title: lldb can't debug string when compiled by clang++
body: <p>This is the test code.</p>
  
  <pre><code>#include &lt;string&gt;
  
  int main(int argc, char const *argv[]) {
      std::string a = "hello";
      std::string b = "world";
      return 0;
  }
  </code></pre>
  
  <p>I compile it by the command:</p>
  
  <pre><code>clang++ test.cpp -g
  </code></pre>
  
  <p>Then I try to debug it:</p>
  
  <pre><code>lldb a.out
  </code></pre>
  
  <p>I add break at 4th line, after the <code>a = "hello"</code> runs. I try to print the <code>a</code> by <code>p a</code>, it show me the following error:</p>
  
  <pre><code>error: incomplete type 'string' (aka 'std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;') where a complete type is requ
  ired
  
  note: forward declaration of 'std::__cxx11::basic_string&lt;char, std::char_traits&lt;char&gt;, std::allocator&lt;char&gt; &gt;'
  error: 1 errors parsing expression
  </code></pre>
  
  <p>I can't figure out. </p>
  
  <p>Though when I try to compile by g++, it's OK.</p>