title: How to fix the error "duplicate symbol _LOG_BUFFER_LENGTH"
body: <p>I have a Unity project embedded into Swift 4 and when I build the project I get an error from a plugin named FFmpeg (used to record the screen) and the error is next:</p>
  
  <pre><code>duplicate symbol _LOG_BUFFER_LENGTH in:
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/cmdutils.o
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/ffmpeg.o
  duplicate symbol _LOG_BUFFER_LENGTH in:
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/cmdutils.o
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/ffmpeg_wrapper.o
  duplicate symbol _LOG_BUFFER_LENGTH in:
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/cmdutils.o
      /Users/developers/Library/Developer/Xcode/DerivedData/DemoApp-bszfgmzljpyourbdjoxkdabtilki/Build/Intermediates.noindex/DemoApp.build/Debug-iphoneos/DemoApp.build/Objects-normal/arm64/intercept.o
  ld: 3 duplicate symbols for architecture arm64
  clang: error: linker command failed with exit code 1 (use -v to see invocation)
  </code></pre>
  
  <p>I want to specify that if I export the project from Unity to Xcode without to embed it is working perfectly with this Plugin. 
  What can be the problem with this error ?</p>
  
  <p>Until now I tried next thing to remove the error but none helped me:</p>
  
  <ul>
  <li>I checked if I have "-ObjC" in Xcode in "Other Linker Flags" and I don't have.</li>
  <li>I removed a duplicate library (“libil2cpp.a”) from "Link Binary With Libraries" (XCODE) </li>
  <li>I changed 'No Common Blocks' from Yes to No (under Targets->Build Settings->Apple LLVM - Code Generation )</li>
  </ul>
  
  <p>At the end I have the same error.
  Here is a print screen:</p>
  
  <p><a href="https://i.stack.imgur.com/GI9lt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GI9lt.png" alt="Duplicate Symbol Errors"></a></p>
  
  <p>Thank you so much if you spend your time to read this and any idea will be helpful. </p>