gdb/python/python-prettyprint.c

   1 /* Python pretty-printing
   2
   3    Copyright (C) 2008, 2009 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "exceptions.h"
  22 #include "objfiles.h"
  23 #include "symtab.h"
  24 #include "language.h"
  25 #include "valprint.h"
  26 #include "python.h"
  27 #include "python-internal.h"
  28
  29 #ifdef HAVE_PYTHON
  30
  31 /* Helper function for find_pretty_printer which iterates over a list,
  32    calls each function and inspects output.  This will return a
  33    printer object if one recognizes VALUE.  If no printer is found, it
  34    will return None.  On error, it will set the Python error and
  35    return NULL.  */
  36 static PyObject *
  37 search_pp_list (PyObject *list, PyObject *value)
  38 {
  39   Py_ssize_t pp_list_size, list_index;
  40   PyObject *function, *printer = NULL;
  41
  42   pp_list_size = PyList_Size (list);
  43   for (list_index = 0; list_index < pp_list_size; list_index++)
  44     {
  45       function = PyList_GetItem (list, list_index);
  46       if (! function)
  47         return NULL;
  48
  49       printer = PyObject_CallFunctionObjArgs (function, value, NULL);
  50       if (! printer)
  51         return NULL;
  52       else if (printer != Py_None)
  53         return printer;
  54
  55       Py_DECREF (printer);
  56     }
  57
  58   Py_RETURN_NONE;
  59 }
  60
  61 /* Find the pretty-printing constructor function for VALUE.  If no
  62    pretty-printer exists, return None.  If one exists, return a new
  63    reference.  On error, set the Python error and return NULL.  */
  64 static PyObject *
  65 find_pretty_printer (PyObject *value)
  66 {
  67   PyObject *pp_list = NULL;
  68   PyObject *function = NULL;
  69   struct objfile *obj;
  70   volatile struct gdb_exception except;
  71
  72   /* Look at the pretty-printer dictionary for each objfile.  */
  73   ALL_OBJFILES (obj)
  74   {
  75     PyObject *objf = objfile_to_objfile_object (obj);
  76     if (!objf)
  77       {
  78         /* Ignore the error and continue.  */
  79         PyErr_Clear ();
  80         continue;
  81       }
  82
  83     pp_list = objfpy_get_printers (objf, NULL);
  84     function = search_pp_list (pp_list, value);
  85
  86     /* If there is an error in any objfile list, abort the search and
  87        exit.  */
  88     if (! function)
  89       {
  90         Py_XDECREF (pp_list);
  91         return NULL;
  92       }
  93
  94     if (function != Py_None)
  95       goto done;
  96
  97     Py_DECREF (function);
  98     Py_XDECREF (pp_list);
  99   }
 100
 101   pp_list = NULL;
 102   /* Fetch the global pretty printer dictionary.  */
 103   if (! PyObject_HasAttrString (gdb_module, "pretty_printers"))
 104     {
 105       function = Py_None;
 106       Py_INCREF (function);
 107       goto done;
 108     }
 109   pp_list = PyObject_GetAttrString (gdb_module, "pretty_printers");
 110   if (! pp_list)
 111     goto done;
 112   if (! PyList_Check (pp_list))
 113     goto done;
 114
 115   function = search_pp_list (pp_list, value);
 116
 117  done:
 118   Py_XDECREF (pp_list);
 119
 120   return function;
 121 }
 122
 123 /* Pretty-print a single value, via the printer object PRINTER.  If
 124    the function returns a string, an xmalloc()d copy is returned.
