How to add Ziplib library in Clion on Ubuntu - cmake

Question

I'm trying to add ZipLip into my project using Clion on ubuntu, but I have this output:
====================[ Build | TryZip | Debug ]==================================
/home/david/Snap/clion-2019.2.4/bin/cmake/linux/bin/cmake --build
/home/david/CLionProjects/TryZip/cmake-build-debug --target TryZip -- -j 2
[ 13%] Built target bzip2
[ 31%] Built target zlib
[ 83%] Built target lzma
[ 95%] Built target ZipLib
Scanning dependencies of target TryZip
[ 97%] Linking CXX executable ../bin/TryZip
/usr/bin/ld: cannot find -lExternalLibrary/ZipLib
collect2: error: ld returned 1 exit status
CMakeFiles/TryZip.dir/build.make:102: recipe for target '../bin/TryZip' failed
make[3]: *** [../bin/TryZip] Error 1
CMakeFiles/Makefile2:109: recipe for target 'CMakeFiles/TryZip.dir/all' failed
make[2]: *** [CMakeFiles/TryZip.dir/all] Error 2
CMakeFiles/Makefile2:116: recipe for target 'CMakeFiles/TryZip.dir/rule' failed
make[1]: *** [CMakeFiles/TryZip.dir/rule] Error 2
Makefile:131: recipe for target 'TryZip' failed
make: *** [TryZip] Error 2
This is my Cmakefile.txt
cmake_minimum_required(VERSION 3.15)
project(TryZip)
if(BOOST_FILESYSTEM)
include_directories(${BOOST_INCLUDE_DIR})
link_directories(${BOOST_LIB_DIR})
add_definitions(-DUSE_BOOST_FILESYSTEM)
else()
if(MSVC)
add_definitions(-DFILESYSTEM_EXPERIMENTAL)
endif()
endif()
if(BOOST_FILESYSTEM)
if(UNIX)
find_package(Boost COMPONENTS system filesystem REQUIRED)
target_link_libraries(${Boost_FILESYSTEM_LIBRARY}
${Boost_SYSTEM_LIBRARY})
endif()
endif()
add_subdirectory(ExternalLibrary/ZipLib)
link_libraries(ExternalLibrary/ZipLib)
include_directories(ExternalLibrary/ZipLib)
set(CMAKE_CXX_STANDARD 17)
add_executable(TryZip main.cpp ExternalLibrary/ZipLib/ZipFile.cpp)
target_link_libraries(TryZip ZipLib)
Can someone help me to solve this please?
My ZipLib folder is in the same folder as my cmakefile.txt file.

Answer 1

The call to link_libraries() appears to accept the wrong arguments in this case. The link_libraries() command takes arguments of existing CMake targets, or library names. It is also redundant with your target_link_libraries() call, as this already links ZipLib to TryZip.
Try removing the call to link_libraries(), as this CMake function is deprecated and its use is highly discouraged. The include_directories() call is similarly deprecated, in favor of the target-specific command, so consider using target_include_directories() instead.
Assuming your added sub-directory ExternalLibrary/ZipLib contains an additional CMakeLists.txt file for configuring the ZipLib target, you should not need to add the ZipFile.cpp file again. If this file is already compiled in the sub-directory into the target ZipLib, you do not need to compile it again into TryZip.
add_subdirectory(ExternalLibrary/ZipLib)
set(CMAKE_CXX_STANDARD 17)
add_executable(TryZip main.cpp)
target_include_directories(TryZip PRIVATE ExternalLibrary/ZipLib)
target_link_libraries(TryZip PRIVATE ZipLib)
EDIT: Based on your feedback, it appears ZipLib also depends on pthread but somehow it is not getting linked correctly. You might try to add the following to your ExternalLibrary/ZipLib/CMakeLists.txt file (if it doesn't already exist), to utilize CMake's FindThreads module:
find_package(Threads REQUIRED)
...
target_link_libraries(ZipLib PUBLIC Threads::Threads)