gdb/python/py-prettyprint.c

   1 /* Python pretty-printing
   2
   3    Copyright (C) 2008-2015 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 "objfiles.h"
  22 #include "symtab.h"
  23 #include "language.h"
  24 #include "valprint.h"
  25 #include "extension-priv.h"
  26 #include "python.h"
  27 #include "python-internal.h"
  28
  29 /* Return type of print_string_repr.  */
  30
  31 enum string_repr_result
  32   {
  33     /* The string method returned None.  */
  34     string_repr_none,
  35     /* The string method had an error.  */
  36     string_repr_error,
  37     /* Everything ok.  */
  38     string_repr_ok
  39   };
  40
  41 /* Helper function for find_pretty_printer which iterates over a list,
  42    calls each function and inspects output.  This will return a
  43    printer object if one recognizes VALUE.  If no printer is found, it
  44    will return None.  On error, it will set the Python error and
  45    return NULL.  */
  46
  47 static PyObject *
  48 search_pp_list (PyObject *list, PyObject *value)
  49 {
  50   Py_ssize_t pp_list_size, list_index;
  51   PyObject *function, *printer = NULL;
  52
  53   pp_list_size = PyList_Size (list);
  54   for (list_index = 0; list_index < pp_list_size; list_index++)
  55     {
  56       function = PyList_GetItem (list, list_index);
  57       if (! function)
  58         return NULL;
  59
  60       /* Skip if disabled.  */
  61       if (PyObject_HasAttr (function, gdbpy_enabled_cst))
  62         {
  63           PyObject *attr = PyObject_GetAttr (function, gdbpy_enabled_cst);
  64           int cmp;
  65
  66           if (!attr)
  67             return NULL;
  68           cmp = PyObject_IsTrue (attr);
  69           Py_DECREF (attr);
  70           if (cmp == -1)
  71             return NULL;
  72
  73           if (!cmp)
  74             continue;
  75         }
  76
  77       printer = PyObject_CallFunctionObjArgs (function, value, NULL);
  78       if (! printer)
  79         return NULL;
  80       else if (printer != Py_None)
  81         return printer;
  82
  83       Py_DECREF (printer);
  84     }
  85
  86   Py_RETURN_NONE;
  87 }
  88
  89 /* Subroutine of find_pretty_printer to simplify it.
  90    Look for a pretty-printer to print VALUE in all objfiles.
  91    The result is NULL if there's an error and the search should be terminated.
  92    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
  93    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
  94
  95 static PyObject *
  96 find_pretty_printer_from_objfiles (PyObject *value)
  97 {
  98   PyObject *pp_list;
  99   PyObject *function;
 100   struct objfile *obj;
 101
 102   ALL_OBJFILES (obj)
 103   {
 104     PyObject *objf = objfile_to_objfile_object (obj);
 105     if (!objf)
 106       {
 107         /* Ignore the error and continue.  */
 108         PyErr_Clear ();
 109         continue;
 110       }
 111
 112     pp_list = objfpy_get_printers (objf, NULL);
 113     function = search_pp_list (pp_list, value);
 114     Py_XDECREF (pp_list);
 115
 116     /* If there is an error in any objfile list, abort the search and exit.  */
 117     if (! function)
 118       return NULL;
 119
 120     if (function != Py_None)
 121       return function;
 122
 123     Py_DECREF (function);
 124   }
 125
 126   Py_RETURN_NONE;
 127 }
 128
 129 /* Subroutine of find_pretty_printer to simplify it.
 130    Look for a pretty-printer to print VALUE in the current program space.
 131    The result is NULL if there's an error and the search should be terminated.
 132    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 133    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 134
 135 static PyObject *
 136 find_pretty_printer_from_progspace (PyObject *value)
 137 {
 138   PyObject *pp_list;
 139   PyObject *function;
 140   PyObject *obj = pspace_to_pspace_object (current_program_space);
 141
 142   if (!obj)
 143     return NULL;
 144   pp_list = pspy_get_printers (obj, NULL);
 145   function = search_pp_list (pp_list, value);
 146   Py_XDECREF (pp_list);
 147   return function;
 148 }
 149
 150 /* Subroutine of find_pretty_printer to simplify it.
