[RFC] Debug Methods in GDB Python

Siva Chandra sivachandra@google.com
Mon Jun 17 19:10:00 GMT 2013


Hi all,

Took me longer than I had expected I but could spend some time last
couple of weeks and address all of Tom's comments from last time. Like
before, I do not have docs or tests as the Python side API is largely
un-reviewed I guess. However, I have put in code comments in the
latest version. The patch is attached and the ChangeLog is as below:

2013-06-17  Siva Chandra Reddy  <sivachandra@google.com>

        * Makefile.in: Add entries for new files
        * data-directory/Makefile.in: Add entery for new Python file
        * eval.c: Use new 'find_overload_match' signature.
        * ext-function.c: Support for working with functions/methods
        defined in an extension language.
        * ext-function.h: Support for working with functions/methods
        defined in an extension language.
        * python/lib/gdb/debugmethods.py: Python side of the support
        for debug methods in Python.
        * python/py-debugmethods.c: C side of the support for debug
        methods in Python.
        * python/py-objfile.c: Add 'debug_methods' attribute to
        gdb.Objfile.
        * python/python-internal.h: Add new function
        gdb.enable_debug_methods to the Python module 'gdb'.
        * python/python.c: Add new function gdb.enable_debug_methods to
        the Python module 'gdb'.
        * python/python.h: Add declarations of new functions.
        * valarith.c: Use methods defined in extension languages.
        * valops.c: Use methods defined in extension languages.
        * value.h: New signature for 'find_overload_match'.

Thanks,
Siva Chandra
-------------- next part --------------
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index a6336a2..0b643e7 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -282,6 +282,7 @@ SUBDIR_PYTHON_OBS = \
 	py-breakpoint.o \
 	py-cmd.o \
 	py-continueevent.o \
+	py-debugmethods.o \
 	py-event.o \
 	py-evtregistry.o \
 	py-evts.o \
@@ -317,6 +318,7 @@ SUBDIR_PYTHON_SRCS = \
 	python/py-breakpoint.c \
 	python/py-cmd.c \
 	python/py-continueevent.c \
+	python/py-debugmethods.c \
 	python/py-event.c \
 	python/py-evtregistry.c \
 	python/py-evts.c \
@@ -725,7 +727,7 @@ SFILES = ada-exp.y ada-lang.c ada-typeprint.c ada-valprint.c ada-tasks.c \
 	dwarf2expr.c dwarf2loc.c dwarf2read.c dwarf2-frame.c \
 	dwarf2-frame-tailcall.c \
 	elfread.c environ.c eval.c event-loop.c event-top.c \
-	exceptions.c expprint.c \
+	exceptions.c expprint.c ext-function.c \
 	f-exp.y f-lang.c f-typeprint.c f-valprint.c filesystem.c \
 	findcmd.c findvar.c frame.c frame-base.c frame-unwind.c \
 	gdbarch.c arch-utils.c gdb_bfd.c gdb_obstack.c \
@@ -825,7 +827,7 @@ rs6000-tdep.h rs6000-aix-tdep.h \
 common/gdb_locale.h common/gdb_dirent.h arch-utils.h trad-frame.h gnu-nat.h \
 language.h nbsd-tdep.h solib-svr4.h \
 macroexp.h ui-file.h regcache.h tracepoint.h i386-tdep.h \
-inf-child.h p-lang.h event-top.h gdbtypes.h user-regs.h \
+inf-child.h p-lang.h event-top.h ext-function.h gdbtypes.h user-regs.h \
 regformats/regdef.h config/alpha/nm-osf3.h  config/i386/nm-i386gnu.h \
 config/i386/nm-fbsd.h \
 config/nm-nto.h config/sparc/nm-sol2.h config/nm-linux.h \
@@ -944,7 +946,7 @@ COMMON_OBS = $(DEPFILES) $(CONFIG_OBS) $(YYOBJ) \
 	inferior.o osdata.o gdb_usleep.o record.o record-full.o gcore.o \
 	gdb_vecs.o jit.o progspace.o skip.o probe.o \
 	common-utils.o buffer.o ptid.o gdb-dlfcn.o common-agent.o \
-	format.o registry.o btrace.o record-btrace.o
+	format.o registry.o btrace.o record-btrace.o ext-function.o
 
 TSOBS = inflow.o
 
@@ -2124,6 +2126,10 @@ py-continueevent.o: $(srcdir)/python/py-continueevent.c
 	$(COMPILE) $(PYTHON_CFLAGS) $(srcdir)/python/py-continueevent.c
 	$(POSTCOMPILE)
 
+py-debugmethods.o: $(srcdir)/python/py-debugmethods.c
+	$(COMPILE) $(PYTHON_CFLAGS) $(srcdir)/python/py-debugmethods.c
+	$(POSTCOMPILE)
+
 py-event.o: $(srcdir)/python/py-event.c
 	$(COMPILE) $(PYTHON_CFLAGS) $(srcdir)/python/py-event.c
 	$(POSTCOMPILE)
diff --git a/gdb/data-directory/Makefile.in b/gdb/data-directory/Makefile.in
index dec6207..212b957 100644
--- a/gdb/data-directory/Makefile.in
+++ b/gdb/data-directory/Makefile.in
@@ -60,6 +60,7 @@ PYTHON_FILES = \
 	gdb/types.py \
 	gdb/printing.py \
 	gdb/prompt.py \
+	gdb/debugmethods.py \
 	gdb/command/__init__.py \
 	gdb/command/frame_filters.py \
 	gdb/command/type_printers.py \
diff --git a/gdb/eval.c b/gdb/eval.c
index 539489f..0444311 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -22,6 +22,7 @@
 #include "symtab.h"
 #include "gdbtypes.h"
 #include "value.h"
+#include "ext-function.h"
 #include "expression.h"
 #include "target.h"
 #include "frame.h"
@@ -1592,7 +1593,7 @@ evaluate_subexp_standard (struct type *expect_type,
                                NON_METHOD, /* not method */
                                NULL, NULL, /* pass NULL symbol since
 					      symbol is unknown */
-                               NULL, &symp, NULL, 0);
+                               NULL, &symp, NULL, NULL, 0);
 
           /* Now fix the expression being evaluated.  */
           exp->elts[save_pos1 + 2].symbol = symp;
@@ -1622,11 +1623,12 @@ evaluate_subexp_standard (struct type *expect_type,
 	      /* Language is C++, do some overload resolution before
 		 evaluation.  */
 	      struct value *valp = NULL;
+              struct ext_fn_descriptor *ext_fnp = NULL;
 
 	      (void) find_overload_match (&argvec[1], nargs, tstr,
 	                                  METHOD, /* method */
 					  &arg2,  /* the object */
-					  NULL, &valp, NULL,
+					  NULL, &valp, NULL, &ext_fnp,
 					  &static_memfuncp, 0);
 
 	      if (op == OP_SCOPE && !static_memfuncp)
@@ -1636,9 +1638,26 @@ evaluate_subexp_standard (struct type *expect_type,
 			   "`this' pointer"),
 			 function_name);
 		}
-	      argvec[1] = arg2;	/* the ``this'' pointer */
-	      argvec[0] = valp;	/* Use the method found after overload
-				   resolution.  */
+
+              if (ext_fnp)
+                {
+                  if (ext_fn_is_method (ext_fnp))
+                    {
+                      struct value *ret_val;
+
+                      ret_val = ext_fn_invoke_method (ext_fnp, arg2, argvec + 2,
+                                                      nargs - 1);
+                      if (ret_val == NULL)
+                        error (_("Error invoking debug method for method %s."),
+                               tstr);
+
+                      return ret_val;
+                    }
+                }
+
+              argvec[1] = arg2;     /* the ``this'' pointer */
+              argvec[0] = valp;     /* Use the method found after overload
+                                       resolution.  */
 	    }
 	  else
 	    /* Non-C++ case -- or no overload resolution.  */
@@ -1697,7 +1716,7 @@ evaluate_subexp_standard (struct type *expect_type,
 					  NULL,        /* no need for name */
 	                                  NON_METHOD,  /* not method */
 	                                  NULL, function, /* the function */
-					  NULL, &symp, NULL, no_adl);
+					  NULL, &symp, NULL, NULL, no_adl);
 
