title: Problem linking to boost_thread
body: <p>I'm trying to link with boost 1.47 on xubuntu with gcc4.6 and glibc 2.13. So far I can't compile the following simple program, main.cpp:</p>
  
  <pre><code>#include &lt;cstdlib&gt;
  #include &lt;boost/ref.hpp&gt;
  #include &lt;boost/thread.hpp&gt;
  int main() {
      size_t n_threads = boost::thread::hardware_concurrency();
      return 0;
  }
  </code></pre>
  
  <p>when I compile with:</p>
  
  <pre><code>    g++ -lboost_thread -lboost_regex -o mc main.cpp -static -lpthread /usr/local/lib/libboost_regex.a /usr/local/lib/libboost_thread.a
  </code></pre>
  
  <p>I get a bunch of errors from boost similar to the following:</p>
  
  <pre><code>/usr/local/lib/libboost_thread.a(thread.o): In function `_ZN5boost9call_onceIPFvvEEEvRNS_9once_flagET_.constprop.100':
  thread.cpp:(.text+0x47): undefined reference to `pthread_mutex_lock'
  thread.cpp:(.text+0x73): undefined reference to `pthread_cond_wait'
  thread.cpp:(.text+0xb9): undefined reference to `pthread_mutex_unlock'
  thread.cpp:(.text+0xc8): undefined reference to `pthread_key_create'
  thread.cpp:(.text+0xd2): undefined reference to `pthread_mutex_lock'
  thread.cpp:(.text+0xf5): undefined reference to `pthread_cond_broadcast'
  thread.cpp:(.text+0x10e): undefined reference to `pthread_mutex_unlock'
  </code></pre>
  
  <p>and also:</p>
  
  <pre><code>/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2.o): In function `uw_init_context_1':
  (.text+0x20bd): undefined reference to `pthread_once'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `__register_frame_info_bases':
  (.text+0x16d4): undefined reference to `pthread_mutex_lock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `__register_frame_info_table_bases':
  (.text+0x179b): undefined reference to `pthread_mutex_lock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `__deregister_frame_info_bases':
  (.text+0x183e): undefined reference to `pthread_mutex_lock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `__deregister_frame_info_bases':
  (.text+0x18c6): undefined reference to `pthread_mutex_unlock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `_Unwind_Find_FDE':
  (.text+0x1976): undefined reference to `pthread_mutex_lock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `_Unwind_Find_FDE':
  (.text+0x19c7): undefined reference to `pthread_mutex_unlock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `__register_frame_info_bases':
  (.text+0x16f3): undefined reference to `pthread_mutex_unlock'
  /usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/libgcc_eh.a(unwind-dw2-fde-glibc.o): In function `__register_frame_info_table_bases':
  (.text+0x17ba): undefined reference to `pthread_mutex_unlock'
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>What would be causing a problem like this?
  Have I provided enough information here?
  Any advice for fixing this is greatly appreciated!</p>