binutils-gdb/gdb/python/python.c

/* General python/gdb code

   Copyright (C) 2008-2012 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 "command.h"
#include "ui-out.h"
#include "cli/cli-script.h"
#include "gdbcmd.h"
#include "progspace.h"
#include "objfiles.h"
#include "value.h"
#include "language.h"
#include "exceptions.h"
#include "event-loop.h"
#include "serial.h"
#include "readline/tilde.h"
#include "python.h"

#include <ctype.h>

/* Declared constants and enum for python stack printing.  */
static const char python_excp_none[] = "none";
static const char python_excp_full[] = "full";
static const char python_excp_message[] = "message";

/* "set python print-stack" choices.  */
static const char *const python_excp_enums[] =
  {
    python_excp_none,
    python_excp_full,
    python_excp_message,
    NULL
  };

/* The exception printing variable.  'full' if we want to print the
   error message and stack, 'none' if we want to print nothing, and
   'message' if we only want to print the error message.  'message' is
   the default.  */
static const char *gdbpy_should_print_stack = python_excp_message;

#ifdef HAVE_PYTHON

#include "libiberty.h"
#include "cli/cli-decode.h"
#include "charset.h"
#include "top.h"
#include "solib.h"
#include "python-internal.h"
#include "linespec.h"
#include "source.h"
#include "version.h"
#include "target.h"
#include "gdbthread.h"
#include "observer.h"
#include "interps.h"

static PyMethodDef GdbMethods[];

PyObject *gdb_module;

/* Some string constants we may wish to use.  */
PyObject *gdbpy_to_string_cst;
PyObject *gdbpy_children_cst;
PyObject *gdbpy_display_hint_cst;
PyObject *gdbpy_doc_cst;
PyObject *gdbpy_enabled_cst;
PyObject *gdbpy_value_cst;

/* The GdbError exception.  */
PyObject *gdbpy_gdberror_exc;

/* The `gdb.error' base class.  */
PyObject *gdbpy_gdb_error;

/* The `gdb.MemoryError' exception.  */
PyObject *gdbpy_gdb_memory_error;

/* Architecture and language to be used in callbacks from
   the Python interpreter.  */
struct gdbarch *python_gdbarch;
const struct language_defn *python_language;

/* Restore global language and architecture and Python GIL state
   when leaving the Python interpreter.  */

struct python_env
{
  PyGILState_STATE state;
  struct gdbarch *gdbarch;
  const struct language_defn *language;
  PyObject *error_type, *error_value, *error_traceback;
};

static void
restore_python_env (void *p)
{
  struct python_env *env = (struct python_env *)p;

  /* Leftover Python error is forbidden by Python Exception Handling.  */
  if (PyErr_Occurred ())
    {
      /* This order is similar to the one calling error afterwards. */
      gdbpy_print_stack ();
      warning (_("internal error: Unhandled Python exception"));
    }

  PyErr_Restore (env->error_type, env->error_value, env->error_traceback);

  PyGILState_Release (env->state);
  python_gdbarch = env->gdbarch;
  python_language = env->language;
  xfree (env);
}

/* Called before entering the Python interpreter to install the
   current language and architecture to be used for Python values.  */

struct cleanup *
ensure_python_env (struct gdbarch *gdbarch,
                   const struct language_defn *language)
{
  struct python_env *env = xmalloc (sizeof *env);

  env->state = PyGILState_Ensure ();
  env->gdbarch = python_gdbarch;
  env->language = python_language;

  python_gdbarch = gdbarch;
  python_language = language;

  /* Save it and ensure ! PyErr_Occurred () afterwards.  */
  PyErr_Fetch (&env->error_type, &env->error_value, &env->error_traceback);
  
  return make_cleanup (restore_python_env, env);
}

/* A wrapper around PyRun_SimpleFile.  FILE is the Python script to run
   named FILENAME.

   On Windows hosts few users would build Python themselves (this is no
   trivial task on this platform), and thus use binaries built by
   someone else instead.  There may happen situation where the Python
   library and GDB are using two different versions of the C runtime
   library.  Python, being built with VC, would use one version of the
   msvcr DLL (Eg. msvcr100.dll), while MinGW uses msvcrt.dll.
   A FILE * from one runtime does not necessarily operate correctly in
   the other runtime.

   To work around this potential issue, we create on Windows hosts the
   FILE object using Python routines, thus making sure that it is
   compatible with the Python library.  */

static void
python_run_simple_file (FILE *file, const char *filename)
{
#ifndef _WIN32

  PyRun_SimpleFile (file, filename);

#else /* _WIN32 */

  char *full_path;
  PyObject *python_file;
  struct cleanup *cleanup;

  /* Because we have a string for a filename, and are using Python to
     open the file, we need to expand any tilde in the path first.  */
  full_path = tilde_expand (filename);
  cleanup = make_cleanup (xfree, full_path);
  python_file = PyFile_FromString (full_path, "r");
  if (! python_file)
    {
      do_cleanups (cleanup);
      gdbpy_print_stack ();
      error (_("Error while opening file: %s"), full_path);
    }
 
  make_cleanup_py_decref (python_file);
  PyRun_SimpleFile (PyFile_AsFile (python_file), filename);
  do_cleanups (cleanup);

