gdb/python/py-finishbreakpoint.c - binutils-gdb - Git at Google

 /* Python interface to finish breakpoints

    Copyright (C) 2011-2023 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 "top.h"
 #include "python-internal.h"
 #include "breakpoint.h"
 #include "frame.h"
 #include "gdbthread.h"
 #include "arch-utils.h"
 #include "language.h"
 #include "observable.h"
 #include "inferior.h"
 #include "block.h"
 #include "location.h"

 /* Function that is called when a Python finish bp is found out of scope.  */
 static const char outofscope_func[] = "out_of_scope";

 /* struct implementing the gdb.FinishBreakpoint object by extending
    the gdb.Breakpoint class.  */
 struct finish_breakpoint_object
 {
   /* gdb.Breakpoint base class.  */
   gdbpy_breakpoint_object py_bp;

   /* gdb.Symbol object of the function finished by this breakpoint.

      nullptr if no debug information was available or return type was VOID.  */
   PyObject *func_symbol;

   /* gdb.Value object of the function finished by this breakpoint.

      nullptr if no debug information was available or return type was VOID.  */
   PyObject *function_value;

   /* When stopped at this FinishBreakpoint, gdb.Value object returned by
      the function; Py_None if the value is not computable; NULL if GDB is
      not stopped at a FinishBreakpoint.  */
   PyObject *return_value;

   /* The initiating frame for this operation, used to decide when we have
      left this frame.  */
   struct frame_id initiating_frame;
 };

 extern PyTypeObject finish_breakpoint_object_type
     CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("finish_breakpoint_object");

 /* Python function to get the 'return_value' attribute of
    FinishBreakpoint.  */

 static PyObject *
 bpfinishpy_get_returnvalue (PyObject *self, void *closure)
 {
   struct finish_breakpoint_object *self_finishbp =
       (struct finish_breakpoint_object *) self;

   if (!self_finishbp->return_value)
     Py_RETURN_NONE;

   Py_INCREF (self_finishbp->return_value);
   return self_finishbp->return_value;
 }

 /* Deallocate FinishBreakpoint object.  */

 static void
 bpfinishpy_dealloc (PyObject *self)
 {
   struct finish_breakpoint_object *self_bpfinish =
 	(struct finish_breakpoint_object *) self;

   Py_XDECREF (self_bpfinish->func_symbol);
   Py_XDECREF (self_bpfinish->function_value);
   Py_XDECREF (self_bpfinish->return_value);
   Py_TYPE (self)->tp_free (self);
 }

 /* Triggered when gdbpy_breakpoint_cond_says_stop is about to execute the `stop'
    callback of the gdb.FinishBreakpoint object BP_OBJ.  Will compute and cache
    the `return_value', if possible.  */

 void
 bpfinishpy_pre_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
 {
   struct finish_breakpoint_object *self_finishbp =
 	(struct finish_breakpoint_object *) bp_obj;

   /* Can compute return_value only once.  */
   gdb_assert (!self_finishbp->return_value);

   if (self_finishbp->func_symbol == nullptr)
     return;

   try
     {
       scoped_value_mark free_values;

       struct symbol *func_symbol =
 	symbol_object_to_symbol (self_finishbp->func_symbol);
       struct value *function =
 	value_object_to_value (self_finishbp->function_value);
       struct value *ret =
 	get_return_value (func_symbol, function);

       if (ret)
 	{
 	  self_finishbp->return_value = value_to_value_object (ret);
 	  if (!self_finishbp->return_value)
 	      gdbpy_print_stack ();
 	}
       else
 	{
 	  Py_INCREF (Py_None);
 	  self_finishbp->return_value = Py_None;
 	}
     }
   catch (const gdb_exception &except)
     {
       gdbpy_convert_exception (except);
       gdbpy_print_stack ();
     }
 }

