Unable to load shared object: undefined symbol - c++

Question

I'm trying to create simple lib for the R with statically linked boost.
CMakeLists.txt
cmake_minimum_required(VERSION 3.3)
project(TheRPath)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Werror")
set(Boost_USE_STATIC_LIBS ON)
find_package(Boost 1.50.0 REQUIRED COMPONENTS filesystem)
include_directories(${Boost_INCLUDE_DIRS})
include_directories("/usr/share/R/include")
set(SOURCE_FILES Path.cpp Path.h)
add_library(therpath SHARED ${SOURCE_FILES})
target_link_libraries(therpath ${Boost_LIBRARIES})
Interpreter gives me an error when I'm trying to load shared object.
> dyn.load("libtherpath.so")
Error in dyn.load("libtherpath.so") :
unable to load shared object 'libtherpath.so':
libtherpath.so: undefined symbol: _ZN5boost6system15system_categoryEv
I have the following code:
Path.h
#ifndef PATH_H
#define PATH_H
#include <Rinternals.h>
extern "C" SEXP foo(SEXP snapshotPath);
#endif // PATH_H
Path.cpp
#include <string>
#include <boost/filesystem.hpp>
#include "Path.h"
extern "C" SEXP foo(SEXP snapshotPath) {
std::string path(R_CHAR(STRING_ELT(snapshotPath, 0)));
std::cerr << path << boost::filesystem::path::preferred_separator << "file.txt" << std::endl;
return R_NilValue;
}
Could you tell me what I'm doing wrong?
UPD 1
Output of make VERBOSE=1:
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -H/home/user/Workspace/TheRPath -B/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug --check-build-system CMakeFiles/Makefile.cmake 0
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_progress_start /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
make -f CMakeFiles/therpath.dir/build.make CMakeFiles/therpath.dir/depend
make[2]: Entering directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
cd /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug && /home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_depends "Unix Makefiles" /home/user/Workspace/TheRPath /home/user/Workspace/TheRPath /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles/therpath.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
make -f CMakeFiles/therpath.dir/build.make CMakeFiles/therpath.dir/build
make[2]: Entering directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
[ 50%] Building CXX object CMakeFiles/therpath.dir/Path.cpp.o
/usr/bin/c++ -Dtherpath_EXPORTS -std=c++11 -Wall -Werror -g -fPIC -I/usr/share/R/include -o CMakeFiles/therpath.dir/Path.cpp.o -c /home/user/Workspace/TheRPath/Path.cpp
[100%] Linking CXX shared library libtherpath.so
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_link_script CMakeFiles/therpath.dir/link.txt --verbose=1
/usr/bin/c++ -fPIC -std=c++11 -Wall -Werror -g -shared -Wl,-soname,libtherpath.so -o libtherpath.so CMakeFiles/therpath.dir/Path.cpp.o /usr/lib/x86_64-linux-gnu/libboost_filesystem.a
make[2]: Leaving directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
[100%] Built target therpath
make[1]: Leaving directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_progress_start /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles 0
UPD 2
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -H/home/user/Workspace/TheRPath -B/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug --check-build-system CMakeFiles/Makefile.cmake 0
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_progress_start /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
make -f CMakeFiles/therpath.dir/build.make CMakeFiles/therpath.dir/depend
make[2]: Entering directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
cd /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug && /home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_depends "Unix Makefiles" /home/user/Workspace/TheRPath /home/user/Workspace/TheRPath /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug /home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug/CMakeFiles/therpath.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
make -f CMakeFiles/therpath.dir/build.make CMakeFiles/therpath.dir/build
make[2]: Entering directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
[ 50%] Building CXX object CMakeFiles/therpath.dir/Path.cpp.o
/usr/bin/c++ -Dtherpath_EXPORTS -std=c++11 -Wall -Werror -g -fPIC -I/usr/share/R/include -o CMakeFiles/therpath.dir/Path.cpp.o -c /home/user/Workspace/TheRPath/Path.cpp
[100%] Linking CXX shared library libtherpath.so
/home/user/Soft/clion-latest/bin/cmake/bin/cmake -E cmake_link_script CMakeFiles/therpath.dir/link.txt --verbose=1
/usr/bin/c++ -fPIC -std=c++11 -Wall -Werror -g -shared -Wl,-soname,libtherpath.so -o libtherpath.so CMakeFiles/therpath.dir/Path.cpp.o /usr/lib/x86_64-linux-gnu/libboost_system.a /usr/lib/x86_64-linux-gnu/libboost_filesystem.a
/usr/bin/ld: /usr/lib/x86_64-linux-gnu/libboost_system.a(error_code.o): relocation R_X86_64_32 against `.rodata.str1.1' can not be used when making a shared object; recompile with -fPIC
/usr/lib/x86_64-linux-gnu/libboost_system.a: error adding symbols: Bad value
collect2: error: ld returned 1 exit status
make[2]: *** [libtherpath.so] Error 1
make[2]: Leaving directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
make[1]: *** [CMakeFiles/therpath.dir/all] Error 2
make[1]: Leaving directory `/home/user/.CLion12/system/cmake/generated/a69e8583/a69e8583/Debug'
make: *** [all] Error 2

Answer 1

libboost_filesystem depends on libboost_system. You need to add it to your CMakeLists.txt:
find_package(Boost REQUIRED COMPONENTS filesystem system)
Note I omitted the optional Boost version number, because you probably don't really need or want to specify it. But you can if you feel compelled.