Question

我最近开始使用CMake（2.8.12.2，CentOS 6.8中包含的那个），我认为它足以帮助实现我想要的功能，但我无法弄清楚如何:-)所以我呼吁你的智慧帮助我找到缺失点。

我有一个像这样的项目布局：

BaseDir
|
+-->bin (generated by the process)
|    |
|    +-->Debug
|    +-->Release
|
+-->lib (generated by the process)
|    |
|    +-->Debug
|    +-->Release
|    
+-->CMakeLists.txt
|
+-->Library_A
|    |
|    +-->CMakeLists.txt
|    +-->include
|    +-->src
|    |    |
|    |    +-->CMakeLists.txt
|    |
|    +-->test # Small binary to test solely the library functions 
|        |
|        +-->CMakeLists.txt
|
+-->Library_B (depends on Library_A)
|    |
|    +-->CMakeLists.txt
|    +-->include
|    +-->src
|    |    |
|    |    +-->CMakeLists.txt
|    |
|    +-->test # Small binary to test solely the library functions 
|        |
|        +-->CMakeLists.txt
|
+-->Application_1 (depends on Library_B, hence transitivitely depends on Library_A)
|    |
|    +-->CMakeLists.txt
|    +-->include
|    +-->src
|        |
|        +-->CMakeLists.txt
|
+-->Application_2 (depends on Library_A)
    |
    +-->CMakeLists.txt
    +-->include
    +-->src
        |
        +-->CMakeLists.txt

当我把自己置于BaseDir并运行“cmake”时，它就像一个魅力。 Application_1，Application_2，Library_A和Libray_B都以正确的顺序构建，链接等等。

但是，我的想法是也能够站在任何子目录（Application_ ，Library _ ）下构建，并且在这种情况下，只构建与其相关的代码（意味着自己，它的测试和依赖）。例如，站在Library_A内部时，只构建该文件夹，而在Library_B中，还构建了Library_A，以及站在Application_1或Application_2下时发生的等效项。另外，独立于我正在触发cmake进程的位置，构建结果（libs或bin）必须始终放在BaseDir / {lib | bin} / {Debug / Release / etc}下，永远不要放在库或应用程序子目录下。例如，它意味着Library_B（依赖于Library_A）或Application_1（依赖于Library_A和B）的链接必须查看BaseDir / lib / {Debug / Release}。

我的目标是在BaseDir下有很多应用程序，所以我想避免每次都要构建它们，如果这不是真的有必要，只需要我想要的单个应用程序。

我已经调查了CMakeLists.txt files for multiple libraries and executables和CMake and finding other projects and their dependencies，但这与我在这里尝试实现的情况并不完全相同。