 /* Triggered when gdbpy_breakpoint_cond_says_stop has triggered the `stop'
    callback of the gdb.FinishBreakpoint object BP_OBJ.  */

 void
 bpfinishpy_post_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
 {

   try
     {
       /* Can't delete it here, but it will be removed at the next stop.  */
       disable_breakpoint (bp_obj->bp);
       bp_obj->bp->disposition = disp_del_at_next_stop;
     }
   catch (const gdb_exception &except)
     {
       gdbpy_convert_exception (except);
       gdbpy_print_stack ();
     }
 }

 /* Python function to create a new breakpoint.  */

 static int
 bpfinishpy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 {
   static const char *keywords[] = { "frame", "internal", NULL };
   struct finish_breakpoint_object *self_bpfinish =
       (struct finish_breakpoint_object *) self;
   PyObject *frame_obj = NULL;
   int thread;
   frame_info_ptr frame = NULL; /* init for gcc -Wall */
   frame_info_ptr prev_frame = NULL;
   struct frame_id frame_id;
   PyObject *internal = NULL;
   int internal_bp = 0;
   CORE_ADDR pc;

   if (!gdb_PyArg_ParseTupleAndKeywords (args, kwargs, "|OO", keywords,
 					&frame_obj, &internal))
     return -1;

   try
     {
       /* Default frame to newest frame if necessary.  */
       if (frame_obj == NULL)
 	frame = get_current_frame ();
       else
 	frame = frame_object_to_frame_info (frame_obj);

       if (frame == NULL)
 	{
 	  PyErr_SetString (PyExc_ValueError,
 			   _("Invalid ID for the `frame' object."));
 	}
       else
 	{
 	  prev_frame = get_prev_frame (frame);
 	  if (prev_frame == 0)
 	    {
 	      PyErr_SetString (PyExc_ValueError,
 			       _("\"FinishBreakpoint\" not "
 				 "meaningful in the outermost "
 				 "frame."));
 	    }
 	  else if (get_frame_type (prev_frame) == DUMMY_FRAME)
 	    {
 	      PyErr_SetString (PyExc_ValueError,
 			       _("\"FinishBreakpoint\" cannot "
 				 "be set on a dummy frame."));
 	    }
 	  else
 	    /* Get the real calling frame ID, ignoring inline frames.  */
 	    frame_id = frame_unwind_caller_id (frame);
 	}
     }
   catch (const gdb_exception &except)
     {
       gdbpy_convert_exception (except);
       return -1;
     }

   if (PyErr_Occurred ())
     return -1;

   if (inferior_ptid == null_ptid)
     {
       PyErr_SetString (PyExc_ValueError,
 		       _("No thread currently selected."));
       return -1;
     }

   thread = inferior_thread ()->global_num;

   if (internal)
     {
       internal_bp = PyObject_IsTrue (internal);
       if (internal_bp == -1)
 	{
 	  PyErr_SetString (PyExc_ValueError,
 			   _("The value of `internal' must be a boolean."));
 	  return -1;
 	}
     }

   /* Find the function we will return from.  */
   self_bpfinish->func_symbol = nullptr;
   self_bpfinish->function_value = nullptr;

   try
     {
       if (get_frame_pc_if_available (frame, &pc))
 	{
 	  struct symbol *function = find_pc_function (pc);
 	  if (function != nullptr)
 	    {
 	      struct type *ret_type =
 		check_typedef (function->type ()->target_type ());

 	      /* Remember only non-void return types.  */
 	      if (ret_type->code () != TYPE_CODE_VOID)
 		{
 		  scoped_value_mark free_values;

