title: Undefined reference char* to string
body: <p>I got the error below by using these as my main and class constructor.</p>
  
  <pre><code>#include&lt;Process.h&gt;
  int main(int argc, char* argv[])
  {
    Process pr (0.01,0.0,argv[3],argv[4],argv[5]);
    return 1;
  }
  </code></pre>
  
  <p>and the process class header:</p>
  
  <pre><code>class Process
  {
    public:
      Process();
      Process(double BinSize,double Offset,const std::string&amp; parameters,const std::string&amp; TDBname,const std::string&amp; DDBname);
      virtual ~Process();
  };
  </code></pre>
  
  <p>and the process class source:</p>
  
  <pre><code>Process::Process()
  {
  //ctor
  }
  Process::Process(double BinSize,double Offset,const std::string&amp; TDBname,const std::string&amp; DDBname,const std::string&amp; parameters)
  {
  //ctor
  cout&lt;&lt;TDBname;
  }
  </code></pre>
  
  <p>but when I compiling the code by Ubuntu 12.10 I got:</p>
  
  <pre><code>main.cpp:(.text.startup+0xf7): undefined reference to `Process::Process(double, double, std::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt; const&amp;, std::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt; const&amp;, std::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt; const&amp;)'
  </code></pre>
  
  <p>I have no idea where the hell this error coming from! Thank you in advance.</p>