make的link_directories命令不起做用

按照《CMake Practice》中第六章的設置，採用include_directories命令去尋找共享庫的路徑，src/CMakeLists.txt以下：

ADD_EXECUTABLE(main main.c) INCLUDE_DIRECTORIES(/tmp/include/hello) LINK_DIRECTORIES(/tmp/lib/) TARGET_LINK_LIBRARIES(main libhello.a)

執行cmake及make後，仍然有link error。

cmake的官網對include_directories的說明以下：

*Specify directories in which the linker will look for libraries.

link_directories(directory1 directory2 …)

Note that this command is rarely necessary. Library locations returned by find_package() and find_library() are absolute paths. Pass these absolute library file paths directly to the target_link_libraries() command. CMake will ensure the linker finds them.*

官網不推薦使用link_directoris，而是推薦使用find_package和find_library尋找共享庫的絕對路徑，再傳給target_link_libraries使用。

按照這裏的例子，改寫了src/CMakeLists.txt以下：

ADD_EXECUTABLE(main main.c) INCLUDE_DIRECTORIES(/tmp/include/hello) find_library(LIBHELLO_PATH hello /tmp/lib) IF(NOT LIBHELLO_PATH) MESSAGE(FATAL_ERROR "libhello not found") ENDIF(NOT LIBHELLO_PATH) MESSAGE(STATUS ${LIBHELLO_PATH} " found") TARGET_LINK_LIBRARIES(main ${LIBHELLO_PATH})

這下能夠編譯經過了。