 		  /* Ignore Python errors at this stage.  */
 		  value *func_value = read_var_value (function, NULL, frame);
 		  self_bpfinish->function_value
 		    = value_to_value_object (func_value);
 		  PyErr_Clear ();

 		  self_bpfinish->func_symbol
 		    = symbol_to_symbol_object (function);
 		  PyErr_Clear ();
 		}
 	    }
 	}
     }
   catch (const gdb_exception_forced_quit &except)
     {
       quit_force (NULL, 0);
     }
   catch (const gdb_exception &except)
     {
       /* Just swallow.  Either the return type or the function value
 	 remain NULL.  */
     }

   if (self_bpfinish->func_symbol == nullptr
       || self_bpfinish->function_value == nullptr)
     {
       /* Won't be able to compute return value.  */
       Py_XDECREF (self_bpfinish->func_symbol);
       Py_XDECREF (self_bpfinish->function_value);

       self_bpfinish->func_symbol = nullptr;
       self_bpfinish->function_value = nullptr;
     }

   bppy_pending_object = &self_bpfinish->py_bp;
   bppy_pending_object->number = -1;
   bppy_pending_object->bp = NULL;

   try
     {
       /* Set a breakpoint on the return address.  */
       location_spec_up locspec
 	= new_address_location_spec (get_frame_pc (prev_frame), NULL, 0);
       create_breakpoint (gdbpy_enter::get_gdbarch (),
 			 locspec.get (), NULL, thread, -1, NULL, false,
 			 0,
 			 1 /*temp_flag*/,
 			 bp_breakpoint,
 			 0,
 			 AUTO_BOOLEAN_TRUE,
 			 &code_breakpoint_ops,
 			 0, 1, internal_bp, 0);
     }
   catch (const gdb_exception &except)
     {
       GDB_PY_SET_HANDLE_EXCEPTION (except);
     }

   self_bpfinish->py_bp.bp->frame_id = frame_id;
   self_bpfinish->py_bp.is_finish_bp = 1;
   self_bpfinish->initiating_frame = get_frame_id (frame);

   /* Bind the breakpoint with the current program space.  */
   self_bpfinish->py_bp.bp->pspace = current_program_space;

   return 0;
 }

 /* Called when GDB notices that the finish breakpoint BP_OBJ is out of
    the current callstack.  Triggers the method OUT_OF_SCOPE if implemented,
    then delete the breakpoint.  */

 static void
 bpfinishpy_out_of_scope (struct finish_breakpoint_object *bpfinish_obj)
 {
   gdbpy_breakpoint_object *bp_obj = (gdbpy_breakpoint_object *) bpfinish_obj;
   PyObject *py_obj = (PyObject *) bp_obj;

   if (bpfinish_obj->py_bp.bp->enable_state == bp_enabled
       && PyObject_HasAttrString (py_obj, outofscope_func))
     {
       gdbpy_ref<> meth_result (PyObject_CallMethod (py_obj, outofscope_func,
 						    NULL));
       if (meth_result == NULL)
 	gdbpy_print_stack ();
     }
 }

 /* Callback for `bpfinishpy_detect_out_scope'.  Triggers Python's
    `B->out_of_scope' function if B is a FinishBreakpoint out of its scope.

    When DELETE_BP is true then breakpoint B will be deleted if B is a
    FinishBreakpoint and it is out of scope, otherwise B will not be
    deleted.  */

 static void
 bpfinishpy_detect_out_scope_cb (struct breakpoint *b,
 				struct breakpoint *bp_stopped,
 				bool delete_bp)
 {
   PyObject *py_bp = (PyObject *) b->py_bp_object;

   /* Trigger out_of_scope if this is a FinishBreakpoint and its frame is
      not anymore in the current callstack.  */
   if (py_bp != NULL && b->py_bp_object->is_finish_bp)
     {
       struct finish_breakpoint_object *finish_bp =
 	  (struct finish_breakpoint_object *) py_bp;

       /* Check scope if not currently stopped at the FinishBreakpoint.  */
       if (b != bp_stopped)
 	{
 	  try
 	    {
 	      struct frame_id initiating_frame = finish_bp->initiating_frame;

 	      if (b->pspace == current_inferior ()->pspace
 		  && (!target_has_registers ()
 		      || frame_find_by_id (initiating_frame) == NULL))
 		{
 		  bpfinishpy_out_of_scope (finish_bp);
 		  if (delete_bp)
 		    delete_breakpoint (finish_bp->py_bp.bp);
 		}
 	    }
 	  catch (const gdb_exception &except)
 	    {
 	      gdbpy_convert_exception (except);
 	      gdbpy_print_stack ();
 	    }
 	}
     }
 }

