• 如何用 CMake 生成 C++ 库（支持 find_package 机制）

    参考链接：
    bottle/cpp_with_cmake/cmake_static_library

    googletest

    CMake官方文档：CMakePackageConfigHelpers

    CMake要生成一个C++静态库，其实非常简单，只需要如下即可

    1. # CMakeLists.txt
    2.  
    3. cmake_minimum_required(VERSION 3.16.6)
    4. project(lib)
    5.  
    6. ##################################################################
    7. # 目标配置
    8. ##################################################################
    9. set(TARGET_NAME lib)
    10.  
    11. ##################################################################
    12. # 源文件
    13. ##################################################################
    14. set(TARGET_SOURCES
    15.     lib.cpp
    16. )
    17. set(TARGET_PUBLIC_HEADERS
    18.     lib.h
    19. )
    20.  
    21. ##################################################################
    22. # 生成库属性
    23. ##################################################################
    24. add_library(${TARGET_NAME} STATIC ${TARGET_PUBLIC_HEADERS} ${TARGET_SOURCES})

    我们的源文件内容如下

    1. // lib.cpp
    2. #include "lib.h"
    3.  
    4. int add(int a, int b) {
    5.     return a + b;
    6. }
    7.  
    8.  
    9. // lib.h
    10. #pragma once
    11.  
    12. int add(int a, int b);

     通过以下命令就可以完成构建

     构建结果如下

    但是我们需要通过 install 命令安装，需要增加 isntall 到 CMakeLists.txt

    1. # CMakeLists.txt
    2.  
    3. cmake_minimum_required(VERSION 3.16.6)
    4. project(lib)
    5.  
    6. ##################################################################
    7. # 目标配置
    8. ##################################################################
    9. set(TARGET_NAME lib)
    10. set(TARGET_NAMESPACE Library)
    11.  
    12. set(TARGET_RUNTIME_INSTALL_DIR bin)
    13. set(TARGET_ARCHIVE_INSTALL_DIR lib)
    14. set(TARGET_LIBRARY_INSTALL_DIR lib)
    15. set(TARGET_PUBLIC_HEADER_INSTALL_DIR include)
    16.  
    17. ##################################################################
    18. # 源文件
    19. ##################################################################
    20. set(TARGET_SOURCES
    21.     lib.cpp
    22. )
    23. set(TARGET_PUBLIC_HEADERS
    24.     lib.h
    25. )
    26.  
    27. ##################################################################
    28. # 生成库属性
    29. ##################################################################
    30. add_library(${TARGET_NAME} STATIC ${TARGET_PUBLIC_HEADERS} ${TARGET_SOURCES})
    31.  
    32. # 配置头文件，install命令执行时将复制这些配置的头文件
    33. set_target_properties(${TARGET_NAME} PROPERTIES
    34.     PUBLIC_HEADER "${TARGET_PUBLIC_HEADERS}"
    35. )
    36.  
    37. # 将头文件包含目录配置到 INTERFACE，便于生成的库在被引用时可以自动添加包含目录
    38. string(REPLACE ";" "$" _include_dirs "${TARGET_INCLUDE_DIRS}")
    39. target_include_directories(${TARGET_NAME} SYSTEM INTERFACE
    40.     "$${_include_dirs}>"
    41.     "$/${TARGET_PUBLIC_HEADER_INSTALL_DIR}>"
    42. )
    43.  
    44. ##################################################################
    45. # 安装目标
    46. ##################################################################
    47. # 配置安装路径
    48. install(
    49.     TARGETS ${TARGET_NAME}
    50.     EXPORT ${TARGET_NAME}
    51.     RUNTIME DESTINATION ${TARGET_RUNTIME_INSTALL_DIR}
    52.     ARCHIVE DESTINATION ${TARGET_ARCHIVE_INSTALL_DIR}
    53.     LIBRARY DESTINATION ${TARGET_LIBRARY_INSTALL_DIR}
    54.     PUBLIC_HEADER DESTINATION ${TARGET_PUBLIC_HEADER_INSTALL_DIR}
    55.     PRIVATE_HEADER DESTINATION ${TARGET_PRIVATE_HEADER_INSTALL_DIR}
    56. )
    57.  
    58. # 生成 Targets*.cmake 文件
    59. install(
    60.     EXPORT ${TARGET_NAME}
    61.     FILE ${TARGET_NAME}Targets.cmake
    62.     NAMESPACE ${TARGET_NAMESPACE}:: # Defines namespace in XXXTargets.cmake
    63.     DESTINATION lib/cmake/${TARGET_NAME}
    64. )