 125    Otherwise, if the function returns a value, a *OUT_VALUE is set to
 126    the value, and NULL is returned.  On error, *OUT_VALUE is set to
 127    NULL and NULL is returned.  */
 128 static char *
 129 pretty_print_one_value (PyObject *printer, struct value **out_value)
 130 {
 131   char *output = NULL;
 132   volatile struct gdb_exception except;
 133
 134   TRY_CATCH (except, RETURN_MASK_ALL)
 135     {
 136       PyObject *result;
 137
 138       result = PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst, NULL);
 139       if (result)
 140         {
 141           if (gdbpy_is_string (result))
 142             output = python_string_to_host_string (result);
 143           else
 144             *out_value = convert_value_from_python (result);
 145           Py_DECREF (result);
 146         }
 147     }
 148
 149   return output;
 150 }
 151
 152 /* Return the display hint for the object printer, PRINTER.  Return
 153    NULL if there is no display_hint method, or if the method did not
 154    return a string.  On error, print stack trace and return NULL.  On
 155    success, return an xmalloc()d string.  */
 156 char *
 157 gdbpy_get_display_hint (PyObject *printer)
 158 {
 159   PyObject *hint;
 160   char *result = NULL;
 161
 162   if (! PyObject_HasAttr (printer, gdbpy_display_hint_cst))
 163     return NULL;
 164
 165   hint = PyObject_CallMethodObjArgs (printer, gdbpy_display_hint_cst, NULL);
 166   if (gdbpy_is_string (hint))
 167     result = python_string_to_host_string (hint);
 168   if (hint)
 169     Py_DECREF (hint);
 170   else
 171     gdbpy_print_stack ();
 172
 173   return result;
 174 }
 175
 176 /* Helper for apply_val_pretty_printer which calls to_string and
 177    formats the result.  */
 178 static void
 179 print_string_repr (PyObject *printer, const char *hint,
 180                    struct ui_file *stream, int recurse,
 181                    const struct value_print_options *options,
 182                    const struct language_defn *language)
 183 {
 184   char *output;
 185   struct value *replacement = NULL;
 186
 187   output = pretty_print_one_value (printer, &replacement);
 188   if (output)
 189     {
 190       if (hint && !strcmp (hint, "string"))
 191         LA_PRINT_STRING (stream, builtin_type (current_gdbarch)->builtin_char,
 192                          (gdb_byte *) output, strlen (output),
 193                          0, options);
 194       else
 195         fputs_filtered (output, stream);
 196       xfree (output);
 197     }
 198   else if (replacement)
 199     common_val_print (replacement, stream, recurse, options, language);
 200   else
 201     gdbpy_print_stack ();
 202 }
 203
 204 static void
 205 py_restore_tstate (void *p)
 206 {
 207   PyFrameObject *frame = p;
 208   PyThreadState *tstate = PyThreadState_GET ();
 209   tstate->frame = frame;
 210 }
 211
 212 /* Create a dummy PyFrameObject, needed to work around
 213    a Python-2.4 bug with generators.  */
 214 static PyObject *
 215 push_dummy_python_frame ()
 216 {
 217   PyObject *empty_string, *null_tuple, *globals;
 218   PyCodeObject *code;
 219   PyFrameObject *frame;
 220   PyThreadState *tstate;
 221
 222   empty_string = PyString_FromString ("");
 223   if (!empty_string)
 224     return NULL;
 225
 226   null_tuple = PyTuple_New (0);
 227   if (!null_tuple)
 228     {
 229       Py_DECREF (empty_string);
 230       return NULL;
 231     }
 232
 233   code = PyCode_New (0,                 /* argcount */
 234                      0,                 /* nlocals */
 235                      0,                 /* stacksize */
 236                      0,                 /* flags */
 237                      empty_string,      /* code */
 238                      null_tuple,        /* consts */
 239                      null_tuple,        /* names */
 240                      null_tuple,        /* varnames */
 241 #if PYTHON_API_VERSION >= 1010
 242                      null_tuple,        /* freevars */
 243                      null_tuple,        /* cellvars */
 244 #endif
 245                      empty_string,      /* filename */
 246                      empty_string,      /* name */
 247                      1,                 /* firstlineno */
 248                      empty_string       /* lnotab */
 249                     );
 250
 251   Py_DECREF (empty_string);
 252   Py_DECREF (null_tuple);
 253
 254   if (!code)
 255     return NULL;
 256
 257   globals = PyDict_New ();
 258   if (!globals)
 259     {
 260       Py_DECREF (code);
 261       return NULL;
 262     }
 263
 264   tstate = PyThreadState_GET ();
 265
 266   frame = PyFrame_New (tstate, code, globals, NULL);
 267
 268   Py_DECREF (globals);
 269   Py_DECREF (code);
 270
 271   if (!frame)
 272     return NULL;
 273
 274   tstate->frame = frame;
 275   make_cleanup (py_restore_tstate, frame->f_back);
 276   return (PyObject *) frame;
 277 }
 278
 279 /* Helper for apply_val_pretty_printer that formats children of the
 280    printer, if any exist.  */
 281 static void
 282 print_children (PyObject *printer, const char *hint,
 283                 struct ui_file *stream, int recurse,