 151    Look for a pretty-printer to print VALUE in the gdb module.
 152    The result is NULL if there's an error and the search should be terminated.
 153    The result is Py_None, suitably inc-ref'd, if no pretty-printer was found.
 154    Otherwise the result is the pretty-printer function, suitably inc-ref'd.  */
 155
 156 static PyObject *
 157 find_pretty_printer_from_gdb (PyObject *value)
 158 {
 159   PyObject *pp_list;
 160   PyObject *function;
 161
 162   /* Fetch the global pretty printer list.  */
 163   if (gdb_python_module == NULL
 164       || ! PyObject_HasAttrString (gdb_python_module, "pretty_printers"))
 165     Py_RETURN_NONE;
 166   pp_list = PyObject_GetAttrString (gdb_python_module, "pretty_printers");
 167   if (pp_list == NULL || ! PyList_Check (pp_list))
 168     {
 169       Py_XDECREF (pp_list);
 170       Py_RETURN_NONE;
 171     }
 172
 173   function = search_pp_list (pp_list, value);
 174   Py_XDECREF (pp_list);
 175   return function;
 176 }
 177
 178 /* Find the pretty-printing constructor function for VALUE.  If no
 179    pretty-printer exists, return None.  If one exists, return a new
 180    reference.  On error, set the Python error and return NULL.  */
 181
 182 static PyObject *
 183 find_pretty_printer (PyObject *value)
 184 {
 185   PyObject *function;
 186
 187   /* Look at the pretty-printer list for each objfile
 188      in the current program-space.  */
 189   function = find_pretty_printer_from_objfiles (value);
 190   if (function == NULL || function != Py_None)
 191     return function;
 192   Py_DECREF (function);
 193
 194   /* Look at the pretty-printer list for the current program-space.  */
 195   function = find_pretty_printer_from_progspace (value);
 196   if (function == NULL || function != Py_None)
 197     return function;
 198   Py_DECREF (function);
 199
 200   /* Look at the pretty-printer list in the gdb module.  */
 201   function = find_pretty_printer_from_gdb (value);
 202   return function;
 203 }
 204
 205 /* Pretty-print a single value, via the printer object PRINTER.
 206    If the function returns a string, a PyObject containing the string
 207    is returned.  If the function returns Py_NONE that means the pretty
 208    printer returned the Python None as a value.  Otherwise, if the
 209    function returns a value,  *OUT_VALUE is set to the value, and NULL
 210    is returned.  On error, *OUT_VALUE is set to NULL, NULL is
 211    returned, with a python exception set.  */
 212
 213 static PyObject *
 214 pretty_print_one_value (PyObject *printer, struct value **out_value)
 215 {
 216   volatile struct gdb_exception except;
 217   PyObject *result = NULL;
 218
 219   *out_value = NULL;
 220   TRY_CATCH (except, RETURN_MASK_ALL)
 221     {
 222       result = PyObject_CallMethodObjArgs (printer, gdbpy_to_string_cst, NULL);
 223       if (result)
 224         {
 225           if (! gdbpy_is_string (result) && ! gdbpy_is_lazy_string (result)
 226               && result != Py_None)
 227             {
 228               *out_value = convert_value_from_python (result);
 229               if (PyErr_Occurred ())
 230                 *out_value = NULL;
 231               Py_DECREF (result);
 232               result = NULL;
 233             }
 234         }
 235     }
 236
 237   return result;
 238 }
 239
 240 /* Return the display hint for the object printer, PRINTER.  Return
 241    NULL if there is no display_hint method, or if the method did not
 242    return a string.  On error, print stack trace and return NULL.  On
 243    success, return an xmalloc()d string.  */
 244 char *
 245 gdbpy_get_display_hint (PyObject *printer)
 246 {
 247   PyObject *hint;
 248   char *result = NULL;
 249
 250   if (! PyObject_HasAttr (printer, gdbpy_display_hint_cst))
 251     return NULL;
 252
 253   hint = PyObject_CallMethodObjArgs (printer, gdbpy_display_hint_cst, NULL);