    那么我们重新进行生成，指定 CMAKE_INSTALL_PREFIX，安装到指定临时文件夹

     生成的结果为

    、

    将被安装到

    我们看看通过 install 命令生成的 Targets*.cmake 内容

    1. # libTargets.cmake
    2.  
    3. # Generated by CMake
    4.  
    5. if("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" LESS 2.8)
    6.    message(FATAL_ERROR "CMake >= 2.8.0 required")
    7. endif()
    8. if(CMAKE_VERSION VERSION_LESS "2.8.3")
    9.    message(FATAL_ERROR "CMake >= 2.8.3 required")
    10. endif()
    11. cmake_policy(PUSH)
    12. cmake_policy(VERSION 2.8.3...3.22)
    13. #----------------------------------------------------------------
    14. # Generated CMake target import file.
    15. #----------------------------------------------------------------
    16.  
    17. # Commands may need to know the format version.
    18. set(CMAKE_IMPORT_FILE_VERSION 1)
    19.  
    20. # Protect against multiple inclusion, which would fail when already imported targets are added once more.
    21. set(_cmake_targets_defined "")
    22. set(_cmake_targets_not_defined "")
    23. set(_cmake_expected_targets "")
    24. foreach(_cmake_expected_target IN ITEMS Library::lib)
    25.   list(APPEND _cmake_expected_targets "${_cmake_expected_target}")
    26.   if(TARGET "${_cmake_expected_target}")
    27.     list(APPEND _cmake_targets_defined "${_cmake_expected_target}")
    28.   else()
    29.     list(APPEND _cmake_targets_not_defined "${_cmake_expected_target}")
    30.   endif()
    31. endforeach()
    32. unset(_cmake_expected_target)
    33. if(_cmake_targets_defined STREQUAL _cmake_expected_targets)
    34.   unset(_cmake_targets_defined)
    35.   unset(_cmake_targets_not_defined)
    36.   unset(_cmake_expected_targets)
    37.   unset(CMAKE_IMPORT_FILE_VERSION)
    38.   cmake_policy(POP)
    39.   return()
    40. endif()
    41. if(NOT _cmake_targets_defined STREQUAL "")
    42.   string(REPLACE ";" ", " _cmake_targets_defined_text "${_cmake_targets_defined}")
    43.   string(REPLACE ";" ", " _cmake_targets_not_defined_text "${_cmake_targets_not_defined}")
    44.   message(FATAL_ERROR "Some (but not all) targets in this export set were already defined.\nTargets Defined: ${_cmake_targets_defined_text}\nTargets not yet defined: ${_cmake_targets_not_defined_text}\n")
    45. endif()
    46. unset(_cmake_targets_defined)
    47. unset(_cmake_targets_not_defined)
    48. unset(_cmake_expected_targets)
    49.  
    50.  
    51. # Compute the installation prefix relative to this file.
    52. get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH)
    53. get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
    54. get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
    55. get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)
    56. if(_IMPORT_PREFIX STREQUAL "/")
    57.   set(_IMPORT_PREFIX "")
    58. endif()
    59.  
    60. # Create imported target Library::lib
    61. add_library(Library::lib STATIC IMPORTED)
    62.  
