def Refresh():
    """looks up symbols within the inferior and caches their names / values.

    If debugging information is only partial, this method does its best to
    find as much information as it can, validation can be done using
    IsSymbolFileSane.
    """
    try:
      GdbCache.DICT = gdb.lookup_type('PyDictObject').pointer()
      GdbCache.TYPE = gdb.lookup_type('PyTypeObject').pointer()
    except gdb.error as err:
      # The symbol file we're using doesn't seem to provide type information.
      pass
    interp_head_name = GdbCache.FuzzySymbolLookup('interp_head')
    if interp_head_name:
      GdbCache.INTERP_HEAD = gdb.parse_and_eval(interp_head_name)
    else:
      # As a last resort, ask the inferior about it.
      GdbCache.INTERP_HEAD = gdb.parse_and_eval('PyInterpreterState_Head()')
    GdbCache.PENDINGBUSY = GdbCache.FuzzySymbolLookup('pendingbusy')
    GdbCache.PENDINGCALLS_TO_DO = GdbCache.FuzzySymbolLookup('pendingcalls_to_do') 

def get_reg(self, name):
        if name == "efl" or name == "eflags":
            value = 0
            for f in self.efl_map:
                if f in str(gdb.parse_and_eval("$eflags")):
                    value |= self.efl_map[f]
            return value
        else:
            reg_val = gdb.parse_and_eval("$" + name)
            if reg_val.type.code == gdb.TYPE_CODE_UNION: #SSE
                value = 0
                for i in range(8):
                    try:
                        v = int(reg_val["v8_int32"][i].cast(self.long_type)) << i * 32
                    except gdb.error:
                        break
                    value |= v
                return value
            else:
                return int(reg_val.cast(self.long_type)) 

def print_stack(self):
        def repr_stack(stack, sp):
            for line in stack.splitlines():
                addr, values = line.split(':')
                values = values.split()
                if addr == sp:
                    top = values[0]
                    rest = ' '.join(values[1:])
                    line = '==> {} {} {}'.format(
                        red(addr), red(top, back='green'),
                        yellow(rest))
                else:
                    line = '    {} {}'.format(
                        red(addr), cyan(' '.join(values)))
                print(line)
        try:
            stack = self.get_stack()
        except IOError as error:
            self.logger.error(error)
        else:
            repr_stack(stack, self.get_reg(self.env.SP))
            print() 

def print_asm(self):
        command = 'u {} l10'.format(self.env.IP)
        try:
            asms = self.execute(command)
        except self.pykd.DbgException as error:
            self.logger.error(error)
        else:
            ip = self.pykd.reg(self.env.IP)
            for line in asms.splitlines()[1:]:
                try:
                    address, opcode, ins = line.split(None, 2)
                except ValueError as error:
                    print(red('{}: {}'.format(line, error)))
                else:
                    line = '{:25} {:25} {}'.format(
                        cyan(address, res=False),
                        yellow(opcode, res=False), red(ins))
                    if int(address, 16) == ip:
                        print(Back.GREEN + line)
                    else:
                        print(line) 

def __init__(self, name, controller, stage, no_rec):
        self.name = name
        self.no_rec = no_rec
        self.stage = stage
        self.depth = 0
        self.plugin = controller.subcommand_parsers[self.plugin_name].plugin
        try:
            i = gdb.execute("x/x %s" % self.name, to_string=True).split()[0]
        except gdb.error as e:
            controller.gdb_print("%s cannot set breakpoint for %s\n" % (e,
                                                                        self.name),
                                 self.plugin.name)
            return
        i = re.sub(':', '', i)
        self.fnloc = long(i, 0)
        spec = "*(0x%x)" % self.fnloc
        self.line = re.sub(":",
                           "::",
                           pure_utils.addr2line(self.fnloc,
                                                stage.elf)) if self.plugin._sourceinfo else ""
        gdb_tools.TargetBreak.__init__(self, spec, controller, True, stage) 