#endif /* _WIN32 */
}

/* Given a command_line, return a command string suitable for passing
   to Python.  Lines in the string are separated by newlines.  The
   return value is allocated using xmalloc and the caller is
   responsible for freeing it.  */

static char *
compute_python_string (struct command_line *l)
{
  struct command_line *iter;
  char *script = NULL;
  int size = 0;
  int here;

  for (iter = l; iter; iter = iter->next)
    size += strlen (iter->line) + 1;

  script = xmalloc (size + 1);
  here = 0;
  for (iter = l; iter; iter = iter->next)
    {
      int len = strlen (iter->line);

      strcpy (&script[here], iter->line);
      here += len;
      script[here++] = '\n';
    }
  script[here] = '\0';
  return script;
}

/* Take a command line structure representing a 'python' command, and
   evaluate its body using the Python interpreter.  */

void
eval_python_from_control_command (struct command_line *cmd)
{
  int ret;
  char *script;
  struct cleanup *cleanup;

  if (cmd->body_count != 1)
    error (_("Invalid \"python\" block structure."));

  cleanup = ensure_python_env (get_current_arch (), current_language);

  script = compute_python_string (cmd->body_list[0]);
  ret = PyRun_SimpleString (script);
  xfree (script);
  if (ret)
    error (_("Error while executing Python code."));

  do_cleanups (cleanup);
}

/* Implementation of the gdb "python" command.  */

static void
python_command (char *arg, int from_tty)
{
  struct cleanup *cleanup;

  cleanup = ensure_python_env (get_current_arch (), current_language);

  make_cleanup_restore_integer (&interpreter_async);
  interpreter_async = 0;

  while (arg && *arg && isspace (*arg))
    ++arg;
  if (arg && *arg)
    {
      if (PyRun_SimpleString (arg))
	error (_("Error while executing Python code."));
    }
  else
    {
      struct command_line *l = get_command_line (python_control, "");

      make_cleanup_free_command_lines (&l);
      execute_control_command_untraced (l);
    }

  do_cleanups (cleanup);
}



/* Transform a gdb parameters's value into a Python value.  May return
   NULL (and set a Python exception) on error.  Helper function for
   get_parameter.  */
PyObject *
gdbpy_parameter_value (enum var_types type, void *var)
{
  switch (type)
    {
    case var_string:
    case var_string_noescape:
    case var_optional_filename:
    case var_filename:
    case var_enum:
      {
	char *str = * (char **) var;

	if (! str)
	  str = "";
	return PyString_Decode (str, strlen (str), host_charset (), NULL);
      }

    case var_boolean:
      {
	if (* (int *) var)
	  Py_RETURN_TRUE;
	else
	  Py_RETURN_FALSE;
      }

    case var_auto_boolean:
      {
	enum auto_boolean ab = * (enum auto_boolean *) var;

	if (ab == AUTO_BOOLEAN_TRUE)
	  Py_RETURN_TRUE;
	else if (ab == AUTO_BOOLEAN_FALSE)
	  Py_RETURN_FALSE;
	else
	  Py_RETURN_NONE;
      }

    case var_integer:
      if ((* (int *) var) == INT_MAX)
	Py_RETURN_NONE;
      /* Fall through.  */
    case var_zinteger:
      return PyLong_FromLong (* (int *) var);

    case var_uinteger:
      {
	unsigned int val = * (unsigned int *) var;

	if (val == UINT_MAX)
	  Py_RETURN_NONE;
	return PyLong_FromUnsignedLong (val);
      }
    }

  return PyErr_Format (PyExc_RuntimeError, 
		       _("Programmer error: unhandled type."));
}

/* A Python function which returns a gdb parameter's value as a Python
   value.  */

PyObject *
gdbpy_parameter (PyObject *self, PyObject *args)
{
  struct cmd_list_element *alias, *prefix, *cmd;
  const char *arg;
  char *newarg;
  int found = -1;
  volatile struct gdb_exception except;

  if (! PyArg_ParseTuple (args, "s", &arg))
    return NULL;

  newarg = concat ("show ", arg, (char *) NULL);

  TRY_CATCH (except, RETURN_MASK_ALL)
    {
      found = lookup_cmd_composition (newarg, &alias, &prefix, &cmd);
    }
  xfree (newarg);
  GDB_PY_HANDLE_EXCEPTION (except);
  if (!found)
    return PyErr_Format (PyExc_RuntimeError,
			 _("Could not find parameter `%s'."), arg);

  if (! cmd->var)
    return PyErr_Format (PyExc_RuntimeError, 
			 _("`%s' is not a parameter."), arg);
  return gdbpy_parameter_value (cmd->var_type, cmd->var);
}

/* Wrapper for target_charset.  */

static PyObject *
gdbpy_target_charset (PyObject *self, PyObject *args)
{
  const char *cset = target_charset (python_gdbarch);

  return PyUnicode_Decode (cset, strlen (cset), host_charset (), NULL);
}

/* Wrapper for target_wide_charset.  */

static PyObject *
gdbpy_target_wide_charset (PyObject *self, PyObject *args)
{
  const char *cset = target_wide_charset (python_gdbarch);

  return PyUnicode_Decode (cset, strlen (cset), host_charset (), NULL);
}

/* A Python function which evaluates a string using the gdb CLI.  */

static PyObject *
execute_gdb_command (PyObject *self, PyObject *args, PyObject *kw)
{
  const char *arg;
  PyObject *from_tty_obj = NULL, *to_string_obj = NULL;
  int from_tty, to_string;
  volatile struct gdb_exception except;
  static char *keywords[] = {"command", "from_tty", "to_string", NULL };
  char *result = NULL;

  if (! PyArg_ParseTupleAndKeywords (args, kw, "s|O!O!", keywords, &arg,
				     &PyBool_Type, &from_tty_obj,
				     &PyBool_Type, &to_string_obj))
    return NULL;

  from_tty = 0;
  if (from_tty_obj)
    {
      int cmp = PyObject_IsTrue (from_tty_obj);
      if (cmp < 0)
	return NULL;
      from_tty = cmp;
    }

  to_string = 0;
  if (to_string_obj)
    {
      int cmp = PyObject_IsTrue (to_string_obj);
      if (cmp < 0)
	return NULL;
      to_string = cmp;
    }