 254   if (hint)
 255     {
 256       if (gdbpy_is_string (hint))
 257         {
 258           result = python_string_to_host_string (hint);
 259           if (result == NULL)
 260             gdbpy_print_stack ();
 261         }
 262       Py_DECREF (hint);
 263     }
 264   else
 265     gdbpy_print_stack ();
 266
 267   return result;
 268 }
 269
 270 /* A wrapper for gdbpy_print_stack that ignores MemoryError.  */
 271
 272 static void
 273 print_stack_unless_memory_error (struct ui_file *stream)
 274 {
 275   if (PyErr_ExceptionMatches (gdbpy_gdb_memory_error))
 276     {
 277       struct cleanup *cleanup;
 278       PyObject *type, *value, *trace;
 279       char *msg;
 280
 281       PyErr_Fetch (&type, &value, &trace);
 282       cleanup = make_cleanup_py_decref (type);
 283       make_cleanup_py_decref (value);
 284       make_cleanup_py_decref (trace);
 285
 286       msg = gdbpy_exception_to_string (type, value);
 287       make_cleanup (xfree, msg);
 288
 289       if (msg == NULL || *msg == '\0')
 290         fprintf_filtered (stream, _("<error reading variable>"));
 291       else
 292         fprintf_filtered (stream, _("<error reading variable: %s>"), msg);
 293
 294       do_cleanups (cleanup);
 295     }
 296   else
 297     gdbpy_print_stack ();
 298 }
 299
 300 /* Helper for gdbpy_apply_val_pretty_printer which calls to_string and
 301    formats the result.  */
 302
 303 static enum string_repr_result
 304 print_string_repr (PyObject *printer, const char *hint,
 305                    struct ui_file *stream, int recurse,
 306                    const struct value_print_options *options,
 307                    const struct language_defn *language,
 308                    struct gdbarch *gdbarch)
 309 {
 310   struct value *replacement = NULL;
 311   PyObject *py_str = NULL;
 312   enum string_repr_result result = string_repr_ok;
 313
 314   py_str = pretty_print_one_value (printer, &replacement);
 315   if (py_str)
 316     {
 317       struct cleanup *cleanup = make_cleanup_py_decref (py_str);
 318
 319       if (py_str == Py_None)
 320         result = string_repr_none;
 321       else if (gdbpy_is_lazy_string (py_str))
 322         {
 323           CORE_ADDR addr;
 324           long length;
 325           struct type *type;
 326           char *encoding = NULL;
 327           struct value_print_options local_opts = *options;
 328
 329           make_cleanup (free_current_contents, &encoding);
 330           gdbpy_extract_lazy_string (py_str, &addr, &type,
 331                                      &length, &encoding);
 332
 333           local_opts.addressprint = 0;
 334           val_print_string (type, encoding, addr, (int) length,
 335                             stream, &local_opts);
 336         }
 337       else
 338         {
 339           PyObject *string;
 340
 341           string = python_string_to_target_python_string (py_str);
 342           if (string)
 343             {
 344               char *output;
 345               long length;
 346               struct type *type;
 347
 348               make_cleanup_py_decref (string);
 349 #ifdef IS_PY3K
 350               output = PyBytes_AS_STRING (string);
 351               length = PyBytes_GET_SIZE (string);
 352 #else
 353               output = PyString_AsString (string);
 354               length = PyString_Size (string);
 355 #endif
 356               type = builtin_type (gdbarch)->builtin_char;
 357
 358               if (hint && !strcmp (hint, "string"))
 359                 LA_PRINT_STRING (stream, type, (gdb_byte *) output,
 360                                  length, NULL, 0, options);
 361               else
 362                 fputs_filtered (output, stream);
 363             }
 364           else
 365             {
 366               result = string_repr_error;
 367               print_stack_unless_memory_error (stream);
