title: Linker command failed with exit code 1 In Xcode
body: <p>I'm writing C program in Xcode, and I got this problem:</p>
  
  <pre><code>ld: 1 duplicate symbol for architecture x86_64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>Any idea to solve it?</p>
  
  <p>Note: I've just update my OS to Mountain Lion yesterday.</p>