 /* Called when gdbpy_breakpoint_deleted is about to delete a breakpoint.  A
    chance to trigger the out_of_scope callback (if appropriate) for the
    associated Python object.  */

 void
 bpfinishpy_pre_delete_hook (struct gdbpy_breakpoint_object *bp_obj)
 {
   breakpoint *bp = bp_obj->bp;
   bpfinishpy_detect_out_scope_cb (bp, nullptr, false);
 }

 /* Attached to `stop' notifications, check if the execution has run
    out of the scope of any FinishBreakpoint before it has been hit.  */

 static void
 bpfinishpy_handle_stop (struct bpstat *bs, int print_frame)
 {
   gdbpy_enter enter_py;

   for (breakpoint &bp : all_breakpoints_safe ())
     bpfinishpy_detect_out_scope_cb
       (&bp, bs == NULL ? NULL : bs->breakpoint_at, true);
 }

 /* Attached to `exit' notifications, triggers all the necessary out of
    scope notifications.  */

 static void
 bpfinishpy_handle_exit (struct inferior *inf)
 {
   gdbpy_enter enter_py (current_inferior ()->arch ());

   for (breakpoint &bp : all_breakpoints_safe ())
     bpfinishpy_detect_out_scope_cb (&bp, nullptr, true);
 }

 /* Initialize the Python finish breakpoint code.  */

 static int CPYCHECKER_NEGATIVE_RESULT_SETS_EXCEPTION
 gdbpy_initialize_finishbreakpoints (void)
 {
   if (!gdbpy_breakpoint_init_breakpoint_type ())
     return -1;

   if (PyType_Ready (&finish_breakpoint_object_type) < 0)
     return -1;

   if (gdb_pymodule_addobject (gdb_module, "FinishBreakpoint",
 			      (PyObject *) &finish_breakpoint_object_type) < 0)
     return -1;

   gdb::observers::normal_stop.attach (bpfinishpy_handle_stop,
 				      "py-finishbreakpoint");
   gdb::observers::inferior_exit.attach (bpfinishpy_handle_exit,
 					"py-finishbreakpoint");

   return 0;
 }

 GDBPY_INITIALIZE_FILE (gdbpy_initialize_finishbreakpoints);


 static gdb_PyGetSetDef finish_breakpoint_object_getset[] = {
   { "return_value", bpfinishpy_get_returnvalue, NULL,
   "gdb.Value object representing the return value, if any. \
 None otherwise.", NULL },
     { NULL }  /* Sentinel.  */
 };

 PyTypeObject finish_breakpoint_object_type =
 {
   PyVarObject_HEAD_INIT (NULL, 0)
   "gdb.FinishBreakpoint",         /*tp_name*/
   sizeof (struct finish_breakpoint_object),  /*tp_basicsize*/
   0,                              /*tp_itemsize*/
   bpfinishpy_dealloc,             /*tp_dealloc*/
   0,                              /*tp_print*/
   0,                              /*tp_getattr*/
   0,                              /*tp_setattr*/
   0,                              /*tp_compare*/
   0,                              /*tp_repr*/
   0,                              /*tp_as_number*/
   0,                              /*tp_as_sequence*/
   0,                              /*tp_as_mapping*/
   0,                              /*tp_hash */
   0,                              /*tp_call*/
   0,                              /*tp_str*/
   0,                              /*tp_getattro*/
   0,                              /*tp_setattro */
   0,                              /*tp_as_buffer*/
   Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
   "GDB finish breakpoint object", /* tp_doc */
   0,                              /* tp_traverse */
   0,                              /* tp_clear */
   0,                              /* tp_richcompare */
   0,                              /* tp_weaklistoffset */
   0,                              /* tp_iter */
   0,                              /* tp_iternext */
   0,                              /* tp_methods */
   0,                              /* tp_members */
   finish_breakpoint_object_getset,/* tp_getset */
   &breakpoint_object_type,        /* tp_base */
   0,                              /* tp_dict */
   0,                              /* tp_descr_get */
   0,                              /* tp_descr_set */
   0,                              /* tp_dictoffset */
   bpfinishpy_init,                /* tp_init */
   0,                              /* tp_alloc */
   0                               /* tp_new */
 };
	/* Python interface to finish breakpoints