 368             }
 369         }
 370
 371       do_cleanups (cleanup);
 372     }
 373   else if (replacement)
 374     {
 375       struct value_print_options opts = *options;
 376
 377       opts.addressprint = 0;
 378       common_val_print (replacement, stream, recurse, &opts, language);
 379     }
 380   else
 381     {
 382       result = string_repr_error;
 383       print_stack_unless_memory_error (stream);
 384     }
 385
 386   return result;
 387 }
 388
 389 #ifndef IS_PY3K
 390 static void
 391 py_restore_tstate (void *p)
 392 {
 393   PyFrameObject *frame = p;
 394   PyThreadState *tstate = PyThreadState_GET ();
 395
 396   tstate->frame = frame;
 397 }
 398
 399 /* Create a dummy PyFrameObject, needed to work around
 400    a Python-2.4 bug with generators.  */
 401 static PyObject *
 402 push_dummy_python_frame (void)
 403 {
 404   PyObject *empty_string, *null_tuple, *globals;
 405   PyCodeObject *code;
 406   PyFrameObject *frame;
 407   PyThreadState *tstate;
 408
 409   empty_string = PyString_FromString ("");
 410   if (!empty_string)
 411     return NULL;
 412
 413   null_tuple = PyTuple_New (0);
 414   if (!null_tuple)
 415     {
 416       Py_DECREF (empty_string);
 417       return NULL;
 418     }
 419
 420   code = PyCode_New (0,                 /* argcount */
 421                      0,                 /* nlocals */
 422                      0,                 /* stacksize */
 423                      0,                 /* flags */
 424                      empty_string,      /* code */
 425                      null_tuple,        /* consts */
 426                      null_tuple,        /* names */
 427                      null_tuple,        /* varnames */
 428 #if PYTHON_API_VERSION >= 1010
 429                      null_tuple,        /* freevars */
 430                      null_tuple,        /* cellvars */
 431 #endif
 432                      empty_string,      /* filename */
 433                      empty_string,      /* name */
 434                      1,                 /* firstlineno */
 435                      empty_string       /* lnotab */
 436                     );
 437
 438   Py_DECREF (empty_string);
 439   Py_DECREF (null_tuple);
 440
 441   if (!code)
 442     return NULL;
 443
 444   globals = PyDict_New ();
 445   if (!globals)
 446     {
 447       Py_DECREF (code);
 448       return NULL;
 449     }
 450
 451   tstate = PyThreadState_GET ();
 452
 453   frame = PyFrame_New (tstate, code, globals, NULL);
 454
 455   Py_DECREF (globals);
 456   Py_DECREF (code);
 457
 458   if (!frame)
 459     return NULL;
 460
 461   tstate->frame = frame;
 462   make_cleanup (py_restore_tstate, frame->f_back);
 463   return (PyObject *) frame;
 464 }
 465 #endif
 466
 467 /* Helper for gdbpy_apply_val_pretty_printer that formats children of the
 468    printer, if any exist.  If is_py_none is true, then nothing has
 469    been printed by to_string, and format output accordingly. */
 470 static void
 471 print_children (PyObject *printer, const char *hint,
 472                 struct ui_file *stream, int recurse,
 473                 const struct value_print_options *options,
 474                 const struct language_defn *language,
 475                 int is_py_none)
 476 {
 477   int is_map, is_array, done_flag, pretty;
 478   unsigned int i;
 479   PyObject *children, *iter;
 480 #ifndef IS_PY3K
 481   PyObject *frame;
 482 #endif
 483   struct cleanup *cleanups;
 484
 485   if (! PyObject_HasAttr (printer, gdbpy_children_cst))
 486     return;
 487
 488   /* If we are printing a map or an array, we want some special
 489      formatting.  */
 490   is_map = hint && ! strcmp (hint, "map");
 491   is_array = hint && ! strcmp (hint, "array");
 492
 493   children = PyObject_CallMethodObjArgs (printer, gdbpy_children_cst,
 494                                          NULL);
