gdb/python/py-utils.c

/* General utility routines for GDB/Python.

   Copyright (C) 2008-2022 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 "charset.h"
#include "value.h"
#include "python-internal.h"

/* Converts a Python 8-bit string to a unicode string object.  Assumes the
   8-bit string is in the host charset.  If an error occurs during conversion,
   returns NULL with a python exception set.

   As an added bonus, the functions accepts a unicode string and returns it
   right away, so callers don't need to check which kind of string they've
   got.  In Python 3, all strings are Unicode so this case is always the
   one that applies.

   If the given object is not one of the mentioned string types, NULL is
   returned, with the TypeError python exception set.  */
gdbpy_ref<>
python_string_to_unicode (PyObject *obj)
{
  PyObject *unicode_str;

  /* If obj is already a unicode string, just return it.
     I wish life was always that simple...  */
  if (PyUnicode_Check (obj))
    {
      unicode_str = obj;
      Py_INCREF (obj);
    }
  else
    {
      PyErr_SetString (PyExc_TypeError,
		       _("Expected a string object."));
      unicode_str = NULL;
    }

  return gdbpy_ref<> (unicode_str);
}

/* Returns a newly allocated string with the contents of the given unicode
   string object converted to CHARSET.  If an error occurs during the
   conversion, NULL will be returned and a python exception will be
   set.  */
static gdb::unique_xmalloc_ptr<char>
unicode_to_encoded_string (PyObject *unicode_str, const char *charset)
{
  /* Translate string to named charset.  */
  gdbpy_ref<> string (PyUnicode_AsEncodedString (unicode_str, charset, NULL));
  if (string == NULL)
    return NULL;

  return gdb::unique_xmalloc_ptr<char>
    (xstrdup (PyBytes_AsString (string.get ())));
}

/* Returns a PyObject with the contents of the given unicode string
   object converted to a named charset.  If an error occurs during
   the conversion, NULL will be returned and a python exception will
   be set.  */
static gdbpy_ref<>
unicode_to_encoded_python_string (PyObject *unicode_str, const char *charset)
{
  /* Translate string to named charset.  */
  return gdbpy_ref<> (PyUnicode_AsEncodedString (unicode_str, charset, NULL));
}

/* Returns a newly allocated string with the contents of the given
   unicode string object converted to the target's charset.  If an
   error occurs during the conversion, NULL will be returned and a
   python exception will be set.  */
gdb::unique_xmalloc_ptr<char>
unicode_to_target_string (PyObject *unicode_str)
{
  return (unicode_to_encoded_string
	  (unicode_str,
	   target_charset (gdbpy_enter::get_gdbarch ())));
}

/* Returns a PyObject with the contents of the given unicode string
   object converted to the target's charset.  If an error occurs
   during the conversion, NULL will be returned and a python exception
   will be set.  */
static gdbpy_ref<>
unicode_to_target_python_string (PyObject *unicode_str)
{
  return (unicode_to_encoded_python_string
	  (unicode_str,
	   target_charset (gdbpy_enter::get_gdbarch ())));
}

/* Converts a python string (8-bit or unicode) to a target string in
   the target's charset.  Returns NULL on error, with a python
   exception set.  */
gdb::unique_xmalloc_ptr<char>
python_string_to_target_string (PyObject *obj)
{
  gdbpy_ref<> str = python_string_to_unicode (obj);
  if (str == NULL)
    return NULL;

  return unicode_to_target_string (str.get ());
}

/* Converts a python string (8-bit or unicode) to a target string in the
   target's charset.  Returns NULL on error, with a python exception
   set.

   In Python 3, the returned object is a "bytes" object (not a string).  */
gdbpy_ref<>
python_string_to_target_python_string (PyObject *obj)
{
  gdbpy_ref<> str = python_string_to_unicode (obj);
  if (str == NULL)
    return str;

  return unicode_to_target_python_string (str.get ());
}

/* Converts a python string (8-bit or unicode) to a target string in
   the host's charset.  Returns NULL on error, with a python exception
   set.  */
gdb::unique_xmalloc_ptr<char>
python_string_to_host_string (PyObject *obj)
{
  gdbpy_ref<> str = python_string_to_unicode (obj);
  if (str == NULL)
    return NULL;

  return unicode_to_encoded_string (str.get (), host_charset ());
}

/* Convert a host string to a python string.  */

gdbpy_ref<>
host_string_to_python_string (const char *str)
{
  return gdbpy_ref<> (PyUnicode_Decode (str, strlen (str), host_charset (),
					NULL));
}

/* Return true if OBJ is a Python string or unicode object, false
   otherwise.  */

int
gdbpy_is_string (PyObject *obj)
{
  return PyUnicode_Check (obj);
}

/* Return the string representation of OBJ, i.e., str (obj).
   If the result is NULL a python error occurred, the caller must clear it.  */

gdb::unique_xmalloc_ptr<char>
gdbpy_obj_to_string (PyObject *obj)
{
  gdbpy_ref<> str_obj (PyObject_Str (obj));

  if (str_obj != NULL)
    return python_string_to_host_string (str_obj.get ());

  return NULL;
}

/* See python-internal.h.  */

gdb::unique_xmalloc_ptr<char>
gdbpy_err_fetch::to_string () const
{
  /* There are a few cases to consider.
     For example:
     value is a string when PyErr_SetString is used.
     value is not a string when raise "foo" is used, instead it is None
     and type is "foo".
     So the algorithm we use is to print `str (value)' if it's not
     None, otherwise we print `str (type)'.
     Using str (aka PyObject_Str) will fetch the error message from
     gdb.GdbError ("message").  */

  if (m_error_value && m_error_value != Py_None)
    return gdbpy_obj_to_string (m_error_value);
  else
    return gdbpy_obj_to_string (m_error_type);
}

/* See python-internal.h.  */

gdb::unique_xmalloc_ptr<char>
gdbpy_err_fetch::type_to_string () const
{
  return gdbpy_obj_to_string (m_error_type);
}

/* Convert a GDB exception to the appropriate Python exception.

