如何正确地将库与 cmake 链接？

Question

我无法将正在使用的其他库正确链接到我的项目中。

我正在使用 CLion，它使用 cmake 来构建它的项目。我正在尝试结合 OpenGL 使用几个库来纹理一些对象。我最初在 Visual Studio 中构建它，因为我无法弄清楚如何让 cmake 与 Clion 一起工作。但是，既然代码都可以正常工作（无论如何在 Visual Studio 中），我希望能够使用 CLion，因为这是我首选的 IDE。

我还是 cmake 的新手，我不明白我的 CMakeLists.txt 做错了什么。这是我所拥有的：

cmake_minimum_required(VERSION 3.3)
project(texture_mapping)
find_package(OpenGL REQUIRED)
link_directories(${OPENGL_gl_LIBRARY})

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

set(SOURCE_FILES main.cpp camera.h display.h display.cpp mesh.cpp mesh.h obj_loader.cpp obj_loader.h shader.cpp shader.h stb_image.c stb_image.h texture.cpp texture.h transform.h)

link_directories(texture_mapping ${PROJECT_SOURCE_DIR}/lib)

add_executable(texture_mapping ${SOURCE_FILES})

target_include_directories(texture_mapping PUBLIC ${PROJECT_SOURCE_DIR}/include)
target_link_libraries(texture_mapping SDL2 SDL2main SDL2test glew32 glew32s ${OPENGL_gl_LIBRARY})

我对其进行了调整，直到它在 CLion 中不再给我任何错误，但我的代码中仍然无法识别头文件。

这是我项目的结构：

所以，我放置了我需要的所有库，但它似乎没有在代码中识别它们。 Clion 在项目中识别它们（它们不会因错误而显示为红色），但是当它被构建时（当我尝试在 CLion 中运行它时），我得到了这些错误：

CMakeFiles\texture_mapping.dir/objects.a(mesh.cpp.obj): In function `ZN4MeshD2Ev':
...texture-mapping/mesh.cpp:30: undefined reference to `_imp____glewDeleteVertexArrays'
CMakeFiles\texture_mapping.dir/objects.a(mesh.cpp.obj): In function `ZN4Mesh8InitMeshERK12IndexedModel':
...texture-mapping/mesh.cpp:36: undefined reference to `_imp____glewGenVertexArrays'
...texture-mapping/mesh.cpp:37: undefined reference to `_imp____glewBindVertexArray'
...texture-mapping/mesh.cpp:39: undefined reference to `_imp____glewGenBuffers'
...texture-mapping/mesh.cpp:40: undefined reference to `_imp____glewBindBuffer'
...texture-mapping/mesh.cpp:41: undefined reference to `_imp____glewBufferData'
...texture-mapping/mesh.cpp:43: undefined reference to `_imp____glewEnableVertexAttribArray'
...texture-mapping/mesh.cpp:44: undefined reference to `_imp____glewVertexAttribPointer'
...texture-mapping/mesh.cpp:46: undefined reference to `_imp____glewBindBuffer'
...texture-mapping/mesh.cpp:47: undefined reference to `_imp____glewBufferData'
...texture-mapping/mesh.cpp:49: undefined reference to `_imp____glewEnableVertexAttribArray'
...texture-mapping/mesh.cpp:50: undefined reference to `_imp____glewVertexAttribPointer'
...texture-mapping/mesh.cpp:52: undefined reference to `_imp____glewBindBuffer'
...texture-mapping/mesh.cpp:53: undefined reference to `_imp____glewBufferData'
...texture-mapping/mesh.cpp:55: undefined reference to `_imp____glewBindVertexArray'
...texture-mapping/mesh.cpp:56: undefined reference to `_imp____glewBindVertexArray'
CMakeFiles\texture_mapping.dir/objects.a(mesh.cpp.obj): In function `ZN4Mesh4DrawEv':
...texture-mapping/mesh.cpp:61: undefined reference to `_imp____glewBindVertexArray'
...texture-mapping/mesh.cpp:65: undefined reference to `_imp____glewBindVertexArray'
CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6ShaderC2ERKSs':
...texture-mapping/shader.cpp:5: undefined reference to `_imp____glewCreateProgram'
...texture-mapping/shader.cpp:11: undefined reference to `_imp____glewAttachShader'
...texture-mapping/shader.cpp:14: undefined reference to `_imp____glewBindAttribLocation'
...texture-mapping/shader.cpp:15: undefined reference to `_imp____glewBindAttribLocation'
...texture-mapping/shader.cpp:17: undefined reference to `_imp____glewLinkProgram'
...texture-mapping/shader.cpp:20: undefined reference to `_imp____glewValidateProgram'
...texture-mapping/shader.cpp:23: undefined reference to `_imp____glewGetUniformLocation'
CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader4BindEv':
...texture-mapping/shader.cpp:28: undefined reference to `_imp____glewUseProgram'
CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader6UpdateERK9TransformRK6Camera':
...texture-mapping/shader.cpp:35: undefined reference to `_imp____glewUniformMatrix4fv'
CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6ShaderD2Ev':
...texture-mapping/shader.cpp:42: undefined reference to `_imp____glewDetachShader'
...texture-mapping/shader.cpp:43: undefined reference to `_imp____glewDeleteShader'
...texture-mapping/shader.cpp:46: undefined reference to `_imp____glewDeleteProgram'
CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader16CheckShaderErrorEjjbRKSs':
...texture-mapping/shader.cpp:79: undefined reference to `_imp____glewGetProgramiv'
...texture-mapping/shader.cpp:81: undefined reference to `_imp____glewGetShaderiv'
...texture-mapping/shader.cpp:86: undefined reference to `_imp____glewGetProgramInfoLog'
...texture-mapping/shader.cpp:88: undefined reference to `_imp____glewGetShaderInfoLog'
CMakeFiles\texture_mapping.dir/objects.a(shader.cpp.obj): In function `ZN6Shader12CreateShaderERKSsj':
...texture-mapping/shader.cpp:96: undefined reference to `_imp____glewCreateShader'
...texture-mapping/shader.cpp:109: undefined reference to `_imp____glewShaderSource'
...texture-mapping/shader.cpp:110: undefined reference to `_imp____glewCompileShader'
CMakeFiles\texture_mapping.dir/objects.a(texture.cpp.obj): In function `ZN7Texture4BindEj':
...texture-mapping/texture.cpp:36: undefined reference to `_imp____glewActiveTexture'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x24): undefined reference to `SDL_SetMainReady'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x55): undefined reference to `SDL_malloc'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x84): undefined reference to `SDL_wcslen'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0xa5): undefined reference to `SDL_iconv_string'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0xcf): undefined reference to `SDL_free'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0xf4): undefined reference to `SDL_wcslen'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x10f): undefined reference to `SDL_iconv_string'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x143): undefined reference to `SDL_malloc'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x17f): undefined reference to `SDL_free'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x18b): undefined reference to `SDL_free'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x1d6): undefined reference to `SDL_isspace'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x295): undefined reference to `SDL_isspace'
...texture-mapping/lib/SDL2main.lib(./Win32/Release/SDL_windows_main.obj):(.text+0x3a2): undefined reference to `SDL_ShowSimpleMessageBox'

