c++ - 使用 CMake ExternalProject_Add 构建 mongo-cxx-driver

Question

我正在尝试在基于 CMake 的项目中构建 mongo-cxx-driver。这个项目应该在 Windows、macOS 和 ubuntu 容器中构建，我想确保我在所有这些平台上的软件都使用相同的驱动程序版本，所以我无法通过 apt-get 安装驱动程序及其依赖项、brew 等。所以我只剩下一个选项:ExternalProject_Add。但鉴于 libmongoc 的设置方式，我很难完成这项工作。下面是我目前拥有的 CMake 模块。

include(ExternalProject)

set(libmongoc_CMAKE_ARGS
    "-DCMAKE_BUILD_TYPE:STRIING=${CMAKE_BUILD_TYPE}"
    "-DENABLE_TESTS:BOOL=OFF"
    "-DENABLE_STATIC:BOOL=OFF"
    "-DENABLE_EXAMPLES:BOOL=OFF"
    "-DENABLE_EXTRA_ALIGNMENT:BOOL=OFF"
)

set(mongocxx_CMAKE_ARGS
    "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
    "-DCMAKE_BUILD_TYPE:STRIING=${CMAKE_BUILD_TYPE}"
    "-DBUILD_SHARED_LIBS:BOOL=ON"
    "-DENABLE_TESTS:BOOL=OFF"
    "-DENABLE_EXAMPLES:BOOL=OFF"
    "-DBSONCXX_POLY_USE_BOOST:BOOL=ON"
    "-DBSONCXX_POLY_USE_MNMLSTC:BOOL=OFF"
    "-Dlibbson-1.0_DIR:PATH=${OTS_DEPDENDENCIES_DIR}/libmongoc/src/libbson"
)

if (NOT TARGET libmongoc)
    ExternalProject_Add(
        libmongoc
        GIT_REPOSITORY  "https://github.com/mongodb/mongo-c-driver.git"
        GIT_TAG         "1.12.0"
        SOURCE_DIR      "${OTS_DEPDENDENCIES_DIR}/libmongoc"
        BINARY_DIR      "${OTS_DEPDENDENCIES_DIR}/libmongoc"
        CMAKE_ARGS      "${libmongoc_CMAKE_ARGS}"
        INSTALL_COMMAND ""
    )
endif()

if (NOT TARGET mongocxx)
    ExternalProject_Add(
        mongocxx
        GIT_REPOSITORY  "https://github.com/mongodb/mongo-cxx-driver.git"
        GIT_TAG         "r3.3.1"
        SOURCE_DIR      "${OTS_DEPDENDENCIES_DIR}/mongocxx"
        BINARY_DIR      "${OTS_DEPDENDENCIES_DIR}/mongocxx"
        CMAKE_ARGS      "${mongocxx_CMAKE_ARGS}"
        INSTALL_COMMAND ""
        DEPENDS         libmongoc
    )
endif()

请注意 CMAKE 选项 libbson-1.0_DIR 作为 mongo-cxx-driver 的 CMAKE_ARGS 之一给出。我对此持怀疑态度，我相信这可能是罪魁祸首。有了它，我得到以下错误:

CMake Error at ${OTS_DEPENDENCIES_DIR}/libmongoc/src/libbson/libbson-1.0-config.cmake:30 (message):
    File or directory
    ${OTS_DEPENDENCIES_DIR}/include/libbson-1.0
    referenced by variable BSON_INCLUDE_DIRS does not exist !
Call Stack (most recent call first):
    ${OTS_DEPENDENCIES_DIR}/libmongoc/src/libbson/libbson-1.0-config.cmake:46 (set_and_check)
    src/bsoncxx/CMakeLists.txt:81 (find_package)

哪种有意义，因为 src/bsoncxx/CMakeLists.txt:81 读取:

get_filename_component(PACKAGE_PREFIX_DIR "${CMAKE_CURRENT_LIST_DIR}/../../../" ABSOLUTE)
set_and_check (BSON_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/include/libbson-1.0")

这使得 CMake 最终在 ${OTS_DEPDENDENCIES_DIR}/include 中寻找不存在的 libbson-1.0。如果我可以告诉 cmake，“嘿，不要运行这个 find_package”，我可以给你 INCLUDE_DIR、LIBRARIES 和 DEFINITIONS 我自己。

如果我删除这个选项，我会收到以下错误:

CMake Error at src/bsoncxx/CMakeLists.txt:81 (find_package):
By not providing "Findlibbson-1.0.cmake" in CMAKE_MODULE_PATH this project
has asked CMake to find a package configuration file provided by
"libbson-1.0", but CMake did not find one.

