Undefined symbols for architecture armv7? What does this error mean?

Question

I just marked all of my CocoaAsyncSocket code as non-ARC code, and it's given me these 3 errors:

Undefined symbols for architecture armv7:
  "_kCFStreamNetworkServiceTypeVoIP", referenced from:
      -[GCDAsyncSocket enableBackgroundingOnSocketWithCaveat:] in GCDAsyncSocket.o
  "_kCFStreamNetworkServiceType", referenced from:
      -[GCDAsyncSocket enableBackgroundingOnSocketWithCaveat:] in GCDAsyncSocket.o
  "_kCFStreamPropertySSLSettings", referenced from:
      -[GCDAsyncSocket maybeStartTLS] in GCDAsyncSocket.o
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Does anybody know what this means and how to fix it?

Answer 1

I think I found the solution to this, by looking in the code comments, but I now see that it's also what Mark Adams suggested above. I had the errors until I added the CFNetwork.framework under Targets->Build Phases->Link Binary With Libraries->Select CFNetwork.framework

Answer 2

It means that some code you are compiling is referencing the constants "kCFStreamNetworkServiceTypeVoIP", "kCFStreamNetworkServiceType", and "kCFStreamPropertySSLSettings", but that those constants weren't found when it tried to link your code with the libraries it uses.

Unfortunately there's a bunch of reasons this could be:

• You could have misspelled them
• They could be #ifdef'd out for that architecture
• You might not be linking the correct librar(y, ies)
• They could be marked as having 'hidden' visibility so that they can only be used in the declaring library
• Probably other reasons

You can use 'nm' to poke at the exported symbols from the binary of a library, and 'otool -L' to check which libraries your binary is linking.