Problem Description

When building Flutter iOS applications, you may encounter the following error:

Error (Xcode): unsupported option '-G' for target 'arm64-apple-ios10.0'

This error can be particularly frustrating as it may appear to be network-related, but connectivity is rarely the actual cause of this issue.

Root Cause

This error is caused by the BoringSSL-GRPC library, which is a common dependency in Flutter iOS projects. The issue occurs when the BoringSSL library attempts to use compiler flags that are incompatible with certain iOS target architectures, specifically when targeting ARM64 devices with iOS 10.0 or later. The error is not related to internet connectivity despite what many online resources suggest. Changing network connections will not resolve this issue.

Solution

To fix this error, you need to modify your project's Podfile to remove the problematic compiler flags from the BoringSSL-GRPC target.

1. Locate Your Podfile
   • Navigate to your Flutter project's iOS directory:
   • yourproject/ios/Podfile
     
2. Add the Fix to Your Podfile
   • Find the post_install section in your Podfile, specifically the line:

     • installer.pods_project.targets.each do |target|

   • Add the following code immediately after this line:

     • if target.name == 'BoringSSL-GRPC'
         target.source_build_phase.files.each do |file|
           if file.settings && file.settings['COMPILER_FLAGS']
             flags = file.settings['COMPILER_FLAGS'].split
             flags.reject! { |flag| flag == '-GCC_WARN_INHIBIT_ALL_WARNINGS' }
             file.settings['COMPILER_FLAGS'] = flags.join(' ')
           end
         end
       end

3. Complete Podfile Example
   • Your post_install section should look similar to this:

   • post_install do |installer|
       installer.pods_project.targets.each do |target|
         # Add the BoringSSL-GRPC fix here
         if target.name == 'BoringSSL-GRPC'
           target.source_build_phase.files.each do |file|
             if file.settings && file.settings['COMPILER_FLAGS']
               flags = file.settings['COMPILER_FLAGS'].split
               flags.reject! { |flag| flag == '-GCC_WARN_INHIBIT_ALL_WARNINGS' }
               file.settings['COMPILER_FLAGS'] = flags.join(' ')
             end
           end
         end
         
         # Other Flutter build settings
         flutter_additional_ios_build_settings(target)
       end
     end

     
     

4. Clean and Rebuild
   • After modifying your Podfile:

   • # Complete project cleanup
     flutter clean
     rm -rf ios/Podfile.lock
     rm -rf ios/Pods
     rm -rf ios/Runner.xcworkspace
     rm -rf ios/.symlinks
     
     # Fresh rebuild
     flutter pub get
     cd ios && pod install
     cd .. && flutter build ios --no-codesign

Why This Solution Works

The fix works by:

1. Targeting the specific problematic library: BoringSSL-GRPC
2. Removing incompatible compiler flags: Specifically the -GCC_WARN_INHIBIT_ALL_WARNINGS flag that causes conflicts with ARM64 targets
3. Preserving other necessary flags: Only removing the problematic flag while keeping others intact

Troubleshooting

If you continue to experience issues:

1. Verify Xcode version compatibility with your Flutter version
2. Check for conflicting pods that might also modify compiler flags
3. Ensure your iOS deployment target is compatible with your dependencies

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