 495   if (! children)
 496     {
 497       print_stack_unless_memory_error (stream);
 498       return;
 499     }
 500
 501   cleanups = make_cleanup_py_decref (children);
 502
 503   iter = PyObject_GetIter (children);
 504   if (!iter)
 505     {
 506       print_stack_unless_memory_error (stream);
 507       goto done;
 508     }
 509   make_cleanup_py_decref (iter);
 510
 511   /* Use the prettyformat_arrays option if we are printing an array,
 512      and the pretty option otherwise.  */
 513   if (is_array)
 514     pretty = options->prettyformat_arrays;
 515   else
 516     {
 517       if (options->prettyformat == Val_prettyformat)
 518         pretty = 1;
 519       else
 520         pretty = options->prettyformat_structs;
 521     }
 522
 523   /* Manufacture a dummy Python frame to work around Python 2.4 bug,
 524      where it insists on having a non-NULL tstate->frame when
 525      a generator is called.  */
 526 #ifndef IS_PY3K
 527   frame = push_dummy_python_frame ();
 528   if (!frame)
 529     {
 530       gdbpy_print_stack ();
 531       goto done;
 532     }
 533   make_cleanup_py_decref (frame);
 534 #endif
 535
 536   done_flag = 0;
 537   for (i = 0; i < options->print_max; ++i)
 538     {
 539       PyObject *py_v, *item = PyIter_Next (iter);
 540       const char *name;
 541       struct cleanup *inner_cleanup;
 542
 543       if (! item)
 544         {
 545           if (PyErr_Occurred ())
 546             print_stack_unless_memory_error (stream);
 547           /* Set a flag so we can know whether we printed all the
 548              available elements.  */
 549           else
 550             done_flag = 1;
 551           break;
 552         }
 553
 554       if (! PyArg_ParseTuple (item, "sO", &name, &py_v))
 555         {
 556           gdbpy_print_stack ();
 557           Py_DECREF (item);
 558           continue;
 559         }
 560       inner_cleanup = make_cleanup_py_decref (item);
 561
 562       /* Print initial "{".  For other elements, there are three
 563          cases:
 564          1. Maps.  Print a "," after each value element.
 565          2. Arrays.  Always print a ",".
 566          3. Other.  Always print a ",".  */
 567       if (i == 0)
 568         {
 569          if (is_py_none)
 570            fputs_filtered ("{", stream);
 571          else
 572            fputs_filtered (" = {", stream);
 573        }
 574
 575       else if (! is_map || i % 2 == 0)
 576         fputs_filtered (pretty ? "," : ", ", stream);
 577
 578       /* In summary mode, we just want to print "= {...}" if there is
 579          a value.  */
 580       if (options->summary)
 581         {
 582           /* This increment tricks the post-loop logic to print what
 583              we want.  */
 584           ++i;
 585           /* Likewise.  */
 586           pretty = 0;
 587           break;
 588         }
 589
 590       if (! is_map || i % 2 == 0)
 591         {
 592           if (pretty)
 593             {
 594               fputs_filtered ("\n", stream);
 595               print_spaces_filtered (2 + 2 * recurse, stream);
 596             }
 597           else
 598             wrap_here (n_spaces (2 + 2 *recurse));
 599         }
 600
 601       if (is_map && i % 2 == 0)
 602         fputs_filtered ("[", stream);
 603       else if (is_array)
 604         {
 605           /* We print the index, not whatever the child method
 606              returned as the name.  */
 607           if (options->print_array_indexes)
 608             fprintf_filtered (stream, "[%d] = ", i);
 609         }
 610       else if (! is_map)
 611         {
 612           fputs_filtered (name, stream);
 613           fputs_filtered (" = ", stream);
 614         }
 615
 616       if (gdbpy_is_lazy_string (py_v))
 617         {
 618           CORE_ADDR addr;
 619           struct type *type;
 620           long length;