 	      if (op == OP_VAR_VALUE)
 		{
diff --git a/gdb/ext-function.c b/gdb/ext-function.c
new file mode 100644
index 0000000..bf30798
--- /dev/null
+++ b/gdb/ext-function.c
@@ -0,0 +1,172 @@
+/* Support for functions defined in extension languages.
+
+   Copyright (C) 2013 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#include "defs.h"
+#include "cleanups.h"
+#include "ext-function.h"
+
+#include "gdb_assert.h"
+#include "vec.h"
+
+struct ext_fn_descriptor
+  {
+    struct ext_lang *lang;
+
+    int is_method;
+
+    void *ext_object;
+  };
+
+typedef struct ext_lang *ext_lang_p;
+DEF_VEC_P (ext_lang_p);
+static VEC (ext_lang_p) *ext_lang_vec = NULL;
+
+/* Registers an extension language with GDB.  */
+
+void
+register_ext_lang (struct ext_lang *lang)
+{
+  if (ext_lang_vec == NULL)
+    ext_lang_vec = VEC_alloc (ext_lang_p, 1);
+      
+  VEC_safe_push (ext_lang_p, ext_lang_vec, lang);
+}
+
+/* Returns a new ext_fn_descriptor object.  LANG is the extention language the
+   new extension function is implemented in.  IS_METHOD indicates whether the
+   new extension function is a method.  EXT_OBJ is the extension language
+   specific data to be encapsulated in the ext_fn_descriptor.  */
+
+struct ext_fn_descriptor *
+new_ext_function (struct ext_lang *lang, int is_method, void *ext_obj)
+{
+  struct ext_fn_descriptor *ext_fn = XCNEW (struct ext_fn_descriptor);
+
+  ext_fn->is_method = is_method;
+  ext_fn->lang = lang;
+  ext_fn->ext_object = ext_obj;
+
+  return ext_fn;
+}
+
+/* Clones EXT_FN and returns a new but identical ext_fn_descriptor.  */
+
+struct ext_fn_descriptor *
+ext_fn_clone (struct ext_fn_descriptor *ext_fn)
+{
+  struct ext_fn_descriptor *new_ext_fn;
+  struct ext_lang *lang = ext_fn->lang;
+
+  new_ext_fn = new_ext_function (lang, ext_fn->is_method,
+                                 lang->clone_ext_object (ext_fn->ext_object));
+
+  return new_ext_fn;
+}
+
+/* If a method of name METHOD is to be invoked on an object of type TYPE, then
+   all entension languages are searched for implementations of methods with 
+   name METHOD in the extension languages.  All matches found are returned as
+   a vector 'struct ent_fn_descriptor' objects.  If no matching methods are
+   found, NULL is returned.  */
+
+VEC (ext_fn_descriptor_p) *
+get_matching_ext_methods (struct type *type, const char *method)
+{
+  VEC (ext_fn_descriptor_p) *ext_methods = NULL;
+  ext_lang_p lang;
+  int i;
+
+  for (i = 0; VEC_iterate (ext_lang_p, ext_lang_vec, i, lang); i++)
+    {
+      VEC (ext_fn_descriptor_p) *lang_methods, *new_vec;
+
+      lang_methods = lang->get_matching_ext_methods (type, method);
+      new_vec = VEC_merge (ext_fn_descriptor_p, ext_methods, lang_methods);
+
+      VEC_free (ext_fn_descriptor_p, ext_methods);
+      VEC_free (ext_fn_descriptor_p, lang_methods);
+      ext_methods = new_vec;
+    }
+
+  return ext_methods;
+}
+
+/* Given an function EXT_FN implemented in an extension language, returns an
+   array of types of the arguments the function accepts.  The length of the
+   array is returned in NARGS.  The type of the 'this' object is returned as
+   the first argument if EXT_FN is a method.  If EXT_FN does not take any
+   arguments, then NULL is returned with 0 in NARGS.  */
+
+struct type **
+ext_fn_get_argtypes (struct ext_fn_descriptor *ext_fn, int *nargs)
+{
+  gdb_assert (ext_fn && ext_fn->lang && ext_fn->lang->get_ext_fn_argtypes);
+
+  return ext_fn->lang->get_ext_fn_argtypes (ext_fn->ext_object, nargs);
+}
+
+/* If EXT_FN is a method implemented in an extension language, invokes  it and
+   returns the resulting value.  The method is invoked on OBJ with arguments
+   ARGS.  NARGS is the length of the ARGS array.  */
+
+struct value *
+ext_fn_invoke_method (struct ext_fn_descriptor *ext_fn, struct value *obj,
+                      struct value **args, int nargs)
+{
+  gdb_assert (ext_fn && ext_fn->is_method && ext_fn->lang
+              && ext_fn->lang->invoke_method);
+
+  return ext_fn->lang->invoke_method (ext_fn->ext_object, obj, args, nargs);
+}
+
+/* Returns true if EXT_FN is a method, 0 otherwise.  */
+
+int
+ext_fn_is_method (struct ext_fn_descriptor *ext_fn)
+{
+  if (ext_fn != NULL)
+    return ext_fn->is_method;
+
+  return 0;
+}
+
+/* Frees a vector of ext_fn_descriptors VEC.  */
+
+static void
+ext_fn_vec_free (void *vec)
+{
+  int i;
+  struct ext_fn_descriptor *ext_fn;
+  VEC (ext_fn_descriptor_p) *v = (VEC (ext_fn_descriptor_p) *) vec;
+
+  for (i = 0; VEC_iterate (ext_fn_descriptor_p, v, i, ext_fn); i++)
+    {
+      ext_fn->lang->free_ext_obj (ext_fn->ext_object);
+      xfree (ext_fn);
+    }
+}
+
+/* Return a cleanup object to free a vector VEC of extension function
+   descriptors.  */
+
+struct cleanup *
+make_ext_fn_vec_cleanup (VEC (ext_fn_descriptor_p) *vec)
+{
+  return make_cleanup (ext_fn_vec_free, (void *) vec);
+}
diff --git a/gdb/ext-function.h b/gdb/ext-function.h
new file mode 100644
index 0000000..42cda14
--- /dev/null
+++ b/gdb/ext-function.h
@@ -0,0 +1,76 @@
+/* Support for functions defined in extension languages.
+
+   Copyright (C) 2013 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#if !defined (EXT_FUNCTION_H)
+#define EXT_FUNCTION_H
+
+#include "vec.h"
+
+struct cleanup;
+struct value;
+struct type;
+struct ext_fn_descriptor;
+
+typedef struct ext_fn_descriptor *ext_fn_descriptor_p;
+DEF_VEC_P (ext_fn_descriptor_p);
+typedef VEC (ext_fn_descriptor_p) ext_fn_vec;
+
+typedef struct value* (invoke_method_ftype) (void *ext_obj,
+                                             struct value *,
+                                             struct value **, int nargs);
+
+typedef void * (clone_ext_obj_ftype) (void *ext_obj);
+
+typedef void (free_ext_obj_ftype) (void *ext_obj);
+
+typedef ext_fn_vec *(get_matching_ext_methods_ftype) (struct type *type,
+                                                      const char *method);
+
+typedef struct type** (get_ext_fn_argtypes_ftype) (void *ext_obj, int *nargs);
+
+struct ext_lang
+  {
+    clone_ext_obj_ftype *clone_ext_object;
+    free_ext_obj_ftype *free_ext_obj;
+    get_matching_ext_methods_ftype *get_matching_ext_methods;
+    get_ext_fn_argtypes_ftype *get_ext_fn_argtypes;
+    invoke_method_ftype *invoke_method;
+  };
+
+extern void register_ext_lang (struct ext_lang *lang);
+
+extern struct value *ext_fn_invoke_method (struct ext_fn_descriptor *,
+                                           struct value *,
+                                           struct value **, int nargs);
+
+extern struct ext_fn_descriptor *ext_fn_clone (struct ext_fn_descriptor *);
+
+extern struct ext_fn_descriptor *new_ext_function (struct ext_lang *lang,
+                                                   int is_method,
+                                                   void *ext_obj);
+
+extern ext_fn_vec *get_matching_ext_methods (struct type *, const char *);
+
+extern struct type **ext_fn_get_argtypes (struct ext_fn_descriptor *, int *);
+
+extern int ext_fn_is_method (struct ext_fn_descriptor *);
+
+extern struct cleanup* make_ext_fn_vec_cleanup (VEC (ext_fn_descriptor_p) *vec);
+
+#endif /* EXT_FUNCTION_H */
diff --git a/gdb/python/lib/gdb/debugmethods.py b/gdb/python/lib/gdb/debugmethods.py
new file mode 100644
index 0000000..7d0a891
--- /dev/null
+++ b/gdb/python/lib/gdb/debugmethods.py
@@ -0,0 +1,118 @@
+# Python side of the support for debug methods.
+# Copyright (C) 2013 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/>.
+
+"""Utilities for defining debug methods"""
+
+import gdb
+import re
+
+DEFAULT_DEBUG_METHOD_GROUP = 'DEFAULT_DEBUG_METHOD_GROUP'
+
+
+class DebugMethod(object):
+    """Base class for all debug methods defined in Python.
+
+    A debug method defined in Python should be derived from this class.  The
+    derived classes should override the methods 'match', 'get_argtypes' and
+    'invoke'.
+
+    Internally, GDB first invokes the 'match' method to match the class type
+    and the method name.  It next get the argument types of these methods via
+    the 'get_argtypes' method to perform overload resolution.
+    """
+
+    def __init__(self, name, group=DEFAULT_DEBUG_METHOD_GROUP):
+        """
+        Args:
+            name: An identifying name for the debug method.
+            group: The group name of the group to which the debug method
+                   belongs to.
+        """
