/Source/include -I../third_party/nrf5_sdk/nrf5_sdk/external/freertos/portable/GCC/nrf52 -I../third_party/nrf5_sdk/nrf5_sdk/external/freertos/portable/CMSIS/nrf52 -I../third_party/wiznet_driver/wiznet_driver/Ethernet -I../gsm0710muxer/gsm0710muxer/include -I../platform/shared/inc -I../third_party/nrf5_sdk -I../third_party/nrf5_sdk/nrf5_sdk/components/toolchain/cmsis/include -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/drivers -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/drivers/include -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/hal -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/mdk -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/hal -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/drivers/src/prs -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/util -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers/nrf52 -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/common -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/mbr/nrf52840/headers -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/fstorage -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/experimental_section_vars -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/crc32 -I../third_party/nrf5_sdk/nrf5_sdk/integration/nrfx/legacy -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/delay -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/log -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/log -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/log/src -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/experimental_section_vars -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/delay -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/queue -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/common -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140 -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers/nrf52 -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/fifo -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic_fifo -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/strerror -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/fstorage -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic_flags -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/usbd -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/usbd/class/cdc -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/usbd/class/cdc/acm -I../third_party/nrf5_sdk/nrf5_sdk/components/ble/common -I../third_party/nrf5_sdk/nrf5_sdk/components/ble/nrf_ble_gatt -I../third_party/nrf5_sdk/nrf5_sdk/components/ble/ble_advertising -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/t2t_lib -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/platform -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/generic/message -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/generic/record -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/lauchapp -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/text -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/uri -I../third_party/nrf5_sdk/nrf5_sdk/external/nrf_cc310/include -I../third_party/nrf5_sdk/nrf5_sdk/external/utf_converter -I../third_party/littlefs/littlefs -I../third_party/miniz/miniz -I../platform/MCU/nRF52840/inc -I../dynalib/inc -I/home/nrobinson/code/neopo/test//src -I./libraries -I. -MD -MP -MF ../build/target/user/platform-12-m/test/src/test.o.d -ffunction-sections -fdata-sections -Wall -Wno-switch -Wno-error=deprecated-declarations -fmessage-length=0 -fno-strict-aliasing -DSPARK=1 -DPARTICLE=1 -Wundef -DSTART_DFU_FLASHER_SERIAL_SPEED=14400 -DSTART_YMODEM_FLASHER_SERIAL_SPEED=28800 -DSPARK_PLATFORM_NET=ESP32 -fno-builtin-malloc -fno-builtin-free -fno-builtin-realloc  -DLOG_INCLUDE_SOURCE_INFO=1 -DPARTICLE_USER_MODULE -DUSER_FIRMWARE_IMAGE_SIZE=0x20000 -DUSER_FIRMWARE_IMAGE_LOCATION=0xD4000 -DMODULAR_FIRMWARE=1 -DMODULE_VERSION=6 -DMODULE_FUNCTION=5 -DMODULE_INDEX=1 -DMODULE_DEPENDENCY=4,1,2008 -DMODULE_DEPENDENCY2=0,0,0 -D_GNU_SOURCE -DLOG_MODULE_CATEGORY="\"app\"" -fno-exceptions -fno-rtti -fcheck-new -std=gnu++14 -c -o ../build/target/user/platform-12-m/test/src/test.o /home/nrobinson/code/neopo/test//src/test.cpp

Here are the flags specified with -D:

STM32_DEVICE
nRF52840
NRF52840_XXAA
PLATFORM_THREADING=1
PLATFORM_ID=12
PLATFORM_NAME=argon
PLATFORM_GEN=3
USBD_VID_SPARK=0x2B04
USBD_PID_DFU=0xD00C
USBD_PID_CDC=0xC00C
SPARK_PLATFORM
INCLUDE_PLATFORM=1
SOFTDEVICE_PRESENT=1
S140
PRODUCT_ID=12
PRODUCT_FIRMWARE_VERSION=65535
_WIZCHIP_=W5500
USE_STDPERIPH_DRIVER
DFU_BUILD_ENABLE
LFS_CONFIG=lfs_config.h
SYSTEM_VERSION_STRING=2.0.0
RELEASE_BUILD
SPARK=1
PARTICLE=1
START_DFU_FLASHER_SERIAL_SPEED=14400
START_YMODEM_FLASHER_SERIAL_SPEED=28800
SPARK_PLATFORM_NET=ESP32
LOG_INCLUDE_SOURCE_INFO=1
PARTICLE_USER_MODULE
USER_FIRMWARE_IMAGE_SIZE=0x20000
USER_FIRMWARE_IMAGE_LOCATION=0xD4000
MODULAR_FIRMWARE=1
MODULE_VERSION=6
MODULE_FUNCTION=5
MODULE_INDEX=1
MODULE_DEPENDENCY=4,1,2008
MODULE_DEPENDENCY2=0,0,0
_GNU_SOURCE
LOG_MODULE_CATEGORY="\"app\""
1 Like

Thank you both for the quick response.
Unfortunately I can’t get to any of the neopo.xyz links. The site cannot be found.
I browsed the github site for neopo, but I cannot find the Windows install instructions.
Maybe it’s time to get myself an RPi400.