  TRY_CATCH (except, RETURN_MASK_ALL)
    {
      /* Copy the argument text in case the command modifies it.  */
      char *copy = xstrdup (arg);
      struct cleanup *cleanup = make_cleanup (xfree, copy);

      make_cleanup_restore_integer (&interpreter_async);
      interpreter_async = 0;

      prevent_dont_repeat ();
      if (to_string)
	result = execute_command_to_string (copy, from_tty);
      else
	{
	  result = NULL;
	  execute_command (copy, from_tty);
	}

      do_cleanups (cleanup);
    }
  GDB_PY_HANDLE_EXCEPTION (except);

  /* Do any commands attached to breakpoint we stopped at.  */
  bpstat_do_actions ();

  if (result)
    {
      PyObject *r = PyString_FromString (result);
      xfree (result);
      return r;
    }
  Py_RETURN_NONE;
}

/* Implementation of gdb.solib_name (Long) -> String.
   Returns the name of the shared library holding a given address, or None.  */

static PyObject *
gdbpy_solib_name (PyObject *self, PyObject *args)
{
  char *soname;
  PyObject *str_obj;
  gdb_py_longest pc;

  if (!PyArg_ParseTuple (args, GDB_PY_LL_ARG, &pc))
    return NULL;

  soname = solib_name_from_address (current_program_space, pc);
  if (soname)
    str_obj = PyString_Decode (soname, strlen (soname), host_charset (), NULL);
  else
    {
      str_obj = Py_None;
      Py_INCREF (Py_None);
    }

  return str_obj;
}

/* A Python function which is a wrapper for decode_line_1.  */

static PyObject *
gdbpy_decode_line (PyObject *self, PyObject *args)
{
  struct symtabs_and_lines sals = { NULL, 0 }; /* Initialize to
						  appease gcc.  */
  struct symtab_and_line sal;
  const char *arg = NULL;
  char *copy_to_free = NULL, *copy = NULL;
  struct cleanup *cleanups;
  PyObject *result = NULL;
  PyObject *return_result = NULL;
  PyObject *unparsed = NULL;
  volatile struct gdb_exception except;

  if (! PyArg_ParseTuple (args, "|s", &arg))
    return NULL;

  cleanups = make_cleanup (null_cleanup, NULL);

  sals.sals = NULL;
  TRY_CATCH (except, RETURN_MASK_ALL)
    {
      if (arg)
	{
	  copy = xstrdup (arg);
	  copy_to_free = copy;
	  sals = decode_line_1 (&copy, 0, 0, 0);
	}
      else
	{
	  set_default_source_symtab_and_line ();
	  sal = get_current_source_symtab_and_line ();
	  sals.sals = &sal;
	  sals.nelts = 1;
	}
    }

  if (sals.sals != NULL && sals.sals != &sal)
    {
      make_cleanup (xfree, copy_to_free);
      make_cleanup (xfree, sals.sals);
    }

  if (except.reason < 0)
    {
      do_cleanups (cleanups);
      /* We know this will always throw.  */
      GDB_PY_HANDLE_EXCEPTION (except);
    }

  if (sals.nelts)
    {
      int i;

      result = PyTuple_New (sals.nelts);
      if (! result)
	goto error;
      for (i = 0; i < sals.nelts; ++i)
	{
	  PyObject *obj;

	  obj = symtab_and_line_to_sal_object (sals.sals[i]);
	  if (! obj)
	    {
	      Py_DECREF (result);
	      goto error;
	    }

	  PyTuple_SetItem (result, i, obj);
	}
    }
  else
    {
      result = Py_None;
      Py_INCREF (Py_None);
    }

  return_result = PyTuple_New (2);
  if (! return_result)
    {
      Py_DECREF (result);
      goto error;
    }

  if (copy && strlen (copy) > 0)
    {
      unparsed = PyString_FromString (copy);
      if (unparsed == NULL)
	{
	  Py_DECREF (result);
	  Py_DECREF (return_result);
	  return_result = NULL;
	  goto error;
	}
    }
  else
    {
      unparsed = Py_None;
      Py_INCREF (Py_None);
    }

  PyTuple_SetItem (return_result, 0, unparsed);
  PyTuple_SetItem (return_result, 1, result);

 error:
  do_cleanups (cleanups);

  return return_result;
}

/* Parse a string and evaluate it as an expression.  */
static PyObject *
gdbpy_parse_and_eval (PyObject *self, PyObject *args)
{
  const char *expr_str;
  struct value *result = NULL;
  volatile struct gdb_exception except;

  if (!PyArg_ParseTuple (args, "s", &expr_str))
    return NULL;

  TRY_CATCH (except, RETURN_MASK_ALL)
    {
      char *copy = xstrdup (expr_str);
      struct cleanup *cleanup = make_cleanup (xfree, copy);

      result = parse_and_eval (copy);
      do_cleanups (cleanup);
    }
  GDB_PY_HANDLE_EXCEPTION (except);

  return value_to_value_object (result);
}

/* Implementation of gdb.find_pc_line function.
   Returns the gdb.Symtab_and_line object corresponding to a PC value.  */

static PyObject *
gdbpy_find_pc_line (PyObject *self, PyObject *args)
{
  struct symtab_and_line sal;
  CORE_ADDR pc;
  gdb_py_ulongest pc_llu;

  if (!PyArg_ParseTuple (args, GDB_PY_LLU_ARG, &pc_llu))
    return NULL;

  pc = (CORE_ADDR) pc_llu;
  sal = find_pc_line (pc, 0);
  return symtab_and_line_to_sal_object (sal);
}