+        self.name = name
+        self.group = group
+        self.enabled = True
+
+    def match(self, class_type, method_name):
+        """Match class type and method name.
+
+        Args:
+            class_type: The class type to match
+            method_name: The name of the method to match.
+        """
+        gdb.GdbError('ERROR: Invoking abstract method \'match\'.')
+
+    def get_argtypes(self, class_type, method_name):
+        """Return a list of types, as gdb.Type objects, of the arguments of
+           the debug method.
+
+        Args: 
+            class_type: The gdb.Type value of the class on which the method
+                        is defined.
+            method_name: The name of the method whose argument types are to
+                         be returned.
+        """
+        gdb.GdbError('ERROR: Invoking abstract method \'get_argtypes\'.')
+
+    def invoke(self, obj, args):
+        """Invoke the debug method.
+
+        Args:
+            obj: The gdb.Value of the object on which the method is to be
+                 invoked.
+            args: The tuple of arguments to the method.
+        """
+        gdb.GdbError('ERROR: Invoking abstract method \'invoke\'.')
+
+
+class SimpleDebugMethod(DebugMethod):
+    """This is a utility class which does name match by class name of the
+    objects on which the debug methods are defined.
+    """
+    def __init__(self, name, group, method_function, class_matcher,
+                 method_matcher, *argtypes):
+        DebugMethod.__init__(self, name, group)
+        self._method_function = method_function
+        self._class_matcher = class_matcher
+        self._method_matcher = method_matcher
+        self._argtypes = argtypes
+
+    def match(self, class_type, method_name):
+        cm = re.match(self._class_matcher, str(class_type.unqualified().tag))
+        mm = re.match(self._method_matcher, method_name)
+        if cm and mm:
+            return True
+        else:
+            return False
+
+    def get_argtypes(self, class_type, method_name):
+        return self._argtypes
+
+    def invoke(self, obj, args):
+        return self._method_function(obj, *args)
+
+
+def register_debug_methods(objfile, debug_methods):
+    existing_method_list = []
+    for new_method in debug_methods:
+        for old_method in objfile.debug_methods:
+            if (new_method.group == old_method.group and
+                new_method.name == old_method.name):
+                print ('WARNING: Replacing debug method with name "%s" in '
+                       'group "%s".' % (old_method.name, old_method.group))
+                existing_method_list.append(old_method)
+    for old_method in existing_method_list:
+        objfile.debug_methods.remove(old_method)
+    objfile.debug_methods.extend(debug_methods)
diff --git a/gdb/python/py-debugmethods.c b/gdb/python/py-debugmethods.c
new file mode 100644
index 0000000..38c1b69
--- /dev/null
+++ b/gdb/python/py-debugmethods.c
@@ -0,0 +1,508 @@
+/* Support for debug methods in Python.
+
+   Copyright (C) 2013 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#include "defs.h"
+#include "arch-utils.h"
+#include "ext-function.h"
+#include "objfiles.h"
+#include "value.h"
+#include "language.h"
+#include "python-internal.h"
+#include "python.h"
+
+struct py_ext_object
+{
+  /* Holds an instance of the DebugMethod class.  */
+  PyObject *object;
+
+  /* Holds the type of the 'this' object.  */
+  PyObject *match_py_obj_type;
+
+  /* Holds the matching method name.  */
+  const char *match_method;
+};
+
+static const char *enabled_field_name = "enabled";
+static const char *match_method_name = "match";
+static const char *get_argtypes_method_name = "get_argtypes";
+static const char *invoke_method_name = "invoke";
+
+static PyObject *match_method_pystring = NULL;
+static PyObject *get_argtypes_method_pystring = NULL;
+static PyObject *invoke_method_pystring = NULL;
+
+static struct ext_fn_descriptor *new_python_ext_method (PyObject *item,
+                                                        PyObject *py_obj_type,
+                                                        const char *method);
+
+/* Implementation of free_ext_obj_ftype.  */
+
+static void
+py_free_ext_object (void *ext_object)
+{
+  struct py_ext_object *o = (struct py_ext_object *) ext_object;
+
+  Py_XDECREF (o->object);
+  Py_XDECREF (o->match_py_obj_type);
+  xfree (o);
+}
+
+/* Implementation of clone_ext_obj_ftype.  */
+
+static void *
+py_clone_ext_object (void *obj)
+{
+  struct py_ext_object *new_obj, *old_obj;
+
+  old_obj = (struct py_ext_object *) obj;
+
+  new_obj = XCNEW (struct py_ext_object);
+  new_obj->object = old_obj->object;
+  new_obj->match_py_obj_type = old_obj->match_py_obj_type;
+  new_obj->match_method = old_obj->match_method;
+
+  Py_XINCREF (new_obj->object);
+  Py_XINCREF (new_obj->match_py_obj_type);
+
+  return (void *) new_obj;
+}
+
+/* Returns true if gdb.Type object PY_OBJ_TYPE has a method defined in Python
+   with name METHOD_NAME.  */
+
+static int
+is_matching_debug_method (PyObject *dm_obj, PyObject *py_obj_type,
+                          const char *method_name)
+{
+  PyObject *method_name_pystring;
+  PyObject *match_method, *enabled_field, *match_result;
+  struct cleanup *cleanups;
+  int enabled, match;
+
+  if (method_name == NULL)
+    return 0;
+
+  cleanups = make_cleanup (null_cleanup, NULL);
+
+  enabled_field = PyObject_GetAttrString (dm_obj, enabled_field_name);
+  if (enabled_field == NULL)
+    {
+      gdbpy_print_stack ();
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+  make_cleanup_py_decref (enabled_field);
+
+  enabled = PyObject_IsTrue (enabled_field);
+  if (enabled == -1)
+    {
+      PyErr_Clear ();
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+  if (enabled == 0)
+    {
+      do_cleanups (cleanups);
+      return 0;
+    }
+
+  match_method = PyObject_GetAttrString (dm_obj, match_method_name);
+  if (match_method == NULL)
+    {
+      gdbpy_print_stack ();
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+  make_cleanup_py_decref (match_method);
+  if (!PyCallable_Check (match_method))
+    {
+      warning (_("Attribute '%s' of a registered Python debug method is not "
+                 "callable.  Ignored!"), match_method_name);
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+
+  method_name_pystring = PyString_FromString (method_name);
+  if (method_name_pystring == NULL)
+    {
+      PyErr_Clear ();
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+  make_cleanup_py_decref (method_name_pystring);
+
+  match_result = PyObject_CallMethodObjArgs (dm_obj,
+                                             match_method_pystring,
+                                             py_obj_type,
+                                             method_name_pystring,
+                                             NULL);
+  if (match_result == NULL)
+    {
+      gdbpy_print_stack ();
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+  make_cleanup_py_decref (match_result);
+
+  match = PyObject_IsTrue (match_result);
+  if (match == -1)
+    {
+      PyErr_Clear ();
+      do_cleanups (cleanups);
+
+      return 0;
+    }
+
+  do_cleanups (cleanups);
+
+  return match;
+}
+
+/* Implementation of get_matching_ext_methods_ftype.
+   Return a of vector methods with name METHOD_NAME defined in Python for
+   objects of type OBJ_TYPE.  Returns NULL if no matches are found.  */
+
+static VEC (ext_fn_descriptor_p) *
+py_debugmethod_name_match (struct type *obj_type, const char *method_name)
+{
+  struct cleanup *cleanups;
+  struct objfile *objfile;
+  VEC (ext_fn_descriptor_p) *method_vec = NULL;
+  PyObject *py_type;
+
+  if (obj_type == NULL || method_name == NULL)
+    return method_vec;
+
+  py_type = type_to_type_object (obj_type);
+  if (py_type == NULL)
+    return method_vec;
+
+  cleanups = ensure_python_env (get_current_arch (), current_language);
+
+  ALL_OBJFILES (objfile)
+    {
+      PyObject *py_debugmethod_list = NULL, *list_iter, *item;
+      PyObject *py_objfile = objfile_to_objfile_object (objfile);
+
+      if (py_objfile == NULL)
+        {
+          PyErr_Clear ();
+          continue;
+        }
+
+      py_debugmethod_list = objfpy_get_debug_methods (py_objfile, NULL);
+      list_iter = PyObject_GetIter (py_debugmethod_list);
+      if (list_iter == NULL)
+        {
