Compile part of application as static library

[wodz]

I am trying to separate part of my application into static library and link it to the app. I have read https://docs.zephyrproject.org/latest/application/index.html and cmake documentation.

In my app folder I have CMakeLists.txt

cmake_minimum_required(VERSION 3.13.1)

find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
project(test)

add_subdirectory(src/mylib)
target_sources(app PRIVATE src/main.c)
target_link_libraries(app PUBLIC mylib)

in src/mylib I have CMakeLists.txt

cmake_minimum_required(VERSION 3.13.1)
add_library(mylib STATIC libfile.c)

Now build process is picking up it needs to build static library and link it to app. The problem is compiler flags are not passed to mylib build process and this end up with unlinkable mylib.a.

How do I pass CFLAGS and defines to the mylib build?

/home/wodz/Datasheet/nordic/gcc-arm-none-eabi-9-2019-q4-major/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld.bfd: failed to merge target specific data of file src/mylib/libmylib.a(libfile.c.obj)
collect2: error: ld returned 1 exit status
ninja: build stopped: subcommand failed.

[Øivind]

Hi,

Are you building this in SEGGER Embedded Studio?
If so, could you try building it on the command line instead?

[wodz]

No, I am using west from comandline

[Øivind]

Ok, I tried reproducing this, and I only got an error in SES.

Could you reproduce this in as simple an application as possible, zip it and attach it here?
You can attach files inline with text using Insert->Image/video/file

[wodz]

static_lib.zip

This is the simplest app I could come with. See README.txt for compile error and output from readelf which illustrate the error origin. Object files are included as well so you can study it yourself. I tried both with command line and vscode nrf extension both giving the same error (no surprise here).

[Torsten Rasmussen]

Hi,

To inherit the compile flags used by the Zephyr project you should link your library to the zephyr_interface interface lib, like this:
```

target_link_libraries(mylib PUBLIC zephyr_interface)
```