/* Read a file as Python code.
   FILE is the file to run.  FILENAME is name of the file FILE.
   This does not throw any errors.  If an exception occurs python will print
   the traceback and clear the error indicator.  */

void
source_python_script (FILE *file, const char *filename)
{
  struct cleanup *cleanup;

  cleanup = ensure_python_env (get_current_arch (), current_language);
  python_run_simple_file (file, filename);
  do_cleanups (cleanup);
}



/* Posting and handling events.  */

/* A single event.  */
struct gdbpy_event
{
  /* The Python event.  This is just a callable object.  */
  PyObject *event;
  /* The next event.  */
  struct gdbpy_event *next;
};

/* All pending events.  */
static struct gdbpy_event *gdbpy_event_list;
/* The final link of the event list.  */
static struct gdbpy_event **gdbpy_event_list_end;

/* We use a file handler, and not an async handler, so that we can
   wake up the main thread even when it is blocked in poll().  */
static struct serial *gdbpy_event_fds[2];

/* The file handler callback.  This reads from the internal pipe, and
   then processes the Python event queue.  This will always be run in
   the main gdb thread.  */

static void
gdbpy_run_events (struct serial *scb, void *context)
{
  struct cleanup *cleanup;

  cleanup = ensure_python_env (get_current_arch (), current_language);

  /* Flush the fd.  Do this before flushing the events list, so that
     any new event post afterwards is sure to re-awake the event
     loop.  */
  while (serial_readchar (gdbpy_event_fds[0], 0) >= 0)
    ;

  while (gdbpy_event_list)
    {
      /* Dispatching the event might push a new element onto the event
	 loop, so we update here "atomically enough".  */
      struct gdbpy_event *item = gdbpy_event_list;
      gdbpy_event_list = gdbpy_event_list->next;
      if (gdbpy_event_list == NULL)
	gdbpy_event_list_end = &gdbpy_event_list;

      /* Ignore errors.  */
      if (PyObject_CallObject (item->event, NULL) == NULL)
	PyErr_Clear ();

      Py_DECREF (item->event);
      xfree (item);
    }

  do_cleanups (cleanup);
}

/* Submit an event to the gdb thread.  */
static PyObject *
gdbpy_post_event (PyObject *self, PyObject *args)
{
  struct gdbpy_event *event;
  PyObject *func;
  int wakeup;

  if (!PyArg_ParseTuple (args, "O", &func))
    return NULL;

  if (!PyCallable_Check (func))
    {
      PyErr_SetString (PyExc_RuntimeError, 
		       _("Posted event is not callable"));
      return NULL;
    }

  Py_INCREF (func);

  /* From here until the end of the function, we have the GIL, so we
     can operate on our global data structures without worrying.  */
  wakeup = gdbpy_event_list == NULL;

  event = XNEW (struct gdbpy_event);
  event->event = func;
  event->next = NULL;
  *gdbpy_event_list_end = event;
  gdbpy_event_list_end = &event->next;

  /* Wake up gdb when needed.  */
  if (wakeup)
    {
      char c = 'q';		/* Anything. */

      if (serial_write (gdbpy_event_fds[1], &c, 1))
        return PyErr_SetFromErrno (PyExc_IOError);
    }

  Py_RETURN_NONE;
}

/* Initialize the Python event handler.  */
static void
gdbpy_initialize_events (void)
{
  if (serial_pipe (gdbpy_event_fds) == 0)
    {
      gdbpy_event_list_end = &gdbpy_event_list;
      serial_async (gdbpy_event_fds[0], gdbpy_run_events, NULL);
    }
}



static void
before_prompt_hook (const char *current_gdb_prompt)
{
  struct cleanup *cleanup;
  char *prompt = NULL;

  cleanup = ensure_python_env (get_current_arch (), current_language);

  if (PyObject_HasAttrString (gdb_module, "prompt_hook"))
    {
      PyObject *hook;

      hook = PyObject_GetAttrString (gdb_module, "prompt_hook");
      if (hook == NULL)
	goto fail;

      if (PyCallable_Check (hook))
	{
	  PyObject *result;
	  PyObject *current_prompt;

	  current_prompt = PyString_FromString (current_gdb_prompt);
	  if (current_prompt == NULL)
	    goto fail;

	  result = PyObject_CallFunctionObjArgs (hook, current_prompt, NULL);

	  Py_DECREF (current_prompt);

	  if (result == NULL)
	    goto fail;

	  make_cleanup_py_decref (result);

	  /* Return type should be None, or a String.  If it is None,
	     fall through, we will not set a prompt.  If it is a
	     string, set  PROMPT.  Anything else, set an exception.  */
	  if (result != Py_None && ! PyString_Check (result))
	    {
	      PyErr_Format (PyExc_RuntimeError,
			    _("Return from prompt_hook must " \
			      "be either a Python string, or None"));
	      goto fail;
	    }

	  if (result != Py_None)
	    {
	      prompt = python_string_to_host_string (result);

	      if (prompt == NULL)
		goto fail;
	      else
		make_cleanup (xfree, prompt);
	    }
	}
    }