+          PyErr_Clear();
+          Py_DECREF (py_debugmethod_list);
+          continue;
+        }
+
+      while ((item = PyIter_Next (list_iter)))
+        {
+          if (is_matching_debug_method (item, py_type, method_name))
+            {
+              struct ext_fn_descriptor *ext_fn;
+
+              ext_fn = new_python_ext_method (item, py_type, method_name);
+              if (method_vec == NULL)
+                method_vec = VEC_alloc (ext_fn_descriptor_p, 1);
+              VEC_safe_push (ext_fn_descriptor_p, method_vec, ext_fn);
+            }
+
+          Py_DECREF (item);
+        }
+      Py_DECREF (list_iter);
+      if (PyErr_Occurred ())
+        PyErr_Clear ();  /* Ignore iteration errors silently.  */
+
+      Py_DECREF (py_debugmethod_list);
+    }
+
+  Py_DECREF (py_type);
+  do_cleanups (cleanups);
+
+  return method_vec;
+}
+
+/* Implementation of get_ext_fn_argtypes_ftype.
+   Return an arry of argument types for extension encapsulated in EXT_OBJ.
+   NARGS contains the length of the array.  */
+
+static struct type **
+py_ext_fn_get_argtypes (void *ext_obj, int *nargs)
+{
+  struct py_ext_object *ext_object = (struct py_ext_object *) ext_obj;
+  PyObject *debug_method_obj = ext_object->object;
+  PyObject *get_argtypes_method;
+  PyObject *py_argtype_list, *list_iter, *item;
+  struct cleanup *cleanups;
+  struct type **type_array, *obj_type;
+  int i = 1;
+
+  /* Set nargs to 0 so that any premature return from this function returns
+     0 arg types.  */
+  *nargs = 0;
+
+  cleanups = ensure_python_env (get_current_arch (), current_language);
+
+  get_argtypes_method =  PyObject_GetAttrString (debug_method_obj,
+                                                 get_argtypes_method_name);
+  if (get_argtypes_method == NULL)
+    {
+      gdbpy_print_stack ();
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+  make_cleanup_py_decref (get_argtypes_method);
+
+  if (!PyCallable_Check (get_argtypes_method))
+    {
+      warning (_("Attribute '%s' of a registered Python debug method is not "
+                 "callable.  Ignored!"), get_argtypes_method_name);
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+
+  py_argtype_list = PyObject_CallMethodObjArgs (debug_method_obj,
+                                                get_argtypes_method_pystring,
+                                                ext_object->match_py_obj_type,
+                                                ext_object->match_method,
+                                                NULL);
+  if (py_argtype_list == NULL)
+    {
+      gdbpy_print_stack ();
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+  make_cleanup_py_decref (py_argtype_list);
+
+  list_iter = PyObject_GetIter (py_argtype_list);
+  if (list_iter == NULL)
+    {
+      PyErr_Clear ();
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+  make_cleanup_py_decref (list_iter);
+
+  /* Include the 'this' argument in the size.  */
+  type_array = XCNEWVEC (struct type *, PyList_GET_SIZE (py_argtype_list) + 1);
+  while ((item = PyIter_Next (list_iter)))
+    {
+      struct type *arg_type = type_object_to_type (item);
+
+      Py_DECREF (item);
+
+      if (arg_type == NULL)
+        {
+          i = -1;
+          break;
+        }
+
+      type_array[i] = arg_type;
+      i++;
+    }
+  if (PyErr_Occurred () || i == -1)
+    {
+      PyErr_Clear ();
+      do_cleanups (cleanups);
+      xfree (type_array);
+
+      return NULL;
+    }
+
+  /* Add the type of 'this' as the first argument.  */
+  obj_type = type_object_to_type (ext_object->match_py_obj_type);
+  type_array[0] = make_cv_type (1, 0, lookup_pointer_type (obj_type), NULL);
+  *nargs = i;
+
+  do_cleanups (cleanups);
+
+  return type_array;
+}
+
+/* Implementation of invoke_method_ftype.
+   Invokes a method defined in Python.  The value returned by the method is
+   returned.  NULL is returned in case of errors.  */
+
+static struct value *
+py_ext_fn_invoke_method (void *ext_obj, struct value *obj, struct value **args,
+                         int nargs)
+{
+  int i;
+  struct cleanup *cleanups;
+  PyObject *py_value_obj, *py_arg_tuple, *py_result, *debug_method_obj;
+  PyObject *invoke_method;
+  struct value *result = NULL;
+
+  cleanups = ensure_python_env (get_current_arch (), current_language);
+
+  debug_method_obj = ((struct py_ext_object *) ext_obj)->object;
+
+  invoke_method =  PyObject_GetAttrString (debug_method_obj,
+                                           invoke_method_name);
+  if (invoke_method == NULL)
+    {
+      gdbpy_print_stack ();
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+  make_cleanup_py_decref (invoke_method);
+
+  if (!PyCallable_Check (invoke_method))
+    {
+      warning (_("Attribute '%s' of a registered Python debug method is not "
+                 "callable.  Ignored!"), invoke_method_name);
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+
+  py_value_obj = value_to_value_object (obj);
+  if (py_value_obj == NULL)
+    {
+      do_cleanups (cleanups);
+      return NULL;
+    }
+  make_cleanup_py_decref (py_value_obj);
+
+  py_arg_tuple = PyTuple_New (nargs);
+  if (py_arg_tuple == NULL)
+    {
+      PyErr_Clear ();
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+  make_cleanup_py_decref (py_arg_tuple);
+
+  for (i = 0; i < nargs; i++)
+    {
+      PyObject *py_value_arg = value_to_value_object (args[i]);
+
+      if (py_value_arg == NULL)
+        {
+          PyErr_Clear ();
+          do_cleanups (cleanups);
+          return NULL;
+        }
+
+      if (PyTuple_SetItem (py_arg_tuple, i, py_value_arg))
+        {
+          PyErr_Clear ();
+          do_cleanups (cleanups);
+
+          return NULL;
+        }
+    }
+
+  py_result = PyObject_CallMethodObjArgs (debug_method_obj,
+                                          invoke_method_pystring,
+                                          py_value_obj, py_arg_tuple, NULL);
+  if (py_result == NULL)
+    {
+      gdbpy_print_stack (); 
+      do_cleanups (cleanups);
+
+      return NULL;
+    }
+  make_cleanup_py_decref (py_result);
+
+  /* Check that a debug method did not return None.  */
+  if (py_result != Py_None)
+    {
+      result = convert_value_from_python (py_result);
+      if (result == NULL)
+        {
+          gdbpy_print_stack ();
+        }
+    }
+  else
+    result = allocate_value (lookup_typename (python_language, python_gdbarch,
+                                              "void", NULL, 0));
+
+  do_cleanups (cleanups);
+
+  return result;
+}
+
+static struct ext_lang python_ext_lang = {
+  py_clone_ext_object,
+  py_free_ext_object,
+  py_debugmethod_name_match,
+  py_ext_fn_get_argtypes,
+  py_ext_fn_invoke_method
+};
+
+/* Creates a new python ext_function_descriptor.  DEBUG_METHOD is the
+   debug method object.  PY_OBJ_TYPE is a gdb.Type value corresponding to the
+   type of the object on which the debug method with name METHOD will be
+   invoked.  */
+
+static struct ext_fn_descriptor *
+new_python_ext_method (PyObject *debug_method, PyObject *py_obj_type,
+                       const char *method)
+{
+  struct py_ext_object *ext_object;
+
+  ext_object = XCNEW (struct py_ext_object);
+  ext_object->object = debug_method;
+  ext_object->match_py_obj_type = py_obj_type;
+  ext_object->match_method = method;
+
+  Py_XINCREF (ext_object->object);
+  Py_XINCREF (ext_object->match_py_obj_type);
+
+  return new_ext_function (&python_ext_lang, 1, ext_object);
+}
+
+/* Initializes the Python debug method support.  */
+
+int
+gdbpy_initialize_debugmethods (void)
+{
+  register_ext_lang (&python_ext_lang);
+
+  match_method_pystring = PyString_FromString (match_method_name);
+  if (match_method_pystring == NULL)
+    return -1;
+
+  invoke_method_pystring = PyString_FromString (invoke_method_name);
+  if (invoke_method_pystring == NULL)
+    return -1;
+
+  get_argtypes_method_pystring = PyString_FromString (get_argtypes_method_name);
+  if (get_argtypes_method_pystring == NULL)
+    return -1;
+
+  return 1;
+}
diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
index a954c9d..16d3f98 100644
--- a/gdb/python/py-objfile.c
+++ b/gdb/python/py-objfile.c
@@ -37,6 +37,9 @@ typedef struct
   PyObject *frame_filters;
   /* The type-printer list.  */
   PyObject *type_printers;
+
+  /* The debug method list.  */
+  PyObject *debug_methods;
 } objfile_object;
 