	Copyright (C) 2011-2023 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 "top.h"
	#include "python-internal.h"
	#include "breakpoint.h"
	#include "frame.h"
	#include "gdbthread.h"
	#include "arch-utils.h"
	#include "language.h"
	#include "observable.h"
	#include "inferior.h"
	#include "block.h"
	#include "location.h"

	/* Function that is called when a Python finish bp is found out of scope. */
	static const char outofscope_func[] = "out_of_scope";

	/* struct implementing the gdb.FinishBreakpoint object by extending
	the gdb.Breakpoint class. */
	struct finish_breakpoint_object
	{
	/* gdb.Breakpoint base class. */
	gdbpy_breakpoint_object py_bp;

	/* gdb.Symbol object of the function finished by this breakpoint.

	nullptr if no debug information was available or return type was VOID. */
	PyObject *func_symbol;

	/* gdb.Value object of the function finished by this breakpoint.

	nullptr if no debug information was available or return type was VOID. */
	PyObject *function_value;

	/* When stopped at this FinishBreakpoint, gdb.Value object returned by
	the function; Py_None if the value is not computable; NULL if GDB is
	not stopped at a FinishBreakpoint. */
	PyObject *return_value;

	/* The initiating frame for this operation, used to decide when we have
	left this frame. */
	struct frame_id initiating_frame;
	};

	extern PyTypeObject finish_breakpoint_object_type
	CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("finish_breakpoint_object");

	/* Python function to get the 'return_value' attribute of
	FinishBreakpoint. */

	static PyObject *
	bpfinishpy_get_returnvalue (PyObject self, void closure)
	{
	struct finish_breakpoint_object *self_finishbp =
	(struct finish_breakpoint_object *) self;

	if (!self_finishbp->return_value)
	Py_RETURN_NONE;

	Py_INCREF (self_finishbp->return_value);
	return self_finishbp->return_value;
	}

	/* Deallocate FinishBreakpoint object. */

	static void
	bpfinishpy_dealloc (PyObject *self)
	{
	struct finish_breakpoint_object *self_bpfinish =
	(struct finish_breakpoint_object *) self;

	Py_XDECREF (self_bpfinish->func_symbol);
	Py_XDECREF (self_bpfinish->function_value);
	Py_XDECREF (self_bpfinish->return_value);
	Py_TYPE (self)->tp_free (self);
	}

	/* Triggered when gdbpy_breakpoint_cond_says_stop is about to execute the `stop'
	callback of the gdb.FinishBreakpoint object BP_OBJ. Will compute and cache
	the `return_value', if possible. */

	void
	bpfinishpy_pre_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
	{
	struct finish_breakpoint_object *self_finishbp =
	(struct finish_breakpoint_object *) bp_obj;

	/* Can compute return_value only once. */
	gdb_assert (!self_finishbp->return_value);

	if (self_finishbp->func_symbol == nullptr)
	return;

	try
	{
	scoped_value_mark free_values;

	struct symbol *func_symbol =
	symbol_object_to_symbol (self_finishbp->func_symbol);
	struct value *function =
	value_object_to_value (self_finishbp->function_value);
	struct value *ret =
	get_return_value (func_symbol, function);

	if (ret)
	{
	self_finishbp->return_value = value_to_value_object (ret);
	if (!self_finishbp->return_value)
	gdbpy_print_stack ();
	}
	else
	{
	Py_INCREF (Py_None);
	self_finishbp->return_value = Py_None;
	}
	}
	catch (const gdb_exception &except)
	{
	gdbpy_convert_exception (except);
	gdbpy_print_stack ();
	}
	}