 284                 const struct value_print_options *options,
 285                 const struct language_defn *language)
 286 {
 287   int is_map, is_array, done_flag, pretty;
 288   unsigned int i;
 289   PyObject *children, *iter, *frame;
 290   struct cleanup *cleanups;
 291
 292   if (! PyObject_HasAttr (printer, gdbpy_children_cst))
 293     return;
 294
 295   /* If we are printing a map or an array, we want some special
 296      formatting.  */
 297   is_map = hint && ! strcmp (hint, "map");
 298   is_array = hint && ! strcmp (hint, "array");
 299
 300   children = PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
 301                                          NULL);
 302   if (! children)
 303     {
 304       gdbpy_print_stack ();
 305       return;
 306     }
 307
 308   cleanups = make_cleanup_py_decref (children);
 309
 310   iter = PyObject_GetIter (children);
 311   if (!iter)
 312     {
 313       gdbpy_print_stack ();
 314       goto done;
 315     }
 316   make_cleanup_py_decref (iter);
 317
 318   /* Use the prettyprint_arrays option if we are printing an array,
 319      and the pretty option otherwise.  */
 320   pretty = is_array ? options->prettyprint_arrays : options->pretty;
 321
 322   /* Manufacture a dummy Python frame to work around Python 2.4 bug,
 323      where it insists on having a non-NULL tstate->frame when
 324      a generator is called.  */
 325   frame = push_dummy_python_frame ();
 326   if (!frame)
 327     {
 328       gdbpy_print_stack ();
 329       goto done;
 330     }
 331   make_cleanup_py_decref (frame);
 332
 333   done_flag = 0;
 334   for (i = 0; i < options->print_max; ++i)
 335     {
 336       PyObject *py_v, *item = PyIter_Next (iter);
 337       char *name;
 338       struct cleanup *inner_cleanup;
 339
 340       if (! item)
 341         {
 342           if (PyErr_Occurred ())
 343             gdbpy_print_stack ();
 344           /* Set a flag so we can know whether we printed all the
 345              available elements.  */
 346           else
 347             done_flag = 1;
 348           break;
 349         }
 350
 351       if (! PyArg_ParseTuple (item, "sO", &name, &py_v))
 352         {
 353           gdbpy_print_stack ();
 354           Py_DECREF (item);
 355           continue;
 356         }
 357       inner_cleanup = make_cleanup_py_decref (item);
 358
 359       /* Print initial "{".  For other elements, there are three
 360          cases:
 361          1. Maps.  Print a "," after each value element.
 362          2. Arrays.  Always print a ",".
 363          3. Other.  Always print a ",".  */
 364       if (i == 0)
 365         fputs_filtered (" = {", stream);
 366       else if (! is_map || i % 2 == 0)
 367         fputs_filtered (pretty ? "," : ", ", stream);
 368
 369       /* In summary mode, we just want to print "= {...}" if there is
 370          a value.  */
 371       if (options->summary)
 372         {
 373           /* This increment tricks the post-loop logic to print what
 374              we want.  */
 375           ++i;
 376           /* Likewise.  */
 377           pretty = 0;
 378           break;
 379         }
 380
 381       if (! is_map || i % 2 == 0)
 382         {
 383           if (pretty)
 384             {
 385               fputs_filtered ("\n", stream);
 386               print_spaces_filtered (2 + 2 * recurse, stream);
 387             }
 388           else
 389             wrap_here (n_spaces (2 + 2 *recurse));
 390         }
 391
 392       if (is_map && i % 2 == 0)
 393         fputs_filtered ("[", stream);
 394       else if (is_array)
 395         {
 396           /* We print the index, not whatever the child method
 397              returned as the name.  */
 398           if (options->print_array_indexes)
 399             fprintf_filtered (stream, "[%d] = ", i);
 400         }
 401       else if (! is_map)
 402         {
 403           fputs_filtered (name, stream);
 404           fputs_filtered (" = ", stream);
 405         }
 406
 407       if (gdbpy_is_string (py_v))
 408         {
 409           char *text = python_string_to_host_string (py_v);
 410           if (! text)
 411             gdbpy_print_stack ();
 412           else
 413             {
 414               fputs_filtered (text, stream);
 415               xfree (text);
 416             }
 417         }
 418       else
 419         {
 420           struct value *value = convert_value_from_python (py_v);
 421
 422           if (value == NULL)
 423             {
 424               gdbpy_print_stack ();
 425               error (_("Error while executing Python code."));
 426             }
 427           else
 428             common_val_print (value, stream, recurse + 1, options, language);
 429         }
 430
 431       if (is_map && i % 2 == 0)
 432         fputs_filtered ("] = ", stream);
 433
 434       do_cleanups (inner_cleanup);
 435     }
 436
 437   if (i)
 438     {
 439       if (!done_flag)
 440         {
 441           if (pretty)
 442             {
 443               fputs_filtered ("\n", stream);
 444               print_spaces_filtered (2 + 2 * recurse, stream);
 445             }
