I deleted all reference to GoogleMobileAdsSDKiOS-7.1 from my project and added 7.4.1. When I ran app on simulator everything works fine but when running on device I get App Mach-O Linker Error.
duplicate symbol l017 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS- 7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADAdNetworkJavaScriptAdViewDelegate.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADRewardBasedVideoAd+Mediation.o)
duplicate symbol l018 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADMRAIDPicture.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADRewardBasedVideoAd+Mediation.o)
duplicate symbol l016 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADBannerAdViewDelegate.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADAdAppViewController.o)
duplicate symbol l021 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADLocation.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADNativeAdAttribution.o)
duplicate symbol l016 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADBannerAdViewDelegate.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADNativeAdImage.o)
duplicate symbol l005 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADMWebViewRenderedChecker.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADAdViewRenderedChecker.o)
duplicate symbol l006 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADMWebViewRenderedChecker.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADAdViewRenderedChecker.o)
duplicate symbol l012 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADPinger.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADCSIReporter.o)
duplicate symbol l016 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADBannerAdViewDelegate.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADAdNetworkJavaScriptAdViewDelegate.o)
duplicate symbol l021 in:
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADLocation.o)
/Users/ib/Desktop/Monster GoogleAds7.4.1/GoogleMobileAdsSdkiOS-7.4.1/GoogleMobileAds.framework/GoogleMobileAds(GADMRAIDResizeProperties.o)
ld: 21 duplicate symbols for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I know this error means I have duplicates of the above but my problem is where in Xcode 6.1 do I find these duplicates so I can delete them? I've looked in info.plist, build settings, can't find any duplicates. Where in Xcode 6.1 are the duplicates located ?
Try remove the "-ObjC" linker flag from the "Other Linker Flags" section of build settings.
Had the same issue, here is how I "solved" it: simply give up on 7.4.1
The issue goes away if you go back to an earlier version: https://dl.google.com/googleadmobadssdk/googlemobileadssdkios-7.3.1.zip
I do not know if I did anything wrong, but I'll take a wild guess and put the blame on Google on this one. It is likely nobody bothered testing the arm64 build of this framework.
No matter how much time I spent trying to tweak it it would always fail, while for some reason the 32bits version would work fine.
Since you need both 32 and 64 to work in order to push an ipa to the iTunes store, we'll have to do with the previous version.
Hope this will save other the pain I had to go through.
I have a feeling you're somehow still getting the old framework linked into your app in addition to the new one, but I'm not certain of that. Take a look at the build log and see what exact ld command is being used to link things together.
来源：https://stackoverflow.com/questions/32159983/duplicate-symbols-for-architecture-arm64-xcode-error