  /* If a prompt has been set, PROMPT will not be NULL.  If it is
     NULL, do not set the prompt.  */
  if (prompt != NULL)
    set_prompt (prompt);

  do_cleanups (cleanup);
  return;

 fail:
  gdbpy_print_stack ();
  do_cleanups (cleanup);
  return;
}



/* Printing.  */

/* A python function to write a single string using gdb's filtered
   output stream .  The optional keyword STREAM can be used to write
   to a particular stream.  The default stream is to gdb_stdout.  */

static PyObject *
gdbpy_write (PyObject *self, PyObject *args, PyObject *kw)
{
  const char *arg;
  static char *keywords[] = {"text", "stream", NULL };
  int stream_type = 0;
  
  if (! PyArg_ParseTupleAndKeywords (args, kw, "s|i", keywords, &arg,
				     &stream_type))
    return NULL;

  switch (stream_type)
    {
    case 1:
      {
	fprintf_filtered (gdb_stderr, "%s", arg);
	break;
      }
    case 2:
      {
	fprintf_filtered (gdb_stdlog, "%s", arg);
	break;
      }
    default:
      fprintf_filtered (gdb_stdout, "%s", arg);
    }
     
  Py_RETURN_NONE;
}

/* A python function to flush a gdb stream.  The optional keyword
   STREAM can be used to flush a particular stream.  The default stream
   is gdb_stdout.  */

static PyObject *
gdbpy_flush (PyObject *self, PyObject *args, PyObject *kw)
{
  static char *keywords[] = {"stream", NULL };
  int stream_type = 0;
  
  if (! PyArg_ParseTupleAndKeywords (args, kw, "|i", keywords,
				     &stream_type))
    return NULL;

  switch (stream_type)
    {
    case 1:
      {
	gdb_flush (gdb_stderr);
	break;
      }
    case 2:
      {
	gdb_flush (gdb_stdlog);
	break;
      }
    default:
      gdb_flush (gdb_stdout);
    }
     
  Py_RETURN_NONE;
}

/* Print a python exception trace, print just a message, or print
   nothing and clear the python exception, depending on
   gdbpy_should_print_stack.  Only call this if a python exception is
   set.  */
void
gdbpy_print_stack (void)
{
  /* Print "none", just clear exception.  */
  if (gdbpy_should_print_stack == python_excp_none)
    {
      PyErr_Clear ();
    }
  /* Print "full" message and backtrace.  */
  else if (gdbpy_should_print_stack == python_excp_full)
    {
      PyErr_Print ();
      /* PyErr_Print doesn't necessarily end output with a newline.
	 This works because Python's stdout/stderr is fed through
	 printf_filtered.  */
      begin_line ();
    }
  /* Print "message", just error print message.  */
  else
    {
      PyObject *ptype, *pvalue, *ptraceback;
      char *msg = NULL, *type = NULL;

      PyErr_Fetch (&ptype, &pvalue, &ptraceback);

      /* Fetch the error message contained within ptype, pvalue.  */
      msg = gdbpy_exception_to_string (ptype, pvalue);
      type = gdbpy_obj_to_string (ptype);
      if (msg == NULL)
	{
	  /* An error occurred computing the string representation of the
	     error message.  */
	  fprintf_filtered (gdb_stderr,
			    _("Error occurred computing Python error"	\
			      "message.\n"));
	}
      else
	fprintf_filtered (gdb_stderr, "Python Exception %s %s: \n",
			  type, msg);

      Py_XDECREF (ptype);
      Py_XDECREF (pvalue);
      Py_XDECREF (ptraceback);
      xfree (msg);
    }
}



/* Return the current Progspace.
   There always is one.  */

static PyObject *
gdbpy_get_current_progspace (PyObject *unused1, PyObject *unused2)
{
  PyObject *result;

  result = pspace_to_pspace_object (current_program_space);
  if (result)
    Py_INCREF (result);
  return result;
}

/* Return a sequence holding all the Progspaces.  */

static PyObject *
gdbpy_progspaces (PyObject *unused1, PyObject *unused2)
{
  struct program_space *ps;
  PyObject *list;

  list = PyList_New (0);
  if (!list)
    return NULL;

  ALL_PSPACES (ps)
  {
    PyObject *item = pspace_to_pspace_object (ps);

    if (!item || PyList_Append (list, item) == -1)
      {
	Py_DECREF (list);
	return NULL;
      }
  }

  return list;
}



/* The "current" objfile.  This is set when gdb detects that a new
   objfile has been loaded.  It is only set for the duration of a call to
   source_python_script_for_objfile; it is NULL at other times.  */
static struct objfile *gdbpy_current_objfile;

/* Set the current objfile to OBJFILE and then read FILE named FILENAME
   as Python code.  This does not throw any errors.  If an exception
   occurs python will print the traceback and clear the error indicator.  */

void
source_python_script_for_objfile (struct objfile *objfile, FILE *file,
                                  const char *filename)
{
  struct cleanup *cleanups;

  cleanups = ensure_python_env (get_objfile_arch (objfile), current_language);
  gdbpy_current_objfile = objfile;

  python_run_simple_file (file, filename);

  do_cleanups (cleanups);
  gdbpy_current_objfile = NULL;
}

/* Return the current Objfile, or None if there isn't one.  */

static PyObject *
gdbpy_get_current_objfile (PyObject *unused1, PyObject *unused2)
{
  PyObject *result;

  if (! gdbpy_current_objfile)
    Py_RETURN_NONE;

  result = objfile_to_objfile_object (gdbpy_current_objfile);
  if (result)
    Py_INCREF (result);
  return result;
}

/* Return a sequence holding all the Objfiles.  */

static PyObject *
gdbpy_objfiles (PyObject *unused1, PyObject *unused2)
{
  struct objfile *objf;
  PyObject *list;

  list = PyList_New (0);
  if (!list)
    return NULL;

