Undefined symbols for architecture x86_64 for Boost C++

Question

I was trying to compile the following simple thread example for the Boost library:

        #include <iostream>
        #include <boost/thread.hpp>
        #include <boost/chrono.hpp>

        using namespace std;

        void thread()
        {
          for (int i = 0; i < 5; ++i)
          {
            cout << i << '\n';
          }
        }

        int main()
        {
          boost::thread t{thread};
          t.join();
        }

using

  g++ -std=c++11 -I /usr/local/boost_1_57_0 simpleThreadExample.cpp

and the compiler gave this back to me:

       Undefined symbols for architecture x86_64:
        "boost::detail::thread_data_base::~thread_data_base()", referenced from:
        boost::detail::thread_data<void (*)()>::~thread_data() in simpleThreadExample-7cec5e.o
        "boost::system::system_category()", referenced from:
        ___cxx_global_var_init2 in simpleThreadExample-7cec5e.o
        boost::thread_exception::thread_exception(int, char const*) in simpleThreadExample-7cec5e.o
       "boost::system::generic_category()", referenced from:
      ___cxx_global_var_init in simpleThreadExample-7cec5e.o
      ___cxx_global_var_init1 in simpleThreadExample-7cec5e.o
      "boost::thread::join_noexcept()", referenced from:
          boost::thread::join() in simpleThreadExample-7cec5e.o
      "boost::thread::native_handle()", referenced from:
          boost::thread::get_id() const in simpleThreadExample-7cec5e.o
      "boost::thread::start_thread_noexcept()", referenced from:
          boost::thread::start_thread() in simpleThreadExample-7cec5e.o
      "boost::thread::detach()", referenced from:
          boost::thread::~thread() in simpleThreadExample-7cec5e.o
      "typeinfo for boost::detail::thread_data_base", referenced from:
          typeinfo for boost::detail::thread_data<void (*)()> in simpleThreadExample-7cec5e.o
      "vtable for boost::detail::thread_data_base", referenced from:
          boost::detail::thread_data_base::thread_data_base() in simpleThreadExample-7cec5e.o
      NOTE: a missing vtable usually means the first non-inline virtual member function has no definition.
    ld: symbol(s) not found for architecture x86_64
    clang: error: linker command failed with exit code 1 (use -v to see invocation)

Now, the following two programs compile and run just fine:

        #include <locale>
        #include <boost/date_time/gregorian/gregorian.hpp>
        #include <boost/date_time/posix_time/posix_time.hpp>

        using namespace std;
        using namespace boost::gregorian;
        using namespace boost::posix_time;

        int main() 
        {

          date today = day_clock::local_day(); 
          cout << today << endl;

        }

And

        #include <iostream>
        #include <iomanip>
        #include <boost/geometry.hpp>
        #include <boost/geometry/geometries/point.hpp>

        using namespace std;

        int main()
        {

            //point_type p = boost::geometry::make<point_type>(1, 2, 3);
            //std::cout << boost::geometry::dsv(p) << std::endl;
            //return 0;


            boost::geometry::model::point<int, 3, boost::geometry::cs::cartesian> p;
            boost::geometry::assign_values(p,1, 2, 3);

            boost::geometry::model::point<int, 3, boost::geometry::cs::cartesian> p2;

            p2 = p;

            cout << boost::geometry::dsv(p) << endl;

            cout << boost::geometry::dsv(p2) << endl;

            return 0;
        }

And, when I compile, I do:

g++ -std=c++11 -I /usr/local/boost_1_57_0 <nameOfProgram.cpp>

So, I'm wondering why the thread program won't compile while these other two will when the only thing I'm changing is the name of the program?

If it helps, I am using Boost 1.57 and the path to it is:

 /usr/local/Cellar/boost/1.57.0

And the path to the header files is:

/usr/local/Cellar/boost/1.57.0/include/boost

If anyone could provide some insight, that would be brilliant. Thanks!

Answer 1

You have to link against the boost library too:

-lboost_thread

Possibly with additional -L argument for path, and likely the standard -lpthread too.