def invoke(self, arg, from_tty):
        result = gdb.execute('mo leak full', False, True)
        while result.find('are definitely lost in loss record') is -1:
            try:
                gdb.execute('step', to_string = True)  # QUIETLY step
            except gdb.error:
                print('error while stepping')  # BOZO handle
                break
            result = gdb.execute('mo leak full', False, True)
        print('loss report:\n%s'%result)
        print('leak first noticed at:\n')
        gdb.execute('bt') 

def invoke (self, arg, from_tty):
        try:
            print(FramePrinter(gdb.newest_frame()))
        except gdb.error:
            print("gdb got an error. Maybe we are not currently running?") 

def FuzzySymbolLookup(symbol_name):
    try:
      gdb.parse_and_eval(symbol_name)
      return symbol_name
    except gdb.error as err:
      # No symbol in current context. We might be dealing with static symbol
      # disambiguation employed by compilers. For example, on debian's current
      # python build, the 'interp_head' symbol (which we need) has been renamed
      # to 'interp_head.42174'. This mangling is of course compiler-specific.
      # We try to get around it by using gdb's built-in regex support when
      # looking up variables
      # Format:
      # All variables matching regular expression "<symbol_name>":
      #
      # File <source_file>:
      # <Type><real_symbol_name>;
      #
      # Non-debugging symbols:
      # 0x<address>  <real_symbol_name>

      # We're only interested in <real_symbol_name>. The latter part
      # ('Non-debugging symbols') is only relevant if debugging info is partial.
      listing = gdb.execute('info variables %s' % symbol_name, to_string=True)
      # sigh... We want whatever was in front of ;, but barring any *s.
      # If you are a compiler dev who mangles symbols using ';' and '*',
      # you deserve this breakage.
      mangled_name = (re.search(r'\**(\S+);$', listing, re.MULTILINE)
                      or re.search(r'^0x[0-9a-fA-F]+\s+(\S+)$', listing, re.MULTILINE))
      if not mangled_name:
        raise err
      try:
        gdb.parse_and_eval('\'%s\'' % mangled_name.group(1))
        return '\'%s\'' % mangled_name.group(1)
      except gdb.error:
        # We could raise this, but the original exception will likely describe
        # the problem better
        raise err 

def Attach(self, position):
    pos = [position[0], position[1], None]
    # Using ExecuteRaw here would throw us into an infinite recursion, we have
    # to side-step it.
    gdb.execute('attach ' + str(pos[0]), to_string=True)

    try:
      # Shortcut for handling single-threaded python applications if we've got
      # the right symbol file loaded already
      GdbCache.Refresh()
      self.selected_tstate = self._ThreadPtrs(pos)[0]
    except gdb.error:
      pass 

def show_error(e):
    """
    Decorate a function so it masks tracebacks when debug=False
    """
    if gxf.basics.debug:
        # Gdb can't give us a full traceback. If this is a tty
        # or if error occured during argument parsing we do it.
        print("%s" % (traceback.format_exc(),), end="")
    print(e)
    if not gxf.basics.debug:
        print("    If that's weird check `python gxf.basics.debug = True`") 

def get_stack(self):
        wide = '32wx' if self.env.BITS == 32 else '16gx'
        command = 'x/{} ${}'.format(wide, self.env.SP)
        try:
            output = self.execute(command)
        except gdb.error:
            raise IOError()
        else:
            return output 

def get_pc_asm(self):
        command = 'x/i ${}'.format(self.env.IP)
        try:
            output = self.execute(command)
        except self.gdb.MemoryError as error:
            self.logger.debug('Original error: %s', error)
            sp = self.get_reg(self.env.SP)
            pattern = error.args[0].split()[-1]
            self.logger.debug('sp: %s pattern: %s', sp, pattern)
            raise IOError(sp, pattern)
        else:
            return output 