我尝试过以下内容：

BaseDir/CMakeLists.txt
|
|    cmake_minimum_required (VERSION 2.8)
|    project (BASE_DIR)
|
|    add_subdirectory (Library_A)     # No local dependencies
|    add_subdirectory (Library_B)     # Depends on A
|    add_subdirectory (Application_1) # Depends on A and B
|    add_subdirectory (Application_2) # Depends on A
|
|    # I want all binary outputs (executables and libraries) placed under BaseDir/{lib|bin}/{Debug|Release}
|    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/bin/${CMAKE_BUILD_TYPE}") # For the executables
|    set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/lib/${CMAKE_BUILD_TYPE}") # For the static libraries
|    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_SOURCE_DIR}/lib/${CMAKE_BUILD_TYPE}") # For the dynamic libraries
|
+-->BaseDir/Library_A/CMakeLists.txt (again, no dependencies)
|    |
|    |    cmake_minimum_required (VERSION 2.8)
|    |    project (LIB_A)
|    |    
|    |    # In case CMake is run from within BaseDir/Library_A and not from BaseDir, I still want the outputs being placed under BaseDir/{lib|bin}/{Debug|Release}
|    |    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../bin/${CMAKE_BUILD_TYPE}") # For the test executables
|    |    set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../lib/${CMAKE_BUILD_TYPE}") # For the static libraries
|    |    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../lib/${CMAKE_BUILD_TYPE}") # For the dynamic libraries
|    |
|    |    include_directories(include)
|    |    add_subdirectory (src)
|    |    add_subdirectory (test)
|    |    set(${PROJECT_NAME}_INCLUDE_DIRECTORIES ${PROJECT_SOURCE_DIR}/include CACHE INTERNAL "${PROJECT_NAME}: Include Directories" FORCE)
|    |
|    +-->BaseDir/Library_A/src/CMakeLists.txt
|    |
|    |        cmake_minimum_required (VERSION 2.8)
|    |
|    |        # add all files in the current directory
|    |        file(GLOB LIB_A_SRCS "*.h" "*.cpp")
|    |
|    |        # Create a library called libA.a
|    |        add_library(A ${LIB_A_SRCS})
|    |
|    +-->BaseDir/Library_A/test/CMakeLists.txt
|    
|            cmake_minimum_required (VERSION 2.8)
|    
|            # add all files in the current directory
|            file(GLOB TEST_A_SRCS "*.h" "*.cpp")
|    
|            # Create an executable file from sources
|            add_executable(TEST_A ${TEST_A_SRCS})
|    
|            # Link this executable to the library it's testing
|            target_link_libraries(TEST_A A)
|    
+-->BaseDir/Library_B/CMakeLists.txt (dependency on A)
|    |    
|    |    cmake_minimum_required (VERSION 2.8)
|    |    project (LIB_B)
|    |    
|    |    # In case CMake is run from within BaseDir/Library_B and not from BaseDir, I still want the outputs being placed under BaseDir/{lib|bin}/{Debug|Release}
|    |    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../bin/${CMAKE_BUILD_TYPE}") # For the test executables
|    |    set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../lib/${CMAKE_BUILD_TYPE}") # For the static libraries
|    |    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../lib/${CMAKE_BUILD_TYPE}") # For the dynamic libraries
|    |
|    |    include_directories(include)
|    |    add_subdirectory (src)
|    |    add_subdirectory (test)
|    |    set(${PROJECT_NAME}_INCLUDE_DIRECTORIES ${PROJECT_SOURCE_DIR}/include CACHE INTERNAL "${PROJECT_NAME}: Include Directories" FORCE)
|    |
|    +-->BaseDir/Library_B/src/CMakeLists.txt
|    |
|    |        cmake_minimum_required (VERSION 2.8)
|    |
|    |        # add all files in the current directory
|    |        file(GLOB LIB_B_SRCS "*.h" "*.c")
|    |
|    |        # Create a library called libB.a
|    |        add_library(B ${LIB_B_SRCS})
|    |        
|    |        # Add a dependency to Library_A
|    |        find_library(LIBRARY_A A PATHS ${CMAKE_CURRENT_SOURCE_DIR}/../../Library_A)
|    |        include_directories("$LIB_A_INCLUDE_DIRECTORIES")
|    |        target_link_libraries(B ${LIBRARY_A}) 
|    |
|    +-->BaseDir/Library_B/test/CMakeLists.txt
|
|            cmake_minimum_required (VERSION 2.8)
|
|            # add all files in the current directory
|            file(GLOB TEST_B_SRCS "*.h" "*.cpp")
|
|            # Create an executable file from sources, for both versions of the library
|            add_executable(TEST_B ${TEST_B_SRCS})
|            
|            # Link this executable to the library it's testing
|            target_link_libraries(TEST_B B)
|
+-->BaseDir/Application_1/CMakeLists.txt
|    |
|    |    cmake_minimum_required (VERSION 2.8)
|    |    project (APP_1)
|    |    
|    |    # In case CMake is run from within BaseDir/Application_1 and not from BaseDir, I still want the outputs being placed under BaseDir/{lib|bin}/{Debug|Release}
|    |    # In this case, only executables are generated.
|    |    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../bin/${CMAKE_BUILD_TYPE}")
|    |
|    |    include_directories(include)
|    |    add_subdirectory (src)
|    |
|    +-->BaseDir/Application_1/src/CMakeLists.txt
|
|            cmake_minimum_required (VERSION 2.8)
|
|            # add all files in the current directory
|            file(GLOB APP_1_SRCS "*.cpp")
|
|            # Create an executable file from sources
|            add_executable(EXE_1 ${APP_1_SRCS})
|            
|            # This should automatically bring Library_A
|            find_library(LIBRARY_B B PATHS ${CMAKE_CURRENT_SOURCE_DIR}/../../Library_B)
|            include_directories(${LIB_B_INCLUDE_DIRECTORIES})
|            target_link_libraries(EXE_1 ${LIBRARY_B})
|
+-->BaseDir/Application_2/CMakeLists/CMakeLists.txt
    |
    |    cmake_minimum_required (VERSION 2.8)
    |    project (APP_2)
    |    
    |    # In case CMake is run from within BaseDir/Application_2 and not from BaseDir, I still want the outputs being placed under BaseDir/{lib|bin}/{Debug|Release}
    |    # In this case, only executables are generated.
    |    set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/../bin/${CMAKE_BUILD_TYPE}")
    |
    |    include_directories(include)
    |    add_subdirectory (src)
    |
    +-->BaseDir/Application_2/src/CMakeLists.txt