基本上，每次使用 SDL 和 glew 都会出错，但 glm 不会出错，这很奇怪。

我的CMakeLists.txt 做错了什么？

Answer 1

我的建议是从简单开始，然后进一步复杂化您的项目。

让我试着解释一下 CMake 中的链接是如何工作的。这个想法是您在 CMake 中构建 modules，并将它们链接在一起。让我们暂时忽略头文件，因为它们都可以包含在您的源文件中。

假设你有 file1.cpp、file2.cpp、main.cpp。您将它们添加到您的项目中：

ADD_LIBRARY(LibsModule 
    file1.cpp
    file2.cpp
)

现在您将它们添加到名为 LibsModule 的模块中。记住这一点。 假设您想链接到pthread，例如系统中已经存在的链接。您可以使用以下命令将其与LibsModule 结合使用：

target_link_libraries(LibsModule -lpthread)

如果你也想链接一个静态库，你可以这样做：

target_link_libraries(LibsModule liblapack.a)

如果你想添加这些库所在的目录，你可以这样做：

target_link_libraries(LibsModule -L/home/user/libs/somelibpath/)

现在您添加一个可执行文件，并将其与您的主文件链接：

ADD_EXECUTABLE(MyProgramExecBlaBla main.cpp)

（我添加了 BlaBla 只是为了表明名称是自定义的）。然后你将LibsModule 与你的可执行模块MyProgramExecBlaBla 链接起来

target_link_libraries(MyProgramExecBlaBla LibsModule)

这样就可以了。

我在您的 CMake 文件中看到了很多冗余。例如，为什么你有texture_mapping，这是你包含目录中的一个可执行模块？所以你需要清理它并遵循我解释的简单逻辑。希望它有效。

---

总而言之，它看起来像这样：

project (MyProgramExecBlaBla)  #not sure whether this should be the same name of the executable, but I always see that "convention"
cmake_minimum_required(VERSION 2.8)

ADD_LIBRARY(LibsModule 
    file1.cpp
    file2.cpp
)

target_link_libraries(LibsModule -lpthread)
target_link_libraries(LibsModule liblapack.a)
target_link_libraries(LibsModule -L/home/user/libs/somelibpath/)
ADD_EXECUTABLE(MyProgramExecBlaBla main.cpp)
target_link_libraries(MyProgramExecBlaBla LibsModule)

要了解的最重要的事情是模块结构，您可以在其中创建模块并将它们与可执行文件链接在一起。一旦这工作，您可以使用更多细节使您的项目进一步复杂化。祝你好运！

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注意：请记住，这是使用 CMake 的简单方法。更好的跨平台方法是使用find_package，它定位一个包/库，并提供库并包含在 CMake 变量中，以便您可以将程序链接到它们。以Here's how to do this for boost 为例。