C-files in Arduino libraries. Not enough compilation flags.

[kukuyok]

OS: Linux
Distribution: Xubuntu
OS Version: 16.04
Platform: Arduino Mega
Platform SDK Version: 1.8.5
Arduino-CMake-NG: cbfebf9

CMake options:

-DCMAKE_TOOLCHAIN_FILE=/home/petro/install/arduino-cmake/cmake/Arduino-Toolchain.cmake -DARDUINO_SDK_PATH=/home/petro/install/arduino-1.8.5

I use arduino-timer-api library in my project, and its source-code is written in C, not in C++, as three libraries, which you use in arduino-library example. And there are some problems to build it. That's what I found:

1. If not architectures set in library.properties library file, I have no -DARDUINO_ARCH_AVR definition for avr-gcc, if compile library C-files. If I specify avr for arch: architecutres=avr,pic32,sam this flag is in place.
2. I try to convert C-files into C++. It was a perfect cure in my case. Here is the difference between compilation commands.

   Compiling C++

   /home/petro/install/arduino-1.8.5/hardware/tools/avr/bin/avr-g++
   -DARDUINO_ARCH_AVR
   -I/home/petro/install/arduino-1.8.5/libraries/Arduino-timer-api/src
   -I/home/petro/install/arduino-1.8.5/hardware/arduino/avr/cores/arduino
   -I/home/petro/install/arduino-1.8.5/hardware/arduino/avr/variants/mega
   -c
   -g
   -Os
   -w
   -std=gnu++11
   -fpermissive
   -fno-exceptions
   -ffunction-sections
   -fdata-sections
   -fno-threadsafe-statics
   -MMD
   -flto
   -mmcu=atmega2560
   -DF_CPU=16000000L
   -DARDUINO=10805
   "-DARDUINO_AVR_MEGA2560
   "
   -o
   CMakeFiles/timer_api_lib.dir/home/petro/install/arduino-1.8.5/libraries/Arduino-timer-api/src/avr/timer_setup.cpp.obj
   -c
   /home/petro/install/arduino-1.8.5/libraries/Arduino-timer-api/src/avr/timer_setup.cpp

   Compiling C

   /home/petro/install/arduino-1.8.5/hardware/tools/avr/bin/avr-gcc
   -DARDUINO_ARCH_AVR
   -I/home/petro/install/arduino-1.8.5/libraries/Arduino-timer-api/src
   -I/home/petro/install/arduino-1.8.5/hardware/arduino/avr/cores/arduino
   -I/home/petro/install/arduino-1.8.5/hardware/arduino/avr/variants/mega
   -o
   CMakeFiles/timer_api_lib.dir/home/petro/install/arduino-1.8.5/libraries/Arduino-timer-api/src/avr/timer_setup.c.obj
   -c
   /home/petro/install/arduino-1.8.5/libraries/Arduino-timer-api/src/avr/timer_setup.c

3. If I just add missing flags to my CMakeLists.txt, arduino-timer-api library and the whole project also builds successfully (may be not totally correctly):

   add_definitions(-DARDUINO_ARCH_AVR -DARDUINO_AVR_MEGA2560 -DARDUINO=10802 -DF_CPU=16000000L)
   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mmcu=atmega2560")

SuperThnx for your tool!

[MrPointer]

@kukuyok Thanks for the feedback and contribution! I'll review this sometime soon, it seems really really strange that you get such behavior. BTW, could you attach your CMakeLists.txt file please?

[kukuyok]

Thanks! Sure:

cmake_minimum_required(VERSION 3.8)

set(project_name Cocktail)

## Команда для запуска CMake (run CMake in bash)
## cmake -DCMAKE_TOOLCHAIN_FILE=/home/petro/install/arduino-cmake/cmake/Arduino-Toolchain.cmake -DARDUINO_SDK_PATH=/home/petro/install/arduino-1.8.5 -Darduino_port=/dev/ttyUSB0 ..

## Команда для генерации файлов проекта Eclipse (Eclipse project files generator)
## cmake -G "Eclipse CDT4 - Unix Makefiles" -DCMAKE_BUILD_TYPE=Debug -DCMAKE_ECLIPSE_GENERATE_SOURCE_PROJECT=TRUE -DCMAKE_ECLIPSE_MAKE_ARGUMENTS=-j8 -DCMAKE_TOOLCHAIN_FILE=/home/petro/install/arduino-cmake/cmake/Arduino-Toolchain.cmake -DARDUINO_SDK_PATH=/home/petro/install/arduino-1.8.5 -Darduino_port=/dev/ttyUSB0 ../firmware-ecl

set(CMAKE_VERBOSE_MAKEFILE ON)

## Флаги, компенсирующие косяк в сборке C-файлов Arduino-CMake-NG (temporary cure)
#add_definitions(-DARDUINO_ARCH_AVR -DARDUINO_AVR_MEGA2560 -DARDUINO=10802 -DF_CPU=16000000L)
#set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -mmcu=atmega2560")

#set(ARDUINO_CMAKE_SKETCHBOOK_PATH /home/petro/Arduino)

project(${project_name} LANGUAGES C CXX ASM)

set(arduino_board mega)
set(board_cpu atmega2560)
get_board_id(board_id ${arduino_board} ${board_cpu})

add_arduino_executable(${project_name} ${board_id} main.cpp)

find_arduino_library(timer_api_lib arduino-timer-api ${board_id})
link_arduino_library(${project_name} timer_api_lib ${board_id})

set(arduino_port /dev/ttyUSB0)
upload_arduino_target(${project_name} ${board_id} ${arduino_port})

I build it in two ways: with Eclipse project (outside project directory) and directly using bash (within project subdirectory) and have same result.

[kukuyok]

+1 more notice: I need to rename library directory from arduino-timer-api to Arduino-timer-api. Otherwise library can't be found.