C / C++ Library Linking with CMake - c++

Question

I need to use MongoDB C Drivers in a c++ project. I want to use CMake because the IDE i'm using is well integrated with it but the compiler doesn't recognize the MongoDB drivers
So, I've tried a couple more things and to provide you with a bit more information. I've made the following script:
cmake_minimum_required(VERSION 3.2)
project(sorting)
set(ENV{PKG_CONFIG_PATH} "/usr/lib64")
find_package(PkgConfig REQUIRED)
pkg_search_module(MONGO REQUIRED mongoc-1.0)
message(SEND_ERROR "A ${MONGO_FOUND}") # Error:A 1
message(SEND_ERROR "B ${MONGO_LIBRARIES}") # Error:B ssl;crypto;rt;mongoc-1.0;bson-1.0
message(SEND_ERROR "C ${MONGO_LIBRARY_DIRS}") # Error:C /usr/lib64
message(SEND_ERROR "D ${MONGO_LDFLAGS}") # Error:D -L/usr/lib64;-lssl;-lcrypto;-lrt;-lmongoc-1.0;-lbson-1.0
message(SEND_ERROR "E ${MONGO_LDFLAGS_OTHER}")# Error:E
message(SEND_ERROR "F ${MONGO_INCLUDE_DIRS}") # Error:F /usr/include/libmongoc-1.0;/usr/include/libbson-1.0
message(SEND_ERROR "G ${MONGO_CFLAGS}") # Error:G -I/usr/include/libmongoc-1.0;-I/usr/include/libbson-1.0
message(SEND_ERROR "H ${MONGO_CFLAGS_OTHER}") # Error:H
include_directories(${MONGO_LIBRARY_DIRS})
include_directories(${MONGO_INCLUDE_DIRS})
#link_directories(${MONGO_LIBRARY_DIRS})
#link_directories(${MONGO_INCLUDE_DIRS})
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
set(SOURCE_FILES main.cpp)
add_executable(sorting ${SOURCE_FILES})
target_link_libraries(sorting ${MONGO_LIBRARIES})
When i remove all the message() functions from my cmake file and try to build run the project whith the include_directories uncomented i get this error:
error while loading shared libraries: libmongoc-1.0.so.0: cannot open shared object file: No such file or directory
When i comment the include_directories and uncomment link_directories i get this error:
fatal error: mongoc.h: No such file or directory
#include <mongoc.h>
Also, just out of curiosity why is it that if i chage the name MONGO in pkg_search_module to something like MONGODB or MONG i get this error:
Error:None of the required 'mongoc-1.0' found

Answer 1

You need to tell cmake to link to the monog library, that is achieved by means of the
TARGET_LINK_LIBRARIES
command, in your specific case it would go right after the ADD_EXECUTABLE command, and exactly like
TARGET_LINK_LIBRARIES(sorting ${MONGO_DB_LIBRARIES})
Also, your PKG_SEARCH_MODULE seems to be wrong, it seems that it should be
PKG_SEARCH_MODULE(MONGO_DB REQUIRED libmongoc-1.0)

Answer 2

I am able to compile the mongo sample code given using
cmake_minimum_required(VERSION 2.8)
project(sorting)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
set(SOURCE_FILES main.cpp)
include_directories(/usr/include/libmongoc-1.0 /usr/include/libbson-1.0)
find_library(MONGODB_LIBRARY mongoc-1.0)
find_library(BSON_LIBRARY bson-1.0)
add_executable(sorting ${SOURCE_FILES})
target_link_libraries(sorting ${MONGODB_LIBRARY} ${BSON_LIBRARY})
Can you try with this CMakeFiles.txt ?
BTW it exists a mongo driver c++ for c++ projects !

Answer 3

I was finally able to do it!
The environment variable LD_LIBRARY_PATH was being overwritten by my IDE (CLION). I set it in the IDE settings to point to the library dir and now everything works fine.
This was the configuration i used:
cmake_minimum_required(VERSION 3.2)
project(sorting C)
set(ENV{PKG_CONFIG_PATH} "")
find_package(PkgConfig REQUIRED)
pkg_search_module(MONGO REQUIRED mongoc)
include_directories(${MONGO_INCLUDE_DIRS})
include_directories(${MONGO_LIBRARY_DIRS})
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
set(SOURCE_FILES main.c)
add_executable(sorting ${SOURCE_FILES})
target_link_libraries(sorting ${MONGO_LIBRARIES} )