 static PyTypeObject objfile_object_type
@@ -66,6 +69,7 @@ objfpy_dealloc (PyObject *o)
   Py_XDECREF (self->printers);
   Py_XDECREF (self->frame_filters);
   Py_XDECREF (self->type_printers);
+  Py_XDECREF (self->debug_methods);
   Py_TYPE (self)->tp_free (self);
 }
 
@@ -98,6 +102,13 @@ objfpy_new (PyTypeObject *type, PyObject *args, PyObject *keywords)
 	  Py_DECREF (self);
 	  return NULL;
 	}
+
+      self->debug_methods = PyList_New (0);
+      if (!self->debug_methods)
+	{
+	  Py_DECREF (self);
+	  return NULL;
+	}
     }
   return (PyObject *) self;
 }
@@ -192,6 +203,17 @@ objfpy_get_type_printers (PyObject *o, void *ignore)
   return self->type_printers;
 }
 
+/* Get the 'debug_methods' attribute.  */
+
+PyObject *
+objfpy_get_debug_methods (PyObject *o, void *ignore)
+{
+  objfile_object *self = (objfile_object *) o;
+
+  Py_INCREF (self->debug_methods);
+  return self->debug_methods;
+}
+
 /* Set the 'type_printers' attribute.  */
 
 static int
@@ -291,6 +313,13 @@ objfile_to_objfile_object (struct objfile *objfile)
 	      return NULL;
 	    }
 
+	  object->debug_methods = PyList_New (0);
+	  if (!object->debug_methods)
+	    {
+	      Py_DECREF (object);
+	      return NULL;
+	    }
+
 	  set_objfile_data (objfile, objfpy_objfile_data_key, object);
 	}
     }
@@ -332,6 +361,8 @@ static PyGetSetDef objfile_getset[] =
     objfpy_set_frame_filters, "Frame Filters.", NULL },
   { "type_printers", objfpy_get_type_printers, objfpy_set_type_printers,
     "Type printers.", NULL },
+  { "debug_methods", objfpy_get_debug_methods, NULL,
+    "Debug methods.", NULL },
   { NULL }
 };
 
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index d947be6..2627069 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -321,6 +321,7 @@ PyObject *objfile_to_objfile_object (struct objfile *)
     CPYCHECKER_RETURNS_BORROWED_REF;
 PyObject *objfpy_get_printers (PyObject *, void *);
 PyObject *objfpy_get_frame_filters (PyObject *, void *);
+PyObject *objfpy_get_debug_methods (PyObject *, void *);
 
 PyObject *gdbarch_to_arch_object (struct gdbarch *gdbarch);
 
@@ -399,6 +400,8 @@ int gdbpy_initialize_new_objfile_event (void)
   CPYCHECKER_NEGATIVE_RESULT_SETS_EXCEPTION;
 int gdbpy_initialize_arch (void)
   CPYCHECKER_NEGATIVE_RESULT_SETS_EXCEPTION;
+int gdbpy_initialize_debugmethods (void)
+  CPYCHECKER_NEGATIVE_RESULT_SETS_EXCEPTION;
 
 struct cleanup *make_cleanup_py_decref (PyObject *py);
 struct cleanup *make_cleanup_py_xdecref (PyObject *py);
diff --git a/gdb/python/python.c b/gdb/python/python.c
index c94198e..4f4b46b 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1686,7 +1686,8 @@ message == an error message without a stack will be printed."),
       || gdbpy_initialize_exited_event () < 0
       || gdbpy_initialize_thread_event () < 0
       || gdbpy_initialize_new_objfile_event ()  < 0
-      || gdbpy_initialize_arch () < 0)
+      || gdbpy_initialize_arch () < 0
+      || gdbpy_initialize_debugmethods () < 0)
     goto fail;
 
   observer_attach_before_prompt (before_prompt_hook);
diff --git a/gdb/valarith.c b/gdb/valarith.c
index 18c14fc..f105200 100644
--- a/gdb/valarith.c
+++ b/gdb/valarith.c
@@ -30,6 +30,7 @@
 #include <math.h>
 #include "infcall.h"
 #include "exceptions.h"
+#include "ext-function.h"
 
 /* Define whether or not the C operator '/' truncates towards zero for
    differently signed operands (truncation direction is undefined in C).  */
@@ -285,21 +286,27 @@ unop_user_defined_p (enum exp_opcode op, struct value *arg1)
    explicitly, and perform correct overload resolution in all of the above
    situations or combinations thereof.  */
 
-static struct value *
+static void
 value_user_defined_cpp_op (struct value **args, int nargs, char *operator,
+                           struct value **src_fn,
+                           struct ext_fn_descriptor **ext_fn,
                            int *static_memfuncp)
 {
 
   struct symbol *symp = NULL;
   struct value *valp = NULL;
+  struct ext_fn_descriptor *ext_fnp = NULL;
 
   find_overload_match (args, nargs, operator, BOTH /* could be method */,
                        &args[0] /* objp */,
                        NULL /* pass NULL symbol since symbol is unknown */,
-                       &valp, &symp, static_memfuncp, 0);
+                       &valp, &symp, &ext_fnp, static_memfuncp, 0);
 
   if (valp)
-    return valp;
+    {
+      *src_fn = valp;
+      return;
+    }
 
   if (symp)
     {
@@ -307,7 +314,14 @@ value_user_defined_cpp_op (struct value **args, int nargs, char *operator,
          expect a reference as its first argument
          rather the explicit structure.  */
       args[0] = value_ind (args[0]);
-      return value_of_variable (symp, 0);
+      *src_fn = value_of_variable (symp, 0);
+      return;
+    }
+
+  if (ext_fnp)
+    {
+      *ext_fn = ext_fnp;
+      return;
     }
 
   error (_("Could not find %s."), operator);
@@ -316,19 +330,22 @@ value_user_defined_cpp_op (struct value **args, int nargs, char *operator,
 /* Lookup user defined operator NAME.  Return a value representing the
    function, otherwise return NULL.  */
 
-static struct value *
+static void
 value_user_defined_op (struct value **argp, struct value **args, char *name,
-                       int *static_memfuncp, int nargs)
+                       int *static_memfuncp, int nargs,
+                       struct value **src_fn, struct ext_fn_descriptor **ext_fn)
 {
   struct value *result = NULL;
 
   if (current_language->la_language == language_cplus)
-    result = value_user_defined_cpp_op (args, nargs, name, static_memfuncp);
+    value_user_defined_cpp_op (args, nargs, name, src_fn, ext_fn,
+                               static_memfuncp);
   else
-    result = value_struct_elt (argp, args, name, static_memfuncp,
-                               "structure");
-
-  return result;
+    {
+      result = value_struct_elt (argp, args, name, static_memfuncp,
+                                 "structure");
+      *src_fn = result;
+    }
 }
 
