Clarification about cmake targets

[maruncz]

Hi, I'm trying to use this template for my project and I'm bit confused about targets to link to.

Based on your readme, CMSIS contains family specific headers like U5, but i allways thought that CMSIS only contains ARM stuff, like core type.
Your readme also describes HAL targets and i probably understand them.

When i was transfering my project into this template, I noticed that components that are not dependent on any platform were missing -mcpu ... flags. I looked into toolchain files and found STM32::U5 which seem to contain them. Right now i link this target to all my targets. I guess that tis is a way to support multiple cpus in one project, but it also complicates linking third party libraries, beacue i have to add STM32::U5 as dependency to all targets inside those libraries and i may not be able to add it to all targets. What is the correct approach in this scenario?

[Hish15]

Hello @maruncz. Can you link an example of a case where having an external library require linking STM32::U5 to it ?

[maruncz]

Hi, I use Cmake's FetchContent to include this https://github.com/maruncz/io6Library into my project, and i need to tell compiler to use -mcpu=cortex-m33 -mfpu=fpv5-sp-d16 -mfloat-abi=hard on all compilation units throughout my project.

[Hish15]

The library you gave, does not have a cmake. Can you share the branch where you tried to link it please ?

[maruncz]

sorry, it's in cmake branch

[Hish15]

Ok I had a deeper look into this. I hope I understood your question properly.

flowchart LR
    STM32::U5
    Project --> LibA
    Project --> LibB
    STM32::U5 --> LibA
    STM32::U5 --> LibB

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If for some reason LibA and/or LibB do need STM32::U5, then they do need it and you have to link them together...
You don't have to do this on libA and/or LibB repository. You can instead do it on the CMakeLists.txt of Project where you will link LibA and LibB to Project anyway.

target_link_libraries(LibA PUBLIC STM32::U5)
target_link_libraries(LibB PUBLIC STM32::U5)

target_link_libraries(Project PUBLIC LibA LibB)

This is the way things work in cmake.