  ALL_OBJFILES (objf)
  {
    PyObject *item = objfile_to_objfile_object (objf);

    if (!item || PyList_Append (list, item) == -1)
      {
	Py_DECREF (list);
	return NULL;
      }
  }

  return list;
}

#else /* HAVE_PYTHON */

/* Dummy implementation of the gdb "python" command.  */

static void
python_command (char *arg, int from_tty)
{
  while (arg && *arg && isspace (*arg))
    ++arg;
  if (arg && *arg)
    error (_("Python scripting is not supported in this copy of GDB."));
  else
    {
      struct command_line *l = get_command_line (python_control, "");
      struct cleanup *cleanups = make_cleanup_free_command_lines (&l);

      execute_control_command_untraced (l);
      do_cleanups (cleanups);
    }
}

void
eval_python_from_control_command (struct command_line *cmd)
{
  error (_("Python scripting is not supported in this copy of GDB."));
}

void
source_python_script (FILE *file, const char *filename)
{
  throw_error (UNSUPPORTED_ERROR,
	       _("Python scripting is not supported in this copy of GDB."));
}

int
gdbpy_should_stop (struct breakpoint_object *bp_obj)
{
  internal_error (__FILE__, __LINE__,
		  _("gdbpy_should_stop called when Python scripting is  " \
		    "not supported."));
}

int
gdbpy_breakpoint_has_py_cond (struct breakpoint_object *bp_obj)
{
  internal_error (__FILE__, __LINE__,
		  _("gdbpy_breakpoint_has_py_cond called when Python " \
		    "scripting is not supported."));
}

#endif /* HAVE_PYTHON */



/* Lists for 'set python' commands.  */

static struct cmd_list_element *user_set_python_list;
static struct cmd_list_element *user_show_python_list;

/* Function for use by 'set python' prefix command.  */

static void
user_set_python (char *args, int from_tty)
{
  help_list (user_set_python_list, "set python ", all_commands,
	     gdb_stdout);
}

/* Function for use by 'show python' prefix command.  */

static void
user_show_python (char *args, int from_tty)
{
  cmd_show_list (user_show_python_list, from_tty, "");
}

/* Initialize the Python code.  */

/* Provide a prototype to silence -Wmissing-prototypes.  */
extern initialize_file_ftype _initialize_python;

void
_initialize_python (void)
{
  char *cmd_name;
  struct cmd_list_element *cmd;

  add_com ("python", class_obscure, python_command,
#ifdef HAVE_PYTHON
	   _("\
Evaluate a Python command.\n\
\n\
The command can be given as an argument, for instance:\n\
\n\
    python print 23\n\
\n\
If no argument is given, the following lines are read and used\n\
as the Python commands.  Type a line containing \"end\" to indicate\n\
the end of the command.")
#else /* HAVE_PYTHON */
	   _("\
Evaluate a Python command.\n\
\n\
Python scripting is not supported in this copy of GDB.\n\
This command is only a placeholder.")
#endif /* HAVE_PYTHON */
	   );

  /* Add set/show python print-stack.  */
  add_prefix_cmd ("python", no_class, user_show_python,
		  _("Prefix command for python preference settings."),
		  &user_show_python_list, "show python ", 0,
		  &showlist);

  add_prefix_cmd ("python", no_class, user_set_python,
		  _("Prefix command for python preference settings."),
		  &user_set_python_list, "set python ", 0,
		  &setlist);

  add_setshow_enum_cmd ("print-stack", no_class, python_excp_enums,
			&gdbpy_should_print_stack, _("\
Set mode for Python stack dump on error."), _("\
Show the mode of Python stack printing on error."), _("\
none  == no stack or message will be printed.\n\
full == a message and a stack will be printed.\n\
message == an error message without a stack will be printed."),
			NULL, NULL,
			&user_set_python_list,
			&user_show_python_list);

#ifdef HAVE_PYTHON
#ifdef WITH_PYTHON_PATH
  /* Work around problem where python gets confused about where it is,
     and then can't find its libraries, etc.
     NOTE: Python assumes the following layout:
     /foo/bin/python
     /foo/lib/pythonX.Y/...
     This must be done before calling Py_Initialize.  */
  Py_SetProgramName (concat (ldirname (python_libdir), SLASH_STRING, "bin",
			     SLASH_STRING, "python", NULL));
#endif

  Py_Initialize ();
  PyEval_InitThreads ();

  gdb_module = Py_InitModule ("gdb", GdbMethods);

  /* The casts to (char*) are for python 2.4.  */
  PyModule_AddStringConstant (gdb_module, "VERSION", (char*) version);
  PyModule_AddStringConstant (gdb_module, "HOST_CONFIG", (char*) host_name);
  PyModule_AddStringConstant (gdb_module, "TARGET_CONFIG",
			      (char*) target_name);

  /* Add stream constants.  */
  PyModule_AddIntConstant (gdb_module, "STDOUT", 0);
  PyModule_AddIntConstant (gdb_module, "STDERR", 1);
  PyModule_AddIntConstant (gdb_module, "STDLOG", 2);
  