Here are the instructions for installing neopo on Windows but they are very outdated since I’m now using pip to manage the installation of neopo.

I’ll update the instructions tomorrow if you’re interested.

EDIT:
I’ve kept the man page updated with the latest changes to the script, but I need to catch up on the rest of the online documentation.

@Pescatore,
I have whipped up a new Windows VM and tested installing neopo in Command Prompt. The installation process is nearly identical to installing it on *nix thankfully.

I’ve updated the Windows tutorial above to contain the steps.

1 Like

Thank you again @nrobinson2000.
The process seems really simple. I will not be at my computer for a few days. I will report back soon.

1 Like

Hi @nrobinson2000, I was able to install and compile a simple blink program by following your install instructions.
I used the flags “-D” option and build verbose. I cannot find the file that would have the list you showed above. I looked in all the files for my test project.

Thanks,
P

You probably won’t find a file like that with all the -D flags listed out since they are all sourced from various makefiles, but in order to produce the list above I did the following in Python:

output = """
Building cpp file: /home/nrobinson/code/neopo/test//src/test.cpp
Invoking: ARM GCC CPP Compiler
mkdir -p ../build/target/user/platform-12-m/test/src/
arm-none-eabi-gcc -DSTM32_DEVICE -DnRF52840 -DNRF52840_XXAA -DPLATFORM_THREADING=1 -DPLATFORM_ID=12 -DPLATFORM_NAME=argon -DPLATFORM_GEN=3 -DUSBD_VID_SPARK=0x2B04 -DUSBD_PID_DFU=0xD00C -DUSBD_PID_CDC=0xC00C -DSPARK_PLATFORM -g3 -gdwarf-2 -Os -mcpu=cortex-m4 -mthumb -mabi=aapcs -mfloat-abi=hard -mfpu=fpv4-sp-d16 --specs=nano.specs -DINCLUDE_PLATFORM=1 -DSOFTDEVICE_PRESENT=1 -DS140 -DPRODUCT_ID=12 -DPRODUCT_FIRMWARE_VERSION=65535 -D_WIZCHIP_=W5500 -DUSE_STDPERIPH_DRIVER -DDFU_BUILD_ENABLE -DLFS_CONFIG=lfs_config.h -DSYSTEM_VERSION_STRING=3.0.0-beta.1 -DRELEASE_BUILD -I./inc -I../wiring/inc -I../system/inc -I../services/inc -I../third_party/nanopb/nanopb -I../communication/inc -I../hal/inc -I../hal/shared -I../hal/src/argon -I../hal/network/lwip/esp32 -I../hal/network/ncp/wifi -I../hal/src/nRF52840 -I../hal/src/armv7 -I../hal/src/nRF52840 -I../hal/src/nRF52840/lwip -I../hal/src/nRF52840/freertos -I../hal/src/nRF52840/mbedtls -I../hal/src/nRF52840/littlefs -I../hal -I../hal/src/nRF52840/posix -I../hal/network -I../hal/network/api -I../hal/network/lwip -I../hal/network/lwip/posix -I../hal/network/lwip/wiznet -I../hal/network/ncp -I../hal/network/ncp/at_parser -I../hal/network/util -I../third_party/lwip/lwip/src/include -I../third_party/freertos/freertos/FreeRTOS/Source/include -I../third_party/nrf5_sdk/nrf5_sdk/external/freertos/portable/GCC/nrf52 -I../third_party/nrf5_sdk/nrf5_sdk/external/freertos/portable/CMSIS/nrf52 -I../third_party/wiznet_driver/wiznet_driver/Ethernet -I../gsm0710muxer/gsm0710muxer/include -I../platform/shared/inc -I../third_party/nrf5_sdk -I../third_party/nrf5_sdk/nrf5_sdk/components/toolchain/cmsis/include -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/drivers -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/drivers/include -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/hal -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/mdk -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/hal -I../third_party/nrf5_sdk/nrf5_sdk/modules/nrfx/drivers/src/prs -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/util -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers/nrf52 -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/common -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/mbr/nrf52840/headers -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/fstorage -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/experimental_section_vars -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/crc32 -I../third_party/nrf5_sdk/nrf5_sdk/integration/nrfx/legacy -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/delay -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/log -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/log -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/log/src -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/experimental_section_vars -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/delay -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/queue -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/common -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140 -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers -I../third_party/nrf5_sdk/nrf5_sdk/components/softdevice/s140/headers/nrf52 -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/fifo -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic_fifo -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/strerror -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/fstorage -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/atomic_flags -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/usbd -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/usbd/class/cdc -I../third_party/nrf5_sdk/nrf5_sdk/components/libraries/usbd/class/cdc/acm -I../third_party/nrf5_sdk/nrf5_sdk/components/ble/common -I../third_party/nrf5_sdk/nrf5_sdk/components/ble/nrf_ble_gatt -I../third_party/nrf5_sdk/nrf5_sdk/components/ble/ble_advertising -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/t2t_lib -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/platform -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/generic/message -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/generic/record -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/lauchapp -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/text -I../third_party/nrf5_sdk/nrf5_sdk/components/nfc/ndef/uri -I../third_party/nrf5_sdk/nrf5_sdk/external/nrf_cc310/include -I../third_party/nrf5_sdk/nrf5_sdk/external/utf_converter -I../third_party/littlefs/littlefs -I../third_party/miniz/miniz -I../platform/MCU/nRF52840/inc -I../dynalib/inc -I/home/nrobinson/code/neopo/test//src -I./libraries -I. -MD -MP -MF ../build/target/user/platform-12-m/test/src/test.o.d -ffunction-sections -fdata-sections -Wall -Wno-switch -Wno-error=deprecated-declarations -fmessage-length=0 -fno-strict-aliasing -DSPARK=1 -DPARTICLE=1 -Wundef -DSTART_DFU_FLASHER_SERIAL_SPEED=14400 -DSTART_YMODEM_FLASHER_SERIAL_SPEED=28800 -DSPARK_PLATFORM_NET=ESP32 -fno-builtin-malloc -fno-builtin-free -fno-builtin-realloc  -DLOG_INCLUDE_SOURCE_INFO=1 -DPARTICLE_USER_MODULE -DUSER_FIRMWARE_IMAGE_SIZE=0x20000 -DUSER_FIRMWARE_IMAGE_LOCATION=0xD4000 -DMODULAR_FIRMWARE=1 -DMODULE_VERSION=6 -DMODULE_FUNCTION=5 -DMODULE_INDEX=1 -DMODULE_DEPENDENCY=4,1,3002 -DMODULE_DEPENDENCY2=0,0,0 -D_GNU_SOURCE -DLOG_MODULE_CATEGORY="\"app\"" -fno-exceptions -fno-rtti -fcheck-new -flto -ffat-lto-objects -DPARTICLE_COMPILE_LTO_FAT -std=gnu++14 -c -o ../build/target/user/platform-12-m/test/src/test.o /home/nrobinson/code/neopo/test//src/test.cpp
"""