 621           char *encoding = NULL;
 622           struct value_print_options local_opts = *options;
 623
 624           make_cleanup (free_current_contents, &encoding);
 625           gdbpy_extract_lazy_string (py_v, &addr, &type, &length, &encoding);
 626
 627           local_opts.addressprint = 0;
 628           val_print_string (type, encoding, addr, (int) length, stream,
 629                             &local_opts);
 630         }
 631       else if (gdbpy_is_string (py_v))
 632         {
 633           char *output;
 634
 635           output = python_string_to_host_string (py_v);
 636           if (!output)
 637             gdbpy_print_stack ();
 638           else
 639             {
 640               fputs_filtered (output, stream);
 641               xfree (output);
 642             }
 643         }
 644       else
 645         {
 646           struct value *value = convert_value_from_python (py_v);
 647
 648           if (value == NULL)
 649             {
 650               gdbpy_print_stack ();
 651               error (_("Error while executing Python code."));
 652             }
 653           else
 654             common_val_print (value, stream, recurse + 1, options, language);
 655         }
 656
 657       if (is_map && i % 2 == 0)
 658         fputs_filtered ("] = ", stream);
 659
 660       do_cleanups (inner_cleanup);
 661     }
 662
 663   if (i)
 664     {
 665       if (!done_flag)
 666         {
 667           if (pretty)
 668             {
 669               fputs_filtered ("\n", stream);
 670               print_spaces_filtered (2 + 2 * recurse, stream);
 671             }
 672           fputs_filtered ("...", stream);
 673         }
 674       if (pretty)
 675         {
 676           fputs_filtered ("\n", stream);
 677           print_spaces_filtered (2 * recurse, stream);
 678         }
 679       fputs_filtered ("}", stream);
 680     }
 681
 682  done:
 683   do_cleanups (cleanups);
 684 }
 685
 686 enum ext_lang_rc
 687 gdbpy_apply_val_pretty_printer (const struct extension_language_defn *extlang,
 688                                 struct type *type, const gdb_byte *valaddr,
 689                                 int embedded_offset, CORE_ADDR address,
 690                                 struct ui_file *stream, int recurse,
 691                                 const struct value *val,
 692                                 const struct value_print_options *options,
 693                                 const struct language_defn *language)
 694 {
 695   struct gdbarch *gdbarch = get_type_arch (type);
 696   PyObject *printer = NULL;
 697   PyObject *val_obj = NULL;
 698   struct value *value;
 699   char *hint = NULL;
 700   struct cleanup *cleanups;
 701   enum ext_lang_rc result = EXT_LANG_RC_NOP;
 702   enum string_repr_result print_result;
 703
 704   /* No pretty-printer support for unavailable values.  */
 705   if (!value_bytes_available (val, embedded_offset, TYPE_LENGTH (type)))
 706     return EXT_LANG_RC_NOP;
 707
 708   if (!gdb_python_initialized)
 709     return EXT_LANG_RC_NOP;
 710
 711   cleanups = ensure_python_env (gdbarch, language);
 712
 713   /* Instantiate the printer.  */
 714   if (valaddr)
 715     valaddr += embedded_offset;
 716   value = value_from_contents_and_address (type, valaddr,
 717                                            address + embedded_offset);
 718
 719   set_value_component_location (value, val);
 720   /* set_value_component_location resets the address, so we may
 721      need to set it again.  */
 722   if (VALUE_LVAL (value) != lval_internalvar
 723       && VALUE_LVAL (value) != lval_internalvar_component
 724       && VALUE_LVAL (value) != lval_computed)
 725     set_value_address (value, address + embedded_offset);
 726
 727   val_obj = value_to_value_object (value);
 728   if (! val_obj)
 729     {
 730       result = EXT_LANG_RC_ERROR;
