我正在尝试建立mongo-cxx-driver在基于 CMake 的项目中。该项目应该在 Windows、macOS 和 ubuntu 容器中构建，我想确保所有这些平台上的软件将使用相同的驱动程序版本，因此我无法通过以下方式安装驱动程序及其依赖项apt-get, brew等等所以我只剩下一个选择：ExternalProject_Add。但鉴于如何做到这一点，我很难做到这一点libmongoc已设置。
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()
注意 CMAKE 选项libbson-1.0_DIR作为其中之一给出CMAKE_ARGS for mongo-cxx-driver。我对此表示怀疑，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):
${OTS_DEPENDENCIES_DIR}/libmongoc/src/libbson/libbson-1.0-config.cmake:46 (set_and_check)
src/bsoncxx/CMakeLists.txt:81 (find_package)
这是有道理的，因为src/bsoncxx/CMakeLists.txt:81 reads:
get_filename_component(PACKAGE_PREFIX_DIR "${CMAKE_CURRENT_LIST_DIR}/../../../" ABSOLUTE)
set_and_check (BSON_INCLUDE_DIRS "${PACKAGE_PREFIX_DIR}/include/libbson-1.0")
这使得 CMake 最终在中寻找 libbson-1.0${OTS_DEPDENDENCIES_DIR}/include那不存在。如果只是，我可以告诉 cmake，“嘿，不要运行这个find_package“我可以给你一条路INCLUDE_DIR, LIBRARIES and DEFINITIONS myself.
如果我删除此选项，则会收到以下错误：
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 尝试 find_package libbson-1.0 但无法弄清楚它的安装位置。
