binutils-gdb/gdb/python/python-prettyprint.c

/* Python pretty-printing

   Copyright (C) 2008, 2009 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 "exceptions.h"
#include "objfiles.h"
#include "symtab.h"
#include "language.h"
#include "valprint.h"
#include "python.h"
#include "python-internal.h"

#ifdef HAVE_PYTHON

/* Helper function for find_pretty_printer which iterates over a list,
   calls each function and inspects output.  This will return a
   printer object if one recognizes VALUE.  If no printer is found, it
   will return None.  On error, it will set the Python error and
   return NULL.  */
static PyObject *
search_pp_list (PyObject *list, PyObject *value)
{
  Py_ssize_t pp_list_size, list_index;
  PyObject *function, *printer = NULL;

  pp_list_size = PyList_Size (list);
  for (list_index = 0; list_index < pp_list_size; list_index++)
    {
      function = PyList_GetItem (list, list_index);
      if (! function)
	return NULL;

      printer = PyObject_CallFunctionObjArgs (function, value, NULL);
      if (! printer)
	return NULL;
      else if (printer != Py_None)
	return printer;

      Py_DECREF (printer);
    }

  Py_RETURN_NONE;
}

/* Find the pretty-printing constructor function for VALUE.  If no
   pretty-printer exists, return None.  If one exists, return a new
   reference.  On error, set the Python error and return NULL.  */
static PyObject *
find_pretty_printer (PyObject *value)
{
  PyObject *pp_list = NULL;
  PyObject *function = NULL;
  struct objfile *obj;
  volatile struct gdb_exception except;

  /* Look at the pretty-printer dictionary for each objfile.  */
  ALL_OBJFILES (obj)
  {
    PyObject *objf = objfile_to_objfile_object (obj);
    if (!objf)
      {
	/* Ignore the error and continue.  */
	PyErr_Clear ();
	continue;
      }

    pp_list = objfpy_get_printers (objf, NULL);
    function = search_pp_list (pp_list, value);

    /* If there is an error in any objfile list, abort the search and
       exit.  */
    if (! function)
      {
	Py_XDECREF (pp_list);
	return NULL;
      }

    if (function != Py_None)
      goto done;
    
    Py_DECREF (function);
    Py_XDECREF (pp_list);
  }

  pp_list = NULL;
  /* Fetch the global pretty printer dictionary.  */
  if (! PyObject_HasAttrString (gdb_module, "pretty_printers"))
    {
      function = Py_None;
      Py_INCREF (function);
      goto done;
    }
  pp_list = PyObject_GetAttrString (gdb_module, "pretty_printers");
  if (! pp_list)
    goto done;
  if (! PyList_Check (pp_list))
    goto done;

  function = search_pp_list (pp_list, value);

 done:
  Py_XDECREF (pp_list);
  
  return function;
}

/* Pretty-print a single value, via the printer object PRINTER.  If
   the function returns a string, an xmalloc()d copy is returned.
   Otherwise, if the function returns a value, a *OUT_VALUE is set to
   the value, and NULL is returned.  On error, *OUT_VALUE is set to
   NULL and NULL is returned.  */
static char *
pretty_print_one_value (PyObject *printer, struct value **out_value)
{
  char *output = NULL;
  volatile struct gdb_exception except;

  TRY_CATCH (except, RETURN_MASK_ALL)
    {
      PyObject *result;

      result = PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst, NULL);
      if (result)
	{
	  if (gdbpy_is_string (result))
	    output = python_string_to_host_string (result);
	  else
	    *out_value = convert_value_from_python (result);
	  Py_DECREF (result);
	}
    }

  return output;
}

/* Return the display hint for the object printer, PRINTER.  Return
   NULL if there is no display_hint method, or if the method did not
   return a string.  On error, print stack trace and return NULL.  On
   success, return an xmalloc()d string.  */
char *
gdbpy_get_display_hint (PyObject *printer)
{
  PyObject *hint;
  char *result = NULL;

  if (! PyObject_HasAttr (printer, gdbpy_display_hint_cst))
    return NULL;

  hint = PyObject_CallMethodObjArgs (printer, gdbpy_display_hint_cst, NULL);
  if (gdbpy_is_string (hint))
    result = python_string_to_host_string (hint);
  if (hint)
    Py_DECREF (hint);
  else
    gdbpy_print_stack ();

  return result;
}

/* Helper for apply_val_pretty_printer which calls to_string and
   formats the result.  */
static void
print_string_repr (PyObject *printer, const char *hint,
		   struct ui_file *stream, int recurse,
		   const struct value_print_options *options,
		   const struct language_defn *language)
{
  char *output;
  struct value *replacement = NULL;