	/* Triggered when gdbpy_breakpoint_cond_says_stop has triggered the `stop'
	callback of the gdb.FinishBreakpoint object BP_OBJ. */

	void
	bpfinishpy_post_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
	{

	try
	{
	/* Can't delete it here, but it will be removed at the next stop. */
	disable_breakpoint (bp_obj->bp);
	bp_obj->bp->disposition = disp_del_at_next_stop;
	}
	catch (const gdb_exception &except)
	{
	gdbpy_convert_exception (except);
	gdbpy_print_stack ();
	}
	}

	/* Python function to create a new breakpoint. */

	static int
	bpfinishpy_init (PyObject self, PyObject args, PyObject *kwargs)
	{
	static const char *keywords[] = { "frame", "internal", NULL };
	struct finish_breakpoint_object *self_bpfinish =
	(struct finish_breakpoint_object *) self;
	PyObject *frame_obj = NULL;
	int thread;
	frame_info_ptr frame = NULL; /* init for gcc -Wall */
	frame_info_ptr prev_frame = NULL;
	struct frame_id frame_id;
	PyObject *internal = NULL;
	int internal_bp = 0;
	CORE_ADDR pc;

	if (!gdb_PyArg_ParseTupleAndKeywords (args, kwargs, "\|OO", keywords,
	&frame_obj, &internal))
	return -1;

	try
	{
	/* Default frame to newest frame if necessary. */
	if (frame_obj == NULL)
	frame = get_current_frame ();
	else
	frame = frame_object_to_frame_info (frame_obj);

	if (frame == NULL)
	{
	PyErr_SetString (PyExc_ValueError,
	_("Invalid ID for the `frame' object."));
	}
	else
	{
	prev_frame = get_prev_frame (frame);
	if (prev_frame == 0)
	{
	PyErr_SetString (PyExc_ValueError,
	_("\"FinishBreakpoint\" not "
	"meaningful in the outermost "
	"frame."));
	}
	else if (get_frame_type (prev_frame) == DUMMY_FRAME)
	{
	PyErr_SetString (PyExc_ValueError,
	_("\"FinishBreakpoint\" cannot "
	"be set on a dummy frame."));
	}
	else
	/* Get the real calling frame ID, ignoring inline frames. */
	frame_id = frame_unwind_caller_id (frame);
	}
	}
	catch (const gdb_exception &except)
	{
	gdbpy_convert_exception (except);
	return -1;
	}

	if (PyErr_Occurred ())
	return -1;

	if (inferior_ptid == null_ptid)
	{
	PyErr_SetString (PyExc_ValueError,
	_("No thread currently selected."));
	return -1;
	}

	thread = inferior_thread ()->global_num;

	if (internal)
	{
	internal_bp = PyObject_IsTrue (internal);
	if (internal_bp == -1)
	{
	PyErr_SetString (PyExc_ValueError,
	_("The value of `internal' must be a boolean."));
	return -1;
	}
	}

	/* Find the function we will return from. */
	self_bpfinish->func_symbol = nullptr;
	self_bpfinish->function_value = nullptr;

	try
	{
	if (get_frame_pc_if_available (frame, &pc))
	{
	struct symbol *function = find_pc_function (pc);
	if (function != nullptr)
	{
	struct type *ret_type =
	check_typedef (function->type ()->target_type ());

	/* Remember only non-void return types. */
	if (ret_type->code () != TYPE_CODE_VOID)
	{
	scoped_value_mark free_values;