 /* We know either arg1 or arg2 is a structure, so try to find the right
@@ -345,6 +362,7 @@ value_x_binop (struct value *arg1, struct value *arg2, enum exp_opcode op,
 	       enum exp_opcode otherop, enum noside noside)
 {
   struct value **argvec;
+  struct ext_fn_descriptor *ext_fn = NULL;
   char *ptr;
   char tstr[13];
   int static_memfuncp;
@@ -359,6 +377,7 @@ value_x_binop (struct value *arg1, struct value *arg2, enum exp_opcode op,
     error (_("Can't do that binary op on that type"));	/* FIXME be explicit */
 
   argvec = (struct value **) alloca (sizeof (struct value *) * 4);
+  argvec[0] = NULL;
   argvec[1] = value_addr (arg1);
   argvec[2] = arg2;
   argvec[3] = 0;
@@ -471,8 +490,8 @@ value_x_binop (struct value *arg1, struct value *arg2, enum exp_opcode op,
       error (_("Invalid binary operation specified."));
     }
 
-  argvec[0] = value_user_defined_op (&arg1, argvec + 1, tstr,
-                                     &static_memfuncp, 2);
+  value_user_defined_op (&arg1, argvec + 1, tstr, &static_memfuncp, 2,
+                         &argvec[0], &ext_fn);
 
   if (argvec[0])
     {
@@ -492,6 +511,19 @@ value_x_binop (struct value *arg1, struct value *arg2, enum exp_opcode op,
       return call_function_by_hand (argvec[0], 2 - static_memfuncp,
 				    argvec + 1);
     }
+  if (ext_fn)
+    {
+      if (ext_fn_is_method (ext_fn))
+        {
+          struct value *ret_val = ext_fn_invoke_method (ext_fn, arg1, &arg2, 1);
+
+          if (ret_val == NULL)
+              error (_("Error invoking debug method implementation for "
+                       "method %s"), tstr);
+
+          return ret_val;
+        }
+    }
   throw_error (NOT_FOUND_ERROR,
                _("member function %s not found"), tstr);
 #ifdef lint
@@ -510,6 +542,7 @@ value_x_unop (struct value *arg1, enum exp_opcode op, enum noside noside)
 {
   struct gdbarch *gdbarch = get_type_arch (value_type (arg1));
   struct value **argvec;
+  struct ext_fn_descriptor *ext_fn;
   char *ptr;
   char tstr[13], mangle_tstr[13];
   int static_memfuncp, nargs;
@@ -523,6 +556,7 @@ value_x_unop (struct value *arg1, enum exp_opcode op, enum noside noside)
     error (_("Can't do that unary op on that type"));	/* FIXME be explicit */
 
   argvec = (struct value **) alloca (sizeof (struct value *) * 4);
+  argvec[0] = NULL;
   argvec[1] = value_addr (arg1);
   argvec[2] = 0;
 
@@ -574,8 +608,8 @@ value_x_unop (struct value *arg1, enum exp_opcode op, enum noside noside)
       error (_("Invalid unary operation specified."));
     }
 
-  argvec[0] = value_user_defined_op (&arg1, argvec + 1, tstr,
-                                     &static_memfuncp, nargs);
+  value_user_defined_op (&arg1, argvec + 1, tstr, &static_memfuncp, nargs,
+                         &argvec[0], &ext_fn);
 
   if (argvec[0])
     {
@@ -594,6 +628,19 @@ value_x_unop (struct value *arg1, enum exp_opcode op, enum noside noside)
 	  return value_zero (return_type, VALUE_LVAL (arg1));
 	}
       return call_function_by_hand (argvec[0], nargs, argvec + 1);
+    } 
+  if (ext_fn)
+    {
+      if (ext_fn_is_method (ext_fn))
+        {
+          struct value *ret_val = ext_fn_invoke_method (ext_fn, arg1, NULL, 0);
+
+          if (ret_val == NULL)
+              error (_("Error invoking debug method implementation for "
+                       "method %s"), tstr);
+
+          return ret_val;
+        }
     }
   throw_error (NOT_FOUND_ERROR,
                _("member function %s not found"), tstr);
diff --git a/gdb/valops.c b/gdb/valops.c
index 93c09d8..1d0cb80 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -45,6 +45,7 @@
 #include "objfiles.h"
 #include "symtab.h"
 #include "exceptions.h"
+#include "ext-function.h"
 
 extern unsigned int overload_debug;
 /* Local functions.  */
@@ -73,8 +74,8 @@ int find_oload_champ_namespace_loop (struct value **, int,
 				     const int no_adl);
 
 static int find_oload_champ (struct value **, int, int, int,
-			     struct fn_field *, struct symbol **,
-			     struct badness_vector **);
+			     struct fn_field *, VEC (ext_fn_descriptor_p) *,
+                             struct symbol **, struct badness_vector **);
 
 static int oload_method_static (int, struct fn_field *, int);
 
@@ -101,9 +102,10 @@ static CORE_ADDR allocate_space_in_inferior (int);
 
 static struct value *cast_into_complex (struct type *, struct value *);
 
-static struct fn_field *find_method_list (struct value **, const char *,
-					  int, struct type *, int *,
-					  struct type **, int *);
+static void find_method_list (struct value **, const char *,
+                              int, struct type *, struct fn_field **, int *,
+                              VEC (ext_fn_descriptor_p) **,
+                              struct type **, int *);
 
 void _initialize_valops (void);
 
@@ -2432,40 +2434,58 @@ value_struct_elt (struct value **argp, struct value **args,
       method is found.
    BOFFSET is the offset of the base subobject where the method is found.  */
 
-static struct fn_field *
+static void
 find_method_list (struct value **argp, const char *method,
-		  int offset, struct type *type, int *num_fns,
+		  int offset, struct type *type,
+                  struct fn_field **fn_list, int *num_fns,
+                  VEC (ext_fn_descriptor_p) **ext_fn_vec,
 		  struct type **basetype, int *boffset)
 {
   int i;
-  struct fn_field *f;
-  CHECK_TYPEDEF (type);
+  struct fn_field *f = NULL;
 
-  *num_fns = 0;
+  CHECK_TYPEDEF (type);
 
   /* First check in object itself.  */
-  for (i = TYPE_NFN_FIELDS (type) - 1; i >= 0; i--)
-    {
-      /* pai: FIXME What about operators and type conversions?  */
-      const char *fn_field_name = TYPE_FN_FIELDLIST_NAME (type, i);
 
-      if (fn_field_name && (strcmp_iw (fn_field_name, method) == 0))
-	{
-	  int len = TYPE_FN_FIELDLIST_LENGTH (type, i);
-	  struct fn_field *f = TYPE_FN_FIELDLIST1 (type, i);
+  if (fn_list && !(*fn_list))
+    for (i = TYPE_NFN_FIELDS (type) - 1; i >= 0; i--)
+      {
+        /* pai: FIXME What about operators and type conversions?  */
+        const char *fn_field_name = TYPE_FN_FIELDLIST_NAME (type, i);
+  
+        if (fn_field_name && (strcmp_iw (fn_field_name, method) == 0))
+  	{
+  	  int len = TYPE_FN_FIELDLIST_LENGTH (type, i);
+  	  f = TYPE_FN_FIELDLIST1 (type, i);
+          *fn_list = f;
+  
+  	  *num_fns = len;
+  	  *basetype = type;
+  	  *boffset = offset;
+  
+  	  /* Resolve any stub methods.  */
+  	  check_stub_method_group (type, i);
+  
+          break;
+  	}
+      }
 
-	  *num_fns = len;
-	  *basetype = type;
-	  *boffset = offset;
+  if (ext_fn_vec)
+    {
+      VEC (ext_fn_descriptor_p) *ef_vec = NULL, *new_vec = NULL;
 
-	  /* Resolve any stub methods.  */
-	  check_stub_method_group (type, i);
+      ef_vec = get_matching_ext_methods (type, method);
+      new_vec = VEC_merge (ext_fn_descriptor_p, *ext_fn_vec, ef_vec);
 
-	  return f;
-	}
+      VEC_free (ext_fn_descriptor_p, *ext_fn_vec);
+      VEC_free (ext_fn_descriptor_p, ef_vec);
+      *ext_fn_vec = new_vec;
     }
 
