title: boost::program_options undefined reference
body: <p>I use ubuntu 10.04 and libboost1.40. </p>
  
  <pre><code>ls -l /usr/lib | grep boost_pro
      -rw-r--r--  1 root root   640800 2010-04-01 05:19 libboost_program_options.a
      lrwxrwxrwx  1 root root       26 2011-11-03 22:40 libboost_program_options-mt.a -&gt;                  libboost_program_options.a
      lrwxrwxrwx  1 root root       34 2011-11-03 22:40 libboost_program_options-mt.so -&gt;                libboost_program_options.so.1.40.0
      lrwxrwxrwx  1 root root       34 2011-11-03 22:40 libboost_program_options.so -&gt;    libboost_program_options.so.1.40.0
      -rw-r--r--  1 root root   289336 2010-04-01 05:19 libboost_program_options.so.1.40.0
  </code></pre>
  
  <p>this is main.cpp(just for testing)</p>
  
  <pre><code>     #include &lt;string&gt; 
  #include &lt;iostream&gt; 
  #include &lt;boost/date_time/gregorian/gregorian.hpp&gt; 
  #include &lt;boost/date_time/posix_time/posix_time.hpp&gt;
  #include &lt;boost/program_options/options_description.hpp&gt;
  //--------------------------------------------------------------------- 
  int main(int argc,char** argv) 
  { 
   boost::gregorian::date now(boost::gregorian::day_clock::local_day());
   //is works fine 
   std::cout&lt;&lt;boost::gregorian::to_iso_string(now)&lt;&lt;std::endl;
   boost::program_options::options_description a; //but here i get an error when the                constructor have started
   return 0; 
   }
  
      g++ -o main -lboost_date_time -lboost_program_options   main.cpp &amp;&amp; ./main
      /tmp/cc3RJHsG.o: In function `main':
      main.cpp:(.text+0x81): undefined reference to   `boost::program_options::options_description::options_description(unsigned int, unsigned     int)'
      collect2: ld returned 1 exit status
  </code></pre>
  
  <p>i do </p>
  
  <pre><code>    find /usr/include/ -name "*description*"
  /usr/include/boost/program_options/options_description.hpp
  </code></pre>
  
  <p>and there's only a prototype ofcouse. 
  Any ideas?</p>