title: Duplicate interface declaration for class 'Foo'
body: <p>I was working on my program, and it seems something in the settings changed. Suddenly I have the error "Duplicate interface declaration for class 'Foo'". It mentions a header file being duplicated but there's only one copy.</p>
  
  <p>Interestingly this is only happening in debug mode, not device mode.</p>
  
  <p>Does anyone have any idea what might be wrong?</p>
  
  <p>I am using Objective-C++ and some static libraries.</p>