text: #!/usr/bin/env python
  import sys
  
  import chpl_platform, overrides
  from utils import error, memoize
  
  
  @memoize
  def get():
      platform_val = chpl_platform.get('target')
      linux = platform_val.startswith('linux64')
      osx = platform_val.startswith('darwin')
      val = overrides.get('CHPL_UNWIND')
  
      if linux:
          if val == 'libunwind':
              return 'libunwind'
          elif val == 'system':
              return 'system'
      if osx:
          if val == 'libunwind':
              error("Using CHPL_UNWIND=libunwind is not supported on Mac OS X."
                    "\nUse CHPL_UNWIND=system instead.", ValueError)
          elif val == 'system':
              return 'system'
      return 'none'
  
  
  def _main():
      unwind_val = get()
      sys.stdout.write("{0}\n".format(unwind_val))
  
  
  if __name__ == '__main__':
      _main()
  