-  /* Not found in object, check in base subobjects.  */
+  /* If source methods are not found in current class, look for them in the
+     base classes.  We have to go through the base classes to gather extension
+     methods anyway.  */
   for (i = TYPE_N_BASECLASSES (type) - 1; i >= 0; i--)
     {
       int base_offset;
@@ -2482,13 +2502,11 @@ find_method_list (struct value **argp, const char *method,
 	{
 	  base_offset = TYPE_BASECLASS_BITPOS (type, i) / 8;
 	}
-      f = find_method_list (argp, method, base_offset + offset,
-			    TYPE_BASECLASS (type, i), num_fns, 
-			    basetype, boffset);
-      if (f)
-	return f;
+      
+      find_method_list (argp, method, base_offset + offset,
+                        TYPE_BASECLASS (type, i), fn_list, num_fns,
+                        ext_fn_vec, basetype, boffset);
     }
-  return NULL;
 }
 
 /* Return the list of overloaded methods of a specified name.
@@ -2501,9 +2519,11 @@ find_method_list (struct value **argp, const char *method,
       method.
    BOFFSET is the offset of the base subobject which defines the method.  */
 
-static struct fn_field *
+static void
 value_find_oload_method_list (struct value **argp, const char *method,
-			      int offset, int *num_fns, 
+                              int offset, struct fn_field **fn_list,
+                              int *num_fns,
+                              VEC (ext_fn_descriptor_p) **ext_fn_vec,
 			      struct type **basetype, int *boffset)
 {
   struct type *t;
@@ -2525,8 +2545,32 @@ value_find_oload_method_list (struct value **argp, const char *method,
     error (_("Attempt to extract a component of a "
 	     "value that is not a struct or union"));
 
-  return find_method_list (argp, method, 0, t, num_fns, 
-			   basetype, boffset);
+  /* Clear the lists.  */
+  if (fn_list)
+    {
+      *fn_list = NULL;
+      *num_fns = 0;
+    }
+  if (ext_fn_vec)
+    *ext_fn_vec = VEC_alloc (ext_fn_descriptor_p, 1);
+
+  find_method_list (argp, method, 0, t, fn_list, num_fns, ext_fn_vec,
+                    basetype, boffset);
+}
+
+static struct type *
+value_has_indirect_dynamic_type (struct value *obj)
+{
+  struct type *stype, *dtype, *dtype_ind;
+
+  stype = check_typedef (TYPE_TARGET_TYPE (value_type (obj)));
+  dtype_ind = value_rtti_indirect_type (obj, NULL, NULL, NULL);
+  dtype = dtype_ind ? check_typedef (TYPE_TARGET_TYPE (dtype_ind)) : stype;
+
+  if (class_types_same_p (stype, dtype))
+    return NULL;
+  else
+    return dtype_ind;
 }
 
 /* Given an array of arguments (ARGS) (which includes an
@@ -2574,6 +2618,7 @@ find_overload_match (struct value **args, int nargs,
 		     const char *name, enum oload_search_type method,
 		     struct value **objp, struct symbol *fsym,
 		     struct value **valp, struct symbol **symp, 
+                     struct ext_fn_descriptor **ext_fn,
 		     int *staticp, const int no_adl)
 {
   struct value *obj = (objp ? *objp : NULL);
@@ -2581,16 +2626,24 @@ find_overload_match (struct value **args, int nargs,
   /* Index of best overloaded function.  */
   int func_oload_champ = -1;
   int method_oload_champ = -1;
+  int src_method_oload_champ = -1;
+  int src_method_oload_champ_bkp = -1;
+  int ext_method_oload_champ = -1;
+  int src_and_ext_equal = 0;
 
   /* The measure for the current best match.  */
   struct badness_vector *method_badness = NULL;
   struct badness_vector *func_badness = NULL;
+  struct badness_vector *ext_method_badness = NULL;
+  struct badness_vector *src_method_badness = NULL;
 
   struct value *temp = obj;
   /* For methods, the list of overloaded methods.  */
   struct fn_field *fns_ptr = NULL;
   /* For non-methods, the list of overloaded function symbols.  */
   struct symbol **oload_syms = NULL;
+  /* For extension functions, the VEC of extension function descriptors.  */
+  VEC (ext_fn_descriptor_p) *ext_fn_vec = NULL;
   /* Number of overloaded instances being considered.  */
   int num_fns = 0;
   struct type *basetype = NULL;
@@ -2602,6 +2655,8 @@ find_overload_match (struct value **args, int nargs,
   const char *func_name = NULL;
   enum oload_classification match_quality;
   enum oload_classification method_match_quality = INCOMPATIBLE;
+  enum oload_classification src_method_match_quality = INCOMPATIBLE;
+  enum oload_classification ext_method_match_quality = INCOMPATIBLE;
   enum oload_classification func_match_quality = INCOMPATIBLE;
 
   /* Get the list of overloaded methods or functions.  */
@@ -2630,12 +2685,12 @@ find_overload_match (struct value **args, int nargs,
 	}
 
       /* Retrieve the list of methods with the name NAME.  */
-      fns_ptr = value_find_oload_method_list (&temp, name, 
-					      0, &num_fns, 
-					      &basetype, &boffset);
+      value_find_oload_method_list (&temp, name, 0, &fns_ptr, &num_fns,
+                                    ext_fn ? &ext_fn_vec : NULL,
+                                    &basetype, &boffset);
       /* If this is a method only search, and no methods were found
          the search has faild.  */
-      if (method == METHOD && (!fns_ptr || !num_fns))
+      if (method == METHOD && (!fns_ptr || !num_fns) && !ext_fn_vec)
 	error (_("Couldn't find method %s%s%s"),
 	       obj_type_name,
 	       (obj_type_name && *obj_type_name) ? "::" : "",
@@ -2646,18 +2701,82 @@ find_overload_match (struct value **args, int nargs,
       if (fns_ptr)
 	{
 	  gdb_assert (TYPE_DOMAIN_TYPE (fns_ptr[0].type) != NULL);
-	  method_oload_champ = find_oload_champ (args, nargs, method,
-	                                         num_fns, fns_ptr,
-	                                         oload_syms, &method_badness);
-
-	  method_match_quality =
-	      classify_oload_match (method_badness, nargs,
-	                            oload_method_static (method, fns_ptr,
-	                                                 method_oload_champ));
-
-	  make_cleanup (xfree, method_badness);
+	  src_method_oload_champ = find_oload_champ (args, nargs, method,
+	                                             num_fns, fns_ptr, NULL,
+	                                             oload_syms,
+                                                     &src_method_badness);
+
+	  src_method_match_quality =
+	      classify_oload_match (
+                  src_method_badness, nargs,
+	          oload_method_static (method, fns_ptr,
+                                       src_method_oload_champ));
+
+	  make_cleanup (xfree, src_method_badness);
 	}
 
+      if (ext_fn && VEC_length (ext_fn_descriptor_p, ext_fn_vec))
+        {
+          ext_method_oload_champ = find_oload_champ (args, nargs, method,
+                                                     0, NULL, ext_fn_vec,
+                                                     NULL, &ext_method_badness);
+          ext_method_match_quality = classify_oload_match (ext_method_badness,
+                                                           nargs, 0);
+          make_cleanup (xfree, ext_method_badness);
+          make_ext_fn_vec_cleanup (ext_fn_vec);
+        }
+
+      if (src_method_oload_champ >= 0 && ext_method_oload_champ >= 0)
+        {
+          switch (compare_badness (ext_method_badness, src_method_badness))
+            {
+              case 0: /* Src method and ext method are equally good.  */
+                src_and_ext_equal = 1;
+              case 1: /* Src method and ext method are incompatible  */
+                /* if ext method match is not standard, then let source method
+                   win.  */
+                if (ext_method_match_quality != STANDARD)
+                  {
+                    method_oload_champ = src_method_oload_champ;
+                    method_badness = src_method_badness;
+                    ext_method_oload_champ = -1;
+                    method_match_quality = src_method_match_quality;
+                    break;
+                  }
+              case 2: /* Ext method is champion.  */
+                method_oload_champ = ext_method_oload_champ;
+                method_badness = ext_method_badness;
+                src_method_oload_champ_bkp = src_method_oload_champ;
+                src_method_oload_champ = -1;
+                method_match_quality = ext_method_match_quality;
+                break;
+              case 3: /* Src method is champion.  */
+                method_oload_champ = src_method_oload_champ;
+                method_badness = src_method_badness;
+                ext_method_oload_champ = -1;
+                method_match_quality = src_method_match_quality;
+                break;
+              default:
+                error (_("Internal error: unexpected overload comparison "
+                         "result"));
+                break;
+            }
+        }
+      else
+        {
+          if (src_method_oload_champ >= 0)
+            {
+              method_oload_champ = src_method_oload_champ;
+              method_badness = src_method_badness;
+              method_match_quality = src_method_match_quality;
+            }
+          if (ext_method_oload_champ >= 0)
+            {
+              method_oload_champ = ext_method_oload_champ;
+              method_badness = ext_method_badness;
+              method_match_quality = ext_method_match_quality;
+            }
+        }
     }
 
   if (method == NON_METHOD || method == BOTH)
@@ -2800,21 +2919,6 @@ find_overload_match (struct value **args, int nargs,
 		 func_name);
     }
 
