Error reading a Trajectory File using Chemfiles library - c++

Question

I need to write a piece of cpp code that will read a trajectory file (.pdb or .dcd files). I have followed the steps on the homepage of chemfiles library to read in the file. I am getting an error about undefined symbols for architecture x86_64 (please see a piece of the error log below).
What I want: Able to read the .dcd/.pdb file using the chemfiles library (or any other suitable library to do so) - I need to access the coordinates of the atoms listed in the file.
Code that reproduces the error when compiled using the command below:
#include "/usr/local/include/chemfiles.hpp" //path to library on my mac
int main(int argc, char *argv[]) {
chemfiles::Trajectory testfile("test.dcd");
return 1;
}
Code that compiles successfully in CLI using the command below:
#include "/usr/local/include/chemfiles.hpp" //path to library on my mac
int main(int argc, char *argv[]) {
// chemfiles::Trajectory testfile("test.dcd");
return 1;
}
Command to compile program:
g++-8 -fopenmp trial.cpp -o trial -lchemfiles -L /usr/local/lib
// I am using openmp because my original code is about parallelisation with openmp
Error:
Undefined symbols for architecture x86_64:
"chemfiles::Trajectory::Trajectory(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >, char,
std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > const&)", referenced from:
_main in ccnk7agz.o
"std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::find(char, unsigned long) const",
referenced from:
file_open_info::parse(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&,
std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> > const&) in libchemfiles.a(Trajectory.cpp.o)
split_comment(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >&) in
libchemfiles.a(LAMMPSData.cpp.o)
"std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::rfind(char, unsigned long) const",
referenced from:
file_open_info::parse(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&,
std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> > const&) in libchemfiles.a(Trajectory.cpp.o)
chemfiles::SDFFormat::read(chemfiles::Frame&) in
libchemfiles.a(SDF.cpp.o)
"std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::compare(unsigned long, unsigned long, char
const*, unsigned long) const", referenced from:
file_open_info::parse(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&,
std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> > const&) in libchemfiles.a(Trajectory.cpp.o)
chemfiles::Trajectory::Trajectory(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >, char,
std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> > const&) in libchemfiles.a(Trajectory.cpp.o)
chemfiles::FormatFactory::register_format(chemfiles::FormatInfo,
std::__1::function<std::__1::unique_ptr<chemfiles::Format,
std::__1::default_delete<chemfiles::Format> >
(std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >, chemfiles::File::Mode,
chemfiles::File::Compression)>) in libchemfiles.a(FormatFactory.cpp.o)
chemfiles::Frame::guess_bonds() in
libchemfiles.a(Frame.cpp.o)
chemfiles::FormatInfo::FormatInfo(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >) in
libchemfiles.a(CSSR.cpp.o)
chemfiles::FormatInfo::FormatInfo(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> >) in
libchemfiles.a(MMTF.cpp.o)
chemfiles::MOL2Format::read(chemfiles::Frame&) in
libchemfiles.a(MOL2.cpp.o)
...