CMake library not found

Question

I try to run the makefile that using cmake produced. It generate an error

ld: library not found for -lhello
clang: error: linker command failed with exit code 1 (use -v to see invocation)

the file directory is:

the cmakelists.txt is:

the main.c file is:

the ERROR: I think I set the right directory. How to solve this ERROR?

Answer 1

CMake has a system if you want to link libraries. For many standard libraries we have cmake modules which will allow you to use the find_package command. This will set some variables for include directories and libraries. If there is no such thing for your library you can use find_path for the include files and find_library to search for a library.

Here is what you could do (untested, just out of my head):

add_executable(main main.c)

target_include_directories(
    PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}
    PUBLIC ${CMAKE_SOURCE_DIR}/include/hello
)

find_library (
    HELLO_LIB
    NAMES hello libhello # what to look for
    HINTS "${CMAKE_SOURCE_DIR}/lib" # where to look
    NO_DEFAULT_PATH # do not search system default paths
)

# check if we found the library
message(STATUS "HELLO_LIB: [${HELLO_LIB}]")

if (NOT HELLO_LIB)
    message(SEND_ERROR "Did not find lib hello")
endif

target_link_libraries(main
    ${HELLO_LIB}
)

Use message to debug your cmake files. If you define the library in cmake as well you can link directly against the cmake target.