 446           fputs_filtered ("...", stream);
 447         }
 448       if (pretty)
 449         {
 450           fputs_filtered ("\n", stream);
 451           print_spaces_filtered (2 * recurse, stream);
 452         }
 453       fputs_filtered ("}", stream);
 454     }
 455
 456  done:
 457   do_cleanups (cleanups);
 458 }
 459
 460 int
 461 apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
 462                           int embedded_offset, CORE_ADDR address,
 463                           struct ui_file *stream, int recurse,
 464                           const struct value_print_options *options,
 465                           const struct language_defn *language)
 466 {
 467   PyObject *printer = NULL;
 468   PyObject *val_obj = NULL;
 469   struct value *value;
 470   char *hint = NULL;
 471   struct cleanup *cleanups;
 472   int result = 0;
 473   PyGILState_STATE state;
 474
 475   state = PyGILState_Ensure ();
 476   cleanups = make_cleanup_py_restore_gil (&state);
 477
 478   /* Instantiate the printer.  */
 479   if (valaddr)
 480     valaddr += embedded_offset;
 481   value = value_from_contents_and_address (type, valaddr, address);
 482
 483   val_obj = value_to_value_object (value);
 484   if (! val_obj)
 485     goto done;
 486
 487   /* Find the constructor.  */
 488   printer = find_pretty_printer (val_obj);
 489   Py_DECREF (val_obj);
 490   make_cleanup_py_decref (printer);
 491   if (! printer || printer == Py_None)
 492     goto done;
 493
 494   /* If we are printing a map, we want some special formatting.  */
 495   hint = gdbpy_get_display_hint (printer);
 496   make_cleanup (free_current_contents, &hint);
 497
 498   /* Print the section */
 499   print_string_repr (printer, hint, stream, recurse, options, language);
 500   print_children (printer, hint, stream, recurse, options, language);
 501   result = 1;
 502
 503
 504  done:
 505   if (PyErr_Occurred ())
 506     gdbpy_print_stack ();
 507   do_cleanups (cleanups);
 508   return result;
 509 }
 510
 511 /* Apply a pretty-printer for the varobj code.  PRINTER_OBJ is the
 512    print object.  It must have a 'to_string' method (but this is
 513    checked by varobj, not here) which takes no arguments and
 514    returns a string.  This function returns an xmalloc()d string if
 515    the printer returns a string.  The printer may return a replacement
 516    value instead; in this case *REPLACEMENT is set to the replacement
 517    value, and this function returns NULL.  On error, *REPLACEMENT is
 518    set to NULL and this function also returns NULL.  */
 519 char *
 520 apply_varobj_pretty_printer (PyObject *printer_obj,
 521                              struct value **replacement)
 522 {
 523   char *result;
 524   PyGILState_STATE state = PyGILState_Ensure ();
 525
 526   *replacement = NULL;
 527   result = pretty_print_one_value (printer_obj, replacement);
 528   if (result == NULL);
 529     gdbpy_print_stack ();
 530   PyGILState_Release (state);
 531
 532   return result;
 533 }
 534
 535 /* Find a pretty-printer object for the varobj module.  Returns a new
 536    reference to the object if successful; returns NULL if not.  VALUE
 537    is the value for which a printer tests to determine if it
 538    can pretty-print the value.  */
 539 PyObject *
 540 gdbpy_get_varobj_pretty_printer (struct value *value)
 541 {
 542   PyObject *val_obj;
 543   PyObject *pretty_printer = NULL;
 544   volatile struct gdb_exception except;
 545
 546   TRY_CATCH (except, RETURN_MASK_ALL)
 547     {
 548       value = value_copy (value);
 549     }
 550   GDB_PY_HANDLE_EXCEPTION (except);
 551
 552   val_obj = value_to_value_object (value);
 553   if (! val_obj)
 554     return NULL;
 555
 556   pretty_printer = find_pretty_printer (val_obj);
 557   Py_DECREF (val_obj);
 558   return pretty_printer;
 559 }
 560
 561 /* A Python function which wraps find_pretty_printer and instantiates
 562    the resulting class.  This accepts a Value argument and returns a
 563    pretty printer instance, or None.  This function is useful as an
 564    argument to the MI command -var-set-visualizer.  */
 565 PyObject *
 566 gdbpy_default_visualizer (PyObject *self, PyObject *args)
 567 {
 568   PyObject *val_obj;
 569   PyObject *cons, *printer = NULL;
 570   struct value *value;
 571
 572   if (! PyArg_ParseTuple (args, "O", &val_obj))
 573     return NULL;
 574   value = value_object_to_value (val_obj);
 575   if (! value)
 576     {
 577       PyErr_SetString (PyExc_TypeError, "argument must be a gdb.Value");
 578       return NULL;
 579     }
 580
 581   cons = find_pretty_printer (val_obj);
 582   return cons;
 583 }
 584
 585 #else /* HAVE_PYTHON */
 586
 587 int
 588 apply_val_pretty_printer (struct type *type, const gdb_byte *valaddr,
 589                           int embedded_offset, CORE_ADDR address,
 590                           struct ui_file *stream, int format,
 591                           int deref_ref, int recurse,
 592                           enum val_prettyprint pretty,
 593                           const struct language_defn *language)
 594 {
 595   return 0;
 596 }
 597
 598 #endif /* HAVE_PYTHON */