Why spdlog/pthread include directory is empty via pkg_search_module in CMake on macos?

Question

Environment

• OS: macos
• package manager: homebrew
• build tool: cmake, pkg-config, clang
• repository: https://github.com/xedit/xedit

they're all newest version.

CMakeLists.txt

the CMakeLists.txt are:

project(xeditd LANGUAGES CXX VERSION 0.1)

find_package(PkgConfig REQUIRED)
pkg_search_module(ICU_UC icu-uc)
pkg_search_module(SPDLOG spdlog)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -Wall")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${ICU_UC_CXXFLAGS_OTHER}")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${SPDLOG_CXXFLAGS_OTHER}")

set(SRC_FILE
    xeditd.cpp
    )

set(LIB_DIR
    ${ICU_UC_LIBRARY_DIRS}
    ${SPDLOG_LIBRARY_DIRS}
    )

set(LIB
    ${ICU_UC_LIBRARIES}
    ${SPDLOG_LIBRARIES}
    )

set(INC_DIR
    ${ICU_UC_INCLUDE_DIRS}
    ${SPDLOG_INCLUDE_DIRS}
    )

message(ICU_UC_CXXFLAGS_OTHER: ${ICU_UC_CXXFLAGS_OTHER})
message(SPDLOG_CXXFLAGS_OTHER: ${SPDLOG_CXXFLAGS_OTHER})
message(ICU_UC_LIBRARY_DIRS: ${ICU_UC_LIBRARY_DIRS})
message(SPDLOG_LIBRARY_DIRS: ${SPDLOG_LIBRARY_DIRS})
message(ICU_UC_LIBRARIES: ${ICU_UC_LIBRARIES})
message(SPDLOG_LIBRARIES: ${SPDLOG_LIBRARIES})
message(ICU_UC_INCLUDE_DIRS: ${ICU_UC_INCLUDE_DIRS})
message(SPDLOG_INCLUDE_DIRS: ${SPDLOG_INCLUDE_DIRS})

link_directories(${LIB_DIR})
add_executable(xeditd ${SRC_FILE})
target_include_directories(xeditd PUBLIC ${INC_DIR})
target_link_libraries(xeditd ${LIB})

Error

the message shows:

ICU_UC_CXXFLAGS_OTHER:
SPDLOG_CXXFLAGS_OTHER:
ICU_UC_LIBRARY_DIRS:/usr/local/Cellar/icu4c/64.2/lib
SPDLOG_LIBRARY_DIRS:
ICU_UC_LIBRARIES:icuucicudata
SPDLOG_LIBRARIES:
ICU_UC_INCLUDE_DIRS:/usr/local/Cellar/icu4c/64.2/include
SPDLOG_INCLUDE_DIRS:

header file <spdlog/spdlog.h> not found. Obviously the spdlog header directory is not include in cmake.

Question

Why pkg_search_module works for icu4c, bug not for spdlog ? And not for pthread ?

Answer 1

IF(APPLE)
    FIND_PACKAGE(spdlog REQUIRED)
ENDIF(APPLE)
...
# Translation is your traget
IF(APPLE)
    target_link_libraries(Translation PUBLIC spdlog::spdlog)
ENDIF(APPLE)