   This sets the Python error indicator.  */

void
gdbpy_convert_exception (const struct gdb_exception &exception)
{
  PyObject *exc_class;

  if (exception.reason == RETURN_QUIT)
    exc_class = PyExc_KeyboardInterrupt;
  else if (exception.error == MEMORY_ERROR)
    exc_class = gdbpy_gdb_memory_error;
  else
    exc_class = gdbpy_gdb_error;

  PyErr_Format (exc_class, "%s", exception.what ());
}

/* Converts OBJ to a CORE_ADDR value.

   Returns 0 on success or -1 on failure, with a Python exception set.
*/

int
get_addr_from_python (PyObject *obj, CORE_ADDR *addr)
{
  if (gdbpy_is_value_object (obj))
    {

      try
	{
	  *addr = value_as_address (value_object_to_value (obj));
	}
      catch (const gdb_exception &except)
	{
	  GDB_PY_SET_HANDLE_EXCEPTION (except);
	}
    }
  else
    {
      gdbpy_ref<> num (PyNumber_Long (obj));
      gdb_py_ulongest val;

      if (num == NULL)
	return -1;

      val = gdb_py_long_as_ulongest (num.get ());
      if (PyErr_Occurred ())
	return -1;

      if (sizeof (val) > sizeof (CORE_ADDR) && ((CORE_ADDR) val) != val)
	{
	  PyErr_SetString (PyExc_ValueError,
			   _("Overflow converting to address."));
	  return -1;
	}

      *addr = val;
    }

  return 0;
}

/* Convert a LONGEST to the appropriate Python object -- either an
   integer object or a long object, depending on its value.  */

gdbpy_ref<>
gdb_py_object_from_longest (LONGEST l)
{
  if (sizeof (l) > sizeof (long))
    return gdbpy_ref<> (PyLong_FromLongLong (l));
  return gdbpy_ref<> (PyLong_FromLong (l));
}

/* Convert a ULONGEST to the appropriate Python object -- either an
   integer object or a long object, depending on its value.  */

gdbpy_ref<>
gdb_py_object_from_ulongest (ULONGEST l)
{
  if (sizeof (l) > sizeof (unsigned long))
    return gdbpy_ref<> (PyLong_FromUnsignedLongLong (l));
  return gdbpy_ref<> (PyLong_FromUnsignedLong (l));
}

/* Like PyLong_AsLong, but returns 0 on failure, 1 on success, and puts
   the value into an out parameter.  */

int
gdb_py_int_as_long (PyObject *obj, long *result)
{
  *result = PyLong_AsLong (obj);
  return ! (*result == -1 && PyErr_Occurred ());
}



/* Generic implementation of the __dict__ attribute for objects that
   have a dictionary.  The CLOSURE argument should be the type object.
   This only handles positive values for tp_dictoffset.  */

PyObject *
gdb_py_generic_dict (PyObject *self, void *closure)
{
  PyObject *result;
  PyTypeObject *type_obj = (PyTypeObject *) closure;
  char *raw_ptr;

  raw_ptr = (char *) self + type_obj->tp_dictoffset;
  result = * (PyObject **) raw_ptr;

  Py_INCREF (result);
  return result;
}

/* Like PyModule_AddObject, but does not steal a reference to
   OBJECT.  */

int
gdb_pymodule_addobject (PyObject *module, const char *name, PyObject *object)
{
  int result;

  Py_INCREF (object);
  result = PyModule_AddObject (module, name, object);
  if (result < 0)
    Py_DECREF (object);
  return result;
}

/* See python-internal.h.  */

void
gdbpy_error (const char *fmt, ...)
{
  va_list ap;
  va_start (ap, fmt);
  std::string str = string_vprintf (fmt, ap);
  va_end (ap);

  const char *msg = str.c_str ();
  if (msg != nullptr && *msg != '\0')
    error (_("Error occurred in Python: %s"), msg);
  else
    error (_("Error occurred in Python."));
}

/* Handle a Python exception when the special gdb.GdbError treatment
   is desired.  This should only be called when an exception is set.
   If the exception is a gdb.GdbError, throw a gdb exception with the
   exception text.  For other exceptions, print the Python stack and
   then throw a gdb exception.  */

void
gdbpy_handle_exception ()
{
  gdbpy_err_fetch fetched_error;
  gdb::unique_xmalloc_ptr<char> msg = fetched_error.to_string ();

  if (msg == NULL)
    {
      /* An error occurred computing the string representation of the
	 error message.  This is rare, but we should inform the user.  */
      gdb_printf (_("An error occurred in Python "
		    "and then another occurred computing the "
		    "error message.\n"));
      gdbpy_print_stack ();
    }

  /* Don't print the stack for gdb.GdbError exceptions.
     It is generally used to flag user errors.

     We also don't want to print "Error occurred in Python command"
     for user errors.  However, a missing message for gdb.GdbError
     exceptions is arguably a bug, so we flag it as such.  */

  if (fetched_error.type_matches (PyExc_KeyboardInterrupt))
    throw_quit ("Quit");
  else if (! fetched_error.type_matches (gdbpy_gdberror_exc)
	   || msg == NULL || *msg == '\0')
    {
      fetched_error.restore ();
      gdbpy_print_stack ();
      if (msg != NULL && *msg != '\0')
	error (_("Error occurred in Python: %s"), msg.get ());
      else
	error (_("Error occurred in Python."));
    }
  else
    error ("%s", msg.get ());
}