Question

I was trying to run a small test program on Xcode (4.2) using C++ after encountering error in my project.

#include <boost/thread.hpp>
#include <boost/bind.hpp>    

int main (int argc, const char * argv[])
{
    boost::thread_group tg;
    return 0;
}

But the whole program fails to build, outputting error:

Undefined symbols for architecture x86_64:
  "boost::thread::~thread()", referenced from:
      boost::thread_group::~thread_group()in main.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

Then I tried using

thread_group * tg = new thread_group();

which compiles without issue, up until I tried to invoke

tg->join_all();

where the compiler outputs errors such as:

Undefined symbols for architecture x86_64:
  "boost::detail::get_current_thread_data()", referenced from:
      boost::detail::interruption_checker::interruption_checker(_opaque_pthread_mutex_t*, _opaque_pthread_cond_t*)in main.o
  "boost::this_thread::interruption_point()", referenced from:
      boost::condition_variable::wait(boost::unique_lock<boost::mutex>&) in main.o
  "boost::this_thread::disable_interruption::disable_interruption()", referenced from:
      boost::shared_mutex::lock_shared()      in main.o
  "boost::this_thread::disable_interruption::~disable_interruption()", referenced from:
      boost::shared_mutex::lock_shared()      in main.o
  "boost::thread::join()", referenced from:
      boost::thread_group::join_all()     in main.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

Does anyone know how to resolve these issues ? I’ve been using other functions such as BOOST_FOREACH without any issues. But encounter these while trying to use threads.

Do I need to:

• Specify flags on my ‘Other Linker Flags’?
• reinstall boost or some sort ? Currently I am using Boost 1.49.0, installed using homebrew (i.e. sudo brew install boost)

Or are there any other specific configurations that I need to to include ?

Answer 1

The boost thread library has an actual library object you need to link against (-lboost_thread or sometimes -lboost_thread-mt).