ignoring duplicate libraries: ‘-lc++’

Lee young-jun

3 min readMar 10, 2024

I noticed a new warning I haven’t seen before.

I found out two solutions from Firebase repository.

-Wl,-ld_classic

First solution is appending ‘-Wl,-ld_classic’ into Other Linker Flags.

It‘s not working. why? Because I appened the flags into my project’s build settings.

When I appended the flags into settings for FirebaseCrashlytics project. The warning was disappeared.

-Xlinker -no_warn_duplicate_libraries

Second solutions is ‘-Xlinker -no_warn_duplicate_libraries’. It is also for same Flags.

Both solutions are working. But if I updates Pods?
I have to append the flags whenever ‘pod update’.

Podfile

To make the settings automatic, I decided to modify Podfile.

Target

First I opened Podfile and appended this block under installer.pods_project.targets.each do |target|.

if target.name == 'FirebaseCrashlytics'
end

With this block I can find FirebaseCrashlytics project in Pods.

If you don’t have it, add this block before last end.

post_install do |installer|
      installer.pods_project.targets.each do |target|
      end
end

Config

Second, append this block inside it.

target.build_configurations.each do |config|
end

So I can find config. This means Project’s configuration.

And add condition to find Debug configuration.

if config.name == 'Debug'
end

OTHER_LDFLAGS

Lastly, append the flags into OTHER_LDFLAGS, which indicate Other Linker Flags.

config.build_settings['OTHER_LDFLAGS'] = "$(inherited) -Wl,-ld_classic"

Now I can’t see the warning even after updating Pods!

Full Script

post_install do |installer|
  installer.pods_project.targets.each do |target|
    ...
  
    if target.name == 'FirebaseCrashlytics'
      target.build_configurations.each do |config|
        if config.name == 'Debug'
          config.build_settings['OTHER_LDFLAGS'] = "$(inherited) -Wl,-ld_classic"
        end
      end
    end
  end
end

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References