def get_reg(self, name):
        command = 'info registers {}'.format(name)
        try:
            output = self.execute(command)
        except gdb.error as error:
            self.logger.error(error)
            return None
        else:
            return output.split()[-2] 

def step(self):
        command = 'stepi'
        try:
            self.execute(command)
        except self.gdb.MemoryError as error:
            self.logger.error(error)
            raise IOError 

def get_pc_asm(self):
        self.logger.debug('ip: %s', self.get_reg(self.env.IP))
        try:
            output = self.pykd.disasm().opmnemo()
        except self.pykd.DbgException as error:
            self.logger.error('Original error: %s', error)
            pattern = self.get_reg(self.env.IP)
            sp = self.get_reg(self.env.SP)
            self.logger.debug('sp: %s pattern: %s', sp, pattern)
            raise IOError(sp, pattern)
        else:
            return output 

def print_stack(self):
        command = 'dd {}-0x40'.format(self.env.SP)
        try:
            values = self.execute(command)
        except self.pykd.DbgException as error:
            self.logger.error(error)
        else:
            sp = self.pykd.reg(self.env.SP)
            for line in values.splitlines():
                if int(line.split()[0], 16) == sp:
                    print(red(line))
                else:
                    print(cyan(line)) 

def print_reg(self):
        try:
            ip = hex(self.pykd.getIP()).strip('L')
            sp = hex(self.pykd.getSP())
            bp = self.get_reg(self.env.BP)
        except self.pykd.DbgException as error:
            self.logger.error(error)
        else:
            print('{}: {} {}: {} {}: {}'.format(
                self.env.IP.upper(), red(ip),
                self.env.SP.upper(), yellow(sp),
                self.env.BP.upper(), cyan(bp))) 

def go(self, args):
        if self.gone:
            return
        self.gone = True
        gdb.events.exited.connect(self.gdb_exit)
        self.finalize(args)
        if not self.run_standalone:
            stage = self.stage_order[0]
        else:
            class LocalStage():
                def __init__(self, elf):
                    self.elf = elf
                    self.entrypoint = pure_utils.get_entrypoint(elf)
                    self.exitpc = -1
                    self.stagename = "local"
            stage = LocalStage(gdb.current_progspace().filename)
        s = self.prepare_stage(stage, False)
        self.set_mode()
        stage_entered = False
        try:
            if self.get_reg_value('pc', True) == s.breakpoint.companion.addr:
                self.gdb_print("First stage already entered\n")
                stage_entered = True
        except gdb.error:
            pass
        if stage_entered and not self.run_standalone:
            self.gdb_print("Calling breakpoint hook\n")
            s.stop()
            s.continue_stage()

        self.gdb_print("ready to go\n")
        if not args.prepare_only:
            if args.run_not_cont:
                gdb.execute("r")
            else:
                gdb.execute("c") 

def settable(cls, name, c):
        try:
            i = gdb.execute("x/x %s" % name, to_string=True).split()[0]
        except gdb.error as e:
            #c.gdb_print("%s cannot set breakpoint for %s\n" % (e,
             #                                                           name), "calltrace")
            return False
        return True 

def _breakInFunctions(node):
        breakpoints = []

        # If the child is an "unexposed expression" find its child.
        if node.kind.is_unexposed():
            # Flag error if none or more than one
            if len(list(node.get_children())) != 1:
                raise RuntimeError('Unexposed expression at line %d has more than one child, unsure how to handle'%node.location.line)
            node = next(node.get_children())

        if node.kind.is_unexposed():
            raise RuntimeError('parent and child AST nodes both unexposed at line %d'%node.location.line)

        if node.kind == CursorKind.CALL_EXPR:
            # check for member function call
            body = StepUser._getMemberBody(node)
            if body is None:
                # maybe it's a plain function
                body = StepUser._getFunctionBody(node)

            if body:
                # implement breakpoint pattern match here:
                if re.match(StepUser.stepRegex, getFuncName(body.semantic_parent)):
                    body = None
            else:
                # try lambda
                body = StepUser._getLambdaBody(node)

            if body:
                first_stmt = next(body.get_children())
                breakpoints.append((first_stmt.location.file.name, first_stmt.location.line))