gcc_line = output.splitlines()[-1].rstrip()
d_flags = [word.split("-D")[-1] for word in gcc_line.split() if word.startswith("-D")]
print(*d_flags, sep="\n")

Output:

STM32_DEVICE
nRF52840
NRF52840_XXAA
PLATFORM_THREADING=1
PLATFORM_ID=12
PLATFORM_NAME=argon
PLATFORM_GEN=3
USBD_VID_SPARK=0x2B04
USBD_PID_DFU=0xD00C
USBD_PID_CDC=0xC00C
SPARK_PLATFORM
INCLUDE_PLATFORM=1
SOFTDEVICE_PRESENT=1
S140
PRODUCT_ID=12
PRODUCT_FIRMWARE_VERSION=65535
_WIZCHIP_=W5500
USE_STDPERIPH_DRIVER
DFU_BUILD_ENABLE
LFS_CONFIG=lfs_config.h
SYSTEM_VERSION_STRING=3.0.0-beta.1
RELEASE_BUILD
SPARK=1
PARTICLE=1
START_DFU_FLASHER_SERIAL_SPEED=14400
START_YMODEM_FLASHER_SERIAL_SPEED=28800
SPARK_PLATFORM_NET=ESP32
LOG_INCLUDE_SOURCE_INFO=1
PARTICLE_USER_MODULE
USER_FIRMWARE_IMAGE_SIZE=0x20000
USER_FIRMWARE_IMAGE_LOCATION=0xD4000
MODULAR_FIRMWARE=1
MODULE_VERSION=6
MODULE_FUNCTION=5
MODULE_INDEX=1
MODULE_DEPENDENCY=4,1,3002
MODULE_DEPENDENCY2=0,0,0
_GNU_SOURCE
LOG_MODULE_CATEGORY=""app""
PARTICLE_COMPILE_LTO_FAT

Thanks @nrobinson2000 . I am able to print out the flags by copying the output of the compiler and use python to parse the flags with your script.
It’s interesting to see what flags are set, but it’s only a small portion of what I would like to see.
I guess I will stick with Workbench and pay attention to the screen highlighting.

1 Like