new_contents: """
  Load into LLDB with:
  script import lldbDataFormatters
  type synthetic add -x "^llvm::SmallVectorImpl<.+>$" -l lldbDataFormatters.SmallVectorSynthProvider
  """
  
  # Pretty printer for llvm::SmallVector/llvm::SmallVectorImpl
  class SmallVectorSynthProvider:
      def __init__(self, valobj, dict):
          self.valobj = valobj;
          self.update() # initialize this provider
  
      def num_children(self):
          begin = self.begin.GetValueAsUnsigned(0)
          end = self.end.GetValueAsUnsigned(0)
          return (end - begin)/self.type_size
  
      def get_child_index(self, name):
          try:
              return int(name.lstrip('[').rstrip(']'))
          except:
              return -1;
  
      def get_child_at_index(self, index):
          # Do bounds checking.
          if index < 0:
              return None
          if index >= self.num_children():
              return None;
  
          offset = index * self.type_size
          return self.begin.CreateChildAtOffset('['+str(index)+']',
                                                offset, self.data_type)
  
      def get_type_from_name(self):
          import re
          name = self.valobj.GetType().GetName()
          # This class works with both SmallVectors and SmallVectorImpls.
          res = re.match("^(llvm::)?SmallVectorImpl<(.+)>$", name)
          if res:
              return res.group(2)
          res = re.match("^(llvm::)?SmallVector<(.+), \d+>$", name)
          if res:
              return res.group(2)
          return None
  
      def update(self):
          self.begin = self.valobj.GetChildMemberWithName('BeginX')
          self.end = self.valobj.GetChildMemberWithName('EndX')
          data_type = self.get_type_from_name()
          # FIXME: this sometimes returns an invalid type.
          self.data_type = self.valobj.GetTarget().FindFirstType(data_type)
          self.type_size = self.data_type.GetByteSize()
  
subject: Add an LLDB data formatter script for llvm::SmallVector, maybe this is helpful to someone else.