  output = pretty_print_one_value (printer, &replacement);
  if (output)
    {
      if (hint && !strcmp (hint, "string"))
	LA_PRINT_STRING (stream, builtin_type (current_gdbarch)->builtin_char,
			 (gdb_byte *) output, strlen (output),
			 0, options);
      else
	fputs_filtered (output, stream);
      xfree (output);
    }
  else if (replacement)
    common_val_print (replacement, stream, recurse, options, language);
  else
    gdbpy_print_stack ();
}

static void
py_restore_tstate (void *p)
{
  PyFrameObject *frame = p;
  PyThreadState *tstate = PyThreadState_GET ();
  tstate->frame = frame;
}

/* Create a dummy PyFrameObject, needed to work around
   a Python-2.4 bug with generators.  */
static PyObject *
push_dummy_python_frame ()
{
  PyObject *empty_string, *null_tuple, *globals;
  PyCodeObject *code;
  PyFrameObject *frame;
  PyThreadState *tstate;

  empty_string = PyString_FromString ("");
  if (!empty_string)
    return NULL;

  null_tuple = PyTuple_New (0);
  if (!null_tuple)
    {
      Py_DECREF (empty_string);
      return NULL;
    }

  code = PyCode_New (0,			/* argcount */
		     0,			/* nlocals */
		     0,			/* stacksize */
		     0,			/* flags */
		     empty_string,	/* code */
		     null_tuple,	/* consts */
		     null_tuple,	/* names */
		     null_tuple,	/* varnames */
#if PYTHON_API_VERSION >= 1010
		     null_tuple,	/* freevars */
		     null_tuple,	/* cellvars */
#endif
		     empty_string,	/* filename */
		     empty_string,	/* name */
		     1,			/* firstlineno */
		     empty_string	/* lnotab */
		    );

  Py_DECREF (empty_string);
  Py_DECREF (null_tuple);

  if (!code)
    return NULL;

  globals = PyDict_New ();
  if (!globals)
    {
      Py_DECREF (code);
      return NULL;
    }

  tstate = PyThreadState_GET ();

  frame = PyFrame_New (tstate, code, globals, NULL);

  Py_DECREF (globals);
  Py_DECREF (code);

  if (!frame)
    return NULL;

  tstate->frame = frame;
  make_cleanup (py_restore_tstate, frame->f_back);
  return (PyObject *) frame;
}

/* Helper for apply_val_pretty_printer that formats children of the
   printer, if any exist.  */
static void
print_children (PyObject *printer, const char *hint,
		struct ui_file *stream, int recurse,
		const struct value_print_options *options,
		const struct language_defn *language)
{
  int is_map, is_array, done_flag, pretty;
  unsigned int i;
  PyObject *children, *iter, *frame;
  struct cleanup *cleanups;

  if (! PyObject_HasAttr (printer, gdbpy_children_cst))
    return;

  /* If we are printing a map or an array, we want some special
     formatting.  */
  is_map = hint && ! strcmp (hint, "map");
  is_array = hint && ! strcmp (hint, "array");

  children = PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
					 NULL);
  if (! children)
    {
      gdbpy_print_stack ();
      return;
    }

  cleanups = make_cleanup_py_decref (children);

  iter = PyObject_GetIter (children);
  if (!iter)
    {
      gdbpy_print_stack ();
      goto done;
    }
  make_cleanup_py_decref (iter);

  /* Use the prettyprint_arrays option if we are printing an array,
     and the pretty option otherwise.  */
  pretty = is_array ? options->prettyprint_arrays : options->pretty;

  /* Manufacture a dummy Python frame to work around Python 2.4 bug,
     where it insists on having a non-NULL tstate->frame when
     a generator is called.  */
  frame = push_dummy_python_frame ();
  if (!frame)
    {
      gdbpy_print_stack ();
      goto done;
    }
  make_cleanup_py_decref (frame);

  done_flag = 0;
  for (i = 0; i < options->print_max; ++i)
    {
      PyObject *py_v, *item = PyIter_Next (iter);
      char *name;
      struct cleanup *inner_cleanup;

      if (! item)
	{
	  if (PyErr_Occurred ())
	    gdbpy_print_stack ();
	  /* Set a flag so we can know whether we printed all the
	     available elements.  */
	  else	  
	    done_flag = 1;
	  break;
	}

      if (! PyArg_ParseTuple (item, "sO", &name, &py_v))
	{
	  gdbpy_print_stack ();
	  Py_DECREF (item);
	  continue;
	}
      inner_cleanup = make_cleanup_py_decref (item);

