It's one of benefits that we can have with full C++11. It looks great! But we need to be careful because it doesn't work well on one of platforms. In this case, XCode 9.2 doesn't seem to be able to build it.

From a SO thread, XCode 8 and later should build this code so our CI using XCode 9.2 might have to handle this but it fails to build it. I think this is because of ios deployment target set by podspec.

  s.ios.deployment_target = '7.0'
  s.osx.deployment_target = '10.9'
  s.tvos.deployment_target = '10.0'

@mhaidrygoog Can you update it to 9.0 to see it's working?

@muxi Do you think it's feasible to bump it to 9.0 so that we can use thread_local in our code? I think iOS 9 is pretty old enough so that most of apple devices support it. (ref)

side-note: Another resource is worth reading: ThreadLocal.

No we can't bump it to 9.0. At the very least, Firestore supports 8.0 and depends on gRPC.

There could be other 3rd party users in the wild that support ever older versions

@muxi Thank you for the answer. Disappointing but we keep some workaround for at least Apple. Abseil also does the same thing for Apple because thread_local is not considered available.

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