-  if (staticp != NULL)
-    *staticp = oload_method_static (method, fns_ptr, method_oload_champ);
-
-  if (method_oload_champ >= 0)
-    {
-      if (TYPE_FN_FIELD_VIRTUAL_P (fns_ptr, method_oload_champ))
-	*valp = value_virtual_fn_field (&temp, fns_ptr, method_oload_champ,
-					basetype, boffset);
-      else
-	*valp = value_fn_field (&temp, fns_ptr, method_oload_champ,
-				basetype, boffset);
-    }
-  else
-    *symp = oload_syms[func_oload_champ];
-
   if (objp)
     {
       struct type *temp_type = check_typedef (value_type (temp));
@@ -2824,11 +2928,66 @@ find_overload_match (struct value **args, int nargs,
 	  && (TYPE_CODE (objtype) == TYPE_CODE_PTR
 	      || TYPE_CODE (objtype) == TYPE_CODE_REF))
 	{
-	  temp = value_addr (temp);
+	  *objp = value_addr (temp);
 	}
-      *objp = temp;
+      else
+        *objp = temp;
     }
 
+  if (staticp != NULL)
+    *staticp = oload_method_static (method, fns_ptr, method_oload_champ);
+
+  if (method_oload_champ >= 0)
+    {
+      if (src_method_oload_champ >= 0)
+        {
+          if (TYPE_FN_FIELD_VIRTUAL_P (fns_ptr, method_oload_champ))
+            {
+              struct type *dtype;
+      
+              dtype = value_has_indirect_dynamic_type (args[0]);
+              if (dtype)
+                {
+                  args[0] = value_cast (dtype, args[0]);
+                  do_cleanups (all_cleanups);
+                  return find_overload_match (args, nargs, name, method,
+                                              objp, fsym, valp, symp, ext_fn,
+		                              staticp, no_adl);
+                }
+              else
+                *valp = value_virtual_fn_field (&temp, fns_ptr,
+                                                method_oload_champ,
+                                                basetype, boffset);
+            }
+          else
+            *valp = value_fn_field (&temp, fns_ptr, method_oload_champ,
+                                    basetype, boffset);
+        }
+      else
+        {
+          if (src_and_ext_equal 
+              && TYPE_FN_FIELD_VIRTUAL_P (fns_ptr, src_method_oload_champ_bkp))
+            {
+              struct type *dtype;
+      
+              dtype = value_has_indirect_dynamic_type (args[0]);
+              if (dtype)
+                {
+                  args[0] = value_cast (dtype, args[0]);
+                  do_cleanups (all_cleanups);
+                  return find_overload_match (args, nargs, name, method,
+                                              objp, fsym, valp, symp, ext_fn,
+		                              staticp, no_adl);
+                }
+            }
+
+          *ext_fn = ext_fn_clone (VEC_index (ext_fn_descriptor_p, ext_fn_vec,
+                                             ext_method_oload_champ));
+        }
+    }
+  else
+    *symp = oload_syms[func_oload_champ];
+
   do_cleanups (all_cleanups);
 
   switch (match_quality)
@@ -2962,7 +3121,7 @@ find_oload_champ_namespace_loop (struct value **args, int nargs,
     ++num_fns;
 
   new_oload_champ = find_oload_champ (args, nargs, 0, num_fns,
-				      NULL, new_oload_syms,
+				      NULL, NULL, new_oload_syms,
 				      &new_oload_champ_bv);
 
   /* Case 1: We found a good match.  Free earlier matches (if any),
@@ -3010,10 +3169,12 @@ find_oload_champ_namespace_loop (struct value **args, int nargs,
 static int
 find_oload_champ (struct value **args, int nargs, int method,
 		  int num_fns, struct fn_field *fns_ptr,
+                  VEC (ext_fn_descriptor_p) *ext_fn_vec,
 		  struct symbol **oload_syms,
 		  struct badness_vector **oload_champ_bv)
 {
   int ix;
+  int ext_fn_vec_n = 0;
   /* A measure of how good an overloaded instance is.  */
   struct badness_vector *bv;
   /* Index of best overloaded function.  */
@@ -3023,18 +3184,27 @@ find_oload_champ (struct value **args, int nargs, int method,
   /* 0 => no ambiguity, 1 => two good funcs, 2 => incomparable funcs.  */
 
   *oload_champ_bv = NULL;
+  ext_fn_vec_n = ext_fn_vec ? VEC_length (ext_fn_descriptor_p, ext_fn_vec) : 0;
 
   /* Consider each candidate in turn.  */
-  for (ix = 0; ix < num_fns; ix++)
+  for (ix = 0; (ix < num_fns) || (ix < ext_fn_vec_n); ix++)
     {
       int jj;
-      int static_offset = oload_method_static (method, fns_ptr, ix);
+      int static_offset = 0;
       int nparms;
       struct type **parm_types;
+      struct ext_fn_descriptor *ext_fn = NULL;
+
+      if (ext_fn_vec)
+        ext_fn = VEC_index (ext_fn_descriptor_p, ext_fn_vec, ix);
 
       if (method)
 	{
-	  nparms = TYPE_NFIELDS (TYPE_FN_FIELD_TYPE (fns_ptr, ix));
+          if (fns_ptr)
+            {
+              static_offset = oload_method_static (method, fns_ptr, ix);
+	      nparms = TYPE_NFIELDS (TYPE_FN_FIELD_TYPE (fns_ptr, ix));
+            }
 	}
       else
 	{
@@ -3043,13 +3213,20 @@ find_oload_champ (struct value **args, int nargs, int method,
 	}
 
       /* Prepare array of parameter types.  */
-      parm_types = (struct type **) 
-	xmalloc (nparms * (sizeof (struct type *)));
-      for (jj = 0; jj < nparms; jj++)
-	parm_types[jj] = (method
-			  ? (TYPE_FN_FIELD_ARGS (fns_ptr, ix)[jj].type)
-			  : TYPE_FIELD_TYPE (SYMBOL_TYPE (oload_syms[ix]), 
-					     jj));
+      if (fns_ptr || oload_syms)
+        {
+          parm_types = (struct type **) 
+            xmalloc (nparms * (sizeof (struct type *)));
+          for (jj = 0; jj < nparms; jj++)
+            parm_types[jj] = (method
+                              ? (TYPE_FN_FIELD_ARGS (fns_ptr, ix)[jj].type)
+                              : TYPE_FIELD_TYPE (SYMBOL_TYPE (oload_syms[ix]), 
+                              jj));
+        }
+      else
+        {
+          parm_types = ext_fn_get_argtypes (ext_fn, &nparms);
+        }
 
       /* Compare parameter types to supplied argument types.  Skip
          THIS for static methods.  */
diff --git a/gdb/value.h b/gdb/value.h
index 4e839d3..c4bf51e 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -31,6 +31,7 @@ struct type;
 struct ui_file;
 struct language_defn;
 struct value_print_options;
+struct ext_fn_descriptor;
 
 /* The structure which defines the type of a value.  It should never
    be possible for a program lval value to survive over a call to the
@@ -652,6 +653,7 @@ extern int find_overload_match (struct value **args, int nargs,
 				enum oload_search_type method,
 				struct value **objp, struct symbol *fsym,
 				struct value **valp, struct symbol **symp,
+                                struct ext_fn_descriptor **ext_fn,
 				int *staticp, const int no_adl);
 
 extern struct value *value_field (struct value *arg1, int fieldno);


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