Build failed with c_std_11 option

[bettio]

To Reproduce
When building a project having the following CMakeLists.txt [0] I get the following error [1]:

[0]:

cmake_minimum_required(VERSION 3.20.0)

find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
project(zephyr_avm_platform_app)

list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../../../CMakeModules")
add_subdirectory("${CMAKE_CURRENT_SOURCE_DIR}/../../libAtomVM" "build")

target_sources(app PRIVATE src/main.c)

[1]:

/[...]/AtomVM/src/platforms$ ls
emscripten  esp32  generic_unix  rp2040  stm32  zephyr
/[...]/AtomVM/src/platforms$ west build -b qemu_x86 zephyr

[...]

-- The C compiler identification is GNU 12.2.0
-- The CXX compiler identification is GNU 12.2.0
-- The ASM compiler identification is GNU
-- Found assembler: /[...]/.tools/zephyrproject/zephyr-sdk-0.16.3/x86_64-zephyr-elf/bin/x86_64-zephyr-elf-gcc
CMake Warning at /[...]/.tools/zephyrproject/zephyr/subsys/random/CMakeLists.txt:12 (message):
  

      Warning: CONFIG_TIMER_RANDOM_GENERATOR is not a truly random generator.
      This capability is not secure and it is provided for testing purposes only.
      Use it carefully.


CMake Error at /[...]/AtomVM/src/libAtomVM/CMakeLists.txt:100 (target_compile_features):
  target_compile_features The compiler feature "c_std_11" is not known to C
  compiler

  "GNU"

  version 12.2.0.

libAtomVM/CMakeLists.txt contains the following cmake statement:

add_library(libAtomVM ${SOURCE_FILES} ${HEADER_FILES})
target_include_directories(libAtomVM PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
target_compile_features(libAtomVM PUBLIC c_std_11)

Expected behavior
I expect building the app that needs to use an existing library. I also expect to not duplicate cmake files. So having a Zephyr fork of the original cmake file is something I'd like to avoid.

Impact
I cannot start porting the project to Zephyr.

Environment:

• OS: Ubuntu 22.04.3 LTS
• Toolchain: zephyr-sdk-0.16.3
• Commit SHA or Version: 24085d0

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[nordicjm]

I expect building the app that needs to use an existing library. I also expect to not duplicate cmake files. So having a Zephyr fork of the original cmake file is something I'd like to avoid.

If you want to build the library separately, then you'd need to use ExternalProject_Add() to add it and have it built, then include the library. If you want to have it built inside of zephyr then you'd need to convert it to zephyr project. See https://github.com/zephyrproject-rtos/zephyr/tree/main/samples/application_development/external_lib for a sample. Moving to discussion.

[bettio]

ExternalProject_Add seems to be an option, but honestly feels like a workaround, and maybe the documentation needs to be improved.

Remark: the library I'm trying to build with add_subdirectory is already using cmake build system, hence using add_subdirectory feels like the first obvious option.

The example README says:

A simple example that demonstrates how to include an external static library into the Zephyr build system. The demonstrates both how to build the external library using a different build system and how to include the built static library.

So it doesn't look like the first obvious option for building a cmake-native project (which is not "zephyr-native" too), so maybe the example readme should be integrated or maybe a specific example should be provided.

For instance I'm coming from esp-idf world, where the same approach (using add_subdirectory) works 100% fine, so this doesn't look obvious at all.

Also I would like to inherit options and behavior from the top-level cmake, e.g. same generator option, all -D options, etc...

By the way, is this kind of limitation something wanted by design or something that might be fixed in the future?

[nordicjm]

Remark: the library I'm trying to build with add_subdirectory is already using cmake build system, hence using add_subdirectory feels like the first obvious option.

No, this is not true. That is for zephyr libraries and code, you can't just include any random cmake project and expect it to work, it will not.

By the way, is this kind of limitation something wanted by design or something that might be fixed in the future?

The current behaviour is by design and expected, it will not be changed in future.

[bettio]

Thanks for the information. As I feedback I still suggest mentioning that this is for cmake libraries too.