            # walk through the children
            for arg in node.get_arguments():
                breakpoints = breakpoints + StepUser._breakInFunctions(arg)

        if node.kind == CursorKind.DECL_REF_EXPR:
            # probably an object argument
            # check type against regex
            decl = node.referenced.type.get_declaration()
            if not re.match(StepUser.stepRegex, getFuncName(decl)):
                # locate member function bodies and breakpoint
                members = [next(x.get_children()) for x in StepUser._getMethodBodies(decl)]
                breakpoints = breakpoints + [(x.location.file.name, x.location.line) for x in members]

        return breakpoints 

def EnsureGdbPosition(self, pid, tid, frame_depth):
    """Make sure our position matches the request.

    Args:
      pid: The process ID of the target process
      tid: The python thread ident of the target thread
      frame_depth: The 'depth' of the requested frame in the frame stack
    Raises:
      PositionUnavailableException: If the requested process, thread or frame
          can't be found or accessed.
    """
    position = [pid, tid, frame_depth]
    if not pid:
      return
    if not self.IsAttached():
      try:
        self.Attach(position)
      except gdb.error as exc:
        raise PositionUnavailableException(exc.message)
    if gdb.selected_inferior().pid != pid:
      self.Detach()
      try:
        self.Attach(position)
      except gdb.error as exc:
        raise PositionUnavailableException(exc.message)

    if tid:
      tstate_head = GdbCache.INTERP_HEAD['tstate_head']
      for tstate in self._IterateChainedList(tstate_head, 'next'):
        if tid == tstate['thread_id']:
          self.selected_tstate = tstate
          break
      else:
        raise PositionUnavailableException('Thread %s does not exist.' %
                                           str(tid))
      stack_head = self.selected_tstate['frame']
      if frame_depth is not None:
        frames = list(self._IterateChainedList(stack_head, 'f_back'))
        frames.reverse()
        try:
          self.selected_frame = frames[frame_depth]
        except IndexError:
          raise PositionUnavailableException('Stack is not %s frames deep' %
                                             str(frame_depth + 1)) 

def IsSymbolFileSane(self, position):
    """Performs basic sanity check by trying to look up a bunch of symbols."""
    pos = [position[0], None, None]
    self.EnsureGdbPosition(*pos)
    try:
      if GdbCache.DICT and GdbCache.TYPE and GdbCache.INTERP_HEAD:
        # pylint: disable=pointless-statement
        tstate = GdbCache.INTERP_HEAD['tstate_head']
        tstate['thread_id']
        frame = tstate['frame']
        frame_attrs = ['f_back',
                       'f_locals',
                       'f_localsplus',
                       'f_globals',
                       'f_builtins',
                       'f_lineno',
                       'f_lasti']
        for attr_name in frame_attrs:
          # This lookup shouldn't throw an exception
          frame[attr_name]
        code = frame['f_code']
        code_attrs = ['co_name',
                      'co_filename',
                      'co_nlocals',
                      'co_varnames',
                      'co_lnotab',
                      'co_firstlineno']
        for attr_name in code_attrs:
          # Same as above, just checking whether the lookup succeeds.
          code[attr_name]
        # if we've gotten this far, we should be fine, as it means gdb managed
        # to look up values for all of these. They might still be null, the
        # symbol file might still be bogus, but making gdb check for null values
        # and letting it run into access violations is the best we can do. We
        # haven't checked any of the python types (dict, etc.), but this symbol
        # file seems to be useful for some things, so let's give it our seal of
        # approval.
        return True
    except gdb.error:
      return False
    # looks like the initial GdbCache refresh failed. That's no good.
    return False