static linking mongocxx missing sasl

Question

I am trying to build a simple mongocxx application and I am having linking errors:

-- Found ZLIB: /usr/lib/x86_64-linux-gnu/libz.so (found version "1.2.8") 
-- Configuring done
-- Generating done
-- Build files have been written to: /code/build
[ 50%] Linking CXX executable test_new_mongo
../mongo_cxx_driver/lib/libmongoc-static-1.0.a(mongoc-client.c.o): In function `_mongoc_get_rr_search':
mongoc-client.c:(.text+0xa1): undefined reference to `__res_nsearch'
mongoc-client.c:(.text+0xbd): undefined reference to `ns_initparse'
mongoc-client.c:(.text+0x11e): undefined reference to `ns_parserr'
../mongo_cxx_driver/lib/libmongoc-static-1.0.a(mongoc-client.c.o): In function `srv_callback':
mongoc-client.c:(.text+0x3d0): undefined reference to `__dn_expand'
collect2: error: ld returned 1 exit status
make[2]: *** [test_new_mongo] Error 1
make[1]: *** [CMakeFiles/test_new_mongo.dir/all] Error 2
make: *** [all] Error 2

Please. How do I fix these linking errors?

The main.cpp:

#include "mongocxx/instance.hpp"

int main() {
    mongocxx::instance inst{};
    return 0;
}

The CMakeLists.txt:

cmake_minimum_required(VERSION 3.13)
project(test_new_mongo)

set(CMAKE_CXX_STANDARD 17)

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pthread")

find_library(BSONC NAMES "bson-static-1.0" PATHS mongo_cxx_driver/lib)
find_library(BSONCXX_CLIENT NAMES "bsoncxx-static" PATHS mongo_cxx_driver/lib)
find_library(MONGOC_CLIENT NAMES "mongoc-static-1.0" PATHS mongo_cxx_driver/lib)
find_library(MONGO_CLIENT NAMES "mongocxx-static" PATHS mongo_cxx_driver/lib)

find_library(SASL_SHARED_LIB NAMES "libsasl2${CMAKE_SHARED_LIBRARY_SUFFIX}")
find_package(OpenSSL REQUIRED)
set(THREADS_PREFER_PTHREAD_FLAG ON)
FIND_PACKAGE ( Threads REQUIRED )
find_package(ZLIB REQUIRED)

include_directories(mongo_cxx_driver/include)

add_executable(test_new_mongo main.cpp)


target_link_libraries(test_new_mongo
        ${MONGO_CLIENT}
        ${MONGOC_CLIENT}
        ${BSONCXX_CLIENT}
        ${BSONC}
        ${SASL_SHARED_LIB}
        ${OPENSSL_LIBRARIES}
        "${CMAKE_THREAD_LIBES_INIT}"
        ${ZLIB_LIBRARIES}
        rt
        )

I built mongocxx and its dependent libraries on ubuntu 14.04 like so:

apt-get -y update && apt-get -y install \
g++ \
wget \
build-essential \
autoconf \
automake \
autotools-dev \
dh-make \
debhelper \
devscripts \
fakeroot \
xutils \
lintian \
git \
python-dev \
python-pip \
software-properties-common \
pkg-config \
libssl-dev \
openssh-server \
libsasl2-dev \
zlib1g-dev


add-apt-repository ppa:ubuntu-toolchain-r/test -y && \
apt-get update -y && \
apt-get install -y --force-yes gcc-8 g++-8 -y && \
update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 60 --slave /usr/bin/g++ g++ /usr/bin/g++-8


wget https://cmake.org/files/v3.13/cmake-3.13.0-Linux-x86_64.sh && \
chmod +x cmake-3.13.0-Linux* && \
./cmake-3.13.0-Linux-x86_64.sh --skip-license


cd ~ \
&& wget https://github.com/mongodb/mongo-c-driver/releases/download/1.14.0/mongo-c-driver-1.14.0.tar.gz \
&& tar xzf mongo-c-driver-*.tar.gz \
&& cd mongo-c-driver-* \
&& mkdir cmake-build \
&& cd cmake-build \
&& cmake -DCMAKE_CXX_STANDARD=17 -DENABLE_AUTOMATIC_INIT_AND_CLEANUP=OFF -DCMAKE_BUILD_TYPE=Release .. \
&& make \
&& make install

The next step is to build mongocxx but upon building I got errors which I fixed by applying the patches from these two PRs: https://jira.mongodb.org/browse/CXX-1688 https://jira.mongodb.org/browse/CXX-1689

Then I proceeded to build successfully using:

cd ~ \
&& git clone https://github.com/mongodb/mongo-cxx-driver.git --branch releases/stable --depth 1 \
&& cd mongo-cxx-driver/build \
&& cmake  -DCMAKE_CXX_STANDARD=17 -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_PREFIX_PATH=/usr/local -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF.. \
&& make \
&& make install

I then copied the libbson-static-1.0.a, libbsoncxx-static.a, libmongoc-static-1.0.a and libmongocxx-static.a under the project folder of mongo_cxx_drive/lib and also copied the headers bsoncxx and mongocxx under mongo_cxx_driver/include

So you need to link your executable with sasl library. You would expect this linking is performed automatically by mongoc library, but this is true only for the shared library. As you use static one, you need to link manually. — Tsyvarev

kroiz kroiz · Accepted Answer · 2019-03-03T15:20:22

The undefined reference belong to the library resolv. Add "resolv" to the end of the target_link_libraries. Like so:

target_link_libraries(test_new_mongo
        ${MONGO_CLIENT}
        ${MONGOC_CLIENT}
        ${BSONCXX_CLIENT}
        ${BSONC}
        ${SASL_SHARED_LIB}
        ${OPENSSL_LIBRARIES}
        "${CMAKE_THREAD_LIBES_INIT}"
        ${ZLIB_LIBRARIES}
        rt
        resolv
        )

static linking mongocxx missing sasl

1 Answers