How to instruct CMake to use the build architecture compiler

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CMake can only handle one compiler at a time. So – if you don’t go the long way to set up the other compiler as a new language – you will end up with two configuration cycles.

I see the following approaches to automate this process:

  1. Taking the example “CMake Cross Compiling – Using executables in the build created during the build?” from the CMake pages as a starting point I’ll get:

    CMakeLists.txt

    cmake_minimum_required(VERSION 3.0)
project(FooBarTest)

# When crosscompiling import the executable targets
if (CMAKE_CROSSCOMPILING)
    set(IMPORT_PATH "IMPORTFILE-NOTFOUND" CACHE FILEPATH "Point it to the export file path from a native build")
    file(TO_CMAKE_PATH "${IMPORT_PATH}" IMPORT_PATH_CMAKE)
    include(${IMPORT_PATH_CMAKE}/genfooTargets.cmake)

    # Then use the target name as COMMAND, CMake >= 2.6 knows how to handle this
    add_custom_command(
        OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/foo.h
        COMMAND genfoo
    )

    add_executable(bar bar.cpp ${CMAKE_CURRENT_BINARY_DIR}/foo.h)
    target_include_directories(bar PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
endif()

# Only build the generator if not crosscompiling
if (NOT CMAKE_CROSSCOMPILING)
    add_executable(genfoo genfoo.cpp)
    export(TARGETS genfoo FILE "${CMAKE_CURRENT_BINARY_DIR}/genfooTargets.cmake")
endif()

    Then using a script like:

    build.sh

    #!/bin/bash

if [ ! -d hostBuild ]; then
    cmake -E make_directory hostBuild
    cmake -E chdir hostBuild cmake ..
fi
cmake --build hostBuild

if [ ! -d crossBuild ]; then
    cmake -E make_directory crossBuild
    cmake -E chdir crossBuild cmake .. -DIMPORT_PATH=${PWD}/hostBuild -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake
fi
cmake --build crossBuild

    I’ll get the desired results by calling ./build.sh.

  2. Splitting the CMakeLists.txt and maybe even replace the export()/include() with something where I know the output path of my build tools e.g. by using CMAKE_RUNTIME_OUTPUT_DIRECTORY would simplify things:

    CMakeLists.txt

    cmake_minimum_required(VERSION 3.0)
project(FooBarTest)

# Then use the target name as COMMAND. CMake >= 2.6 knows how to handle this
add_custom_command(
    OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/foo.h
    COMMAND genfoo
)

add_executable(bar bar.cpp ${CMAKE_CURRENT_BINARY_DIR}/foo.h)
target_include_directories(bar PRIVATE ${CMAKE_CURRENT_BINARY_DIR})

    buildTools/CMakeLists.txt

    cmake_minimum_required(VERSION 3.0)
project(BuildTools)

add_executable(genfoo genfoo.cpp)

    build.sh

    #!/bin/bash

if [ ! -d crossBuild ]; then
    cmake -E make_directory crossBuild
    cmake -E chdir crossBuild cmake .. -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake
fi
if [ ! -d hostBuild ]; then
    cmake -E make_directory hostBuild
    cmake -E chdir hostBuild cmake ../buildTools -DCMAKE_RUNTIME_OUTPUT_DIRECTORY:PATH=${PWD}/crossBuild
fi
cmake --build hostBuild
cmake --build crossBuild

References

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