gdb/python/lib/gdb/xmethod.py

   1 # Python side of the support for xmethods.
   2 # Copyright (C) 2013-2014 Free Software Foundation, Inc.
   3
   4 # This program is free software; you can redistribute it and/or modify
   5 # it under the terms of the GNU General Public License as published by
   6 # the Free Software Foundation; either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 """Utilities for defining xmethods"""
  18
  19 import gdb
  20 import re
  21 import sys
  22
  23
  24 if sys.version_info[0] > 2:
  25     # Python 3 removed basestring and long
  26     basestring = str
  27     long = int
  28
  29
  30 class XMethod(object):
  31     """Base class (or a template) for an xmethod description.
  32
  33     Currently, the description requires only the 'name' and 'enabled'
  34     attributes.  Description objects are managed by 'XMethodMatcher'
  35     objects (see below).  Note that this is only a template for the
  36     interface of the XMethodMatcher.methods objects.  One could use
  37     this class or choose to use an object which supports this exact same
  38     interface.  Also, an XMethodMatcher can choose not use it 'methods'
  39     attribute.  In such cases this class (or an equivalent) is not used.
  40
  41     Attributes:
  42         name: The name of the xmethod.
  43         enabled: A boolean indicating if the xmethod is enabled.
  44     """
  45
  46     def __init__(self, name):
  47         self.name = name
  48         self.enabled = True
  49
  50
  51 class XMethodMatcher(object):
  52     """Abstract base class for matching an xmethod.
  53
  54     When looking for xmethods, GDB invokes the `match' method of a
  55     registered xmethod matcher to match the object type and method name.
  56     The `match' method in concrete classes derived from this class should
  57     return an `XMethodWorker' object, or a list of `XMethodWorker'
  58     objects if there is a match (see below for 'XMethodWorker' class).
  59
  60     Attributes:
  61         name: The name of the matcher.
  62         enabled: A boolean indicating if the matcher is enabled.
  63         methods: A sequence of objects of type 'XMethod', or objects
  64             which have at least the attributes of an 'XMethod' object.
  65             This list is used by the 'enable'/'disable'/'info' commands to
  66             enable/disable/list the xmethods registered with GDB.  See
  67             the 'match' method below to know how this sequence is used.
  68             This attribute is None if the matcher chooses not have any
  69             xmethods managed by it.
  70     """
  71
  72     def __init__(self, name):
  73         """
  74         Args:
  75             name: An identifying name for the xmethod or the group of
  76                   xmethods returned by the `match' method.
  77         """
  78         self.name = name
  79         self.enabled = True
  80         self.methods = None
  81
  82     def match(self, class_type, method_name):
  83         """Match class type and method name.
  84
  85         In derived classes, it should return an XMethodWorker object, or a
  86         sequence of 'XMethodWorker' objects.  Only those xmethod workers
  87         whose corresponding 'XMethod' descriptor object is enabled should be
  88         returned.
  89
  90         Args:
  91             class_type: The class type (gdb.Type object) to match.
  92             method_name: The name (string) of the method to match.
  93         """
  94         raise NotImplementedError("XMethodMatcher match")
  95
  96
  97 class XMethodWorker(object):
  98     """Base class for all xmethod workers defined in Python.
  99
 100     An xmethod worker is an object which matches the method arguments, and
 101     invokes the method when GDB wants it to.  Internally, GDB first invokes the
 102     'get_arg_types' method to perform overload resolution.  If GDB selects to
 103     invoke this Python xmethod, then it invokes it via the overridden
 104     '__call__' method.
 105
 106     Derived classes should override the 'get_arg_types' and '__call__' methods.
 107     """
 108
 109     def get_arg_types(self):
 110         """Return arguments types of an xmethod.
 111
 112         A sequence of gdb.Type objects corresponding to the arguments of the
 113         xmethod are returned.  If the xmethod takes no arguments, then 'None'
 114         or an empty sequence is returned.  If the xmethod takes only a single
 115         argument, then a gdb.Type object or a sequence with a single gdb.Type
 116         element is returned.
 117         """
 118         raise NotImplementedError("XMethodWorker get_arg_types")
 119
 120     def __call__(self, *args):
 121         """Invoke the xmethod.
 122
 123         Args:
 124             args: Arguments to the method.  Each element of the tuple is a
 125                 gdb.Value object.  The first element is the 'this' pointer
 126                 value.
 127
 128         Returns:
 129             A gdb.Value corresponding to the value returned by the xmethod.
 130             Returns 'None' if the method does not return anything.
 131         """
 132         raise NotImplementedError("XMethodWorker __call__")
 133
 134
 135 class SimpleXMethodMatcher(XMethodMatcher):
 136     """A utility class to implement simple xmethod mathers and workers.
 137
 138     See the __init__ method below for information on how instances of this
 139     class can be used.
 140
 141     For simple classes and methods, one can choose to use this class.  For
 142     complex xmethods, which need to replace/implement template methods on
 143     possibly template classes, one should implement their own xmethod
 144     matchers and workers.  See py-xmethods.py in testsuite/gdb.python
 145     directory of the GDB source tree for examples.
