text: # Copyright (C) 2015-2019 Free Software Foundation, Inc.
  
  # This program is free software; you can redistribute it and/or modify
  # it under the terms of the GNU General Public License as published by
  # the Free Software Foundation; either version 3 of the License, or
  # (at your option) any later version.
  #
  # This program is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU General Public License for more details.
  #
  # You should have received a copy of the GNU General Public License
  # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  
  """Unwinder class and register_unwinder function."""
  
  import gdb
  
  
  class Unwinder(object):
      """Base class (or a template) for frame unwinders written in Python.
  
      An unwinder has a single method __call__ and the attributes
      described below.
  
      Attributes:
          name: The name of the unwinder.
          enabled: A boolean indicating whether the unwinder is enabled.
      """
  
      def __init__(self, name):
          """Constructor.
  
          Args:
              name: An identifying name for the unwinder.
          """
          self.name = name
          self.enabled = True
  
      def __call__(self, pending_frame):
          """GDB calls this method to unwind a frame.
  
          Arguments:
              pending_frame: gdb.PendingFrame instance.
  
          Returns:
              gdb.UnwindInfo instance.
          """
          raise NotImplementedError("Unwinder __call__.")
  
  
  def register_unwinder(locus, unwinder, replace=False):
      """Register unwinder in given locus.
  
      The unwinder is prepended to the locus's unwinders list. Unwinder
      name should be unique.
  
      Arguments:
          locus: Either an objfile, progspace, or None (in which case
                 the unwinder is registered globally).
          unwinder: An object of a gdb.Unwinder subclass
          replace: If True, replaces existing unwinder with the same name.
                   Otherwise, raises exception if unwinder with the same
                   name already exists.
  
      Returns:
          Nothing.
  
      Raises:
          RuntimeError: Unwinder name is not unique
          TypeError: Bad locus type
      """
      if locus is None:
          if gdb.parameter("verbose"):
              gdb.write("Registering global %s unwinder ...\n" % unwinder.name)
          locus = gdb
      elif isinstance(locus, gdb.Objfile) or isinstance(locus, gdb.Progspace):
          if gdb.parameter("verbose"):
              gdb.write("Registering %s unwinder for %s ...\n" %
                        (unwinder.name, locus.filename))
      else:
          raise TypeError("locus should be gdb.Objfile or gdb.Progspace or None")
  
      i = 0
      for needle in locus.frame_unwinders:
          if needle.name == unwinder.name:
              if replace:
                  del locus.frame_unwinders[i]
              else:
                  raise RuntimeError("Unwinder %s already exists." %
                                     unwinder.name)
          i += 1
      locus.frame_unwinders.insert(0, unwinder)
      gdb.invalidate_cached_frames()
  