Could not find a package configuration file provided by "libbson-1.0"
(requested version 1.10.0) with any of the following names:

libbson-1.0Config.cmake
libbson-1.0-config.cmake

Add the installation prefix of "libbson-1.0" to CMAKE_PREFIX_PATH or set
"libbson-1.0_DIR" to a directory containing one of the above files.  If
"libbson-1.0" provides a separate development package or SDK, be sure it
has been installed.

这也不是很奇怪，因为 CMake 会尝试 find_package libbson-1.0 但无法弄清楚它的安装位置。

Answer 1

初步说明

在查看详细信息时，这里有一些初步评论:

• 为SOURCE_DIR 使用不同的目录和 BINARY_DIR
• 代替CMAKE_ARG , 更喜欢 CMAKE_CACHE_ARGS
• libbson-1.0_DIR不应设置为源目录，而应设置为包含 config-file 的构建目录包(下面的链接提供了有关此概念的更多详细信息)
• 确保始终指定 CMake 参数的类型(-DCMAKE_CXX_COMPILER:PATH=${CMAKE_CXX_COMPILER} 而不是 -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER})
• 不要设置CMAKE_BUILD_TYPE用于多配置生成器

关于最后一点，这意味着您应该执行以下操作:

set(EXTERNAL_PROJECT_OPTIONAL_CMAKE_CACHE_ARGS)
if(NOT DEFINED CMAKE_CONFIGURATION_TYPES)
  list(APPEND EXTERNAL_PROJECT_OPTIONAL_CMAKE_CACHE_ARGS
    -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}
    )
endif()

在这篇文章中，您可以了解如何构建您的项目:Correct way to use third-party libraries in cmake project

允许编译 mongocxx“test.cpp”的工作项目

以下是CMakeLists.txt的内容和 test.cpp允许构建名为 <build-dir>/Test-build/test_mongocxx 的可执行文件:

• CMakeLists.txt:

  cmake_minimum_required(VERSION 3.12)
  
  set(CMAKE_CXX_STANDARD 11) 
  
  project(Test)
  
  option(${PROJECT_NAME}_SUPERBUILD "Build ${PROJECT_NAME} and the projects it depends on." ON)
  
  if(${PROJECT_NAME}_SUPERBUILD)
  
      include(ExternalProject)
  
      set(common_cmake_cache_args
          -DCMAKE_CXX_COMPILER:PATH=${CMAKE_CXX_COMPILER}
      )
      if(NOT DEFINED CMAKE_CONFIGURATION_TYPES)
          list(APPEND common_cmake_cache_args
              -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE}
          )
      endif()
  
      ExternalProject_Add(libmongoc
          GIT_REPOSITORY  "https://github.com/mongodb/mongo-c-driver.git"
          GIT_TAG         "1.12.0"
          GIT_PROGRESS    1
          GIT_SHALLOW     1
          SOURCE_DIR      "${CMAKE_BINARY_DIR}/libmongoc"
          BINARY_DIR      "${CMAKE_BINARY_DIR}/libmongoc-build"
          INSTALL_DIR     "${CMAKE_BINARY_DIR}/libmongoc-install"
          CMAKE_CACHE_ARGS
              ${common_cmake_cache_args}
              -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_BINARY_DIR}/libmongoc-install
              -DENABLE_TESTS:BOOL=OFF
              -DENABLE_STATIC:BOOL=OFF
              -DENABLE_EXAMPLES:BOOL=OFF
              -DENABLE_EXTRA_ALIGNMENT:BOOL=OFF
          #INSTALL_COMMAND ""
      )
      set(libmongoc-1.0_DIR "${CMAKE_BINARY_DIR}/libmongoc-install/lib/cmake/libmongoc-1.0/")
      set(libbson-1.0_DIR "${CMAKE_BINARY_DIR}/libmongoc-install/lib/cmake/libbson-1.0/")
  