    63. set_target_properties(Library::lib PROPERTIES
    64.   INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
    65.   INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
    66. )
    67.  
    68. # Load information for each installed configuration.
    69. file(GLOB _cmake_config_files "${CMAKE_CURRENT_LIST_DIR}/libTargets-*.cmake")
    70. foreach(_cmake_config_file IN LISTS _cmake_config_files)
    71.   include("${_cmake_config_file}")
    72. endforeach()
    73. unset(_cmake_config_file)
    74. unset(_cmake_config_files)
    75.  
    76. # Cleanup temporary variables.
    77. set(_IMPORT_PREFIX)
    78.  
    79. # Loop over all imported files and verify that they actually exist
    80. foreach(_cmake_target IN LISTS _cmake_import_check_targets)
    81.   foreach(_cmake_file IN LISTS "_cmake_import_check_files_for_${_cmake_target}")
    82.     if(NOT EXISTS "${_cmake_file}")
    83.       message(FATAL_ERROR "The imported target \"${_cmake_target}\" references the file
    84.    \"${_cmake_file}\"
    85. but this file does not exist.  Possible reasons include:
    86. * The file was deleted, renamed, or moved to another location.
    87. * An install or uninstall procedure did not complete successfully.
    88. * The installation package was faulty and contained
    89.    \"${CMAKE_CURRENT_LIST_FILE}\"
    90. but not all the files it references.
    91. ")
    92.     endif()
    93.   endforeach()
    94.   unset(_cmake_file)
    95.   unset("_cmake_import_check_files_for_${_cmake_target}")
    96. endforeach()
    97. unset(_cmake_target)
    98. unset(_cmake_import_check_targets)
    99.  
    100. # This file does not depend on other imported targets which have
    101. # been exported from the same project but in a separate export set.
    102.  
    103. # Commands beyond this point should not need to know the version.
    104. set(CMAKE_IMPORT_FILE_VERSION)
    105. cmake_policy(POP)
    1. # libTargets-debug.cmake
    2.  
    3. #----------------------------------------------------------------
    4. # Generated CMake target import file for configuration "Debug".
    5. #----------------------------------------------------------------
    6.  
    7. # Commands may need to know the format version.
    8. set(CMAKE_IMPORT_FILE_VERSION 1)
    9.  
    10. # Import target "Library::lib" for configuration "Debug"
    11. set_property(TARGET Library::lib APPEND PROPERTY IMPORTED_CONFIGURATIONS DEBUG)
    12. set_target_properties(Library::lib PROPERTIES
    13.   IMPORTED_LINK_INTERFACE_LANGUAGES_DEBUG "CXX"
    14.   IMPORTED_LOCATION_DEBUG "${_IMPORT_PREFIX}/lib/lib.lib"
    15.   )
    16.  
    17. list(APPEND _cmake_import_check_targets Library::lib )
    18. list(APPEND _cmake_import_check_files_for_Library::lib "${_IMPORT_PREFIX}/lib/lib.lib" )
    19.  
    20. # Commands beyond this point should not need to know the version.
    21. set(CMAKE_IMPORT_FILE_VERSION)