            cmake_minimum_required (VERSION 2.8)

            # add all files in the current directory
            file(GLOB APP_2_SRCS "*.cpp")

            # Create an executable file from sources
            add_executable(EXE_2 ${APP_2_SRCS})

            # Link this executable to the library it needs
            find_library(LIBRARY_A A PATHS ${CMAKE_CURRENT_SOURCE_DIR}../../Library_A)
            include_directories(${LIB_A_INCLUDE_DIRECTORIES})
            target_link_libraries(EXE_2 ${LIBRARY_A})

但没有运气，因为当我从子目录运行时（例如，BaseDir / Application_1），我得到：

CMake错误：此项目中使用了以下变量，但它们设置为NOTFOUND。请设置它们或确保它们在CMake文件中正确设置和测试：的 LIBRARY_B 的

我想“find_library（）”调用不足以满足我的需要，这基本上是加载库项目中包含的所有设置，不仅包括库本身，还包括该库添加的include目录。 find_library（）的使用方法是什么，将其指向创建库的项目的位置，或实际生成的库（“ .a”或“ .so”）？< / p>

所以，我的主要疑问是：这种布局是否可行？如果是这样，我错过了什么？我应该使用 find_package（）或 find_path（）之类的内容吗？如何触发从另一个“相同级别”CMakeLists.txt解析CMakeLists.txt配置文件？

PS：我真的需要考虑在任何时候使用“add_dependencies（）”吗？如果没有那个命令有什么意义呢？

Answer 1

首先提出一条建议：在CMake中，您总是希望尝试严格地将构建目录与源目录分开。特别是，作为构建过程的一部分，您永远不应将文件写回源目录。编写脚本，以便它们也可以使用挂载在只读文件系统上的源目录。虽然这看起来似乎是一种任意的限制，但从长远来看，它实际上会帮助你避免许多麻烦。

至于你的实际问题：find_library是一个解决依赖问题的非常低级的工具。这里的想法基本上是你在系统的某个地方安装了第三方库（它本身对CMake一无所知）的二进制文件，你知道需要通过检查文件系统的内容来找到它们。这不是这种情况，因为您将依赖关系构建为同一CMake配置运行的一部分。

您要做的事情直接取决于依赖项的目标。所以不要这样做：

find_library(LIBRARY_A A)
target_link_libraries(B ${LIBRARY_A})

你会直接写

target_link_libraries(B A)

这当然只有在A是此时的已知目标时才有效，这是您应该关注的问题。

只要您在同一个CMake运行中继续构建库，这非常简单：如果目标由父目录或兄弟目录添加，您应该能够立即使用它。在您的情况下使事情变得复杂的是，您还希望能够独立构建不同的库。这意味着您需要一种机制，将目标导入您的构建中，使其看起来好像该目标是作为同一CMake运行的一部分再次生成的。

您可以通过添加imported target并设置其界面属性来手动执行此操作，也可以使用CMake的packaging mechanism以自动方式完成此操作。请注意，这些都不是很容易实现的，因此您可能希望从一个CMake运行中发生所有事情的简单情况开始，然后在您更熟悉使用CMake后再添加对分离构建的支持。

CMake配置从根或子目录构建项目

1 个答案: