[SOLVED] Undefined Reference in self-built shared library with cmake

Issue

I am currently trying to utilize a self-built shared library. The Library FooBar utilizes the "Foo" Library to do some costly calculations. "Foo" however needs "Bar", the licensing library. It has been successfully cross-compiled when using the following CMakeLists.txt:

cmake_minimum_required(VERSION 3.12)

project(FooBar LANGUAGES CXX)
set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_POSITION_INDEPENDENT_CODE ON)

set(THREADS_PREFER_PTHREAD_FLAG ON)
find_package(Threads REQUIRED)

find_library(Curl
    NAMES curl)

find_library(Foo
    NAMES foo)

find_library(Bar
    NAMES bar)


file(GLOB OBJECT_FILES CONFIGURE_DEPENDS ${PROJECT_SOURCE_DIR}/src/resources/*.o)
file(GLOB SOURCE_FILES CONFIGURE_DEPENDS ${PROJECT_SOURCE_DIR}/src/*.cpp)

add_library(FooBar SHARED ${SOURCE_FILES} ${OBJECT_FILES})
target_link_libraries(FooBar PRIVATE Threads::Threads)
target_link_libraries(FooBar PRIVATE -L${Foo} -L${Bar} -L${Curl})

The compilation is successful without any errors but when I want to include it in the executable, "FooBar" does give me an undefined reference to an function in "Bar", the licensing library. I already checked the "Bar"-library, it contains the used function!

CMakeLists.txt of the executable:

cmake_minimum_required(VERSION 3.12)
project(FooBarExe)

add_subdirectory(FooBar)

add_executable(FooBarExe ${FooBarExe_SRC} ${FooBarExe_INC}) # FooBarExe is just the placeholder for its original name!
target_link_libraries(FooBarExe PRIVATE FooBar)

Error message:

"FooBarExe/FooBar/FooBar.so: undefined reference to 'function' 
 collect2: error: ld returned 1 exit status" 

Does anyone have another idea to solve this issue? I already reordered the libraries in target_link_libraries, compiled it as a static library, included and linked both libraries to FooBarExe via set_target_properties and INTERFACE_LINK_LIBRARIES without any success...

Edit: I tried the following suggested solutions:

• Removing "-L" when adding Library
• Added a Check after the find_library(Bar ...)

Solution

There was an interface change in the "Bar" Library, which went unnoticed by me. Had to replace the header file and the library. Found the change by looking deeper into the library, using the nm -gDC xxxx.so command.

Thank you all for your help, the error was done by me...

Answered By - DanielW3

Answer Checked By - Mildred Charles (WPSolving Admin)