	/* Ignore Python errors at this stage. */
	value *func_value = read_var_value (function, NULL, frame);
	self_bpfinish->function_value
	= value_to_value_object (func_value);
	PyErr_Clear ();

	self_bpfinish->func_symbol
	= symbol_to_symbol_object (function);
	PyErr_Clear ();
	}
	}
	}
	}
	catch (const gdb_exception_forced_quit &except)
	{
	quit_force (NULL, 0);
	}
	catch (const gdb_exception &except)
	{
	/* Just swallow. Either the return type or the function value
	remain NULL. */
	}

	if (self_bpfinish->func_symbol == nullptr
	\|\| self_bpfinish->function_value == nullptr)
	{
	/* Won't be able to compute return value. */
	Py_XDECREF (self_bpfinish->func_symbol);
	Py_XDECREF (self_bpfinish->function_value);

	self_bpfinish->func_symbol = nullptr;
	self_bpfinish->function_value = nullptr;
	}

	bppy_pending_object = &self_bpfinish->py_bp;
	bppy_pending_object->number = -1;
	bppy_pending_object->bp = NULL;

	try
	{
	/* Set a breakpoint on the return address. */
	location_spec_up locspec
	= new_address_location_spec (get_frame_pc (prev_frame), NULL, 0);
	create_breakpoint (gdbpy_enter::get_gdbarch (),
	locspec.get (), NULL, thread, -1, NULL, false,
	0,
	1 /temp_flag/,
	bp_breakpoint,
	0,
	AUTO_BOOLEAN_TRUE,
	&code_breakpoint_ops,
	0, 1, internal_bp, 0);
	}
	catch (const gdb_exception &except)
	{
	GDB_PY_SET_HANDLE_EXCEPTION (except);
	}

	self_bpfinish->py_bp.bp->frame_id = frame_id;
	self_bpfinish->py_bp.is_finish_bp = 1;
	self_bpfinish->initiating_frame = get_frame_id (frame);

	/* Bind the breakpoint with the current program space. */
	self_bpfinish->py_bp.bp->pspace = current_program_space;

	return 0;
	}

	/* Called when GDB notices that the finish breakpoint BP_OBJ is out of
	the current callstack. Triggers the method OUT_OF_SCOPE if implemented,
	then delete the breakpoint. */

	static void
	bpfinishpy_out_of_scope (struct finish_breakpoint_object *bpfinish_obj)
	{
	gdbpy_breakpoint_object bp_obj = (gdbpy_breakpoint_object ) bpfinish_obj;
	PyObject py_obj = (PyObject ) bp_obj;

	if (bpfinish_obj->py_bp.bp->enable_state == bp_enabled
	&& PyObject_HasAttrString (py_obj, outofscope_func))
	{
	gdbpy_ref<> meth_result (PyObject_CallMethod (py_obj, outofscope_func,
	NULL));
	if (meth_result == NULL)
	gdbpy_print_stack ();
	}
	}

	/* Callback for `bpfinishpy_detect_out_scope'. Triggers Python's
	`B->out_of_scope' function if B is a FinishBreakpoint out of its scope.

	When DELETE_BP is true then breakpoint B will be deleted if B is a
	FinishBreakpoint and it is out of scope, otherwise B will not be
	deleted. */

	static void
	bpfinishpy_detect_out_scope_cb (struct breakpoint *b,
	struct breakpoint *bp_stopped,
	bool delete_bp)
	{
	PyObject py_bp = (PyObject ) b->py_bp_object;

	/* Trigger out_of_scope if this is a FinishBreakpoint and its frame is
	not anymore in the current callstack. */
	if (py_bp != NULL && b->py_bp_object->is_finish_bp)
	{
	struct finish_breakpoint_object *finish_bp =
	(struct finish_breakpoint_object *) py_bp;

	/* Check scope if not currently stopped at the FinishBreakpoint. */
	if (b != bp_stopped)
	{
	try
	{
	struct frame_id initiating_frame = finish_bp->initiating_frame;

	if (b->pspace == current_inferior ()->pspace
	&& (!target_has_registers ()
	\|\| frame_find_by_id (initiating_frame) == NULL))
	{
	bpfinishpy_out_of_scope (finish_bp);
	if (delete_bp)
	delete_breakpoint (finish_bp->py_bp.bp);
	}
	}
	catch (const gdb_exception &except)
	{
	gdbpy_convert_exception (except);
	gdbpy_print_stack ();
	}
	}
	}
	}

