Processing of mbed_app.json

[JojoS62]

When is mbed_app.json processed? I have a project and added "target.printf_lib": "std",, but the change was not not detected, also not when I selected a variant again to trigger a new cmake configuration.
I had to delete the build dir and recompile everything again. Is there some other way to trigger this configuration step?

Which parts are compatible with mbed-os build system? Does this have an effect on the build: "device_has_remove": ["SLEEP"] ?

[JohnK1987]

I had same feeling, but it seems CMake does this correctly.
When I change something in mbed_app.json and do variant re-selecting, then message below will be in output console.

[cmake] -- Mbed: mbed_app.json modified, regenerating configs...

BR, Jan

[multiplemonomials]

mbed_app.json is processed by this CMake script. It watches the json files for changes, and then reruns the Mbed Tools package to generate the configuration whenever the json file is modified.

When you modify mbed_app.json, then rerun CMake, it should notice the changes and reconfigure (the previous modification time is stored as a CMake cache variable. I have seen this work in the past, if it didn't for you, that's a bug.

If you want to manually trigger the configuration, that's easy. You just have to delete the <build dir>/mbed_config.cmake file. CMake will notice this and reconfigure everything.

[multiplemonomials]

Which parts are compatible with mbed-os build system? Does this have an effect on the build: "device_has_remove": ["SLEEP"] ?

Yes, that does have an effect on CMake. It alters the MBED_TARGET_DEFINITIONS list (defined in the generated mbed_config.cmake file) to remove the entry DEVICE_SLEEP=1. It also removes the #define DEVICE_SLEEP 1 compile definition. So, CMake code and/or C++ code can do different things based on that line.

[JojoS62]

selecting a variant works to get modifications in mbed_app.json, thanks for hints.

I've found this about adding depencies to rerun cmake, would that work with the VSCode extension? Where should it be placed?

function(watch)
    set_property(
            DIRECTORY
            APPEND
            PROPERTY CMAKE_CONFIGURE_DEPENDS ${ARGV}
    )
endfunction()

https://www.reddit.com/r/cmake/comments/iokem9/force_cmake_rerun_when_file_changes/

[multiplemonomials]

Ooh interesting, I didn't know about that. It should go in mbed_generate_configuration.cmake.