title: Linking error with iOS app with cross-referencing multiple static libraries
body: <p>I'm splitting up an Xcode iPhone project into multiple smaller projects for code reuse.
  The structure looks like this:</p>
  
  <pre><code>+------------+
  |    App     |
  +------------+
        |
        +------------------+
        |                  |
  +--------------+ +--------------+
  | Static Lib A | | Static Lib B |
  +--------------+ +--------------+
          |                |
          +----------------+
                  |
           +--------------+  +----------------+
           | Static Lib Z |--| Static Lib KAL |
           +--------------+  +----------------+
  </code></pre>
  
  <p>Everything compiles correctly, but as soon as the app is linked, the linker cannot find 2 symbols of the KAL (the open source calendar lib) library.
  Each library has a cross-reference and all the archives are added to the "Link binary with libraries" build phase.</p>
  
  <p>The errors are:</p>
  
  <p>Undefined symbols:<br>
    "_OBJC_CLASS_$_KalViewController", referenced from:<br>
        objc-class-ref-to-KalViewController in libA.a(AViewController.o)<br>
    "_OBJC_CLASS_$_KalDate", referenced from:<br>
        objc-class-ref-to-KalDate in libA.a(AViewController.o)<br>
  ld: symbol(s) not found<br>
  collect2: ld returned 1 exit status  </p>
  
  <p>I'm using a class from LibZ in LibA's AViewController which in his turn is using a class in LibKAL.</p>
  
  <p>PS: the separation of A and B is simply because not every build of App needs the functionality provided by the two.</p>