[Buildroot] Having trouble getting a simple cmake based custom package to wok

[Alexander Dahl]

Hello Vijay,

On Thu, Aug 06, 2020 at 07:44:53PM -0700, Vijay wrote:
> I'm trying to add a simple, custom cmake based package to my buildroot
> build. It's just a simple hello world program so that's not very
> interesting. Here is my .mk file, which is the minimum version required I
> believe.
> 
> MYTOOLS_VERSION=1.0
> MYTOOLS_SITE=$(HOME)/Work/mytools
> MYTOOLS_SITE_METHOD=local
> 
> $(eval $(cmake-package))

Looks okay I guess?

> When I configure this and kick off the build, Cmake seems to be having
> trouble with the cross compiler. Below is the output: Is there any
> additional configuration that I need to do?
> 
> I'm using the latest 2020.05.01 version of buildroot.
> 
> Any help is appreciated.
> 
> Thanks,
> Vijay
> 
> >>> mytools 1.0 Configuring
> (mkdir -p /home/foo/buildroot/output/build/mytools-1.0/ && cd
> /home/foo/buildroot/output/build/mytools-1.0/ && rm -f CMakeCache.txt &&
> PATH="/home/foo/buildroot/output/host/bin:/home/foo/buildroot/output/host/sbin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"
>  /home/foo/buildroot/output/host/bin/cmake
> /home/foo/buildroot/output/build/mytools-1.0/
> -DCMAKE_TOOLCHAIN_FILE="/home/foo/buildroot/output/host/share/buildroot/toolchainfile.cmake"
> -DCMAKE_INSTALL_PREFIX="/usr" -DCMAKE_COLOR_MAKEFILE=OFF -DBUILD_DOC=OFF
> -DBUILD_DOCS=OFF -DBUILD_EXAMPLE=OFF -DBUILD_EXAMPLES=OFF -DBUILD_TEST=OFF
> -DBUILD_TESTS=OFF -DBUILD_TESTING=OFF -DBUILD_SHARED_LIBS=ON   )
> -- The C compiler identification is GNU 8.4.0
> -- The CXX compiler identification is unknown

CMake does not find a C++ compiler.

> -- Check for working C compiler:
> /home/foo/buildroot/output/host/bin/x86_64-buildroot-linux-uclibc-gcc
> -- Check for working C compiler:
> /home/foo/buildroot/output/host/bin/x86_64-buildroot-linux-uclibc-gcc --
> works
> -- Detecting C compiler ABI info
> -- Detecting C compiler ABI info - done
> -- Detecting C compile features
> -- Detecting C compile features - done
> CMake Error at CMakeLists.txt:3 (project):
>   The CMAKE_CXX_COMPILER:
> 
>     /home/foo/buildroot/output/host/bin/x86_64-buildroot-linux-uclibc-g++
> 
>   is not a full path to an existing compiler tool.
> 
>   Tell CMake where to find the compiler by setting either the environment
>   variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full
> path
>   to the compiler, or to the compiler name if it is in the PATH.

Again: there seems to bee no C++ compiler in your cross toolchain.

I think you have two possibilities:

If your hello world project is C only, tell CMake like this in your
CMakeLists.txt file:

  project(hello C)

or

  project(hello
    LANGUAGES C
  )

(CMake assumes "C CXX" by default here.)

Or if your hello world uses C++ tell buildroot you need C++ support in
the toolchain:

make menuconfig -> Toolchain -> Enable C++ support

HTH & Greets
Alex

> 
> 
> -- Configuring incomplete, errors occurred!
> See also
> "/home/foo/buildroot/output/build/mytools-1.0/CMakeFiles/CMakeOutput.log".
> See also
> "/home/foo/buildroot/output/build/mytools-1.0/CMakeFiles/CMakeError.log".
> make[1]: *** [package/pkg-generic.mk:259:
> /home/foo/buildroot/output/build/mytools-1.0/.stamp_configured] Error 1
> make: *** [Makefile:84: _all] Error 2

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