c++ - 为什么 CMake 无法识别库，尽管它已由 'include_directories' 添加？

Question

我的 CMakeList 文件定义了应该包含在构建路径中的目录列表:

set(CMAKE_CXX_STANDARD 11)

include_directories(lib)
include_directories(lib/freeglut)
include_directories(lib/freeglut/include)
include_directories(lib/freeglut/include/GL)
include_directories(lib/matrix)
include_directories(lib/mavlink)
include_directories(lib/mavlink/common)
include_directories(src)
include_directories(src/Drawing)
include_directories(src/Math)
include_directories(src/MavlinkNode)
include_directories(src/Simulation)
include_directories(src/Utility)
...

所有依赖文件都在/lib 下。当我运行 CMake CMakeList.txt & make 时，出现以下错误:

[100%] Linking CXX executable FCND_Controls_CPP
CMakeFiles/FCND_Controls_CPP.dir/src/main.cpp.o: In function `main':
/home/peng/git-drone/__Udacity__/FCND-Controls-CPP/src/main.cpp:68: undefined reference to `glutTimerFunc'
/home/peng/git-drone/__Udacity__/FCND-Controls-CPP/src/main.cpp:70: undefined reference to `glutMainLoop'
...

虽然函数 glutTimerFunc 和 glutMainLoop 都在 'lib/freeglut/include/GL/freeglut.h' 下。然而，CMake 和 make 都忽略了它们。为什么会发生这种情况，我应该如何解决？

我使用的是 cmake 3.9.1，我尝试了 2 个后端:gcc/g++ 和 clang/clang++，但都给出了同样的错误。

Answer 1

您正在使用 include_directories，这是供编译器检查包含的目录。您应该使用的是 target_link_libraries。

但是，由于您使用的是已知库，因此您需要执行类似的操作(您可以在 cmake-modules< 下的 FindGLUT.cmake 文件中找到此信息 目录):

find_package(GLUT REQUIRED)
target_include_directories(your_exe PUBLIC ${GLUT_INCLUDE_DIR}) # could also be PRIVATE, depending on usage
target_link_libraries(your_exe ${GLUT_LIBRARY} )

请注意，您还需要对具有缓存变量 ${OPENGL_INCLUDE_DIR} 和 ${OPENGL_LIBRARIES} 的 OpenGL 库执行相同的操作>.

Note: Try to avoid using include_directories (without target) as that is considered the older style and has the drawback of pollutating the include directories of all targets.