fails to generate project(name C)

[Wirtos]

In default examples project has no explicitly used languages, which implies C and CXX LANGUAGES, but if I set my project to be C only (which is correct), cmake fails to generate it. I think toolchain's internals should be separated from the project completely like VCPKG does.

Error log:

CMake Error: Error required internal CMake variable not set, cmake may not be built correctly.
Missing variable is:
CMAKE_CXX_COMPILE_OBJECT
CMake Error: Error required internal CMake variable not set, cmake may not be built correctly.
Missing variable is:
CMAKE_CXX_LINK_EXECUTABLE

CMake Generate step failed.  Build files cannot be regenerated correctly.

Problems were encountered while collecting compiler information:
    cc1plus: fatal error: /home/wirtos/GithubProjects/pico-sdk/src/common/pico_stdlib/include: No such file or directory
    cc1plus: fatal error: /home/wirtos/GithubProjects/pico-sdk/src/rp2_common/hardware_gpio/include: No such file or directory
    cc1plus: fatal error: /home/wirtos/GithubProjects/pico-sdk/src/common/pico_base/include: No such file or directory
    cc1plus: fatal error: /mnt/c/GithubProjects/picolrn/cmake-build-debug-wsl-gcc/generated/pico_base: No such file or directory
    cc1plus: fatal error: /home/wirtos/GithubProjects/pico-sdk/src/boards/include: No such file or directory
 ...

CMakeLists.txt:

cmake_minimum_required(VERSION 3.16)
include(cmake/pico_sdk_import.cmake)
project(picolrn C)
pico_sdk_init()
set(CMAKE_C_STANDARD 99)
add_executable(picolrn main.c)
target_link_libraries(picolrn PRIVATE pico_stdlib)
pico_add_extra_outputs(picolrn)

[lurch]

Which part of your project was being built when you saw those errors? Note that building the toolchain also builds elf2uf2 (which converts the .elf file that GCC generates into a .uf2 file for copying onto your Pico) which is a native (it runs on your computer rather than on your Pico) program written in C++.

[Wirtos]

Which part of your project was being built when you saw those errors? Note that building the toolchain also builds elf2uf2 (which converts the .elf file that GCC generates into a .uf2 file for copying onto your Pico) which is a native (it runs on your computer rather than on your Pico) program written in C++.

It breaks before the build process during generation as mentioned in the report. Does this regardlessly of me having add_extra_outputs. The toolchain config should be responsible for providing C++ compiler to build elf2uf2, not the project itself. But even considering that I'm not sure whether elf2uf2 is the root of the problem.

[kilograham]

Yeah; fixing this is a bit nasty, because the SDK itself is a CXX project, and reports as such vi ENABLED_LANGUAGES property in cmake. Your project fails, because at the toplevel scope CXX is not a valid language. I had a little play and see that if the SDK doesn't include new_delete.cpp then you are fine, but as I say we can't simply check ENABLED_LANGUAGES as that does contain CXX at this point.

I don't feel strongly enough to expend much effort on it right now, so feel free to post a PR... I guess we could add a CMake build flag at least to say you want nothing to do with C++ assuming it is an actual requirement

See #339 for C99

[Wirtos]

I guess I'll try to toy with the toolchain later and maybe port tools like elf2uf2 to C then

[kilograham]

elf2uf2 is not the problem; that is a separate build and works fine

[Wirtos]

So it's solely the toolchain that breaks because of undefined languages? It seems like it's quite trivial to use gcc-arm toolchain in place of CMAKE_TOOLCHAIN_FILE, but I'm not sure on how to link the libraries in this case. iirc vcpkg adds directories to CMAKE_FIND_ROOT_PATH in order to be able to use find_package or find_path. Can I do the same separately for pico toolchain and if yes, which dirs should I add?

[Bolayniuss]

I manage to solve this by using a variable PICO_SDK_PURE_C to remove new_delete.cpp from the source.

In src/rp2_common/pico_standard_link/CMakeLists.txt replace

target_sources(pico_standard_link INTERFACE
    ${CMAKE_CURRENT_LIST_DIR}/crt0.S
    ${CMAKE_CURRENT_LIST_DIR}/new_delete.cpp
    ${CMAKE_CURRENT_LIST_DIR}/binary_info.c
)

by

set(pico_standard_link_SOURCES ${CMAKE_CURRENT_LIST_DIR}/crt0.S ${CMAKE_CURRENT_LIST_DIR}/binary_info.c)
if(NOT DEFINED PICO_SDK_PURE_C)
    message("C++ enabled, add ${CMAKE_CURRENT_LIST_DIR}/new_delete.cpp")
    set(pico_standard_link_SOURCES ${pico_standard_link_SOURCES} ${CMAKE_CURRENT_LIST_DIR}/new_delete.cpp)
endif()

And then, in your CMakeList.txt define add set(PICO_SDK_PURE_C 1) before include(pico_sdk_import.cmake)

[JannickBremm]

I manage to solve this by using a variable PICO_SDK_PURE_C to remove new_delete.cpp from the source.

In src/rp2_common/pico_standard_link/CMakeLists.txt replace

target_sources(pico_standard_link INTERFACE
    ${CMAKE_CURRENT_LIST_DIR}/crt0.S
    ${CMAKE_CURRENT_LIST_DIR}/new_delete.cpp
    ${CMAKE_CURRENT_LIST_DIR}/binary_info.c
)

by

set(pico_standard_link_SOURCES ${CMAKE_CURRENT_LIST_DIR}/crt0.S ${CMAKE_CURRENT_LIST_DIR}/binary_info.c)
if(NOT DEFINED PICO_SDK_PURE_C)
    message("C++ enabled, add ${CMAKE_CURRENT_LIST_DIR}/new_delete.cpp")
    set(pico_standard_link_SOURCES ${pico_standard_link_SOURCES} ${CMAKE_CURRENT_LIST_DIR}/new_delete.cpp)
endif()

And then, in your CMakeList.txt define add set(PICO_SDK_PURE_C 1) before include(pico_sdk_import.cmake)

Worked for me! Thank's a lot @Bolayniuss