	/* Called when gdbpy_breakpoint_deleted is about to delete a breakpoint. A
	chance to trigger the out_of_scope callback (if appropriate) for the
	associated Python object. */

	void
	bpfinishpy_pre_delete_hook (struct gdbpy_breakpoint_object *bp_obj)
	{
	breakpoint *bp = bp_obj->bp;
	bpfinishpy_detect_out_scope_cb (bp, nullptr, false);
	}

	/* Attached to `stop' notifications, check if the execution has run
	out of the scope of any FinishBreakpoint before it has been hit. */

	static void
	bpfinishpy_handle_stop (struct bpstat *bs, int print_frame)
	{
	gdbpy_enter enter_py;

	for (breakpoint &bp : all_breakpoints_safe ())
	bpfinishpy_detect_out_scope_cb
	(&bp, bs == NULL ? NULL : bs->breakpoint_at, true);
	}

	/* Attached to `exit' notifications, triggers all the necessary out of
	scope notifications. */

	static void
	bpfinishpy_handle_exit (struct inferior *inf)
	{
	gdbpy_enter enter_py (current_inferior ()->arch ());

	for (breakpoint &bp : all_breakpoints_safe ())
	bpfinishpy_detect_out_scope_cb (&bp, nullptr, true);
	}

	/* Initialize the Python finish breakpoint code. */

	static int CPYCHECKER_NEGATIVE_RESULT_SETS_EXCEPTION
	gdbpy_initialize_finishbreakpoints (void)
	{
	if (!gdbpy_breakpoint_init_breakpoint_type ())
	return -1;

	if (PyType_Ready (&finish_breakpoint_object_type) < 0)
	return -1;

	if (gdb_pymodule_addobject (gdb_module, "FinishBreakpoint",
	(PyObject *) &finish_breakpoint_object_type) < 0)
	return -1;

	gdb::observers::normal_stop.attach (bpfinishpy_handle_stop,
	"py-finishbreakpoint");
	gdb::observers::inferior_exit.attach (bpfinishpy_handle_exit,
	"py-finishbreakpoint");

	return 0;
	}

	GDBPY_INITIALIZE_FILE (gdbpy_initialize_finishbreakpoints);



	static gdb_PyGetSetDef finish_breakpoint_object_getset[] = {
	{ "return_value", bpfinishpy_get_returnvalue, NULL,
	"gdb.Value object representing the return value, if any. \
	None otherwise.", NULL },
	{ NULL } /* Sentinel. */
	};

	PyTypeObject finish_breakpoint_object_type =
	{
	PyVarObject_HEAD_INIT (NULL, 0)
	"gdb.FinishBreakpoint", /tp_name/
	sizeof (struct finish_breakpoint_object), /tp_basicsize/
	0, /tp_itemsize/
	bpfinishpy_dealloc, /tp_dealloc/
	0, /tp_print/
	0, /tp_getattr/
	0, /tp_setattr/
	0, /tp_compare/
	0, /tp_repr/
	0, /tp_as_number/
	0, /tp_as_sequence/
	0, /tp_as_mapping/
	0, /tp_hash /
	0, /tp_call/
	0, /tp_str/
	0, /tp_getattro/
	0, /tp_setattro /
	0, /tp_as_buffer/
	Py_TPFLAGS_DEFAULT \| Py_TPFLAGS_BASETYPE, /tp_flags/
	"GDB finish breakpoint object", /* tp_doc */
	0, /* tp_traverse */
	0, /* tp_clear */
	0, /* tp_richcompare */
	0, /* tp_weaklistoffset */
	0, /* tp_iter */
	0, /* tp_iternext */
	0, /* tp_methods */
	0, /* tp_members */
	finish_breakpoint_object_getset,/* tp_getset */
	&breakpoint_object_type, /* tp_base */
	0, /* tp_dict */
	0, /* tp_descr_get */
	0, /* tp_descr_set */
	0, /* tp_dictoffset */
	bpfinishpy_init, /* tp_init */
	0, /* tp_alloc */
	0 /* tp_new */
	};