    第一个文件 libTargets.cmake，主要就是配置了版本号，并通过 add_library 添加了一个 IMPORTED 类型的静态库，并添加了包含路径

    1.  
    2. # CMakeLists.txt
    3.  
    4. string(REPLACE ";" "$" _include_dirs "${TARGET_INCLUDE_DIRS}")
    5. target_include_directories(${TARGET_NAME} SYSTEM INTERFACE
    6.     "$${_include_dirs}>"
    7.     "$/${TARGET_PUBLIC_HEADER_INSTALL_DIR}>"
    8. )
    9.  
    10. # libTargets.cmake 中这一段指定的 INCLUDE 路径，就是通过上面 CMakeLists.txt 的 target_include_directories (INTERFACE) 指定的
    11.  
    12. set_target_properties(Library::lib PROPERTIES
    13.   INTERFACE_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
    14.   INTERFACE_SYSTEM_INCLUDE_DIRECTORIES "${_IMPORT_PREFIX}/include"
    15. )
    16.

     这里如果我们想通过 find_package 去引用此库，会发生以下现象

    虽然库是有的，但是 find-package 并不能找到。

    那么需要通过 CMakePackageConfigHelpers 来完成配置。在 CMakeLists.txt 末尾增加如下内容

    1. # CMakeLists.txt
    2.  
    3. ##################################################################
    4. # Config.cmake and ConfigVersion.cmake 
    5. ##################################################################
    6. # CMakePackageConfigHelpers provides
    7. #   write_basic_package_version_file
    8. #   configure_package_config_file
    9. include(CMakePackageConfigHelpers)
    10.  
    11. # 生成 ConfigVersion.cmake 文件
    12. write_basic_package_version_file(
    13.     ${TARGET_NAME}ConfigVersion.cmake
    14.     VERSION 1.0.0
    15.     COMPATIBILITY SameMajorVersion # AnyNewerVersion|SameMajorVersion|SameMinorVersion|ExactVersion
    16. )
    17. # 生成 Config.cmake 文件 -- 非常重要，find_package 主要就是搜索该文件
    18. configure_package_config_file(
    19.     PackageConfig.cmake.in ${TARGET_NAME}Config.cmake
    20.     INSTALL_DESTINATION  lib/cmake/${TARGET_NAME}
    21. )
    22.  
    23. # 安装生成的 Config.cmake 和 ConfigVersion.cmake 文件
    24. install(
    25.     FILES
    26.         ${CMAKE_CURRENT_BINARY_DIR}/${TARGET_NAME}Config.cmake
    27.         ${CMAKE_CURRENT_BINARY_DIR}/${TARGET_NAME}ConfigVersion.cmake
    28.     DESTINATION lib/cmake/${TARGET_NAME}
    29. )

     这里用到了一个输入文件 PackageConfig.cmake.in，其内容如下，主要就是自动生成 libConfig.cmake 的模板，CMake会将 @PACKAGE_INIT@ 部分用默认的模板填充，后面的部分是我们根据自己库的需要指定的。这里我们只增加了一个组件校验，用作示例（其实这个是可以不需要的）。

    1. @PACKAGE_INIT@
    2.  
    3. include(CMakeFindDependencyMacro)
    4.  
    5. include("${CMAKE_CURRENT_LIST_DIR}/@TARGET_NAME@Targets.cmake")
    6. check_required_components("@TARGET_NAME@")

    好了，那么接下来我们再次生成，得到了如下结果。

    这个时候，再用 find_package 来搜索，就可以搜索到 lib 库了。

    引用库的 CMakeLists.txt 也非常简单，这里简单贴一下

    1. # 引用库的 CMakeLists.txt
    2.  
    3. cmake_minimum_required(VERSION 3.16.6)
    4. project(lib_ref_demo)
    5.  
    6. # 只需要再 CMAKE_PREFIX_PATH 中添加了安装目录即可
    7. # CMake 会按照 .install/lib/cmake//Config.cmake 这个路径去搜索目标
    8. list(APPEND CMAKE_PREFIX_PATH ${CMAKE_CURRENT_LIST_DIR}/library/.install)
    9.  
    10. # 通过 find_package 命令搜索我们构建的库
    11. find_package(lib CONFIG REQUIRED)
    12.  
    13. # 添加 exe 示例程序
    14. add_executable(lib_ref_demo
    15.     ref.cpp
    16. )
    17.  
    18. # 链接刚刚搜索到的 lib 库
    19. target_link_libraries(lib_ref_demo PUBLIC Library::lib)

     具体的工程内容详见 bottle，当然bottle里面还有动态库的生成。补充说明一下的是，bottle 库中的示例要比这里复杂一丢丢，主要验证了库的后缀指定，include多种结构，public/private 头文件等等细节问题。

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  • 原文地址：https://blog.csdn.net/davied9/article/details/126950517