 146     """
 147
 148     class SimpleXMethodWorker(XMethodWorker):
 149         def __init__(self, method_function, arg_types):
 150             self._arg_types = arg_types
 151             self._method_function = method_function
 152
 153         def get_arg_types(self):
 154             return self._arg_types
 155
 156         def __call__(self, *args):
 157             return self._method_function(*args)
 158
 159
 160     def __init__(self, name, class_matcher, method_matcher, method_function,
 161                  *arg_types):
 162         """
 163         Args:
 164             name: Name of the xmethod matcher.
 165             class_matcher: A regular expression used to match the name of the
 166                 class whose method this xmethod is implementing/replacing.
 167             method_matcher: A regular expression used to match the name of the
 168                 method this xmethod is implementing/replacing.
 169             method_function: A Python callable which would be called via the
 170                 'invoke' method of the worker returned by the objects of this
 171                 class.  This callable should accept the object (*this) as the
 172                 first argument followed by the rest of the arguments to the
 173                 method. All arguments to this function should be gdb.Value
 174                 objects.
 175             arg_types: The gdb.Type objects corresponding to the arguments that
 176                 this xmethod takes. It can be None, or an empty sequence,
 177                 or a single gdb.Type object, or a sequence of gdb.Type objects.
 178         """
 179         XMethodMatcher.__init__(self, name)
 180         assert callable(method_function), (
 181             "The 'method_function' argument to 'SimpleXMethodMatcher' "
 182             "__init__ method should be a callable.")
 183         self._method_function = method_function
 184         self._class_matcher = class_matcher
 185         self._method_matcher = method_matcher
 186         self._arg_types = arg_types
 187
 188     def match(self, class_type, method_name):
 189         cm = re.match(self._class_matcher, str(class_type.unqualified().tag))
 190         mm = re.match(self._method_matcher, method_name)
 191         if cm and mm:
 192             return SimpleXMethodMatcher.SimpleXMethodWorker(
 193                 self._method_function, self._arg_types)
 194
 195
 196 # A helper function for register_xmethod_matcher which returns an error
 197 # object if MATCHER is not having the requisite attributes in the proper
 198 # format.
 199
 200 def _validate_xmethod_matcher(matcher):
 201     if not hasattr(matcher, "match"):
 202         return TypeError("Xmethod matcher is missing method: match")
 203     if not hasattr(matcher, "name"):
 204         return TypeError("Xmethod matcher is missing attribute: name")
 205     if not hasattr(matcher, "enabled"):
 206         return TypeError("Xmethod matcher is missing attribute: enabled")
 207     if not isinstance(matcher.name, basestring):
 208         return TypeError("Attribute 'name' of xmethod matcher is not a "
 209                          "string")
 210     if matcher.name.find(";") >= 0:
 211         return ValueError("Xmethod matcher name cannot contain ';' in it")
 212
 213
 214 # A helper function for register_xmethod_matcher which looks up an
 215 # xmethod matcher with NAME in LOCUS.  Returns the index of the xmethod
 216 # matcher in 'xmethods' sequence attribute of the LOCUS.  If NAME is not
 217 # found in LOCUS, then -1 is returned.
 218
 219 def _lookup_xmethod_matcher(locus, name):
 220     for i in range(0, len(locus.xmethods)):
 221         if locus.xmethods[i].name == name:
 222             return i
 223     return -1
 224
 225
 226 def register_xmethod_matcher(locus, matcher, replace=False):
 227     """Registers a xmethod matcher MATCHER with a LOCUS.
 228
 229     Arguments:
 230         locus: The locus in which the xmethods should be registered.
 231             It can be 'None' to indicate that the xmethods should be
 232             registered globally. Or, it could be a gdb.Objfile or a
 233             gdb.Progspace object in which the xmethods should be
 234             registered.
 235         matcher: The xmethod matcher to register with the LOCUS.  It
 236             should be an instance of 'XMethodMatcher' class.
 237         replace: If True, replace any existing xmethod matcher with the
 238             same name in the locus.  Otherwise, if a matcher with the same name
 239             exists in the locus, raise an exception.
 240     """
 241     err = _validate_xmethod_matcher(matcher)
 242     if err:
 243         raise err
 244     if not locus:
 245         locus = gdb
 246     if locus == gdb:
 247         locus_name = "global"
 248     else:
 249         locus_name = locus.filename
 250     index = _lookup_xmethod_matcher(locus, matcher.name)
 251     if index >= 0:
 252         if replace:
 253             del locus.xmethods[index]
 254         else:
 255             raise RuntimeError("Xmethod matcher already registered with "
 256                                "%s: %s" % (locus_name, matcher.name))
 257     if gdb.parameter("verbose"):
 258         gdb.write("Registering xmethod matcher '%s' with %s' ...\n")
 259     locus.xmethods.insert(0, matcher)