title: xcode build error : duplicate symbol when my project has two files with the same name
body: <p>My project has a file named "Reachability.h" (It's very popular, many people use it)</p>
  
  <p>Today I add a framework of others into my project.
  I think the frameword has the same file "Reachability.h".</p>
  
  <p>So there is a conflict.</p>
  
  <p>Is it because there is NO namespace in C?
  How to avoid this problem? </p>
  
  <p>And here is the log:</p>
  
  <pre><code>ld: duplicate symbol _OBJC_IVAR_$_Reachability.reachabilityRef in /Volumes/Data/Project/ios/FreeMaster/FreeMaster/src/ThirdParty/Lmmob/LmmobAdWallSDK.framework/LmmobAdWallSDK(Reachability.o) and /Users/lxp/Library/Developer/Xcode/DerivedData/FreeMaster-hdzirfpzangiuqaavvqkrzlccrku/Build/Intermediates/FreeMaster.build/Debug-iphonesimulator/FreeMaster.build/Objects-normal/i386/Reachability.o for architecture i386
  </code></pre>
  
  <p>Thanks very much</p>