      /* Print initial "{".  For other elements, there are three
	 cases:
	 1. Maps.  Print a "," after each value element.
	 2. Arrays.  Always print a ",".
	 3. Other.  Always print a ",".  */
      if (i == 0)
	fputs_filtered (" = {", stream);
      else if (! is_map || i % 2 == 0)
	fputs_filtered (pretty ? "," : ", ", stream);

      /* In summary mode, we just want to print "= {...}" if there is
	 a value.  */
      if (options->summary)
	{
	  /* This increment tricks the post-loop logic to print what
	     we want.  */
	  ++i;
	  /* Likewise.  */
	  pretty = 0;
	  break;
	}

      if (! is_map || i % 2 == 0)
	{
	  if (pretty)
	    {
	      fputs_filtered ("\n", stream);
	      print_spaces_filtered (2 + 2 * recurse, stream);
	    }
	  else
	    wrap_here (n_spaces (2 + 2 *recurse));
	}

      if (is_map && i % 2 == 0)
	fputs_filtered ("[", stream);
      else if (is_array)
	{
	  /* We print the index, not whatever the child method
	     returned as the name.  */
	  if (options->print_array_indexes)
	    fprintf_filtered (stream, "[%d] = ", i);
	}
      else if (! is_map)
	{
	  fputs_filtered (name, stream);
	  fputs_filtered (" = ", stream);
	}

      if (gdbpy_is_string (py_v))
	{
	  char *text = python_string_to_host_string (py_v);
	  if (! text)
	    gdbpy_print_stack ();
	  else
	    {
	      fputs_filtered (text, stream);
	      xfree (text);
	    }
	}
      else
	{
	  struct value *value = convert_value_from_python (py_v);

	  if (value == NULL)
	    {
	      gdbpy_print_stack ();
	      error (_("Error while executing Python code."));
	    }
	  else
	    common_val_print (value, stream, recurse + 1, options, language);
	}

      if (is_map && i % 2 == 0)
	fputs_filtered ("] = ", stream);

      do_cleanups (inner_cleanup);
    }

  if (i)
    {
      if (!done_flag)
	{
	  if (pretty)
	    {
	      fputs_filtered ("\n", stream);
	      print_spaces_filtered (2 + 2 * recurse, stream);
	    }
	  fputs_filtered ("...", stream);
	}
      if (pretty)
	{
	  fputs_filtered ("\n", stream);
	  print_spaces_filtered (2 * recurse, stream);
	}
      fputs_filtered ("}", stream);
    }

 done:
  do_cleanups (cleanups);
}

int
apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
			  int embedded_offset, CORE_ADDR address,
			  struct ui_file *stream, int recurse,
			  const struct value_print_options *options,
			  const struct language_defn *language)
{
  PyObject *printer = NULL;
  PyObject *val_obj = NULL;
  struct value *value;
  char *hint = NULL;
  struct cleanup *cleanups;
  int result = 0;
  PyGILState_STATE state;

  state = PyGILState_Ensure ();
  cleanups = make_cleanup_py_restore_gil (&state);

  /* Instantiate the printer.  */
  if (valaddr)
    valaddr += embedded_offset;
  value = value_from_contents_and_address (type, valaddr, address);

  val_obj = value_to_value_object (value);
  if (! val_obj)
    goto done;
  
  /* Find the constructor.  */
  printer = find_pretty_printer (val_obj);
  Py_DECREF (val_obj);
  make_cleanup_py_decref (printer);
  if (! printer || printer == Py_None)
    goto done;

  /* If we are printing a map, we want some special formatting.  */
  hint = gdbpy_get_display_hint (printer);
  make_cleanup (free_current_contents, &hint);

  /* Print the section */
  print_string_repr (printer, hint, stream, recurse, options, language);
  print_children (printer, hint, stream, recurse, options, language);
  result = 1;


 done:
  if (PyErr_Occurred ())
    gdbpy_print_stack ();
  do_cleanups (cleanups);
  return result;
}

#else /* HAVE_PYTHON */

int
apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
			  int embedded_offset, CORE_ADDR address,
			  struct ui_file *stream, int format,
			  int deref_ref, int recurse,
			  enum val_prettyprint pretty,
			  const struct language_defn *language)
{
  return 0;
}

#endif /* HAVE_PYTHON */