CMake. Public static library not linking, undefined reference

Question

I am trying to setup a modern cmake project so it can be easily maintainable for my team. But when I compile I get a linker error in the main that my library functions are undefined.

I have a project with the following layout.

CMakeLists.txt
src/
├─ CMakeLists.txt
├─ main.cpp
├─ lib/
│  ├─ include/
│  │  ├─ lib.h
│  ├─ tests/
│  ├─ CMakeLists.txt
│  ├─ src/
│  │  ├─ lib.c

My CMakeLists contains:

root/CMakeLists.txt:

cmake_minimum_required(VERSION 3.13)

set(CMAKE_TOOLCHAIN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/cmake/stm32_gcc.cmake)

project(PROJECTNAME CXX C ASM)
set(CMAKE_INCLUDE_CURRENT_DIR TRUE)

add_subdirectory(src)

src/CMakeLists.txt:

add_subdirectory(freertos)
add_subdirectory(bsp)

set(PROJECT_SOURCES
    main.c
)

add_executable(stm32-freertos.elf ${PROJECT_SOURCES})

target_link_libraries(stm32-freertos.elf
    PRIVATE
       PROJECTNAME::LIBNAME 
)

src/lib/CMakeLists.txt:

set(LIB_NAME "projectname-libame")
set(LIB_ALIAS "PORJECTNAME::LIBNAME")


set(LIB_SOURCES
    src/lib.cpp
)

set(LIB_HEADERS
  include/lib.h
)


add_library(${LIB_NAME}  ${LIB_SOURCES} ${LIB_HEADERS})
add_library(${LIB_ALIAS} ALIAS ${LIB_NAME})

target_include_directories(${LIB_NAME}
    PUBLIC
       $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
       $<INSTALL_INTERFACE:include>
    PRIVATE
       src
  )

main.cpp:

include <lib.h>

int main(){
   call_lib_fun();
}

I am pretty new to cmake so any help or comment even if not directly associated on the problem is appreciated.

And here is the error

/home/user/bin/gcc-arm-none-eabi-9-2020-q2-update/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: CMakeFiles/stm32-freertos.elf.dir/main.c.obj: in function `main':
main.c:(.text+0xa): undefined reference to `call_lib_fun'
collect2: error: ld returned 1 exit status
make[2]: *** [src/CMakeFiles/stm32-freertos.elf.dir/build.make:194: src/stm32-freertos.elf] Error 1
make[2]: Target 'src/CMakeFiles/stm32-freertos.elf.dir/build' not remade because of errors.

Thanks, I've removed a bit of content and added the error now — Xavier Groleau, Nov 03 '20 at 13:15

score 0 · Accepted Answer · edited Aug 24 '22 at 16:28

0

I was calling a C function from C++ code. I simply needed to add this to my header files:

#ifdef __cplusplus
extern "C" {
#endif

...

#ifdef __cplusplus
}
#endif

edited Aug 24 '22 at 16:28

sbugert

345
3
5

answered Nov 03 '20 at 13:54

Xavier Groleau

66
1
7

2

This is why we ask for a [mre], this information wasn't in your question – Alan Birtles Nov 03 '20 at 17:17

CMake. Public static library not linking, undefined reference

1 Answers1