      ExternalProject_Add(libmongocxx
          GIT_REPOSITORY  "https://github.com/mongodb/mongo-cxx-driver.git"
          GIT_TAG         "r3.3.1"
          GIT_PROGRESS    1
          GIT_SHALLOW     1
          SOURCE_DIR      "${CMAKE_BINARY_DIR}/libmongocxx"
          BINARY_DIR      "${CMAKE_BINARY_DIR}/libmongocxx-build"
          INSTALL_DIR     "${CMAKE_BINARY_DIR}/libmongocxx-install"
          CMAKE_CACHE_ARGS
              ${common_cmake_cache_args}
              -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_BINARY_DIR}/libmongocxx-install
              -DBUILD_SHARED_LIBS:BOOL=ON
              -DENABLE_TESTS:BOOL=OFF
              -DENABLE_EXAMPLES:BOOL=OFF
              -DBSONCXX_POLY_USE_BOOST:BOOL=OFF
              -DBSONCXX_POLY_USE_MNMLSTC:BOOL=ON
              -DBSONCXX_POLY_USE_STD:BOOL=OFF
              -Dlibmongoc-1.0_DIR:PATH=${libmongoc-1.0_DIR}
              -Dlibbson-1.0_DIR:PATH=${libbson-1.0_DIR}
          DEPENDS
              libmongoc
      )
      set(libmongocxx_DIR "${CMAKE_BINARY_DIR}/libmongocxx-install/lib/cmake/libmongocxx-3.3.1/")
      set(libbsoncxx_DIR "${CMAKE_BINARY_DIR}/libmongocxx-install//lib/cmake/libbsoncxx-3.3.1/")
  
  
      function(ExternalProject_AlwaysConfigure proj)
        # This custom external project step forces the configure and later
        # steps to run.
        _ep_get_step_stampfile(${proj} "configure" stampfile)
        ExternalProject_Add_Step(${proj} forceconfigure
          COMMAND ${CMAKE_COMMAND} -E remove ${stampfile}
          COMMENT "Forcing configure step for '${proj}'"
          DEPENDEES build
          ALWAYS 1
          )
      endfunction()
  
      ExternalProject_Add(${PROJECT_NAME}
          SOURCE_DIR "${CMAKE_SOURCE_DIR}"
          BINARY_DIR "${CMAKE_BINARY_DIR}/${PROJECT_NAME}-build"
          DOWNLOAD_COMMAND ""
          UPDATE_COMMAND ""
          CMAKE_CACHE_ARGS
              ${common_cmake_cache_args}
              -D${PROJECT_NAME}_SUPERBUILD:BOOL=OFF
              -Dlibbsoncxx_DIR:PATH=${libbsoncxx_DIR}
              -Dlibmongocxx_DIR:PATH=${libmongocxx_DIR}
          INSTALL_COMMAND ""
          DEPENDS
              libmongocxx
      )
      ExternalProject_AlwaysConfigure(${PROJECT_NAME})
      return()
  endif()
  
  message(STATUS "Configuring inner-build")
  
  find_package(libmongocxx REQUIRED)
  
  add_executable(test_mongocxx test.cpp)
  target_link_libraries(test_mongocxx PUBLIC ${LIBMONGOCXX_LIBRARIES})
  target_include_directories(test_mongocxx PUBLIC ${LIBMONGOCXX_INCLUDE_DIRS})
  target_compile_definitions(test_mongocxx PUBLIC ${LIBMONGOCXX_DEFINITIONS})
  

• test.cpp(从 https://mongodb.github.io/mongo-cxx-driver/mongocxx-v3/installation/#step-6-test-your-installation 复制):

  #include <iostream>
  
  #include <bsoncxx/builder/stream/document.hpp>
  #include <bsoncxx/json.hpp>
  
  #include <mongocxx/client.hpp>
  #include <mongocxx/instance.hpp>
  
  int main(int, char**) {
      mongocxx::instance inst{};
      mongocxx::client conn{mongocxx::uri{}};
  
      bsoncxx::builder::stream::document document{};
  
      auto collection = conn["testdb"]["testcollection"];
      document << "hello" << "world";
  
      collection.insert_one(document.view());
      auto cursor = collection.find({});
  
      for (auto&& doc : cursor) {
          std::cout << bsoncxx::to_json(doc) << std::endl;
      }
  }