  /* gdb.parameter ("data-directory") doesn't necessarily exist when the python
     script below is run (depending on order of _initialize_* functions).
     Define the initial value of gdb.PYTHONDIR here.  */
  {
    char *gdb_pythondir;

    gdb_pythondir = concat (gdb_datadir, SLASH_STRING, "python", NULL);
    PyModule_AddStringConstant (gdb_module, "PYTHONDIR", gdb_pythondir);
    xfree (gdb_pythondir);
  }

  gdbpy_gdb_error = PyErr_NewException ("gdb.error", PyExc_RuntimeError, NULL);
  PyModule_AddObject (gdb_module, "error", gdbpy_gdb_error);

  gdbpy_gdb_memory_error = PyErr_NewException ("gdb.MemoryError",
					       gdbpy_gdb_error, NULL);
  PyModule_AddObject (gdb_module, "MemoryError", gdbpy_gdb_memory_error);

  gdbpy_gdberror_exc = PyErr_NewException ("gdb.GdbError", NULL, NULL);
  PyModule_AddObject (gdb_module, "GdbError", gdbpy_gdberror_exc);

  gdbpy_initialize_auto_load ();
  gdbpy_initialize_values ();
  gdbpy_initialize_frames ();
  gdbpy_initialize_commands ();
  gdbpy_initialize_symbols ();
  gdbpy_initialize_symtabs ();
  gdbpy_initialize_blocks ();
  gdbpy_initialize_functions ();
  gdbpy_initialize_parameters ();
  gdbpy_initialize_types ();
  gdbpy_initialize_pspace ();
  gdbpy_initialize_objfile ();
  gdbpy_initialize_breakpoints ();
  gdbpy_initialize_finishbreakpoints ();
  gdbpy_initialize_lazy_string ();
  gdbpy_initialize_thread ();
  gdbpy_initialize_inferior ();
  gdbpy_initialize_events ();

  gdbpy_initialize_eventregistry ();
  gdbpy_initialize_py_events ();
  gdbpy_initialize_event ();
  gdbpy_initialize_stop_event ();
  gdbpy_initialize_signal_event ();
  gdbpy_initialize_breakpoint_event ();
  gdbpy_initialize_continue_event ();
  gdbpy_initialize_exited_event ();
  gdbpy_initialize_thread_event ();
  gdbpy_initialize_new_objfile_event () ;

  observer_attach_before_prompt (before_prompt_hook);

  PyRun_SimpleString ("import gdb");
  PyRun_SimpleString ("gdb.pretty_printers = []");

  gdbpy_to_string_cst = PyString_FromString ("to_string");
  gdbpy_children_cst = PyString_FromString ("children");
  gdbpy_display_hint_cst = PyString_FromString ("display_hint");
  gdbpy_doc_cst = PyString_FromString ("__doc__");
  gdbpy_enabled_cst = PyString_FromString ("enabled");
  gdbpy_value_cst = PyString_FromString ("value");

  /* Release the GIL while gdb runs.  */
  PyThreadState_Swap (NULL);
  PyEval_ReleaseLock ();

#endif /* HAVE_PYTHON */
}

#ifdef HAVE_PYTHON

/* Perform the remaining python initializations.
   These must be done after GDB is at least mostly initialized.
   E.g., The "info pretty-printer" command needs the "info" prefix
   command installed.  */

void
finish_python_initialization (void)
{
  struct cleanup *cleanup;

  cleanup = ensure_python_env (get_current_arch (), current_language);

  PyRun_SimpleString ("\
import os\n\
import sys\n\
\n\
class GdbOutputFile:\n\
  def close(self):\n\
    # Do nothing.\n\
    return None\n\
\n\
  def isatty(self):\n\
    return False\n\
\n\
  def write(self, s):\n\
    gdb.write(s, stream=gdb.STDOUT)\n   \
\n\
  def writelines(self, iterable):\n\
    for line in iterable:\n\
      self.write(line)\n\
\n\
  def flush(self):\n\
    gdb.flush()\n\
\n\
sys.stdout = GdbOutputFile()\n\
\n\
class GdbOutputErrorFile:\n\
  def close(self):\n\
    # Do nothing.\n\
    return None\n\
\n\
  def isatty(self):\n\
    return False\n\
\n\
  def write(self, s):\n\
    gdb.write(s, stream=gdb.STDERR)\n		\
\n\
  def writelines(self, iterable):\n\
    for line in iterable:\n\
      self.write(line)\n \
\n\
  def flush(self):\n\
    gdb.flush()\n\
\n\
sys.stderr = GdbOutputErrorFile()\n\
\n\
# Ideally this would live in the gdb module, but it's intentionally written\n\
# in python, and we need this to bootstrap the gdb module.\n\
\n\
def GdbSetPythonDirectory (dir):\n\
  \"Set gdb.PYTHONDIR and update sys.path,etc.\"\n\
  old_dir = gdb.PYTHONDIR\n\
  gdb.PYTHONDIR = dir\n\
  # GDB's python scripts are stored inside gdb.PYTHONDIR.  So insert\n\
  # that directory name at the start of sys.path to allow the Python\n\
  # interpreter to find them.\n\
  if old_dir in sys.path:\n\
    sys.path.remove (old_dir)\n\
  sys.path.insert (0, gdb.PYTHONDIR)\n\
\n\
  # Tell python where to find submodules of gdb.\n\
  gdb.__path__ = [os.path.join (gdb.PYTHONDIR, 'gdb')]\n\
\n\
  # The gdb module is implemented in C rather than in Python.  As a result,\n\
  # the associated __init.py__ script is not not executed by default when\n\
  # the gdb module gets imported.  Execute that script manually if it\n\
  # exists.\n\
  ipy = os.path.join (gdb.PYTHONDIR, 'gdb', '__init__.py')\n\
  if os.path.exists (ipy):\n\
    execfile (ipy)\n\
\n\
# Install the default gdb.PYTHONDIR.\n\
GdbSetPythonDirectory (gdb.PYTHONDIR)\n\
# Default prompt hook does nothing.\n\
prompt_hook = None\n\
# Ensure that sys.argv is set to something.\n\
# We do not use PySys_SetArgvEx because it did not appear until 2.6.6.\n\
sys.argv = ['']\n\
");

  do_cleanups (cleanup);
}

#endif /* HAVE_PYTHON */



#ifdef HAVE_PYTHON

static PyMethodDef GdbMethods[] =
{
  { "history", gdbpy_history, METH_VARARGS,
    "Get a value from history" },
  { "execute", (PyCFunction) execute_gdb_command, METH_VARARGS | METH_KEYWORDS,
    "Execute a gdb command" },
  { "parameter", gdbpy_parameter, METH_VARARGS,
    "Return a gdb parameter's value" },

