c++ - CMake build multiple targets in different build directories

Question

I have the following CMake structure:

CMakelists.txt
toolchain.cmake
folder1
   ----CMakelists.txt
folder2
   ----CMakelists.txt
etc..

My first-level CMakelists.txt file includes the other subdirectories. Now I want to build my code for a different target.

The manual way is:

1.
    mkdir hostBuild
    cd hostBuild
    cmake ..
    make

2.
    mkdir crossBuild
    cd crossBuild
    cmake .. --DCMAKE_TOOLCHAIN_FILE=toolchain.cmake
    make

Is it possible that this process can run automatically?

For example, I just have to run cmake . at my first level.

Is something like this is possible?

Answer 1

No. The recommendation would be to just put your manual steps into a shell script.

CMake can only handle one compiler/make environment at a time (if you switch the compiler you need a different binary output directory).

Especially a toolchain file that does contain SET(CMAKE_SYSTEM_NAME ...) does change the whole outcome of the configuration/generation process.

For details on what CMake does see: CMake: In which Order are Files parsed (Cache, Toolchain, …)?

And you could make use of some CMake command line options in your shell script:

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