LLVM Debugger shows "Summary Unavailable" for complex c++ structs

I'm using the GLM http://glm.g-truc.net/0.9.8/index.htmlmath library for an opengl game in c++. Xcode's LLVM debugger simply will not reliably show summaries of the basic data types (glm::dvec2, glm::dmat4, etc). Instead, I get "Summary Unavailable" and when I click the disclosure triangle next to the data item, nothing is revealed. If I use the LLVM repl, e.g., I type "e some_vec" I get output like: "(glm::dvec2) $0 = {}" - which is not helpful.

I've tried setting custom summary formats.

~/Library/Developer/Xcode/UserData/Debugger/CustomDataFormatters

      <SummaryFormatter
         formatString = "({$VAR.x},{$VAR.y})"
         type = "glm::dvec2">
      </SummaryFormatter>

No luck!

Any suggestions?

Thanks,