  { "breakpoints", gdbpy_breakpoints, METH_NOARGS,
    "Return a tuple of all breakpoint objects" },

  { "default_visualizer", gdbpy_default_visualizer, METH_VARARGS,
    "Find the default visualizer for a Value." },

  { "current_progspace", gdbpy_get_current_progspace, METH_NOARGS,
    "Return the current Progspace." },
  { "progspaces", gdbpy_progspaces, METH_NOARGS,
    "Return a sequence of all progspaces." },

  { "current_objfile", gdbpy_get_current_objfile, METH_NOARGS,
    "Return the current Objfile being loaded, or None." },
  { "objfiles", gdbpy_objfiles, METH_NOARGS,
    "Return a sequence of all loaded objfiles." },

  { "newest_frame", gdbpy_newest_frame, METH_NOARGS,
    "newest_frame () -> gdb.Frame.\n\
Return the newest frame object." },
  { "selected_frame", gdbpy_selected_frame, METH_NOARGS,
    "selected_frame () -> gdb.Frame.\n\
Return the selected frame object." },
  { "frame_stop_reason_string", gdbpy_frame_stop_reason_string, METH_VARARGS,
    "stop_reason_string (Integer) -> String.\n\
Return a string explaining unwind stop reason." },

  { "lookup_type", (PyCFunction) gdbpy_lookup_type,
    METH_VARARGS | METH_KEYWORDS,
    "lookup_type (name [, block]) -> type\n\
Return a Type corresponding to the given name." },
  { "lookup_symbol", (PyCFunction) gdbpy_lookup_symbol,
    METH_VARARGS | METH_KEYWORDS,
    "lookup_symbol (name [, block] [, domain]) -> (symbol, is_field_of_this)\n\
Return a tuple with the symbol corresponding to the given name (or None) and\n\
a boolean indicating if name is a field of the current implied argument\n\
`this' (when the current language is object-oriented)." },
  { "lookup_global_symbol", (PyCFunction) gdbpy_lookup_global_symbol,
    METH_VARARGS | METH_KEYWORDS,
    "lookup_global_symbol (name [, domain]) -> symbol\n\
Return the symbol corresponding to the given name (or None)." },
  { "block_for_pc", gdbpy_block_for_pc, METH_VARARGS,
    "Return the block containing the given pc value, or None." },
  { "solib_name", gdbpy_solib_name, METH_VARARGS,
    "solib_name (Long) -> String.\n\
Return the name of the shared library holding a given address, or None." },
  { "decode_line", gdbpy_decode_line, METH_VARARGS,
    "decode_line (String) -> Tuple.  Decode a string argument the way\n\
that 'break' or 'edit' does.  Return a tuple containing two elements.\n\
The first element contains any unparsed portion of the String parameter\n\
(or None if the string was fully parsed).  The second element contains\n\
a tuple that contains all the locations that match, represented as\n\
gdb.Symtab_and_line objects (or None)."},
  { "parse_and_eval", gdbpy_parse_and_eval, METH_VARARGS,
    "parse_and_eval (String) -> Value.\n\
Parse String as an expression, evaluate it, and return the result as a Value."
  },
  { "find_pc_line", gdbpy_find_pc_line, METH_VARARGS,
    "find_pc_line (pc) -> Symtab_and_line.\n\
Return the gdb.Symtab_and_line object corresponding to the pc value." },

  { "post_event", gdbpy_post_event, METH_VARARGS,
    "Post an event into gdb's event loop." },

  { "target_charset", gdbpy_target_charset, METH_NOARGS,
    "target_charset () -> string.\n\
Return the name of the current target charset." },
  { "target_wide_charset", gdbpy_target_wide_charset, METH_NOARGS,
    "target_wide_charset () -> string.\n\
Return the name of the current target wide charset." },

  { "string_to_argv", gdbpy_string_to_argv, METH_VARARGS,
    "string_to_argv (String) -> Array.\n\
Parse String and return an argv-like array.\n\
Arguments are separate by spaces and may be quoted."
  },
  { "write", (PyCFunction)gdbpy_write, METH_VARARGS | METH_KEYWORDS,
    "Write a string using gdb's filtered stream." },
  { "flush", (PyCFunction)gdbpy_flush, METH_VARARGS | METH_KEYWORDS,
    "Flush gdb's filtered stdout stream." },
  { "selected_thread", gdbpy_selected_thread, METH_NOARGS,
    "selected_thread () -> gdb.InferiorThread.\n\
Return the selected thread object." },
  { "selected_inferior", gdbpy_selected_inferior, METH_NOARGS,
    "selected_inferior () -> gdb.Inferior.\n\
Return the selected inferior object." },
  { "inferiors", gdbpy_inferiors, METH_NOARGS,
    "inferiors () -> (gdb.Inferior, ...).\n\
Return a tuple containing all inferiors." },
  {NULL, NULL, 0, NULL}
};

#endif /* HAVE_PYTHON */