 731       goto done;
 732     }
 733
 734   /* Find the constructor.  */
 735   printer = find_pretty_printer (val_obj);
 736   Py_DECREF (val_obj);
 737
 738   if (printer == NULL)
 739     {
 740       result = EXT_LANG_RC_ERROR;
 741       goto done;
 742     }
 743
 744   make_cleanup_py_decref (printer);
 745   if (printer == Py_None)
 746     {
 747       result = EXT_LANG_RC_NOP;
 748       goto done;
 749     }
 750
 751   /* If we are printing a map, we want some special formatting.  */
 752   hint = gdbpy_get_display_hint (printer);
 753   make_cleanup (free_current_contents, &hint);
 754
 755   /* Print the section */
 756   print_result = print_string_repr (printer, hint, stream, recurse,
 757                                     options, language, gdbarch);
 758   if (print_result != string_repr_error)
 759     print_children (printer, hint, stream, recurse, options, language,
 760                     print_result == string_repr_none);
 761
 762   result = EXT_LANG_RC_OK;
 763
 764  done:
 765   if (PyErr_Occurred ())
 766     print_stack_unless_memory_error (stream);
 767   do_cleanups (cleanups);
 768   return result;
 769 }
 770
 771
 772 /* Apply a pretty-printer for the varobj code.  PRINTER_OBJ is the
 773    print object.  It must have a 'to_string' method (but this is
 774    checked by varobj, not here) which takes no arguments and
 775    returns a string.  The printer will return a value and in the case
 776    of a Python string being returned, this function will return a
 777    PyObject containing the string.  For any other type, *REPLACEMENT is
 778    set to the replacement value and this function returns NULL.  On
 779    error, *REPLACEMENT is set to NULL and this function also returns
 780    NULL.  */
 781 PyObject *
 782 apply_varobj_pretty_printer (PyObject *printer_obj,
 783                              struct value **replacement,
 784                              struct ui_file *stream)
 785 {
 786   PyObject *py_str = NULL;
 787
 788   *replacement = NULL;
 789   py_str = pretty_print_one_value (printer_obj, replacement);
 790
 791   if (*replacement == NULL && py_str == NULL)
 792     print_stack_unless_memory_error (stream);
 793
 794   return py_str;
 795 }
 796
 797 /* Find a pretty-printer object for the varobj module.  Returns a new
 798    reference to the object if successful; returns NULL if not.  VALUE
 799    is the value for which a printer tests to determine if it
 800    can pretty-print the value.  */
 801 PyObject *
 802 gdbpy_get_varobj_pretty_printer (struct value *value)
 803 {
 804   PyObject *val_obj;
 805   PyObject *pretty_printer = NULL;
 806   volatile struct gdb_exception except;
 807
 808   TRY_CATCH (except, RETURN_MASK_ALL)
 809     {
 810       value = value_copy (value);
 811     }
 812   GDB_PY_HANDLE_EXCEPTION (except);
 813
 814   val_obj = value_to_value_object (value);
 815   if (! val_obj)
 816     return NULL;
 817
 818   pretty_printer = find_pretty_printer (val_obj);
 819   Py_DECREF (val_obj);
 820   return pretty_printer;
 821 }
 822
 823 /* A Python function which wraps find_pretty_printer and instantiates
 824    the resulting class.  This accepts a Value argument and returns a
 825    pretty printer instance, or None.  This function is useful as an
 826    argument to the MI command -var-set-visualizer.  */
 827 PyObject *
 828 gdbpy_default_visualizer (PyObject *self, PyObject *args)
 829 {
 830   PyObject *val_obj;
 831   PyObject *cons;
 832   struct value *value;
 833
 834   if (! PyArg_ParseTuple (args, "O", &val_obj))
 835     return NULL;
 836   value = value_object_to_value (val_obj);
 837   if (! value)
 838     {
 839       PyErr_SetString (PyExc_TypeError,
 840                        _("Argument must be a gdb.Value."));
 841       return NULL;
 842     }
 843
 844   cons = find_pretty_printer (val_obj);
 845   return cons;
 846 }